# What's with this fixation with oversized turbos?



## tdimeister (Feb 19, 1999)

Firstly, allow me to briefly give my qualifications for posting this. I am a mechanical engineer with direct work experience having worked at a German-based engine development consultancy in the Detroit area. I have done design work on engines ranging from methanol-fuelled single cylinder laboratory research concepts to 7000+ BHP 16-cylinder locomotive Diesel engines, and numerous engines in between. I routinely do turbo calculations as part of my job description (albeit for OEM engines), and in my free time I have done some conceptual calcs for some forced-induction VW motors.
So, imagine my chagrin when I'm reading mags like Euro Tuner and the like, and after having been introduced to people who put friggen T3/T4 hybrid turbos in engines like 1.8Ts







Are you insane?
What I observe is this apparent fixation with the "bigger is better" mentality that is especially prevalent in the aftermarket forced induction crowd. A somewhat lighthearted case-in-point was being introduced to some dude last summer who did a T3/T4 conversion into his 1.8T Mk4 Jetta. He quotes about 21 PSI of boost and "over 300" WHP. Upon asking to see his dyno chart, which he proudly produced for me, I was alarmed to see what looked more like a *seismograph* than a dyno chart -- massive detonation above 3500 rpm or so







. I asked if he was running a reduced compression ratio, to which he replied "No," and more alarming was his attitude and expression on his face like *I* was the dumb one for asking, and his response that followed, something to the effect of, "Well, I just pulled 13-something on the 1/4 yesterday so the turbo must work, and I don't worry about the detonation as I just don't go there with the throttle pedal." SHEESH!!!!
I have also read that a lot of people are putting in T3 S-60s in former G60s, 1.8/2.0 8-valvers and some 16Vs. WOW!!! Is surge not in anyone's vocab??
In my calculations, I have found that a GT25 with good intercooling will be more than ample for a 1.8T making over 350 HP -- provided the CR is reduced and proper trims and A/Rs are selected for the compressor and turbine sides.
Also, I'm hoping to soon build a 3.2 VR6 with a minimum of 600 BHP using a pair of GT22 turbos and other peripheral mods. These things are tiny compared to the T3s and up that most people seem to be using.
The benefit of both above examples, are that the smaller GT tubos will spool up much quicker and make useful boost from a lower RPM than the much larger, heavier, less responsive, and less efficient T-series units. The HP will be available from a lower RPM; lag will be less; and with higher turbo efficiencies, the engine is less stressed. With some smart design work to improve the VE independently of forced induction, the same power can be made with less boost, or as a corollary, more power made with the same boost.

Flame away.


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Hmm... You haven't seen Killa's famous detonation dyno. Very cool, looks like a big earthquake.
Why do you say a S-60 will surge? I really doubt surge would happen on such a small compressor, especially on a 16V. T3/T4E 60 trims on an 8v ok.
The point is bigger IS better because more HP IS better.
Oh, and congrats on your resume, I worked on the Chrystler Patriot project.
Speedy G


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

But Corky Bell says that Porsche is really good at making turbo'd cars because they place large turbo's on their cars which is smarter than the turbo choice Nissan made on the 300ZX.
OK I know Corky leaves a lot of usefull information out of Max Boost, but isn't there two sides of the story? You can build a 300+HP turbo'd G60 with large turbos. It might not be the best, smoothest design but it certainly hurles you down the 401 in a hurry.
I myself am interested to learn the experience between driving a 300HP 16vT using s T3/T4 .48/.50 vs something like a GT25 that would perhaps only make 250HP. The power curves in each car would be quite different, so how does it feel? Will 250HP accelerate faster because it gets to the power more quickly thant he 300HP motor? (more lag and power falling in the upper RPM band)
This is what I want to know.


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

Lag is your friend if you're talking HP and traction. Getting a 300hp GT28R and a T3/T4E 50 trim to grip is a different story. For drag racing you only look at 4k+ rpm so the 1/4 would look about the same. If you're going rallying or autocrossing, it's a different story. Also, daily drivers have different priorities as well.
Another word in favour of large turbos. If the multiple turbo design is so great, in the past, why did formula 1 cars use a single huge turbo on their engines? They could've used 4 or 6 mini-turbos to flow the same.
Speedy G


_Modified by Speedy G at 6:22 PM 1-6-2004_


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

Don't F1 cars stay in the same RPM rage relitively speaking? They aren't daily drivers widing out at 13000 rpm or whatever they're at. One turbo is less complex than two, and if it works at the high rpm.. then great.
I think Dave is talking about the daily driver car.


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

Agree with you, Speedy R, on this one point: All-out race cars are designed to live and operate almost exclusively in a very narrow operating range compared to street cars. Therefore a single turbo that is optimized for that narrow range can serve that requirement and application well. I guess my OEM engineering conditions me to think that I must design to optimise the widest possible range.
However, to your question as to why F1 and other spec racing classes are mostly single turbo, that's too easy, and here're why: Most of these racing classes are limited through air restrictors. Every effort is done to minimize restrictions elsewhere in the engine and to reduce frictional losses. Introducing more turbos and more unnecessary components mean more restrictions and more losses that are impediments to improved all out performance, again at a relatively narrow operating range.
Furthermore, splitting the exhaust gasses from say, 8 or 10 cylinders as F1 and Le Mans prototype engines have into 4 or more turbos would be terrible for gas flow dynamics as the pressure pulses hitting the turbine blade would kill turbo efficiency, and the reflecting pressure waves would kill scavenging efficiency of the engine.
AJ, I submit to you that a small turbo like a GT25 will make more power in a 2.0 16V than your heart's desires and than you can handle, and the engine would make power over a wider and more useful range.
To your remark about Porsche turbos and Corky Bell, hmmmm... interesting isn't it, that Porsche has gone universally from single large turbos in the `80s and prior to smaller twins??? GASP?! Might they be on to something here?


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (tdimeister)*


_Quote »_To your remark about Porsche turbos and Corky Bell, hmmmm... interesting isn't it, that Porsche has gone universally from single large turbos in the `80s and prior to smaller twins???

AND... making more specific power at the same time, with higher compression ratios and meeting insanely stringent emissions regs and on little-changed pump gas, I might add...


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## need_a_VR6 (May 19, 1999)

*Re: What's with this fixation with oversized turbos? (tdimeister)*


_Quote, originally posted by *tdimeister* »_...I have also read that a lot of people are putting in T3 S-60s in former G60s, 1.8/2.0 8-valvers and some 16Vs. WOW!!! Is surge not in anyone's vocab??...

If you think a T3 S60 is surging on a 1.8L you must be using a .32hsg and a stg 1 wheel .. or even smaller. A T3/60 doesn't hit it's surge point. 
Time to put a TS04 on my 1.8, just to balance guys like you out.


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (Speedy G)*


_Quote, originally posted by *Speedy G* »_Lag is your friend if you're talking HP and traction

It sounds like somebody needs syncro!


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## streetpower (Sep 6, 2002)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Ok I will chime in with my limeted expertise and give you a different perspective on why t3/t4's are used vs a finely tuned gt25/28...and the answer is $$$$$ and availabilty of tuning products(programs etc, maps, fuel maps, tricks, parts) it becomes alot easier to tune a car or *fix* a car when you can pretty much pick up the parts anywhere you go. Now granted the "T" engineering is starting to fade to more precise smaller turbos but those are not as readily available and are not near as cheap as picking up a good hybrid turbo. As far as lag goes my car doesnt fully spool up till close to 4k and I love it. When im driving around town or using it as a daily drive it runs almost as if it was a stock car, minus the oil leak







, however when I want to run it at the track or get on it its there for me waiting...
just my outlook on things..


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## GoFaster (Jun 18, 1999)

*Re: What's with this fixation with oversized turbos? (streetpower)*

I think the point being made is that if your turbocharger were a bit smaller, it would be able to develop full boost pressure at less than 4000 rpm while still maintaining that boost pressure up to the useful maximum speed of the engine, thus having the power available over a wider speed range.
It is possible that a smaller-turbo setup *might* have a wee bit less peak power, but this begs the question, is it better for the engine to develop "X" lb.ft of output torque at (say) 6000 rpm with major drop-off on either side of that, or "X-5%" lb.ft of output torque between 4000 and 6000, or "X-10%" between 3000 and 6000? Depends on whether you are looking for a big number on a chart, or a big number useful in day-to-day operation ...
Granted, parts availability is a factor; it's one thing for a particular setup to be ideal but it's quite another if the parts aren't available to do it (or cost an arm and a leg - same result).
I've also seen (many times over) people looking for a big number on a chart, and losing out day-to-day operation as a result ...


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## Vr6Fidelity (Oct 4, 2001)

*Re: What's with this fixation with oversized turbos? (streetpower)*

Obviously porsche used a large turbo to mimimize backpressure, why? because its an air cooled engine!! and Why is porsche now using twin turbos? how about the radiator they now have, Porsche can now tolerate the higher backpressures and resultant heat because they have a water cooled block. Simple. And much like the 300zx porsche is probably doing this so there cars feel more powerfull at lower speeds like during a test drive for instance.


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## Quiz (Sep 13, 2002)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Perhaps finding a dyno plot of a 1.8/2.0 properly tuned above 300hp will ease your worries of detonation. Anyone can slap on a turbo and dyno it, but can most correctly fine-tune it?


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (Vr6Fidelity)*

I'm aware that Porsche made the shift from air-cooled to water. However, whatever benefits an air-cooled motor (e.g. backpressure, etc.) no less benefits a water-cooled unit.
It can be shown from a first law derivation that -- choking flow aside -- backpressure is a function of the total efficiency of the turbochager (i.e. the combined sum of compressor-, turbine- and mechanical efficiencies), not of its physical size. Therefore the designer endeavours to design the turbo/engine combination to operate at the highest turbo efficiency over the widest, most prevalent operating range for the application.
A small turbo operating near its efficiency peak will outperform ANY larger-sized unit operating at a lower efficiency point WITHOUT exception, and that includes lower exhaust backpressure and intake charge heating.
So far I've only touched on the thermodynamics of smaller turbos versus larger; I haven't even begun to discuss frictional and inertial losses.
I'm not saying that we should downsize turbos. I'm just saying we should *right-size*. And frankly, some just aren't right....
A dedicated drag- or high-speed track racer whose engine always stays north of, say, 4000 RPM has a case for a big turbo; a street driven engine that runs on pump gas and needs some semblance of driveability and durability does not. IMO.


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## VR6T-Rex (May 6, 2003)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Why would you twin turbo a VR6


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## need_a_VR6 (May 19, 1999)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

More or less you just said that you'd rather have 180whp and lots of "driveable" low end and not some 400whp monster that doesn't make boost until 3.5k. 
Well, riddle me this.. I know that it's hard to get traction with much more then 200whp on a fwd car in any case on the street.. and who drives around "legally" at full tilt anyway. So why not have a ton of lag so you can put around the streets, and then have twice the power available for your legal trips to the track.


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## DSSA (Nov 20, 2003)

Yes, completely dependent on what type of power production you're looking at. 
Personally, I have no dislikes about driving a 400+ h.p. on pump gas, 2.0 4 cylinder, with a bit of lag. By "bit of lag" I mean 3500-4000 spool-up. The car still drives smoothly enough around town off-boost, and when there is a chance to open it up, the power is there. Sure, you're gonna see more a better torque-curve with a smaller turbo, however, your driving preferences will alone dictate what setup you'll personally require. 
As far as "larger turbo" vs. "smaller turbo" aspect, have you figured in heat production in there? On paper, the GT series look great, however, I've yet to see that much of a difference in either 1/4 mile mph measures or dyno pulls which make the extreme price bump worthwhile.
The T-72 car (also 2.0 4 cylinder), yes, is overkill, however, with a little giggle gas to get the ball rolling, and the fact that it'll see 90% of life at a dragstrip becomes less obnoxious than it sounds.
The "peripherals", as you state, have a huge effect on what you're worried about, so you may want to completely factor those into the equation before you decide on turbos for your VR6. For example (and I hate going back to these cars, as this is a VW site, however, my experience lies within) a DSM in stock trim will spool around 2800 or so rpms. However, properly set up (porting of the exhaust manifold, 02 housing, less restrictive exhaust, etc.) a TD05/TD06 20G (650 cfm vs. 405 on the stock unit) will spool just as quickly with a lot less heat. A 50-trim t3/t4 (.48 exducer housing, Stage III wheel) isn't all that much more inclined to become peaky. 
I do agree with some of what you're saying though. It's just easier for some people to make that extra *peak* power with a larger compressor attached then to maximize the potential of a smaller one. 
However, I've seen "engineering people" state things are theoretically impossible by crunching the #s, only to have to eat their words later. One such case recently was an engineer stating that it was physically impossible for someone to put down over 400 h.p. in a 2.0 motor on 93 Octane fuel according to his math (and yes, this was an actual engineer). Unfortunately for him, many people have put down well over 400 on pump gas (most recently, one person broke the 500 h.p. mark on Mobil 93 Octane with a "smaller" turbo).
If you're interested in turbo "theory" vs. "real world" instance, another engineer in this thread http://forums.vwvortex.com/zerothread?id=1168345 stated some "theoretical fact" that just didn't fit with what has actually been "done".
Not slamming people in the Engineering Community one bit (it'd be a sad world for all of us without you guys), just stating where certain engineers' math didn't do them justice.


_Modified by DSSA at 9:26 PM 1-6-2004_


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## 92-8valver (Oct 9, 2003)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

just adding this to my recent topics list so i can find it easier


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_So why not have a ton of lag so you can put around the streets, and then have twice the power available for your legal trips to the track. 

If that's how you like it, I'm cool with that








My car makes >250 lb.ft of torque at ~2000 RPM but has nothing above 4000...


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## need_a_VR6 (May 19, 1999)

*Re: What's with this fixation with oversized turbos? (tdimeister)*


_Quote, originally posted by *tdimeister* »_
If that's how you like it, I'm cool with that








My car makes >250 lb.ft of torque at ~2000 RPM but has nothing above 4000...









EXACTLY. My Mk2 doesn't make crap for power until after 4k.. and I'm sure I like it that way. Turbo car or NA car, I'm all about the top end.


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

BTW, my car with 235k km (146k miles) on the odo is equipped with a positively puny (and original) GT15 turbo with a 1.73" compressor wheel. With a 1.9L displacement and pretty decent VE, it will hold 22 PSI of boost to 4500 RPM and still have compressor efficiency over 70%.
I have run this little turbo with anywhere between 19-24 PSI peak sustained boost for the past 120k km (75k miles). Numerous drag racing and autocross sessions are also included in this mileage figure.
The notion that turbos have to be big to perform well and make big power is about as misguided and outdated as 3000 mile oil changes.


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## streetpower (Sep 6, 2002)

*Re: What's with this fixation with oversized turbos? (need_a_VR6)*

See thats exactly how i designed my setup, I dont want to be putting down 300hp at 2-3K rpm I want that range for driving "normally" if I wanted a power from zero to redline I would have bought a vr6 and supercharged it. I wanted a car that could be daily drivable but as well have a hidden sweet spot that she could take advantage of.
I dont think anyone will disagree with that bigger is not always better, simple analogy is look at our 4cyl beating 8cyl. Its not that bigger is better, its just how its tuned of course if you properly tune a big turbo(sg5,dualbb,360 thrust,etc) your going to end up putting more power down than a smaller turbo with the sacrifice of the lower range. 
Its all how you design it, I think the notion of this original thread might have been steemed from the influx of "big turbo" vw starting to pop-up on the board. I think that the mk4's are just now graduating to the point where enough aftermarket and attention is being focused to "safely" take the next step that dsm and rotary guys have been taking for years. Be that it may along with that you will find the people who hop on the bandwagon without truely understanding the complexity of putting a big turbo on. Im still learning stuff everyday, this is a hobby not a job and I will continue to learn till I come to a crossroad where ive extended my limits and must learn a new route be it a gt series of some other newly enginered turbo.


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## turbojeta3 (Feb 23, 2002)

*Re: What's with this fixation with oversized turbos? (Quiz)*


_Quote, originally posted by *Quiz* »_Perhaps finding a dyno plot of a 1.8/2.0 properly tuned above 300hp will ease your worries of detonation. Anyone can slap on a turbo and dyno it, but can most correctly fine-tune it?

Id be more than happy to show you a 8v pulling power out of a turbo off a Lotus if you like?
there it is right there. go poking threw the hp thread that is in the next couple pages. I will tell you this yes there are alot of over-sized turbos running around. Why? Well that is simple front wheel drive.
You might go out there and get a yourself a turbo that hits full boost at 2000rpm and dies out at 5500 which might be fine to you. There are alot of guys out there who have already experienced this in lower engines such as 8v. Take me for instance. I had a t3 super 60. Nothing like a front wheel drive burn out. Yeah whatever that $hit got old quick. Real quick. Moved up to a T3T4 48,50 stage 1 wheel and the responce was better. The boost was readily available past 4000 by down shifting. 
You can use all the technical jargon you want. It comes down to what people have used and how they have helped others by making sure they pick the right turbo for there power output. Sure some types i want 600whp. Fine here you go T66 there you go. Then sure enough why do i get 6psi at 6700 rpm????? 
Yes everyone wants boost and they want it as fast as possible but this is one of the best forums that i have been on. Guys are always willing to help, but then there are some who question there experience. 
Read alittle bit around this forum and find out for yourself why guys pick what they do. These are not some rocket jets. Picking a turbo isn't a science for us. Its called doing research and asking questions.


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (turbojeta3)*

streetpower, turbojeta3, I don't disagree with you.
Technical jargon aside, it's just a different way from achieving the same goal. Like building a house, some prefer to do it from a picture inside their heads and build it the way their experience has guided them. I prefer to do methodical calculations to make sure the roof is not going to fall on my head, and I like to use plans and drawings.


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## streetpower (Sep 6, 2002)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

http://****************.com/smile/emthup.gif On that reply, honestly I am the same way with my job I mean when Im rolling out a network I dont want to guess on what should go where and what routes here and there I want a defined plan of action step by step....
Either way this is a great topic, and thanks for starting it because overall I think this might lead some of the "bandwagons" to think twice when building up there car and getting better performance out of things.


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (Hardcore VW)*

A small A/R on the turbine side allows the turbo to spool quicker and build boost at lower RPMs. That's to make up for the fact the the T-series turbos are relatively large and heavy (read high rotating inertia) for the given air flow. The downside, as has already been mentioned by someone else, is that turbo matching is like playing a game of give-and-take. What you gain on the low end, you lose up top. That's why you may see better numbers this year with different setups.
However, I daresay that the progress we're seeing with improving numbers has less to do with the turbos that are being used, but people are becoming more savvy and informed, and building their engines better (i.e. proper compression ratio, better breathing, better intercooling, better engine management). The latter point is key. Can you imagine how much HP is lost when an engine is detonating itself to death and the ECU is pulling timing back.
The point I have been trying to make in ALL my posts above is that if I sit down and say to myself, I want *x* horsepower out of a certain engine, the "bandwagon" and the general wisdom out there based on my observation are using turbos that are way too big for that requirement, and I'm asserting that that one can build a motor with the same peak HP on paper that is more driveable, more reliable, more efficient, more responsive, less high-strung, and overall more "spread out" in its power delivery with a smaller turbo.


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## jwatts (Mar 11, 2001)

*Re: What's with this fixation with oversized turbos? (Hardcore VW)*

The one thing you learn about turbos is that whatever you pick, it will always be a compromise in one way, or another. Therefore, if you set realistic goals for your project, then you won't be disappointed with the performance when it's all said and done. 
Right now, I have a stand-in T3 60/.48 turbo on my ABA 16V. If my goals were 200whp at full operating temps with super quick boost response, then I would be finished with it. There will be a T3/4 going on in the near future, so I will have some comparisons to leverage against eachother.
Here is a video clip of what 200whp is like in a Corrado.
http://home.test-afl.homecom.c...t.wmv
Here is what I got so far with a loose dyno tune and conservative timing.












_Modified by jwatts at 6:03 PM 1-6-2004_


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## 2kjettaguy (Dec 24, 2000)

*Re: What's with this fixation with oversized turbos? (streetpower)*

There's a million points to be brought up in regards to why people use oversized turbos. Here's a few.
It's all a part of the big ***** game. "hey, I've got a bigger turbo than you." My intercooler's bigger, my piping's bigger, my turbo's bigger - that must mean I'm faster than you. In the end - it's all in the tuning and it takes some brains and patience to really accomplish reliable power. 
Another reason along the same lines is that many of the 1.8t guys are just looking for a number on paper that says they are better than the next guy. That's not saying every 1.8t owner going bigger turbo is doing it wrong - just pointing out a fact. BillyT (respect) worked and worked to squeeze some big HP numbers out of his car. He went from a K03 to a T3 to a T3/T4 hybrid and each time was able to rasie the notch and get a bigger dyno sheet. I think alot of guys are just looking for that big HP # and don't care about driveability or useable torque. Fine by me - it's not my car. 
To reach those big HP #'s they sacrifice low end torque for high end horsepower (like a Honda motor!). Part of achieving these big numbers means big ports, big exhaust, big turbine and even bigger compressor. All these mods really concentrate on getting large volume airflow out of the system with little mind to air velocities, required backpressure, etc. Basically removing that which brings nice torque numbers lower in the powerband. 
I don't know about you but my car makes 250wtq daily peaking at 3200 roms. I run 225/45/17 Pilot Sport Z rated tires and if prompted to floor it in first or second gear I spin those tires to redline. All in all a waste of that gear. Sure, I can lay off the gas and get less wheelspin but most people just love to floor it. Getting rid of that low end powe just means you get more power up top where your less likely to spin the wheels. 
Torque is a momentary measure. Horsepower is a measure of sustained torque. Torque rips the tires loose and horwpower moves you along. This is one reason why there are so many sucessful Hondas in the drag scene. 
Personally I like my .48/.60 T3 on my 8v. It hold out long enough and makes fun power down low. It's a daily driver. Though I'd like to boast a huge WHP #, I'd rather boast my torque # and tell them all about throttle response, etc. My car is not a drag racer. 
(This post is all based on my opinion experience and learned knowledge in tuning my car and others. If i've made a mistake, please correct but don't rip on me for being incorrect







)


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Why have a small turbo that makes no power? Why run so much backpressure? Why be slow? If 200whp is that you're looking for then great, if on the other hand you're looking for 400whp then don't gimme that small turbo talk because you just wont get it. Also, why twin turbo a VR6? Single turbo does just fine and you'll have less piping to worry about, want faster spoolup, run a BB unit. Also, you'll have 3cyls creating exhaust energy to push each turbo whereas on a single application you'll have 6 pushing just one, sounds like a catch 22 to me except the Twin turbo setup will have more piping.


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## DSSA (Nov 20, 2003)

*Re: What's with this fixation with oversized turbos? (tdimeister)*


_Quote, originally posted by *tdimeister* »_
The latter point is key. Can you imagine how much HP is lost when an engine is detonating itself to death and the ECU is pulling timing back.


I keep seeing you make this comment. Where are you getting the formula for "bigger turbo + same peak power = more detonation" from?
Two systems (with proper A/F and timing maps) using two different turbos (simplifying here), the larger turbo will produce less heat at a given flow rate. Less heat in the intake charge will decrease chance of detonation.

_Quote »_
The point I have been trying to make in ALL my posts above is that if I sit down and say to myself, I want *x* horsepower out of a certain engine, the "bandwagon" and the general wisdom out there based on my observation are using turbos that are way too big for that requirement, and I'm asserting that that one can build a motor with the same peak HP on paper that is more driveable, more reliable, more efficient, more responsive, less high-strung, and overall more "spread out" in its power delivery with a smaller turbo.

This is a highly subjective statement. "Bigger" than "what"? "Smaller" than "what?" This statement is just saying X + Y > A + B with no reference point as to what X, Y, A, or B are. 
As far as "more reliable", when taking bearing loads out of the equation (for larger inducer/exducer wheels/shafts) a larger turbo (within reason of course) will produce less heat (once again) than a smaller turbo at any given CFM point. 
If you're talking about building an auto-x car, yes, your ideas/theories are correct. If you want to build a docile street car, once again, your theories ideas are correct. But, if you're trying to squeeze big power out of a small displacement motor for outright acceleration, it's not best to go out and buy "the smallest turbo which will just flow what you need to make your peak h.p. goals".
The aspect that I would argue (as opposed to just "big turbos") would more specifically be people who just throw a large compressor-equipped turbo on a car thinking that it will make more power, when in fact the exducer side, and overall manifold pressure (exhaust..not Intake) are just as important in the scheme of things, and in some cases, more-so.
Exducer wheel and housing sizing is my pet-peeve. So many people put so little investigation into it.
Edit: One other aspect to look at. A lot of people (notice I didn't say "all") aren't interested in building a 250-300 h.p. car and calling it a day. With that in mind, they aren't going to go out and buy the smallest turbo to fit the bill for what they're currently planning on putting down, but one that will allow for headroom. 


_Modified by DSSA at 11:29 PM 1-6-2004_


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (Hardcore VW)*


_Quote, originally posted by *Hardcore VW* »_ shave the cat.


shaved p*ssy?








Sorry, I just had to do it


_Modified by GTibunny16v at 6:32 PM 1-6-2004_


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (killa)*

*My car is not a drag racer.* 
exactly. Some folks car's are DRAG racers. If you spend 90% of your time on the freeway rocking out at 3500+ rpm's, and like to drag, then a bigger turbo would yield better results.
Me i sit in city traffic so that doesn't buy it. So i puts around with my g-lader with makes [email protected], and [email protected], about shy of 150wft/lbs @ 2000rpm. I don't have any lag (g-lader). I am not a drag racer either. If i was, i would have a big turbo on a well breathing motor..
then again i have an automatic ls1, so i guess i do like to drag race








until i can afford a 4 door 11 second factory car, i guess i'll have to stick to several cars to meet all my needs







ultimately it is less costly than the path some others choose.


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## Nuzzi (Oct 18, 2001)

*Re: What's with this fixation with oversized turbos? (killa)*

i have a question about a VR6 turbo, what would you say is a better size exhaust to use, 2.5inch or 3inch? ill be using a 95mm maf, and an intercooler with 3inch in and out, so i want a turbo with a 4in inlet and 3inch outlet, just dont know whether to go with 2.5 or 3inch exhaust out. and itll be a 3L too


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## streetpower (Sep 6, 2002)

*Re: What's with this fixation with oversized turbos? (Nuzzi)*


_Quote, originally posted by *Nuzzi* »_ 95mm maf


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## DSSA (Nov 20, 2003)

*Re: What's with this fixation with oversized turbos? (Nuzzi)*


_Quote, originally posted by *Nuzzi* »_i have a question about a VR6 turbo, what would you say is a better size exhaust to use, 2.5inch or 3inch? ill be using a 95mm maf, and an intercooler with 3inch in and out, so i want a turbo with a 4in inlet and 3inch outlet, just dont know whether to go with 2.5 or 3inch exhaust out. and itll be a 3L too

I'm not trying to be a dick, but if you have to ask if a 2.5" or 3" on a turbocharged car of that magnitude would be better, you might want to do some research on building a turbocharged car before starting out on it.
As for the answer to your question, 3.5".


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## 87GolfKart (Apr 3, 2001)

*Re: What's with this fixation with oversized turbos? (2kjettaguy)*

I am the most ignorance of the people in here. It looks like the size of the turbo depends on what you want to do with your car. It depend on where your powerband to be at. If you are drag racing and big on top end power, maybe you want a bigger turbo. Especially if the way you shift always keep you at around 4000rpm or higher. But I always thought fueling and timing was the most important part of dealing/tuning a turbo. I also heard that the cfm of air a turbo flow is also crucial...you can get more hp from 15psi with a t3/t4 than a 60 at the same psi due to the cfm. Guys with 1.8T 300hp maybe maxing out his injectors and fuel pressure systems. Maybe if he have good engine management that will retard/advance timing accordingly it will be ok? So why is bigger turbo a problem? I always thought that once you max out the smaller turbo you should go to a bigger one (within an ideal size), provided that you adjsut the compression, fueling and engine management accordingly. Maybe some people jsut slap on bigger turbo w/out thinking. But I head of alot of supra guys who swap their twin turbo for a single large turbo to achieve 800-1000hp. Again, I'm just throwing out stuff...I don't know what I'm talking about.


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## Nuzzi (Oct 18, 2001)

*Re: What's with this fixation with oversized turbos? (87GolfKart)*

thats why im asking man


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## vdubspeed (Jul 19, 2002)

*Re: What's with this fixation with oversized turbos? (Nuzzi)*

tdimeister-I won't say you don't know your $hit b/c you obviously have crunched some numbers. So I will definitely give you that.
However you never mentioned the way you grew up around cars. For me personally, when I was in America I would go out every Fri. and Sat. night and hang out with car guys. We talk about big HP, low 60', and good 1/4 times. No one cares about all that mathematical stuff.
So when people starting making big HP and running real fast times with hybrids then everyone hoped on board. I agree with you about running bigger turbos. My Honda friend wants a t61 for his H22 and says he doesn't care about lag because it's a honda. That's his deal.
For me though...like always I'm going to follow the fastest guys because they have the numbers and cars. Oversteer and Hardcore come to mind immediately and so do Killa, mrkrad, bottlefed, holy piston, 2kjettaguy and a slew of guys running real cars with real numbers,
Make that Vr run 11s or something with that TT setup and I'll listen. Until then...I can't wait to get my new t3/t04e turbo from Killa http://****************.com/smile/emthup.gif 
Jason


_Modified by vdubspeed at 6:41 PM 1-6-2004_


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## speed51133! (Aug 5, 2002)

*Re: What's with this fixation with oversized turbos? (streetpower)*

what about me???
















might i add this is a 2.0L 8v motor with a 100% stock head and 100% stock block with 2 headgaskets for low compression. know how i made that power? with a big ass turbo. and i plan on muuch more in spring time. Tell me, what turbo SHOULD I be using to get into 300hp? I'd like to know. I am using a t3 .63 ar turbine housing with a t4 O trim turbine, and a t04E .57 trim .52 ar compressor, but I guess after reading your post, I should go SMALLER.

all i read is the first 2 paragraphs of the first post, and i have to say that regardless of your qualifications, i'll bet money you have never built a high hp motor by yourself. i'll also wager that you never made a slow car become a fast car.
by high hp, i mean proven numbers with like a dyno or a track time.
by slow car fast car i mean again, track time.
you can babble on all you want, but you need to buy something in the clue department when it comes to power. bigger turbos make more power than small turbos. i dont know how else to put it for you. with the kind of turbo YOU think belongs on a motor like a 1.8t, youd probably stick with the stock turbo, and complain about how it has so much turbo lag.














i cant hit that roll eyes button enough times.


_Modified by speed51133! at 4:49 PM 1-6-2004_


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (streetpower)*

I have another point going for big turbos. First, if you look at compressor diagrams, smaller turbos usually have a pretty small high efficiency island, and the peak efficiency is lower than in larger turbos. Let's take a 1.8T engine since I know a bit about how it behaves, your favourite GT15, and a Gt30 for comparison's sake. Let's use the compressor maps from the ATP site. So:
2 GT15 flow about 23 lbs/min each so 46lbs/min total.
1 GT30 flows about 52 lbs/min
Let's say we want to make 400whp which is well within the flow specs of the turbos. We'll need around 24-26 psi to make that power (if you take Billy T's achievement with his T3/T4E 50 trim as data). We're talking about 1.8 bar of boost so the turbo will se a pressure ratio of say 3. Um.... well... so you can only make that type of power using the GT30 since the GT15 cannot operate at that type of pressure. Too bad!
Meanwhile, the GT30R is running at better than 72% efficiency until 45lbs/min. This is usually the case with smaller turbos, they can't handle big boost. Oh, and the efficiency of the GT30R flowing 45 lbs/min at a pressure ratio of 3 is the same as the 2 GT15s at only 1 bar of boost. Sorry to say, but I don't see the better efficiency in going with 2 smaller turbos. Higher efficiency means less heat which means less danger of detonation. In other words a GT30 is less prone to causing detonation than 2 small turbos.
Speedy G




_Modified by Speedy G at 6:50 PM 1-6-2004_


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

Hey tdi dude. I realize you know your shït... That's why I like this thread. I was wondering if you could explain to us how to read the GT series turbine flow maps. So far I've tried looking at it, but it tells me absolutely nothing. 
The question is if airflow doesn't increase beyond 8 lbs/min, but the pressure ratio increases (with RPM I'm guessing), how can you make 200hp on the engine, if the exhaust is being blocked by a turbine that will only flow enough for 80hp?








And another poke at tdi dude. Notice the GT30R has a much more efficient turbine than the GT15:








Speedy G


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

A questions for the big number chasers...
on the drag strip or race track, will big numbers always win? I'm tempted to think that a car like mkrads with a G60 will win many races over a car with more power simply because of the wider power band found. Now apply a small turbo that yeilds less peaky and high end biased power but a more broad power curve. Will that car be faster? I know it all depends on how long you race for, and what the other car has.. but as a general observation I would rather have a smaller turbo that generates quick accel and good torque down low then to have huge nubmers up high with a screaming motor. I of course am after a daily driver though. I wonder if some of these drag guys paid more attention to tuning with a slightly smaller turbo as TDIMiester suggests.. will they get through just as quickly? Wouldn't it make sense that the motor that has the highest mean (avg) HP/Tor over a rev range be the quickest car?

And one point that bothers me.. those who suggest that the bigger turbo is an advantage becuase the boost doesn't kick in until higher RPM's therefore you have better traction... I'm sorry but that's a sorry ass way of saying I can't drive. If all you can do is floor it then stick a monkey behind your wheel and see him do the same thing. Where's the pride in that? Learn to drive the car properly and respect and have control over the power it makes.
and don't get me worng, I am no way stating that I'm the best driver. But tjust think about what I said... it really seems silly to say when I floor it I lose traction therefore I need something that doesn't make as much power downlow. I know what makes less power down low... less foot action.


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## speed51133! (Aug 5, 2002)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

tell me why pro drag races all the the biggest turbos that are made?
they must be doing somehting wrong


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (speed51133!)*

well with anti-lag you can pre-spool the turbo to full boost and launch, which negates the benefits of a g-lader blower. The amount of time you are doing this will probably not have any harsh effects since most of us dont live at the track, or if you do, you buy hardcore parts that can take the abuse.
That leaves the drivetrain. Gotta beef it up, lsd, slicks, etc. to actually hook.. no point in building a 1 wheel powered drag racer eh? And what fun is it if your axles break off on launch.
It is a to launch a turbo without some sort of anti-lag , or automatic. You notice all the pro drag racers don't bother with stick shift, with torque converter's and such you can launch much harder without shocking the drivetrain as much. Going from a 5/6 speed to auto can easily clip a second off your ET if you got a nice automatic, even though the car may trap at the same speed.
GN's and Fbody's are both a great street car testament to auto's win, manuals lose, dollar for dollar at the strip.
probably why them dodge's are running 10-12's at the strip all day long. They got the big turbo, they got the automatic, and a great motor thats way old in design. Of course thats a drag car, and not everyone wants a drag car.
but it is fun to have a streetable car that you can take to the track, deflate the nitto's, run 11's and 12's, then inflate tires and drive to the grocery store, pick up some beer, and head home. werd.


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (speed51133!)*

The point in drag racing is to start without spinning the tires, and have the most torque possible between shift points. That said on a 1.8t with a big turbo, my shift points are 6.5krpm and I fall to more than 4krpm. The problem with traction arises when you have 300ftlbs of torque at 3700RPM for launching, but only 240ftlbs at your shift point (APR stage III GT28R). nedless to say, a well matched turbo for the 1.8t engine (APR stage III) is no good for drag racing.
On the other end of the spectrum is a totally oversized turbo (GT35/40R used by ATP). You get 300ftlbs all the way to redline. Also, the torque is the same because they're running about the same amount of boost, although the APR stage III peaks higher:








Speedy G


_Modified by Speedy G at 7:57 PM 1-6-2004_


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

gotta flat shift that baby







Hmm where's that quote..
Granny shifting, not double clutchin' like you should. Im surprized that 6.5k revving didnt blow the welds on the intake.
heh


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## Peter Tong (Jun 17, 1999)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

OT: How are you folks holding your drivelines together with that much torque? I mean making power is one thing but how *reliable* is your drivetrain is my question...?


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (Peter Tong)*

Word of mouth and Jabbasport in the UK say 1.8Ts can do 330ftlbs with an LSD. Some people have gotten up to more than 400ftlbs.
Speedy G


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (Speedy G)*

wheel hop kills the driveline, thats and dip**** drivers








burnouts are not cool unless your in the waterbox.


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## jettatech (Oct 26, 2001)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

"I am a mechanical engineer ." well at least you arent an electrical engineer for vw.


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## Holy Piston (Oct 24, 2003)

*Re: What's with this fixation with oversized turbos? (jettatech)*

It is pretty easy "in real life" to figure it out yourself............I had a T3 and it was a great street car,but 2.5 60 fts. were not the hot ticket,and on a low revving 8V the response was welcome,but there really wasn't much there after 5300or so rpm.I moved up to a "small trim" T3 T4 and I honestly can stomp it in 3rd gear going about 20 mph and yes,I have lag,but 2 seconds later it is rocking,so it was still OK for street.Take it to the track and when you are pulling ahead in 1-3rd gears you think you won the race (with a responsive turbo)but at the end of the track that big turbo Honda,or Supra shoots past you and gets 115-120mph+ traps,then you realize that your top end isn't there and you need a bigger turbo/turbine.Like everybody said before,you can have a "fun"car with a small turbo,but when you arer at the track the greenlight drops and the BS stops and that is where a big turbo shines. I have learned,thrue trial and error and will be going for that big turbo powerband(57trim To4E)and (to me) it is more impressive to have a FAST car with high traps,than it is to have a "quick car,with good 60ft. and low traps",cuz if you ever met that car on a open stretch of road,rolling star,you know who would win,the FAST car!!!I finally realized what the big hitters were saying is true,"Lag is your friend when it comes to racing".BTW I have a street car,I just need to go faster!







Calculations,Smalculations,take it to the track and figure it out yourself!1 more thing,I don't usually see people "upgrading" their OEM turbo for a smaller one.........................


_Modified by Holy Piston at 4:06 AM 1-7-2004_


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## Agtronic (May 14, 2001)

*Re: What's with this fixation with oversized turbos? (Holy Piston)*

I think people don't give enough credit to driver diversity. People assume that everyone is looking for the same feeling from their cars. I'm a highway guy, 3rd gear and up. That's why I chose a T3/T4 ...
I heard people talking about larger A/R exhaust housings and how they could just go around driving all day without hitting boost, or letting their girls / mom's drive the car without them ever even knowing the cars were capable of tire-shred in 3rd, it sparked my interest in "larger" turbos. My goal from the begining was to have a car that would behave as close to stock as possible when driving legally, and be able to become an absolute animal when I wanted it to.
Low-end torque is fun for taking off hard on people, but I think it gets old quickly if the top end dies off. If you're talking about a V8 where the low-end seamlessly turns into high-end and never really dies off, then that's a different story. But with our tiny 4-cyl VWs and their relatively poor volumetric efficiency (compared to Hondas), we have to live with what we can get. Some prefer low-end that dies off, some people prefer no low-end and plenty of top end. I guess it's somewhat counter-intutive to try and get top-end power with an 8V head, but that's a whole other thing.


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## Angular (Mar 12, 2002)

*Re: What's with this fixation with oversized turbos? (Agtronic)*

All I can say is... I am sooooo glad I stayed out of this one!








I'm gonna stay firmly planted in the middle here and get a reasonably "big" turbo (smallest GT30 available) but not a HUUUUGE turbo. Still going after the widest possible torque curve I can get. And yes, I will sacrifice some max top end power for low end response because I will enjoy and get more use out of the low end on a daily basis. I'm not trying to win races or impress anybody and it will save me from needing to downshift as often.








That is all.


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## GoFaster (Jun 18, 1999)

*Re: What's with this fixation with oversized turbos? (speed51133!)*


_Quote, originally posted by *speed51133!* »_what about me???
















might i add this is a 2.0L 8v motor with a 100% stock head and 100% stock block with 2 headgaskets for low compression. know how i made that power? with a big ass turbo. and i plan on muuch more in spring time. Tell me, what turbo SHOULD I be using to get into 300hp? I'd like to know. I am using a t3 .63 ar turbine housing with a t4 O trim turbine, and a t04E .57 trim .52 ar compressor, but I guess after reading your post, I should go SMALLER.

all i read is the first 2 paragraphs of the first post, and i have to say that regardless of your qualifications, i'll bet money you have never built a high hp motor by yourself. i'll also wager that you never made a slow car become a fast car.
by high hp, i mean proven numbers with like a dyno or a track time.
by slow car fast car i mean again, track time.
you can babble on all you want, but you need to buy something in the clue department when it comes to power. bigger turbos make more power than small turbos. i dont know how else to put it for you. with the kind of turbo YOU think belongs on a motor like a 1.8t, youd probably stick with the stock turbo, and complain about how it has so much turbo lag.














i cant hit that roll eyes button enough times.

_Modified by speed51133! at 4:49 PM 1-6-2004_

I'm not going to comment upon precisely what torbo you should be using instead of what you have, but I will comment on the shape of your graph and what could be done (if the required parts were available).
You're not one of those complaining about Honda engines having no low-end torque, are you? Relative to its peak, your engine has an extremely narrow and peaky power-band - there's very little available outside the peak. No bottom-end torque, no midrange torque, killer top-end power. Much narrower and peakier than any Honda production engine. Narrower and much peakier than my little Yamaha motorcycle engine (and yes, that's a race bike, and no, it's not stock. No turbo, though.)
You have hardly more than stock below 3000 rpm, it doesn't really get going until 4400 rpm, and it looks like the party's over by 6000 rpm (actually the graph shuts down at 5750 but things are headed downward).
In a racing application, where it doesn't matter what the engine does at low revs except perhaps at the start, this type of torque curve may be acceptable IF you have a close-ratio gearbox OR a WRC-style anti-lag system so that it doesn't come off boost after a gearchange. In a street application, you have a turbocharger that is oversized in terms of its design flow-rate. (NOTE difference between FLOW and PRESSURE, more on this later.) I can't comment on whether the lack of boost at low revs is due to issues on the intake side, or the exhaust side, or both.
I am going to guess by the shape of your graph that you are using stock (or close-to-stock) camshaft and ports. Note how the torque is dropping off after your boost pressure hits its control point and starts opening the wastegate (which I'll bet happens right at the peak torque at 4400 rpm).
If you want 300 horses with the same torque, you need to extend your peak torque (about 280 lb.ft) until you reach about 5600 rpm. This means you either crank up the boost even more, or do something about the camshaft and the head so that it breathes better at high revs. Both will result in an engine having an even more top-heavy torque curve than it already is.
A decent turbo can deliver full boost at a more-or-less constant turbo shaft speed over a range of at least 2:1 in terms of flow. In other words, if you size the FLOW of the compressor so that at the maximum engine speed it's towards the upper range of the compressor's rated flow, then you'll have full boost down to half of that engine speed or probably a bit lower. In your application, you should be able to find a turbo in which, if you size it for rated flow at 6000 engine rpm, you'll have full torque down to 3000 rpm or thereabouts. The way it is now, you've only got full torque down to about 4500 rpm, so (roughly) you have a setup with a rated *flow* of about 50% too much.
If you want 300 horse from that engine - never mind the required strengthening of the bottom end - you could do it if you had a turbo with about two-thirds of the *flow* rating and perhaps 10% more *pressure* rating, or the same pressure rating if you do some work to the head and the cams to get the engine itself to breathe better. I presume you've already got as much intercooling as you can get, because you're gonna need that too. This would give a setup with a wider powerband than what you have now.
Keep in mind that this is a theoretical discussion. It's academic if you can't actually *get* a turbo that's rated for two-thirds the flow and 10% more pressure.
Once again, I'm going to repeat something here. It is possible that the small-turbo setup may make a wee bit less power right at the peak, but it will allow a setup that has full mid-range torque instead of about half. As I said before, and I'm saying it again in an attempt to be crystal clear, IF all you are interested in is a big peak number and don't care about off-peak OR it is a racing application where the engine will only be operated in a narrow speed range, it results in a different selection than if the objective is to have good useful power output over a relatively wide range of engine speeds. What's right depends on what your criteria are.
Personally ... I would rather have a broad powerband rather than a narrow spike to a slightly bigger number, and in a street application, I want midrange even if it's at some cost in high-rpm power.


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## Slow1.8 (Oct 9, 2003)

*Re: What's with this fixation with oversized turbos? (GoFaster)*

You're Hired!


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## Holy Piston (Oct 24, 2003)

*Re: What's with this fixation with oversized turbos? (GoFaster)*

Go Faster,you do have some good points,but you do realize that that 8V motor makes about 115hp and 130 ftlbs stock right? and his torque isn't much lower at all than stock(under 3k,and he has more than doubled his stock output of his 8V motor?I think his torque peak has to also do with his cam timing(probably at 0 deg) But if you really do know your stuff then I assume you have a car that is atleast 13 sec or 200whp right?Well if you do then you definitely know that it is hard to have it all,and guys looking for high hp can't have full torque at 2500rpms!!!!Why would you want that??You would just be spinning tires if you attempted to launch your car!!It is not easy making a slow car fast,and if you want to go fast,you can do it with a small turbo,but it hits a brick wall after so much boost&hp.I have seen dynos with very peaky powerbands(in your opinion "poor" powerbands),but those cars sure were fast!!!







Go figure! EDIT:I just read your sig,you have a TDI!! THAT IS WHY you like a big torque powerband,sorry man horsepower wins races,torque is good for tooling around in traffic,and towing boats................












_Modified by Holy Piston at 9:44 AM 1-8-2004_


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## j-dub (Oct 22, 2000)

*Re: What's with this fixation with oversized turbos? (Holy Piston)*

I just want to say that I have really enjoyed this discussion. Having never built my own turbo car yet, I can't add to it. I can say that I have driven several OEM turbo cars, and yes they are a rush at 2500 rpm, but they fall on their face at 4000 rpm.
Back to you guys


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## DSSA (Nov 20, 2003)

*Re: What's with this fixation with oversized turbos? (j-dub)*


_Quote, originally posted by *j-dub* »_
Back to you guys

I've noticed that the original poster has seemingly bowed out of this discussion.
Very unfortunate.


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (DSSA)*

No I haven't







I have reply notification on and I have been reading each post with interest. I have simply been so busy at work and I don't have Net access at home at the moment.
I promise I will respond to everyone's comments in turn just as soon as I can find some free time. http://****************.com/smile/emthup.gif


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## Holy Piston (Oct 24, 2003)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Remember 1 point please,MOST peeps here are looking for better than OE performance,which a bigger turbo will allow,usually at some sacrifice down low.That is all part of the game,you (usually)can't get something for nothing.................yin+yang


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (Holy Piston)*

Nowhere have I said that a bigger turbo than OE is a bad thing without exception. I am referring here to cases where the turbo is not just Biggie-sized, but Stupid-sized (for the engine and the intended operating conditions).
Plus, you make my point quite well. A stock 1.8T makes 150hp (or 170 or 180 or 225 depending on the year and model). Particularly with the lesser rated engines, there is still sufficient headroom with the stock turbo that as much as a 40% increase in power is possible without actually replacing the turbo for a bigger one.
A turbo that falls flat on its face? A 40% HP increase over stock doesn't seem to agree with that assertion. I submit that there are far more variables to tuning an engine than the size of the turbo. As chiptuning shows, up to the point of the physical limitations of the engine hardware (e.g. turbo, fuel injectors, compression ratio, etc.), engine management is a big determinant of the final power output.
NOTE!: I am not talking here about those of you who want 250, 300, or more HP out of a 1.8T, or those of you who drag race your cars or are building dedicated race motors.


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## GoFaster (Jun 18, 1999)

*Re: What's with this fixation with oversized turbos? (Holy Piston)*


_Quote, originally posted by *Holy Piston* »_Go Faster,you do have some good points,but you do realize that that 8V motor makes about 115hp and 130 ftlbs stock right? and his torque isn't much lower at all than stock(under 3k,and he has more than doubled his stock output of his 8V motor?I think his torque peak has to also do with his cam timing(probably at 0 deg) But if you really do know your stuff then I assume you have a car that is atleast 13 sec or 200whp right?Well if you do then you definitely know that it is hard to have it all,and guys looking for high hp can't have full torque at 2500rpms!!!!Why would you want that??You would just be spinning tires if you attempted to launch your car!!It is not easy making a slow car fast,and if you want to go fast,you can do it with a small turbo,but it hits a brick wall after so much boost&hp.I have seen dynos with very peaky powerbands(in your opinion "poor" powerbands),but those cars sure were fast!!!







Go figure! EDIT:I just read your sig,you have a TDI!! THAT IS WHY you like a big torque powerband,sorry man horsepower wins races,torque is good for tooling around in traffic,and towing boats................









That torque graph shows 130 lb.ft of torque at 3000 rpm. Basically at 3000 rpm, it is making NO MORE than a bone stocker! Sure it kicks madly beyond that point, but there's nothing down low.
If you're getting wheelspin upon launch due to "too much" midrange torque, then issue #1 is that the vehicle's gearing is not correct, and issue #2 is that the vehicle is being driven from the wrong set of wheels (front). Yes, I know people have done what they think is fast quarter-mile times with wrong-wheel-drive. Vehicles that have serious dragstrip performance are ALL propelled from the correct end, the rear!
Relying on having next-to-no low-end torque is a poor crutch to use in place of tuning the engine to have a broader spread of power but with the right gearing and driven by the proper wheels (rear!). (Yeah, I know what you're thinking ...)
I am not denying that a vehicle tuned with such a high, narrow powerband can indeed run fast on the racetrack. I never said that. In fact, if that's the only usage pattern being considered, it may be close to the best that can be done with available parts and especially if you are stuck with the wrong-wheel-drive. But if the vehicle is being used for other things, like daily driving (or towing my trailer!), it isn't the optimum solution.


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (GoFaster)*

vw's crux has always been poor driveline. Otherwise they would have made a good 3 speed auto (ok maybe 4th overdrive for mpg) that would hold up to mad power. Afterall why would you want to drag race a manual tranny when an automatic will hands down spank the piss out of the same car..
Hell with a nice torque converter, that big-ass turbo, maybe with a little anti-lag to pre-spool it to 15psi off the line would be one wicked car on the strip..
Dodge didn't have a problem producing a decent auto, and the mopar aftermarket made it stand up to mad hp to propel some crazy ass cars into insane 1/4 mile times.
Then again dodge/chrysler probably sold more turbo cars than anyone else (gasoline) in the usa.

still waiting for those guys hooking up a good auto the vw powertrain to come forth and spill the beans







I loved my auto-g60 for the 2 months the tranny lasted. 15psi off the line with barely any wheelspin (open diff, rotten old tires, stock worn suspension). Sure did give a few people a double take when a silent (stock exhaust) g60 auto left them looking stupid at the stoplight..


----------



## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (GoFaster)*

GoFaster hit my previous point, about power band braodness... and about people stating that no low end torque is good becasue they other wise couldn't launch properly.
So like I stated before... take a few different dyno charts to compare an engine that has the same work done to it, except different sized turbos. Take the HP and torque readings from say 2500, 3000, 4000, 5000 and 6000 rpm's and calculate the average. Now wouldn't you want the car that has the highest average? Wouldn't that car be the best overall daily driver car that is providing a good balence of low end and high end torque/HP? I supose some motor with a diesel bus turbo on it making 800 hp at 9000 rpm and no power a 6000 might throw out my point.. but if you were rational about it all...
It makes sense to me.


----------



## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (mrkrad)*


_Quote, originally posted by *mrkrad* »_Then again dodge/chrysler probably sold more turbo cars than anyone else (gasoline) in the usa.
 
and they used VNT's too. Something I haven't seen in the masses here. I wonder why they went with a VNT? cuz its small and big all at the same time!


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## vdubspeed (Jul 19, 2002)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

VNT=?


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (vdubspeed)*

garrett's variable nozzle technology. This allows you to use no wastegate. The Diesels TDI use this type of turbo to spool mad fast (they have to theres not much rpm to spool lol), and also you can change the geometry to control boost instead of wastgating it.
(basically the geometry of the blades can change, roughly speaking using both pressure and vacuum to modulate the geometry, which is hard to adapt to most boost controllers)
Garrett also made a prototype turbo (think of the weight of the shaft/wheels) that used an electric 40-50amp motor to pre-spool the turbo, not sure if that ever got into production or not, cool idea. Cept you'd need some mad alternator at low rpm's to crank that kinda amps long term unless you had a spare battery or something to absorb the amp load.
garrett designed some pretty cool innovative turbo's... But there is a cost for everything..



_Modified by mrkrad at 5:44 PM 1-8-2004_


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (tdimeister)*


_Quote, originally posted by *tdimeister* »_Nowhere have I said that a bigger turbo than OE is a bad thing without exception. I am referring here to cases where the turbo is not just Biggie-sized, but Stupid-sized (for the engine and the intended operating conditions).
Plus, you make my point quite well. A stock 1.8T makes 150hp (or 170 or 180 or 225 depending on the year and model). Particularly with the lesser rated engines, there is still sufficient headroom with the stock turbo that as much as a 40% increase in power is possible without actually replacing the turbo for a bigger one.
A turbo that falls flat on its face? A 40% HP increase over stock doesn't seem to agree with that assertion. I submit that there are far more variables to tuning an engine than the size of the turbo. As chiptuning shows, up to the point of the physical limitations of the engine hardware (e.g. turbo, fuel injectors, compression ratio, etc.), engine management is a big determinant of the final power output.
NOTE!: I am not talking here about those of you who want 250, 300, or more HP out of a 1.8T, or those of you who drag race your cars or are building dedicated race motors.


A 40% increase of power while spinning the crap out of the turbo and killing it in 10k miles.







But just look at that 40% increase of power, it sucks ass. It's only 200whp (high side). Take a larger turbo, ie. t3 super 60 .48 stage 2 and with 10psi compared to 16-22psi the K03 is running at. It will make the same power or more w/o killing the turbo. It will also make more power past 5000rpm unlike the k03 that has run out of its effiecency and still produce very good mid range power. 
Why do you think the 225hp 1.8T makes more power than the 180hp. Is it because its run more boost? No, its because it runs a k04 instead of a k03.
Driving a modded 1.8t, it was fun but spinning the tires though first gear sucked. Id rather have power from 4000-7000rpms than 2000-5000rpm. As would most people in this forum.


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (GoFaster)*


_Quote, originally posted by *GoFaster* »_
That torque graph shows 130 lb.ft of torque at 3000 rpm. Basically at 3000 rpm, it is making NO MORE than a bone stocker! Sure it kicks madly beyond that point, but there's nothing down low.


Hes make 130 wtq not crank like the stock output. A stock 2l puts out around 115 wtq at 3200 rpms.
To me it looks like he puts out more power than most modded n/a aba's though out the entire powerband.
Could he make a flatter torque curve on the top end? Yes. But for his motor combo, he makes impressive power and an impressive power curve. Remember the motor is stock except a 2 headgaskets. He's more than doubled hp output of a stock motor.


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

Hmm... still wondering about turbine maps. I've seen so much discussion about compressor maps and boost/flow characteristics of turbos (meaning compressors actually), but little is said about turbines. Since we have the attention of knowledgeable folks on this thread, could we get some info on the other half of the turbos? The turbine end, after all is what really determines the spoolup characteristics of any turbo, not the diameter of the compressor. What can we tell from turbine flow diagrams?
Speedy G


_Modified by Speedy G at 6:01 PM 1-8-2004_


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (Speedy G)*


_Quote, originally posted by *Speedy G* »_Hmm... still wondering about turbine maps. I've seen so much discussion about compressor maps and boost/flow characteristics of turbos (meaning compressors actually), but little is said about turbines. Since we have the attention of knowledgeable folks on this thread, could we get some info on the other half of the turbos? The turbine end, after all is what really determines the spoolup characteristics of any turbo. What can we tell from turbine flow diagrams?
Speedy G

I think its time for me to call up turbonetics or ITS and see if someone there has the answer to this question.


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## Peter Tong (Jun 17, 1999)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

I still think that a Lysholm is far better for day to day *street* driving...IMHO, the best mix would probably be a Lysholm compressor to run with on the street with say a Garrett GT series turbo to pump torque non linearly up on top...for races... I'm actually mighty tempted to do dual setup for the fun of the challenge...if any of you turbo folks can point me in the right direction (with regards to off the shelf turbo manifolds, etc) to accomplish this I'd be mightly obliged...I think a Lysholm would spool a turbo pretty well...
regards,
Peter Tong



_Modified by Peter Tong at 7:05 PM 1-8-2004_


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (Peter Tong)*

Will you turn the lysholm "off" when the turbo is spooled? I would contact zornig on here for a exhaust manifold, but I would run something like a straight t4 on the car since spool up part of it wont be a big deal.


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## SSj4G60 (Aug 13, 2001)

*Re: What's with this fixation with oversized turbos? (GTibunny16v)*

yea youd probably what a clutch setup to cut off at certain RPM since the lysholm will probably be slowing down the turbo after its spooled


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## Peter Tong (Jun 17, 1999)

*Re: What's with this fixation with oversized turbos? (GTibunny16v)*

I'm actually going over different plumbing scenarios...there's a bit of research to do here since I don't know how well the Lysholm compressors react to large amounts of heated air being applied to their intake...I'm sure you folks will have a heyday picking apart the plumbing scenario however...sorry for the OT...


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (Peter Tong)*

why dont you just ask BBM? They've done it already. They are pretty cool and if you search (ask repoman) you'll probably find the plumbing pics etc.
I think they had to intercool it twice


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## MA_XXX (Apr 10, 2002)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

i'm using 2 air to water IC's in my setup. oopps!!! cat's out of the bag now!!! i'm also using a G lader instead of a lysholm 'cause it's what i've got.
i think john blew the car to smithereens though...i remember talking to him about it and the engine saw over 30psi of boost...
a clutched eaton and a T04e might be the way to go. i'm doing it a slightly different way.


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## Holy Piston (Oct 24, 2003)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

I saw a picture of it,but it blew up right?I think that was the end of that.Let's try to stop re-inventing the wheel and if you open your eyes you will see what guys are using to make the hp you want. I am running a 7.?:1 comp motor,and some of you would hate driving my car,but if you know how to downshift and plan ahead,you can drive it with boost and pass most anybody you want!!People say they want torque for daily driving,and I guess it is OK to pass people in traffic quickly,but if(some) you guys ever get to drive a nicely tuned,bigger than stock,high boost turbo car,you will see that it is quite a rush!!!Sure if you have a V8 you may get good power under 2500rpm,but with small 4 bangers,(unless you are G60 or Lysholm,which don't have much up top)yo want to use some revs to make power(over 2500rpm) http://****************.com/smile/emthup.gif


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## Agtronic (May 14, 2001)

*Re: What's with this fixation with oversized turbos? (GoFaster)*


_Quote, originally posted by *GoFaster* »_I am not denying that a vehicle tuned with such a high, narrow powerband can indeed run fast on the racetrack. I never said that. In fact, if that's the only usage pattern being considered, it may be close to the best that can be done with available parts and especially if you are stuck with the wrong-wheel-drive. But if the vehicle is being used for other things, like daily driving (or towing my trailer!), it isn't the optimum solution.

I don't understand why people keep bringing up daily driving. What's the difference between daily driving under boost and drag racing under boost? And if you mean daily driving as in "driving nice and easy", why do you even need boost to come on at low RPM? I think the whole beauty of having a somewhat peaky curve is to be able to "hide" the turbo for when you need it, almost like a nitrous system ... When you drive normally, the turbo never spools up, and when you want to take off hard or act like an idiot on the highway, downshift and you're gone!
I just don't understand the "daily driver" argument.


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## jsnVR6 (Feb 5, 2001)

good point AG


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (Agtronic)*

Daily Driver - meaning a car used by its owner everyday for commuting and recreational driving.
Why would you want a car that will spool up at lower revs? Well the many people would like to have a car who's 4 banger beahves like a bigger motor. Big motors have nice broad torque curves. When you step on the gas it moves because it has power. Downshifting not a definate requirement.
I don't get it. It seems to me that people are after the fastest most powerful car, but are willing to have to downshift and continue shifting to keep the car operating within a particular rev range to achive/maintain that power. I though shifting takes time? Why build a motor that requires you to make a .5 or 1 second or more shift to gain access to the potentail power it can make. Why not build a motor that has the ability to pull not matter where you are in the rev range (generally speaking - do flame me - I'm not looking to make a car that's under full boost and peak torque at 1500 rpm)
Have you ever drivin a car like TDIMiesters or GoFaster. Ya, they're _slow_







diesels, but they damn near pull away from anybody on the highway without a shift. Its soo nice to just step on it and go.


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## gruppe5 (May 10, 2003)

*Re: (JsnVR6Corrado)*

since alot of people here seem to have alot of knowledge, can any post ALL of the spec for a K03, K04, and K24 turbos?????? A/R, inlet & oulet size ect......this would help me out greatly.


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## GoFaster (Jun 18, 1999)

*Re: What's with this fixation with oversized turbos? (Agtronic)*


_Quote, originally posted by *Agtronic* »_
I don't understand why people keep bringing up daily driving. What's the difference between daily driving under boost and drag racing under boost? And if you mean daily driving as in "driving nice and easy", why do you even need boost to come on at low RPM? I think the whole beauty of having a somewhat peaky curve is to be able to "hide" the turbo for when you need it, almost like a nitrous system ... When you drive normally, the turbo never spools up, and when you want to take off hard or act like an idiot on the highway, downshift and you're gone!
I just don't understand the "daily driver" argument.

Because with a good torquey motor, I can trundle along at reasonably low revs, without having to make a helluva lot of noise and without having to shift gears all the time, and when that opening comes up in traffic, I can tramp on the pedal and it responds NOW. And then I can let off the pedal and resume previous cruising. No downshifting, no waiting, no making lots of noise with high revs, no fuss, no hassle.
Because with a good torquey motor, I can load two motorcycles in my trailer, hitch the trailer to the car, maneuver the rig in my driveway without burning up the clutch







, get out on the highway and get into top gear and forget about it. No downshifting at the slightest uphill, still have some reserve for passing.
I can start off from a standstill by easing out the clutch without touching the accelerator, shift to second gear without touching the accelerator, shift to third without touching the accelerator. With my trailer in tow! Try that without bottom-end torque (and a governed idle speed) ...
I wouldn't say that my hot-rodded TDI has the torque of a good old pushrod V8 available, but it sure does a good impression of a V6, and yet still with the fuel consumption of the 4-cylinder diesel.


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## GTibunny16v (Aug 12, 2001)

*Re: What's with this fixation with oversized turbos? (GoFaster)*

After owning a turbo car w/ good midrange and low end. 
Step on the gas slightly in 1st gear and end up smoking the tires. Real nice when you're driving by a cop at 2mph. Cruising in 5th gear and stuck in boost eating gas http://****************.com/smile/emthdown.gif 
Those are just some of my reasons not to have a quick spooling turbo. If I wanted good lowend power and gas milage. I would buy a TDI. But I dont want that right now, I like to drive around town as if my car was a stock N/A car and have boost when I wanted to get into it. 
For me taking a sec to down shift and then walk away from the guy that just steped on it. It makes it all worth it.


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## charrington (Apr 25, 2002)

*Re: What's with this fixation with oversized turbos? (GTibunny16v)*

thats what the gas pedal was made for..... it's not a On off switch.








If your having traction problems... buy some RA1's or somthing(soft compound tires).... or let off the gas. 

OR.... if you want to have less power to the ground put on BIG 18" rims... thats going to slow you down in the bottom end... and allow you to Press the gas pedal a bit more









this is a amazingly long thread about what people like and dont like... and i think we've all got the just of it...
Some people like lagging turbo's....cause... they do
some people like to have power when the press the gas...
Some people don't like having power when they press the gas and would rather shift down first


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## Quiz (Sep 13, 2002)

You guys do realize this argument can't be won.
The small turbo guys will b!tch about having to down shift.
The large turbo guys will b!tch about wheel spin.
Why dont you guy's just start listing your preference.


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (Quiz)*

but the large turbo guys will always make more power.


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## Quiz (Sep 13, 2002)

*Re: What's with this fixation with oversized turbos? (killa)*

Shhh! not to loud they might here you.


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (GTibunny16v)*


_Quote, originally posted by *GTibunny16v* »_Cruising in 5th gear and stuck in boost eating gas http://****************.com/smile/emthdown.gif 

It was my understanding that when cruising in gassers you do not maintain constant boost unlike some diesels do. So unless you are on and off the gas I can't see how cruising at a rev range smack dead center of your max spool up point would make any difference, other than you only need to touch the gas a bit to get instant power instead of having to downshift first.

_Quote, originally posted by *killa* »_but the large turbo guys will always make more power

Ya, I don't argue that at all. And I respect the knowledge you've put into the 16v forums and this forum too. But what I would like to know is how does it feel to drive a 250+ hp turbo car with a very broad power band vs a 300+ hp turbo car with a narrow power band. Depending on so many other variables.. I'm starting to rethink the more power = better faster car attitude I was having. I'm betting I'd be more happy with the former than the latter. That could change, but right now that's the side of the fence I'm sitting on.
'
I think in the end tdimeisters intention was to bring to the attention of some, the rewards and benefits of good tuning and well though out planing put into building a turbo motor with a smaller turbo. It seems so many people on this forum who ask for suggestions of what turbo buy get the same answer; its often the T3/T4 series units. This works for some yes, but there are many other turbos to choose from that could make for a very fast, intersting and fun everyday car. It seems that poeple are becoming too reliant on turbo size as the *what counts to make power* and not planing so much into tuning and other turbo system components like engine managment and IC'ing.


_Modified by Action Jackson at 5:32 PM 1-9-2004_


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## tdimeister (Feb 19, 1999)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*


_Quote, originally posted by *Action Jackson* »_
I think in the end tdimeisters intention was to bring to the attention of some, the rewards and benefits of good tuning and well though out planing put into building a turbo motor with a smaller turbo. It seems so many people on this forum who ask for suggestions of what turbo buy get the same answer; its often the T3/T4 series units. This works for some yes, but there are many other turbos to choose from that could make for a very fast, intersting and fun everyday car. It seems that poeple are becoming too reliant on turbo size as the *what counts to make power* and not planing so much into tuning and other turbo system components like engine managment and IC'ing.

You pretty much summed up perfectly, AJ, what I have been trying to say.


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (tdimeister)*

Well you took to long!







So I jumped in. http://****************.com/smile/emthup.gif


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

if your want a broad powerband and 250whp just get a 60 trim T3 and run 15psi with a .48/1 hotside or .48/2 for a bit more power. http://****************.com/smile/emthup.gif Fast spoolup and somewhat of a broad powerband


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## Angular (Mar 12, 2002)

*Re: What's with this fixation with oversized turbos? (killa)*


_Quote, originally posted by *killa* »_if your want a broad powerband and 250whp just get a 60 trim T3 and run 15psi with a .48/1 hotside or .48/2 for a bit more power. http://****************.com/smile/emthup.gif Fast spoolup and somewhat of a broad powerband

Pretty much what I did (T3 Super 60) although I've been obsessing over the compressor maps and deciding I need something with more efficiency and room to grow. I'll be upgrading to the smallest available GT30 later this year.
GT28R is a good choice too if your power goals are modest and you want a fast spooling dual-BB turbo. It's much cheaper than the GT28RS or GT30R.
Bradley


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## MA_XXX (Apr 10, 2002)

*Re: What's with this fixation with oversized turbos? (killa)*

i'm going to try to get a merkur T3 for my 16V 'cause i heard that the saab ones spool up a little more quickly than i'd like for my project. does anyone know the specs for the merkur one?


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## charrington (Apr 25, 2002)

*Re: What's with this fixation with oversized turbos? (MA_XXX)*

I like how Turbo lag is viewed as a comodity on this forum


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (MA_XXX)*


_Quote, originally posted by *MA_XXX* »_i'm going to try to get a merkur T3 for my 16V 'cause i heard that the saab ones spool up a little more quickly than i'd like for my project. does anyone know the specs for the merkur one? 









It's a 60 trim T3, some came with a .63 exhaust housing but most came with a .48.


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## Sleepy Mk1 (Nov 16, 2002)

*Re: What's with this fixation with oversized turbos? (MA_XXX)*


_Quote, originally posted by *MA_XXX* »_i'm going to try to get a merkur T3 for my 16V 'cause i heard that the saab ones spool up a little more quickly than i'd like for my project. does anyone know the specs for the merkur one? 









My buddy has a 1.8 16v with a Saab turbo and I have a Merkur one for the time being on my 2L. He's at full boost by 2800 or so, me by about 3000. I'm faster every time, both in Mk1 sciroccos with SDS.


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## Holy Piston (Oct 24, 2003)

*Re: What's with this fixation with oversized turbos? (Sleepy Mk1)*

This is a good thread!To be honest,you guys talking about the small turbos,and towing motorcycles on a trailer,etc. We are on totally different ends of the spectrum..............you guys are happy with OEM and "enhanced" hp ,while others are really more trying to get PERFORMANCE. Sorry,but I think I can take on a TDI on the highway anyday!!!







J/J but really it is useless arguing,that is why I am glad everybody is discussing this,we all have valid points,but a big turbo will always be better for top end(usually where turbos shine!!


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## Agtronic (May 14, 2001)

*Re: What's with this fixation with oversized turbos? (Holy Piston)*

I think I figured it out.
The older or more educated guys want "the most power possible on the widest possible rpm range, while the younger, less "law abiding" guys want the car to RIP and GET ANGRY when they want it to.
Wheelspin has never been my reason for chosing a larger turbo. If it spins in first, don't press the gas as much is kinda what I'm thinking. It doesn't even have to do with the fact that I'm making more power at the top than a smaller turbo would make, it has to do with the FEEL. I ENJOY the feeling of a car that is building up it's rage before it explodes into acceleration. I HATE a turbo that spools instantly. It pulls real hard right from the bottom, but it stays too linear, it feels like you're accelerating from the feeling in the seat, but you're just not going anywhere. 
Another point I'd like to make about the "daily driving" argument. I have always downshifted to pass or accelerate, even with cars that had 300+ hp (LS1 Camaros etc ...) I ALWAYS need "maximum thrust" when I decided to go.
So I guess the instant spool turbos are for those who don't know how to drive and just floor it from 2000 rpm when they want to have fun.


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (Agtronic)*

if you got a problem with lag run a stutter box or anti-lag ,but we can't discuss street racing or illegal driving on these forums, so i guess that would be a good solution for the strip and launching hard


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## blackbunny (Jan 31, 2003)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

my goal is 200whp in my 2.0l 16v rabbit i plan to use a small turbo from a t-bird turbo coupe its an IHI i think its a 51t-21 i dont really remember. yes i would like a big turbo but the one i have was free and its in good shape. ive seen it hold 20psi no problem in the t-bird so i dont think my goals are unrealistic. i want to build it like it was a stock vw built motor so im thinking 9:1 c/r and like 8-10 psi. im not old like some of you may think im just looking for something reliable with a linear power curve and no lag. so what do you guys think of this set up


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## lugnuts (Jul 26, 2001)

*Re: What's with this fixation with oversized turbos? (Agtronic)*

The older or more educated guys want "the most power possible on the widest possible rpm range, while the younger, less "law abiding" guys want the car to RIP and GET ANGRY when they want it to.>>>
does this mean I'm still "young"? ..... sweet!
<<So I guess the instant spool turbos are for those who don't know how to drive and just floor it from 2000 rpm when they want to have fun. >>>
exactly..... back when I was "young" I had a full T4 on the rocco with a 8-1 CR 1.8 8v motor.... nobody who ever rode in it said a damn thing about "lag", and I sure as hell never got caught in the same zip code with any diesel.... 
a setup with 2000 rpm spool-up is just protection against "r!cer fly by's" ,basically people who dont use their mirrors - 1.8t's are good for this -
but it's still a 15 sec car http://****************.com/smile/emthdown.gif 
T3/4's being "oversized" http://****************.com/smile/emthdown.gif 





_Modified by lugnuts at 2:56 AM 1-10-2004_


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (lugnuts)*

Ya, acording to Agtronic, I'm old and educated.. well http://****************.com/smile/emthup.gif Thanks







I can't argue with that! haha
The comment about downshifting.. well I see your point. I don't expect full boost at 2000 rpm either, but my B3 is reving at 3200 rpm going 120 in 5th gear. Sometimes when drving ont he highway I don't want to *slam it* into 4th and fly off my wheels to get by someone. I'd rather just step on it and whiz on by quickly, quietly and smoothly.

_Quote, originally posted by *lugnuts* »_nobody who ever rode in it said a damn thing about "lag"

Maybe you are the kind of driver who stays in the higher rmps, and you don't feel much lag because you are _right there_ all the time.
But remember, - and I need this reminder myself - there is a difference between lag and boost thresh hold. I myself keep forgetting this finer point in the heat of debate. Bigger turbo's = bigger lag plain and simple. Even if you drive at 4500+ rmp all the time you will still have to wait for your turbo to generate boost when you give it more gas becasue lag is the time it takes the turbo to spin up. Lag is not the time it takes your motor to rev up the point at which your turbos begins to generate boost. Less lag eqautes to smoothness in the throtle response and engine power increase. Smoothness in throtle repsonse will also create a controled increase in torque equaling less wheelspin. So, in some ways, those who do view turbo lag as a commodity, and argue that it helps maintain traction really aren't doing them selves a favor. A motor that generates a smooth yet quick increase in power will lay down that power more efficiently than a motor that's wiating for an explosion. Further more, your driveline components will thank you. I'd sooner lay off the gas a bit when I feel wheel spin only to be able to get back on the gas and have that power right back. With a larger turbo that has lag, if you have wheelspin and you let off the gas, and then get back on the gas for more power the boost is already gone and the turbo has to spin up (lag... waiting) and then boom you got your power again but it was too much because it _exploded_ so you're off the gas again and now you've lost your boost.. and a vicious cylce has started. For those drivers less experienced, more lag will make for eager and impatient drivers and will most likey cause a "floor it" mentality which will lend to lack of control, and stick you in the senario I described above.


lugnuts said:


> and I sure as hell never got caught in the same zip code with any diesel....
> 
> 
> > It's also disappointing to hear your comment about diesels. What's your beef against them? If you lived in europe you'd be beside one 50% of the time... in fact I think some countries sell more diesel VW's than gassers. Diesel isn't a bad thing, its just different. I would hope that you could be understanding than what I see above as ignorant about this fact. But these's no flame here, just a call for an understanding.


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## 1.8T3t04e (Jun 4, 2003)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

well now that it took me over an hour to absorbe all the good info in this thread, i aint got nothing to say but ... great thread!
ill never doubt speedy g... he's been there for me on a couple of occasions with some good technical info...


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

He's got no beef against dieselpowah. It's just his way to say that his T4 powerered rocco would blow the doors away out of any diesel, which i totally agree.
What it comes down to is that there's Plenty of T3/T4's, so many that it's not fair to say that T3/T4's are oversized. A nice sized T3/T4 will have less backpressure thus increasing your engine's volumetric efficiency and dropping egt's. You'll also be able to cruise normal at lower rpms without boost kicking in, then let the engine get up in rpm's and make use of your "hidden" power up top. What do you think it'll happend if you run a turbo diesel setup in a gas motor? It spools up quick too


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (killa)*

A bigger turbo will also move your torque curve upwards causing it to be much easier on your drivetrain, we still got a stock clutch on our digi1 jetta which some of you might have seen or read about. Clutch never slipped and trust me when i say that it'll easily blow the doors off 90% of the cars in here.


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (killa)*

Killa;
No doubt. You've built some nice setups. I'll most likely never get to ride in one either.. you're in NJ? Ah, anyway its not often I go south of the boarder.
But I bet I'd be pulling away from most others even with a smaller turbo. Ultimately, to each there own. But it is important to inform others that there are other choices in turbo's besides the T hybrids. I completely understand that they are the most popular and that has a lot of good reason to use one. But I also see many other good reasons to build a trubo motor with smaller turbo.


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## BubonicCorrado (Jul 24, 2003)

*Re: What's with this fixation with oversized turbos? (Speedy G)*


_Quote, originally posted by *Speedy G* »_










YOUR CAR NEEDS TO BE TUNED...
You are running a bit lean... well... ALL OVER THE PLACE
I feel sorry for your knock sensors
Your aif fuel curve should be FLAT somewhere between 11.5:1 & 12.5:1 depending on your climate


_Modified by BubonicCorrado at 10:57 PM 1-10-2004_


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## lugnuts (Jul 26, 2001)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

killas right, I wasnt trying to diss diesel power. I actually wouldnt mind a TDI swap in my pickup.


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## Agtronic (May 14, 2001)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*


_Quote, originally posted by *Action Jackson* »_I don't expect full boost at 2000 rpm either, but my B3 is reving at 3200 rpm going 120 in 5th gear. Sometimes when drving ont he highway I don't want to *slam it* into 4th and fly off my wheels to get by someone. I'd rather just step on it and whiz on by quickly, quietly and smoothly.

See, that's exactly what I'm saying. Why do you need boost to pass "quickly, quietly and smoothly"? But I admit that a turbo with a threshold above 3200 is starting to get pretty big, but still ...
Lugnuts understood EXACTLY what I was trying to say. 
Let me just make sure ... when I say big turbo, I don't mean a T04B 60-1 on a stock 8V motor, nor am I'm talking about a peaky curve like Speed's. I'm talking about a curve that is relatively "fat", but doesn't die off at the top.


_Modified by Agtronic at 6:11 PM 1-10-2004_


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## Action Jackson (Nov 20, 2001)

*Re: What's with this fixation with oversized turbos? (lugnuts)*

I know a guy who's just finnished building a pickup powered by a TDI. its wicked! He says he can't drive it in the rain due to wheel spin.







crazy stuff man! its even got a height adjustable air-ride like suspension!
Anyway. This has been a good discussion. I can't wait until I can start building my turbo motor, but I'll give a crack at the smaller turbo and see how it works out.


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## mrkrad (Nov 9, 2000)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*

don't knock turbo diesels i've seen f350's run 11 seconds on the hose







shaming z06 vettes. I almost got setup on a drag race with one.
ran 18.0 without the hose, and 13 on the hose (propane).
but as we all know power is useless without traction. Burnouts do not impress me, hookin' and pulling that insane 60 does..


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## FrankenFox (Oct 29, 2003)

*Re: What's with this fixation with oversized turbos? (need_a_VR6)*


_Quote, originally posted by *need_a_VR6* »_So why not have a ton of lag so you can put around the streets, and then have twice the power available for your legal trips to the track. 

Lag _can_ be your friend, but it isn't a great thing on the street. If you have an engine built for big boost, which would necessarily have rather low CR, you will experience very poor off-boost power. Putting around at low RPM will produce a very loagy, sluggish car. That's fine if you are willing to make that sacrifice. Personally, I would be willing to make that sacrifice if I had AWD and wanted to make 400+ HP. But I have FWD, and a light car at that. I would rather make 200-250 HP and be able to stick it all--with a little discretion on the loud pedal--than try to go for big dyno-only numbers. 
I said on another thread not too long ago that I can make all the power I need to cast pieces of my transmission all over the street. 300 HP would only cast the pieces farther, or make smaller pieces. For my car, I want to make only enough power to be _able_ to break the tires loose in third gear. My gearbox stands between my engine and the ground, and must negotiate between the two. More than 250 HP is going to break parts in my car, and I can't just buy upgrade parts like a lot of you can. (I drive a Fox.)
So--I am with tdimeister. I say use a smaller turbo unless you are building a race engine. 7.8:1 to 8:1 CR and a moderately sized turbo will make all kinds of power in a street driven car.


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## lugnuts (Jul 26, 2001)

*Re: What's with this fixation with oversized turbos? (mrkrad)*

oh yeah those truck guys are insane.... nothing like pegging a dynojet torque readout for 1100 rpm cuz its topped out at 1200!!! 
I heard when the same truck lost a head gasket the coolant shot half way across the shop haha.


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## killa (Nov 26, 2000)

*Re: What's with this fixation with oversized turbos? (Action Jackson)*


_Quote, originally posted by *Action Jackson* »_Killa;
Ultimately, to each there own. But it is important to inform others that there are other choices in turbo's besides the T hybrids. 

I hear ya on that, if i had the loot i'd be looking for a nice GT series turbo, dual BB units http://****************.com/smile/emthup.gif


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## Hamster Wheel Turbo (Sep 18, 2002)

If its a matter of size.. well...


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## tdimeister (Feb 19, 1999)

Interesting quote from another thread:

_Quote »_Meanwhile, a few miles away at Garrett, turbo engineer Jay Kavanagh wanted to boost his Miata. Having full access to the newest Garrett technology, *he concocted a physically small turbo* with a ball-bearing center section and internal aerodynamics 20 years more modern than the T3/T4 standard the aftermarket is used to.
A few cubicles from Kavanagh, Rob Cadle, a good friend of Mitchell and Kojima, realized Kavanagh's Miata turbo would be perfect for the SR20DET the Nissan boys were planning for the Sentra. He brewed up a turbo, stuffed it under his shirt, and went out the back door.
Jim Wolf Technology built a very mild SR20 for the Sentra, making it functionally equivalent to a stock Japanese-spec SR20DET. The turbo was installed, and amazing things started happening. *The car's power was impressive, 280 hp at the wheels, but not earth-shattering. The driving experience however, was. Throttle response was excellent, turbo lag virtually non-existent, and the tire-shredding power was easily modulated. The turbo spooled up early, making so much torque, that the best quarter-mile time (13.7 at 104.5 mph) was achieved launching in second gear.*
Mitchell brought the Disco Potato to the Ultimate Street Car Challenge in 2001, and placed an impressive fourth overall. The rest of the time, the car was stashed away in Nissan USA's service garage and used strategically as an attitude adjustment tool. Whenever Nissan or Garret executives needed an injection of gasoline in their veins, they were offered the keys. They would inevitably come back grinning from ear to ear and breathing heavily, eager to bring horsepower to the masses.
There's no telling how many decisions were nudged in the right direction by the Disco Potato, but it did prompt two that are critical to this story. We drove the car for a week, including a 1,000-mile road trip and track day at Thunderhill Raceway. After outrunning every car at the track, and blasting down the freeway at 140 mph, we knew we must have that engine. Ours, however, had to be in a rear-drive chassis. Thus was born Project Silvia.
Several Garret executives also experienced the Potato. They were so impressed, they decided to produce the turbo, double the engineering staff in the aftermarket department, and start applying this modern Garrett technology to a whole range of aftermarket turbos. Technically, this is a GT28R with a 62 trim compressor (.60 A/R) and a 76 trim turbine (.86 A/R), but you don't need to know that. Ask anyone at Garrett for a Disco Potato turbo, and this is what you'll get.

Over to the big turbo guys.


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## MrCornBread (Oct 13, 2003)

*Re: (tdimeister)*


_Quote, originally posted by *tdimeister* »_Over to the big turbo guys.









Although he got an 'impressive 280hp at the wheels' Most of us on this board would be more happy with a graph like this:








Same Sr20 Motor... only with a 62-1 Turbo.... (EDIT: Car went a best of 10.503 @ 139.4 mph)

Back to the same endless debate.... you want more power? or do you want to scoot past the 18 wheelers on the highway without pressing the clutch.















http://****************.com/smile/emthup.gif 


_Modified by MrCornBread at 1:19 PM 1-18-2004_


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## mrkrad (Nov 9, 2000)

boost spool is definitely relative to current speed and rpm. If the gearing was setup for that big turbo that you cruised at 75mph at 5000rpm, it wouldn't be that bad.

but if you were in the city, stoplight to stoplight you'd have not much boost in 1st gear im guessing.
It's probably better to g-tech log the car to determine how fast it is at XX-XX mph.
0-60, 40-60, 60-80, 80-140 etc..
I would not like that car with my drive (2 miles,30mph limit, stoplight to stoplight city), but if i drove on the freeway at cruising speeds (atlanta ~75-85mph) then it would be sick.
Alot of it has to do with gearing and weight too. Dyno's are very much useless when comparing different cars. That dyno on a mk1 rabbitt would be a totally different beast than on a heavier chassis.
All that car needs is some nitrous or anti-lag to bring the torque curve in faster







or an automatic transmission.. lol.
Brake stand the auto or trans-brake with a nice 'verter than that dyno would look alot meaner, setup shift extensions to 6000-6500rpm







woot!


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## Holy Piston (Oct 24, 2003)

*Re: (mrkrad)*

TDI master,that is exactly the point,why would you want so much torque that you have to launch in 2nd gear?Responsiveness is nice,but power is better (IMO) you know,for the "other" gears ,3rd,4th,and 5th..................


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## sold on expense (Mar 22, 2003)

*Re: (tdimeister)*


_Quote, originally posted by *tdimeister* »_Interesting quote from another thread:


I posted that, found it from a magazine online site...they recreated that engine, with the turbo, and it cost somewhere around $8000, just for engine work. So, smaller turbo, but an insane amount of work.


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## tropicorange20v (Jul 28, 2002)

*Re: (sold on expense)*


_Quote, originally posted by *sold on expense* »_
I posted that, found it from a magazine online site...they recreated that engine, with the turbo, and it cost somewhere around $8000, just for engine work. So, smaller turbo, but an insane amount of work. 

I don't know where you got that from. The motor is a stock DET, which can be had for $1300. The turbo is another $1300. The GT28RS uses a T25 flange that bolts directly to the stock manifold and downpipe. Add $500 for a JWT ECU, another $350 for injectors and fuel rail, and $150 for a MAF sensor. Thats not exactly what I would call "engine work". I personally probably have $5k total into my SR20, including the car, making almost 300whp.


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## Peter Tong (Jun 17, 1999)

*Re: (mrkrad)*

Sam, I have to say I totally agree with your logic...
Folks usually post up WOT dyno runs when 95% of the time during street driving you are not in WOT. It would be interesting (if it were easily possible which I doubt) dynoing the cars at 1/4, 1/2, and 3/4 throttle and seeing what the torque curves looked like...
To me a car needs to boost and respond well even during part throttle, and not just WOT...
I'm all for doing in gear interval tests... I would love to see how well these large turbo cars do...
just my $.02 worth,
Peter T.


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## tdimeister (Feb 19, 1999)

*Re: (Holy Piston)*


_Quote, originally posted by *Holy Piston* »_TDI master,that is exactly the point,why would you want so much torque that you have to launch in 2nd gear?Responsiveness is nice,but power is better (IMO) you know,for the "other" gears ,3rd,4th,and 5th..................









If you have to ask, I'm definitely in the wrong crowd. See ya out there and don't be blowing any turbos or motors


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## Speedy G (Apr 1, 2002)

*Re: What's with this fixation with oversized turbos? (BubonicCorrado)*


_Quote, originally posted by *BubonicCorrado* »_
YOUR CAR NEEDS TO BE TUNED...
You are running a bit lean... well... ALL OVER THE PLACE
I feel sorry for your knock sensors
Your aif fuel curve should be FLAT somewhere between 11.5:1 & 12.5:1 depending on your climate
_Modified by BubonicCorrado at 10:57 PM 1-10-2004_

Hmm... you misunderstood. Neither of those dyno curves are mine, and my car is Skoda Octavia with a T3 super 60, and my dyno doesn't look like that. The dyno I posted is of a GT35/40R in an Audi A4, tuning by ATP. On their site, under the dyno, they do state that the curve goes a bit lean. What's even weirder though is that when boost comes on, they didn't flood the hell out of the cylinders with a less than 10/1 A/F (normal for ATP). It think I posted this was an ATP dyno, and I was making a point about oversized turbos making big HP up top with not so big torque.
Speedy G


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## GoFaster (Jun 18, 1999)

*Re: (Holy Piston)*


_Quote, originally posted by *Holy Piston* »_TDI master,that is exactly the point,why would you want so much torque that you have to launch in 2nd gear?Responsiveness is nice,but power is better (IMO) you know,for the "other" gears ,3rd,4th,and 5th..................









Because the correct, but presumably unobtainable, solution is to have a gearbox with taller gear ratios, particularly in the lower gears ... and a gearbox which is strong enough to withstand what the engine is dishing out.
Nobody ever said that this was a cheap thing to do ...


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## jwatts (Mar 11, 2001)

*Re: (tdimeister)*

Back to the Disco Potato... does anybody even make a T25 flanged manifold for a VW 8V? 16V? 20V? I know a custom manifold can be fabbed, but the majority of manifolds out there are for a T3 turbine. 280whp is definitely a good chunk for a street VW... heck, so is 200whp.
Whatever direction anybody takes, you have to admit that forced induction has more of a tendency to make the person in the passenger seat







than the same motor naturally aspirated







.


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## tropicorange20v (Jul 28, 2002)

*Re: (jwatts)*


_Quote, originally posted by *jwatts* »_Back to the Disco Potato... does anybody even make a T25 flanged manifold for a VW 8V? 16V? 20V? I know a custom manifold can be fabbed, but the majority of manifolds out there are for a T3 turbine. 280whp is definitely a good chunk for a street VW... heck, so is 200whp.


If you look at ATPs site, they offer the GT28RS in a T3 flange, http://www.atpturbo.com/Mercha...e=GRT


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## speed51133! (Aug 5, 2002)

*Re: (tropicorange20v)*

hey man, my car is faster than almost any car i ever see on the road.
I also daily drive it EVERY DAY.
i dont know what else to say. after having a bite size turbo, and now a big one, the small turbo sucks. im not getting into compressor charts, nuumbers, figures, and what not.
plain and simple, for daily driving you dont need 200ftlbs at idle. i dont see why you would want that torque. to tow a trailor? get a real car if you want to tow something. if i need a tow car, i dont build a turbosystem for my car, i buy a different car.....


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## MarcoVR6SC (May 3, 2003)

*Re: (speed51133!)*

Didn’t they use to say, if you have no lag, you have no turbo


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## Agtronic (May 14, 2001)

*Re: (Peter Tong)*


_Quote, originally posted by *Peter Tong* »_Folks usually post up WOT dyno runs when 95% of the time during street driving you are not in WOT. It would be interesting (if it were easily possible which I doubt) dynoing the cars at 1/4, 1/2, and 3/4 throttle and seeing what the torque curves looked like...

THIS IS WHAT I DON'T UNDERSTAND! Who cares how much power you make at 1/4 and 1/2 throttle? You're obviously not booting around town if you're not stomping on it right? I mean, why do you need power when you're not trying to accelerate? I just don't get it. You want to drive fast, you step on it, isn't that what everyone does? Why not have a system that makes 300 hp at idle, you know what I mean?
I understand people have different opinions of where they want their boost in the RPM range, but that's entirely different. You don't need power to put around town.


_Modified by Agtronic at 2:22 PM 1-19-2004_


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## sold on expense (Mar 22, 2003)

*Re: (Agtronic)*


_Quote, originally posted by *Agtronic* »_
THIS IS WHAT I DON'T UNDERSTAND! Who cares how much power you make at 1/4 and 1/2 throttle? You're obviously not booting around town if you're not stomping on it right? I mean, why do you need power when you're not trying to accelerate? I just don't get it. You want to drive fast, you step on it, isn't that what everyone does? Why not have a system that makes 300 hp at idle, you know what I mean?
I understand people have different opinions of where they want their boost in the RPM range, but that's entirely different. You don't need power to put around town.


Exactly, and if you need power, just give it a little gas. That's the one thing that impressed me about my brother's WRX. Stock turbo, but a lot more boost...the thing would behave just like a regular Impreza in town, but once you put your foot on the gas you couldn't shift fast enough. Turbo cars are great like that. My G60 is good like that too, with the boost return, but without the speed.


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## Impact_Wrench (Nov 22, 2003)

*Re: (Agtronic)*

I can't explain my position on this without sounding like an Azz so how about this:
"If you want to drive fast, you step on it" 
next time your out driving around in your turbocharged car, shift into third and take your foot off the gas, let the revs drop till your almost idling ( below 2000 rpm) then floor it. how hard does it pull at 2500? 3000? 4000? does it kick you in the nads and keep pushing till you shift or does it bog along for a few seconds then light up like a rocket?
everybody is going to have a different preference for when/where a motor should boost but the original point of this thread was to discuss the current trend towards turbos that build huge HP at max RPM and do very little for the car during everyday operation
two very different schools of though on the same subject.


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## speed51133! (Aug 5, 2002)

*Re: (Impact_Wrench)*


_Quote, originally posted by *Impact_Wrench* »_"If you want to drive fast, you step on it" 
next time your out driving around in your turbocharged car, shift into third and take your foot off the gas, let the revs drop till your almost idling ( below 2000 rpm) then floor it. how hard does it pull at 2500? 3000? 4000? 

this is such a stupid argument.
so let me get this straight. your in a situation where you want to go fast, and what do you do? you shift up and basically almost stall your motor, then you hit it??????
someone needs to learn how to drive. its not just a user preference. if you want to go fast, you dont UPshift, and let the car stall, then hit it......thats just stupid


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## Impact_Wrench (Nov 22, 2003)

*Re: (speed51133!)*

I'm not telling him to drive like that all the time, I'm saying "go out and try that once" and you'll get a better understanding of how much power your motor puts out across the rev range, you can look at all the dyno charts you want but until you actually feel that torque under your foot you won't completely understand it.
All I'm saying is that, when your driving on the street, having a broad torque curve that starts low and pull through the rev range changes the whole feel of the car and how it performs.
you can shift (up or down) and when the tach is sitting at 3000 you have enough power to move the car, you dont' have to wait till the AR .76 turbine has spooled up before you feel boost.
now obviously this is not ideal for every situation, a larger turbo would be better for drag racing, whereas Auto-x drivers would probably prefer something in the middle...


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## need_a_VR6 (May 19, 1999)

*Re: (Impact_Wrench)*

Is there a choice to take that SR20's hp curve? Thanks.


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## Angular (Mar 12, 2002)

*Re: (Impact_Wrench)*


_Quote, originally posted by *Impact_Wrench* »_I'm not telling him to drive like that all the time, I'm saying "go out and try that once" and you'll get a better understanding of how much power your motor puts out across the rev range, you can look at all the dyno charts you want but until you actually feel that torque under your foot you won't completely understand it.
All I'm saying is that, when your driving on the street, having a broad torque curve that starts low and pull through the rev range changes the whole feel of the car and how it performs.
you can shift (up or down) and when the tach is sitting at 3000 you have enough power to move the car, you dont' have to wait till the AR .76 turbine has spooled up before you feel boost.
now obviously this is not ideal for every situation, a larger turbo would be better for drag racing, whereas Auto-x drivers would probably prefer something in the middle...


Well stated. If I mash the pedal down in 3rd at 2000 RPM it pulls nicely with steadily increasing power. There's not a real kick in the pants because the power comes in so smoothly and progressively. I can drive around town between 2500 and 3500 RPM all day and keep it in boost as I row through the gears. Feels like a bigger engine than it really is. Above 3500 RPM is where the torque steer and wheelspin lurk. And for whoever asked it, yes... I like to pass those damn 18 wheelers (and Hondas, etc, etc) without downshifting.
Hasn't anyone here thought of simply running boost control of 5 PSI in 1st, 7 PSI in 2nd, and full boost in 3rd through 5th? It's not rocket science to rig up something to the shift linkage to provide a gear select signal to your electronic boost controller or even just operate solenoids that switch in a ball/spring valve dialed to the desired max boost level.
I'm not going to waste my time trying to convince the "big turbo people" to go smaller. It's really just a matter of personal preference and what your goals are.
Bradley


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