# AWP vs AEB Head



## fullsize94 (Apr 16, 2008)

So I am in the middle of building my MK1. I have a AWP motor which is going to be sent to my engine builder for balancing here soon. Its a 06a block, ALH crank, IE 20mm rods, JE 9.5:1 83mm pistons. The head that I have for it is a AWP head with ferrea valve train, and stock lifters (still don't have cams yet). I am planning on using a dbb 6466 or dbb 6766, was wanting some insight on if I should take the parts I have and swap them into a AEB head, if I make a huge gain or not. Car is going be running on a Haltech elite 1500 ecu. 


Sorry all the threads I have read on this dealt with baby turbo's, which don't pertain to my build


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## NaSMK4 (Dec 12, 2011)

thats a big turbo if ur goin that big of a turbo i would suggest aeb since u arent going to even care about low end torque at all... that turbo is not going to wake up until after 5krpms for sure so i suggest building the AEB setup 100% but this topic has been beat to death i have a gt3071r with billet blade upgrade and i kept my awp since i wanted more low end power and more mid range power. but my turbo is considerably smaller than your turbo selections.


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## Vegeta Gti (Feb 13, 2003)

I'm mk1 bt.....stay with the awp head. It's superior. 

You can have all the flow in the world but if you don't have velocity is no way for it to do what it's supposed to do on a turbo car which is still as fast as possible and exit as fast as possible. There's a reason they left the AEB you went to the AWP head. I'm building an AWP head on the side already and I've been on my AEB had for years and it's just not the same. The drive it bilities better the top end is more crisp midrange and bottom end of superior especially if you're going to be tracking the car and definitely for daily driving. I made better peak power and superior torque on my AWP which was just barely touched versus a very well built and worked AEB head.

Plus if you did all the research she'd see the lot of the big power guys from four five and six years ago like myself have all stated it to stay with the AWP.


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## Vegeta Gti (Feb 13, 2003)

Btw.... the only thing you can swap over our the cams none of the other valve train from the AWP will go into the AEB.

And there are people with turbos as big or bigger than yours that are still staying on the AWP headed.


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## woodywoods86 (Jul 29, 2008)

Vegeta Gti said:


> Btw.... the only thing you can swap over our the cams none of the other valve train from the AWP will go into the AEB.
> 
> And there are people with turbos as big or bigger than yours that are still staying on the AWP headed.


Wait hold on a second. The valvetrain is same between the two heads. All the seats need to be cut and I wouldn't recommend reusing oem valves w/ having the professionally checked.

Big thing is VVT and Intake Shutter window.

I have heard good things about a AWP ported to large port size. Unfortunately I made the jump to AEB without see all the details. Definitely to going to build a AWP side head :thumbup:

My vote ported AWP.


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## Vegeta Gti (Feb 13, 2003)

The valve springs are different from what I remember.

Regardless.....AWP ftw


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## Vegeta Gti (Feb 13, 2003)

a lot of guys making huge power didn't go aeb size completely(fwir), they went big, but they took advantage of the superior casting, bowl design and ability to have huge exhaust ports.

Seriously, do some searching. No spoon feeding


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## fullsize94 (Apr 16, 2008)

Vegeta Gti said:


> a lot of guys making huge power didn't go aeb size completely(fwir), they went big, but they took advantage of the superior casting, bowl design and ability to have huge exhaust ports.
> 
> Seriously, do some searching. No spoon feeding


Was looking for information, and technical date on turbo's bigger than a gt35r with awp and aeb, all the information I was seeing didn't pertain to what I was doing. I don't have time to sit here all day and look for the 2 people that have tried to make more than 700hp. lol 


Anyways carrier on.


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## Gulfstream (Jul 28, 2010)

AGU head (largeport), catcams and PPT5935R. E85 fuel and 35psi. Too small intercooler gave me 35c+ IAT climb which I later fixed but here's the dyno with the small intercooler:


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## Vegeta Gti (Feb 13, 2003)

There are a few dozen guys sitting at 600+

But if you ask for help and receive info, then act like a dick, well. You'll start getting that attitude back.


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## Gulfstream (Jul 28, 2010)

Vegeta Gti said:


> a lot of guys making huge power didn't go aeb size completely(fwir), they went big, but they took advantage of the superior casting, bowl design and ability to have huge exhaust ports.
> 
> Seriously, do some searching. No spoon feeding


Actually largeport heads already have larger exhaustports as well as inlet ports. 

I read you claim smallport flow better than largeport and I'd have to disagree with you there buddy. For me an engine is only an air pump. Max flow in and out = magic.


Smaller ports flow less than larger ports regardless of any venturi design integrated in the runners.


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## Twopnt016v (Jul 5, 2009)

I've run both heads and the AWP is superior IMHO. I ditched the AEB and there is no looking back. I have AEB for sale if anyone wants it.


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## Gulfstream (Jul 28, 2010)

I think there is another reason why you couldn't get it to run properly with a largerport. More cfm is better. 

Sent fra min SM-T900 via Tapatalk


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## 20v master (May 7, 2009)

Gulfstream said:


> I think there is another reason why you couldn't get it to run properly with a largerport. More cfm is better.


While this is an age old topic for the 1.8T 20v motor, I tend to agree with you here, regardless of all the people who claim to have gone from AEB to AWP and picked up all this low end and midrange power over the larger ports. These are relatively small turbo motors. There is no low end until you get boost. Less restrictive intake and exhaust tract = spool sooner = more torque sooner. The obvious top end benefits are easily seen from all out flowbench results. AEB it is for me.


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## dane. (Nov 16, 2007)

I didn't even think this was a topic that needed covered anymore. CFM reigns supreme in the case of head flow. It's a no argument situation to use an AEB for medium frame turbos and larger.


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## AmIdYfReAk (Nov 8, 2006)

Vegeta Gti said:


> But if you ask for help and receive info, then act like a dick, well. You'll start getting that attitude back.


How I've always treated this place, this is not a job, no one is paid to help anyone, we help with what we can/are willing and its your choice what you do with the info.


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## Vegeta Gti (Feb 13, 2003)

See but a concern for velocity is also represented by integral cylinder-head design protocols such as port taper and entry angle along with the valve angles in reference to the bore centerline. The angle is different on the AEB vs the AWP, and overflow and the lack of velocity with the AEB makes a difference up top, if you lose the velocity you lose cylinder filling. Velocity of the charge will affect VE. The larger the port area, the slower the velocity and the higher the rpm the engine will need to turn to use the space effectively. Larger CI engines require increased port volumes to promote good cylinder fill rates obviously, but ours love the feed velocity, and being forced induced, they obviously love over CFM as well. The ideal scenario would be an intake port that has sufficient area to support a column of air that is voluminous enough to satisfy the displacement needs of the engine, but small enough to keep the velocity high. So the fact that you can come damn close to matching an AEB flow amount but have superior velocity proves the AEB is inferior.


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## Gulfstream (Jul 28, 2010)

I just think you're overcomplicating it. Larger ports have more CFM. More CFM is more airflow. More airflow is more power. POWER! :beer:


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## Vegeta Gti (Feb 13, 2003)

yes, but it's far more complicated than that. why simplify something that is so detailed and capable of giving great gains and efficiency. it is that complicated. i've seen the gains across many dyno's on my car and on many many others, as well as what others have done. seem then oem to oem as well as worked to worked. only literally a handful, half a dozen or less, will show the difference of sheer flow versus the balance of both and the need for velocity over crazy cfm.

sooo much more to it than we have touched upon here. writing it off so simply is unacceptable, you know the thirst for knowledge and data:beer::beer:


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## Gulfstream (Jul 28, 2010)

You ever heard of k.i.s.s. ?

That's how I look at most things at least in regards to getting most power out of my motor. In the end it's all about how much fuel and air you can force into the cylinders. One giant airpump.

:beer:


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## mainstayinc (Oct 4, 2006)

Here is a link to a article about high velocity porting:

http://www.mototuneusa.com/think_fast.htm

The guy makes the ports smaller on his Yamaha using epoxy and consequently makes more power.

Stock Ports 103.1 HP (BLUE)
20% Smaller Ports 104.1 HP (GREEN)
30% Smaller Ports 108.3 HP !! (RED)










He debunks the myth of flowbench tuning as CFM only measures the suction phase and not the charging phase of combustion.


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## Gulfstream (Jul 28, 2010)

One 100hp NA motor being optimized has zero relevance to a big turbo 4 banger pushing 700hp.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> One 100hp NA motor being optimized has zero relevance to a big turbo 4 banger pushing 700hp.


How is it not relevant?


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> How is it not relevant?


NA vs Turbo. It's different....


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## Vegeta Gti (Feb 13, 2003)

it's completely relevant and many times proven O. Velocity is the key to VE, how fast can you fill it and compress it? CFM is a strange term for what it does as "flow" numbers usually lack actual velocity.and the way "flow" numbers are calculated do not apply to most modern engines and how they run in real time. it's been proven by NASA/JPL, SpaceX and many top manufacturers..like VW/Audi, Porcsche, Puegot, Toyota, etc.
look at boosted 1000cc bike engines..small, high velocity ports that out flow our heads with a turbo attached.....

Many people have proven it even with the 1.8T and i'm not talking users like i said earlier. Engineers and tuners.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> NA vs Turbo. It's different....


Ok.


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## Gulfstream (Jul 28, 2010)

Sorry guys, have to disagree with you there. The principle of how a NA motor makes power has no relevance to forced induction. 

Also, here is a pic to compare flow. Again, more flow = more power :beer:

By all means, if you can actually PROVE a smallport makes more power than a bigport using a big turbo I'd love to see it....


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## superkarl (Dec 18, 2012)

I'm no expert or engineer but it seems to me you are talking about 'cylinder filling' as though it's an N/A engine. 
Forced induction changes things. You fill the cylinder however much you want or don't want dependant on the turbo and boost level. Larger ports, larger CFM, more volume of air for a given boost level is going to fill the cylinder. Smaller ports will likely take more boost/airflow for same amount of filling. 
It's not a steady state system tho so unless you are WOT and boosting 100% then things may change yet again. I'd imagine the only time port velocity is dominant over Volume is in lower rpm/loads


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Sorry guys, have to disagree with you there. The principle of how a NA motor makes power has no relevance to forced induction.
> 
> Also, here is a pic to compare flow. Again, more flow = more power :beer:
> 
> By all means, if you can actually PROVE a smallport makes more power than a bigport using a big turbo I'd love to see it....


According to the chart, the AEB flows 215 CFM at 0.475 inches as compared to 165 CFM for the AWP at the same lift. That's 130% more flow. Therefore, according to your logic, the AEB should produce 130% more power than the AWP simply because it flows 130% more static air on a bench.

I don't think you can maintain that the AEB head will give you a 130% power increase. That would be the best bolt-on ever. So, the CFM chart doesn't tell the whole story.

Obviously port velocity plays a huge role in cylinder charge filling.



EDIT: I'm going to let you have the last word. Wife is calling me for dinner. I'll follow up later.


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## Gulfstream (Jul 28, 2010)

I can see how you would think so looking at the intake port alone. But you need to look at the exhaust ports as well and all other limitations to flow through an engine to get the big picture. Again, you use the static flow in an NA setting to argue about what makes power in a TURBO motor. I'm sure the velocity and design of the intake ports is extremely important in an NA engine which rely on atmospheric pressure to force air into the engine, however.... 

This is a 1.8 Turbo motor and we use a turbocharger to force air into the engine. With a turbocharged engine you want as little restrictions as possible... a smallport is more restrictive than a bigport as the CFM chart above depicts. 


Another thing is.... just to argue against your Honda motor: If that's the case why does many ppl see gains by porting their NA heads? Something just don't make no sense here... 


If you find an example where someone with a big turbo 1.8T lost power by going to a largeport head while optimizing the maps for both smallport and largeport I'd really like to see it. Evidence makes the rules. 


bon apetite


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## Gulfstream (Jul 28, 2010)

I suspect, without being an engineer by any stretch of the imagination, that VAG went with a smallport over largeport because of emissions and better low end response. Not top end power.... 

There's probably some engineers reading this who can clarify. 

:wave:


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> I can see how you would think so looking at the intake port alone. But you need to look at the exhaust ports as well and all other limitations to flow through an engine to get the big picture. Again, you use the static flow in an NA setting to argue about what makes power in a TURBO motor. I'm sure the velocity and design of the intake ports is extremely important in an NA engine which rely on atmospheric pressure to force air into the engine, however....
> 
> This is a 1.8 Turbo motor and we use a turbocharger to force air into the engine. With a turbocharged engine you want as little restrictions as possible... a smallport is more restrictive than a bigport as the CFM chart above depicts.
> 
> ...


Thanks. I just did a quick search and it looks like this topic has come up before on vwvortex. This guy claims he made more power on a ported AWP head as compared to his AEB. I'm not trying to make rules here, for sure. Just throwing out some examples I came across.

http://forums.vwvortex.com/showthread.php?5355083-good-TECHNICAL-discussion-on-head-porting-and-SM-vs-LG-port-heads&p=72409487&viewfull=1#post72409487



Powdered Toast Man said:


> yes, the simon-says is mine.
> 
> and yes i do and always have made more power/less torque on the PORTED AWP.
> 
> ...


BTW, I never claimed that an AEB head would cause the 1.8T to lose power. It makes sense that the AEB head would make more top end power under high boost, high RPMs.


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## Gulfstream (Jul 28, 2010)

Vegeta Gti said:


> it's completely relevant and many times proven O. Velocity is the key to VE, how fast can you fill it and compress it? CFM is a strange term for what it does as "flow" numbers usually lack actual velocity..
> 
> Many people have proven it even with the 1.8T and i'm not talking users like i said earlier. Engineers and tuners.


You can have a 1cm diameter intake port with 100 times the velocity compared to a 5cm diameter port and still the 5cm port have more flow and make more power. CFM

How fast can you fill it, you ask? -How big is your turbo, I reply


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> Thanks. I just did a quick search and it looks like this topic has come up before on vwvortex. This guy claims he made more power on a ported AWP head as compared to his AEB. I'm not trying to make rules here, for sure. Just throwing out some examples I came across.
> 
> http://forums.vwvortex.com/showthread.php?5355083-good-TECHNICAL-discussion-on-head-porting-and-SM-vs-LG-port-heads&p=72409487&viewfull=1#post72409487
> 
> ...


I asked Aaron about those nr's and he replied:

"And no i have not done a back to back straight across comparison. I'm not going to shim and lash a solid lifter head just so people on vortex have some information. That just takes way too much time effort and money that I don't care to waste for people that I really could give a f*** less about
That said my new motor is the same exact block with the integrated engineering CNC AEB head and big big big big cams
288 exhaust and 310 intake."

So, I'll question the validity of those nrs and besides we don't know what else was changed.... 

To convince me that a smallport makes more power than a bigport you need to swap the two heads over and try it. I don't think anyone has done that or would bother to do so as we have something called CFM measurements. 

Anyways, I use a ported AGU head (largeport) and it seems to do the trick for me... remembering when I went from a BAM 225 (smallport) engine to my first AGU (largeport) I had better response at low end rpm before boost in either cases. CR, manifold, portsize, DP, all and everything which restricts flow plays a part.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> I asked Aaron about those nr's and he replied:
> 
> "And no i have not done a back to back straight across comparison. I'm not going to shim and lash a solid lifter head just so people on vortex have some information. That just takes way too much time effort and money that I don't care to waste for people that I really could give a f*** less about
> That said my new motor is the same exact block with the integrated engineering CNC AEB head and big big big big cams
> ...


Swapping the heads over and doing a back to back comparison would definately settle the question. One thing I find interesting is that both small port and large port heads have the same valve area. You would think that that would present a restriction on the large port head. There's an optimal ratio between intake port area and valve area. On a NA application, this ratio is between 0.85 and 0.90. I created a spreadsheet a few months ago (just out of curiosity) to calculate these areas for a small port and large port but haven't finished it. Of course that would be different for a turbocharged application, as boost pressure creates higher velocity. On a boosted application, you can probably go above a 1.0 ratio and increase your overall through put. But that only applies to when the engine is under boost. Off boost the engine would be less optimal and slower to spoolup. I think that's what most people see with their large port head on most cases.

Here's an interesting article that discusses this issue.

The other comment I want to make is that the boba motoring MK2 uses a ported 2.0L 16 valvehead making 1234 Wheel PS (1217 WHP). On the bottom, right of the picture below you can see the intake ports. They don't seem much larger than AWP.










Nice video 100 to 200 KPH in 3.03 secs.


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## Gulfstream (Jul 28, 2010)

As for what head create better spoolup I can only refer to the CFM chart. Largeport flow better already from low vavle lift. I would however agree that the valves on a largeport is the biggest restriction to flow and that's something I will have to look at down the road... :laugh:

As for your comparison between the 1.8t smallport and 2.0 16v head.... 










In fact they don't even look the same. Compeletely different design.

No velocity venturi. Intake it to the right:










Compare to the 1.8t largeport and smallport. Intake is to the left:










The smallport ventury was designed to improve combustion where the engine spend 99% of it's life - 2000rpm. Nothing to do with performance in fact. 


I had a look at boba motoring's head and it interesting to see their head does not have the venturi which exists in the 1.8t smallport. If they ported it away or if it's just not there by design I couldn't tell you, it's not a 1.8t. Their intake runners have been ported out to the max and they have this 3rd runner opening above the normal oval shaped opening to bring air on the topside of the valve. Cool design. If you combine this triangle desisgn into an oval shape I bet it's would be similar to the cross section of a 1.8t largeport.

That said, 2.0 16v don't come in smallport / largeport version, just one largeport version. 

http://www.clubgti.com/showthread.p...cutaway-and-maximum-porting-dimensions-thread



So, from looking at Boba Motoring's 2.0L 16V head I can see they had NG Motorsport porting their head out to the maximum making it's already largeport even larger. Very different from 1.8t smallport head.


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## Marcus_Aurelius (Mar 1, 2012)

opcorn:


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> *As for what head create better spoolup I can only refer to the CFM chart. Largeport flow better already from low vavle lift.* I would however agree that the valves on a largeport is the biggest restriction to flow and that's something I will have to look at down the road... :laugh:


CFM (flow) is only one part of the equation. You have to also look at intake velocity and volume when discussing cylinder head design. Those play a critical role in how well the cylinder is filled at the end of the intake stroke. I don't think you can maintain that the AEB head will give you a 130% power increase across the entire engine operating range (i.e: spoolup and top end). That would be like saying that a 0.63 A/R turbine housing will help spool a turbo faster and give better top end as compared to a 0.48 A/R housing. There is always a tradeoff.



Gulfstream said:


> As for your comparison between the 1.8t smallport and 2.0 16v head....
> 
> In fact they don't even look the same. *Compeletely different design*.
> 
> No velocity venturi.


Yes. Completely different design. But, there is, in fact, a velocity venturi. I've drawn a line in red below to show the venturi (narrowest point):










Knowing the size of the intake valve (32mm), you can estimate the diameter of the venturi. According to my calculations, it's about 22mm wide. That's about 69% of the flow area of the two (2) intake valves (22mm/32mm).



Gulfstream said:


> The smallport ventury was designed to improve combustion where the engine spend 99% of it's life - 2000rpm. *Nothing to do with performance in fact.*


The smallport venturi has everything to do with performance. Combustion efficiency and power output are directly related. The more efficient the combustion cycle, the more power generated. The smallport venturi was created to induce tumble into the cylinder and, at the same time, increase port velocity. Both of these help vaporize fuel in the combustion chamber and increase flame speed during ignition. These create more peak torque during the expansion phase. More torque equates to more horsepower at a given engine speed.

The most important question is at what point does a venturi choke flow? In a book published by the MIT press "The Internal Combustion Engine" studies suggest that if port velocities anywhere in the system exceed 60% the speed of sound, a limiting condition exists.

Below I estimated the diameter of the venturi for the AWP and AEB engine codes. For the AWP, the three venturi leading up to the intake valve are about 16mm in diameter. For the AEB, they are about 21mm or +5mm. For the 9A/ABF, they are about 22mm as stated above.










Below is the finished spreadsheet which calculates, among other things, port area, venturi area and port velocity.










The three different columns represent the AWP (smallport), AEB (largeport) and 9A/ABF engine codes. The blue colors represent unrestricted flow through the venturi for each cylinder head (from 0 to 60% speed of sound). The yellow colors represent some restriction (from 61% to 75% speed of sound). The orange represents restricted flow (>75% speed of sound).

As you can see in column 1, the AWP has unrestricted flow (blue) up to 5170 RPMs. From there, flow becomes somewhat restricted up to 6500 RPMs. After than point, I would characterize flow as being significantly restricted (>75% speed of sound). It is very clear that VW/Audi engineers designed the AWP head to flow not much more than 6500 RPMs while giving more emphasis to low end torque production.

In column 2 you can see the results for the AEB engine code. As you can see, the AEB head has free, unrestricted flow up to 8900 RPMs. From there, flow becomes somewhat restricted up to 11,000 RPMs where it begins to choke off.

In column 3 you can see the results for the 9A/ABF engine code. It is somewhat in the middle of the AWP and AEB. It has unrestricted flow up to 6500 RPMs on 2.0 liter displacement. From there, it is somewhat restricted up to 8100 RPMs and chokes off above that point.

I would optimize each cylinder head as follows:

AWP: port venturi from 16mm to 18mm.
AEB: epoxy port from 21mm to 19mm.
9A/ABF: port venturi from 22 to 23mm.

For the AWP cylinder head, that would mean simply enlarging the radius of the venturi by 1mm. It would look like this:










IMO it would not take a lot of porting to get the AWP to flow more optimally. Here is what the charts would look like with ports optimized:










Free, unrestricted flow for the optimized AWP cylinder head would increase from 5170 RPMs to 6500+ RPMs. From there, flow becomes somewhat restricted to 8200 RPMs. You could, of course, port the AWP venturi more and get better flow numbers if you like. But I don't think that's necessary in most cases.

For the optimized AEB cylinder head, free, unrestricted flow would decrease from 8900 RPMs to 7300 RPMs while, at the same time, benefit from increase port velocity and cylinder charging at lower RPMs. From there, flow becomes somewhat restricted to 9100 RPMs.

It's also worth mentioning that the intake valves do not present a flow restriction on the AWP and AEB cylinder heads, as their port velocities are well below 60% speed of sound.

Conclusion. The stock AWP cylinder head is designed to flow optimally below 5200 RPMs and becomes restricted above 6500 RPMs. A mildly ported AWP cylinder head can easily flow more by increasing the size of the venturi to 18mm (or larger). The stock AEB head has free, unrestricted flow up to 8900 RPMs and is the best choice for applications requiring engine speeds up to 11000 RPMs. A mild epoxy would help port velocity and cylinder charging below 9100 RPMs. Measurements of the different venturi are estimated based on my calculations. Perhaps someone can actually measure the venturi for the most accurate analysis. 

Before deciding on which cylinder head to choose or whether or not porting is required, you should first select which turbo you will be using. The turbo's efficiency range (i.e. compressor map) will determine your engine operating range. In the case of the 1233 PS Boba Motoring 2.0L 16V engine, the effective operating range is between 5000 and 8000 RPMs, with maximum horsepower achieved at 8000 RPMs. A mildly ported 9A/ABF cylinder head IMO would be a good choice.


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## Gulfstream (Jul 28, 2010)

First of all, grat job calculating all that. :thumbup:

I think you misunderstood when I said velocity ventury has nothing to do with performance. For me performance is effect while on boost ie 5 - 9k rpm and not sub 5k rpm as you correctly stated where the design of the ventury comes into play. So I think we agree in fact, smallport will NOT give you the top end flow as compared to a largeport but it will give you better economy and response before you come into boost. 

If you go bigger turbo than a K04, you have benefits of a largeport head :beer:

I see the little venturi in the 16V on the topside. If you look at Boba's ported head, the picture you linked to earlier you can see they ported out any signs of ventury. That's what I mean by performance... you can be sure VW didn't design the smallport head for top end performance but rather low end economy.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> First of all, grat job calculating all that. :thumbup:
> 
> I think you misunderstood when I said velocity ventury has nothing to do with performance. For me performance is effect while on boost ie 5 - 9k rpm and not sub 5k rpm as you correctly stated where the design of the ventury comes into play. So I think we agree in fact, smallport will NOT give you the top end flow as compared to a largeport but it will give you better economy and response before you come into boost.
> 
> If you go bigger turbo than a K04, you have benefits of a largeport head :beer:


Yes. We agree. Small port will not give you top end flow unless mildly ported. AEB is best used for turbo applications requiring very high engine speeds (>8500). I would go with a ported AWP for anything between 6500 to 8000 RPMs. Yes. Looks like the Boba Motoring removed venturi. Glad you like the analysis.:thumbup:


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## mainstayinc (Oct 4, 2006)

Just a few notes. A K04 would not require engine speeds over 6500 RPMs to maximize power so AWP is perfectly fine. I definately would not go up to an AEB with a K04. Even with my GTX2867R, my maximum power should be just below 6500 RPMs. However, I could probably benefit from some mild porting as that would benefit the 5200 to 6500 range. It really depends on where the turbo makes power.

Also, even though the yellow areas are 'somewhat restricted' that might only translate into a 2 psi penalty. Meaning that the turbo would have to produce an extra 2 psi for the same output as the AEB. More serious choke off would occur much closer to the speed of sound I think (85 to 95%). I might have to get another copy of volumes 1 and 2 of MIT Press' "The Internal Combustion Engine" as I discarded those a few years ago.


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## superkarl (Dec 18, 2012)

How have you calculated port velocity?
Is it dependant on boost, or more importantly, the compressor flow of the turbo? Another variable.


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## mainstayinc (Oct 4, 2006)

superkarl said:


> How have you calculated port velocity?
> Is it dependant on boost, or more importantly, the compressor flow of the turbo? Another variable.


Here is the formula I used to calculate (Limiting) Port Velocity: LPV=(.00353*RPM*S*B^2)/CA, where:

S = stroke (in)
B = bore (in)
CA = minimum port cross sectional area in sq./in.’s
RPM = peak power rpm
LPV = limiting port velocity

The formula does not take into account boost pressure. However, in a closed system, higher boost pressure would only cause the fluid to become slightly more dense and would not increase velocity much. It would, obviously, be much different if one end of the venturi was under high pressure and the other end was under low pressure (atmosphere).

Here is a link to a relevant article on the venturi effect: https://en.wikipedia.org/wiki/Venturi_effect

Here is a calculator for determining LPV: http://users.erols.com/srweiss/calcplv.htm


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## Gulfstream (Jul 28, 2010)

With fluid he means air/gass. Fluid is not compressible. 

Sent fra min SM-T900 via Tapatalk


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> With fluid he means air/gass. Fluid is not compressible.
> 
> Sent fra min SM-T900 via Tapatalk


Yes.


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## MÄDDNESSS (Oct 18, 2010)

Not to repeat the "dead horse" comment but its kinda crazy to see this up for discussion again.

I didn't read it at but I was under the impression that small port was for low end power because velocity and large port was for high end power because of more volume.

Seems theres a few good points to dispute that and as well as to back that up.

FWIW, I went from AWP to AEB because I have a Franken Turbo. I decided on the AEB to try to shift some of that low end torque towards the top for some mid and high end hp.
I did notice a difference. Lag increase by about 100-300 rpms but still plenty of pep with more of that larger frame turbo pull up top.
Im very happy with it.

But I digress. I know the OP and the majority of this thread is focused of BATs.


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## superkarl (Dec 18, 2012)

Gulfstream said:


> With fluid he means air/gass. Fluid is not compressible.
> 
> Sent fra min SM-T900 via Tapatalk


In fluid dynamics it's always referred to as fluid whether air, gas, water, oil etc


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## Gulfstream (Jul 28, 2010)

superkarl said:


> In fluid dynamics it's always referred to as fluid whether air, gas, water, oil etc


Yes, but not all who reads this thread will have background in fluid dynamics and it can be confusing to use the term fluid for air.


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## mainstayinc (Oct 4, 2006)

One thing that is not accounted for in the above analysis is the cooling effect of port fuel injection. That will effectively increase the flow area of the venturi. Although the fuel will take up some space, it will also cool the charge effectively increasing the size of the venturi. This depends on the spray pattern of the fuel injector and the type of fuel used. Alcohol will have a greater cooling effect than gasoline. Without looking at the math, I am thinking maybe 5 to 10% increase for gas, 10 to 20% for alcohol. Not sure. Also, this benefit does not apply to direct injection engines. This cooling effect will result in less restriction through the venturi and will raise the 'unrestricted flow' range of the engine.


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## Vegeta Gti (Feb 13, 2003)

i need to go ver this at home, this her..is what this forum should be about. outfuknstanding work. this is what i live for, research and discussion and data.


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## ticketed2much (Feb 18, 2012)

mainstayinc said:


> Conclusion. The stock AWP cylinder head is designed to flow optimally below 5200 RPMs and becomes restricted above 6500 RPMs. A mildly ported AWP cylinder head can easily flow more by increasing the size of the venturi to 18mm (or larger). The stock AEB head has free, unrestricted flow up to 8900 RPMs and is the best choice for applications requiring engine speeds up to 11000 RPMs. A mild epoxy would help port velocity and cylinder charging below 9100 RPMs. Measurements of the different venturi are estimated based on my calculations. Perhaps someone can actually measure the venturi for the most accurate analysis.


I just learned a lot. Thanks for taking the time to calculate all that.


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## mainstayinc (Oct 4, 2006)

ticketed2much said:


> I just learned a lot. Thanks for taking the time to calculate all that.


Glad you like.:thumbup:


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## superkarl (Dec 18, 2012)

Im tempted to play around with a spare small port head i have and fit that. Id probably aim to take more material off the roof of the port and behind the valve seat and very little off the floor of the port, just smoothing the casting, to try and keep entry into the cylinder a little more 'square':

Id open the initial opening to largeport to accept a large port manifold, and take the port diameter to about 19mm like your calculations suggest. 
I would also take the exhaust ports to largeport size. 34 vs 36mm i believe. 

I lightly ported my current largeport, mainly gasket matched, smoothed the castings, nothing too drastic as im limited in skill, experience and tooling at the time. I took my inspiration from Andrew @ ALD, if you haven't seen his work you must, its epic. 

My AEB head:


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## Marcus_Aurelius (Mar 1, 2012)

The difference with the exhaust ports is 33mm to 36mm karl. However I would also suggest looking into the port size on the exhaust manifold in use as not all of them offer 36mm runner ID. :thumbup:

As for the topic, I chose to lurk in the sideline this time instead of offering my imputs because I felt that I have spent too much time over the years arguing the point that a massaged small port will likely outperform a large port in 90 percent of applications due to the velocity advantage (the all-drag monster turbos with 10k+ powerbands being the 10%, and I'm being generous with the numbers). People making the comparison always seem to omit one huge factor, we do not operate these cars at WOT in steady state all the time. Part-throttle and transient operation seem to be something that doesn't exist with the all-flow proponents . Unfortunately, it's something that we all have to deal with in real life...

Do share your work with the SP head massaging, as it is something I'm looking to tackle myself on a spare head I'm building for high revs. :beer:


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## Gulfstream (Jul 28, 2010)

For those who are worried about transiet response with a largeport can have a look at my car.

AGU largeport head further ported out for maximum flow. PPT5935R 0.82ar turbo and catcams 3651 advanced 2.5degrees.


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## mainstayinc (Oct 4, 2006)

superkarl said:


> Im tempted to play around with a spare small port head i have and fit that. *Id probably aim to take more material off the roof of the port and behind the valve seat and very little off the floor of the port*, just smoothing the casting, to try and keep entry into the cylinder a little more 'square':
> 
> *Id open the initial opening to largeport to accept a large port manifold, and take the port diameter to about 19mm like your calculations suggest*.


Yes. Taking more material off the roof of the port looks like the way to go. That's a nice, smooth shape. I think the 18mm to 19mm range will give you plenty of flow. I forgot to mention that the smallport opening (where intake manifold connect to cylinder head) does not present a follow restriction.

Below I ran the same calculations for the port opening into the cylinder head. As you can see, the AWP port is about 1.5 inches square and has unrestricted flow up to about 8400 RPMs and is good to 10,400+ RPMs where is begins to choke off.


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## Gulfstream (Jul 28, 2010)

8400rpm? Pretty sure it was sub 5000rpm earlier ;-) 
No point porting a smallport head to make it look like a largeport. Just get a largeport and bob's your uncle. 


Sent fra min SM-T900 via Tapatalk


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> I forgot to mention that the smallport opening (where intake manifold connect to cylinder head) does not present a follow restriction.


That's incorrect. Bare with me, let's just pretend for a moment someone never actually measured the flow through the heads(which they have, I linked it earlier) and just look at your claim:

A smallport does not represent any restriction vs largeport judged by it's smalles size measured at the inlet. You say the velocity barely change, only the density(boost) and that's why your math seems legit. Well you can have 25psi boost from a K04 and 25psi from a GT35R. Which makes more power and why? The density is the same and you say the flow is the same... so how come the GT35R setup makes 3 times the power? 

It's because the flow/velocity change and if you add a largeport you will open up even more flow... Hate to argue against all your math but it just don't make any sense. 

If there was only a way to make sure.. if only someone actually measured the flow of small vs largeport... Oh, yeah.. someone did.

I agree with you that the smallport inlet doesn't represent any restriction in one case only and that's if you run the oem turbo. Per manufacturers design: K03/K04...


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> 8400rpm? Pretty sure it was sub 5000rpm earlier ;-)
> No point porting a smallport head to make it look like a largeport. Just get a largeport and bob's your uncle.
> 
> 
> Sent fra min SM-T900 via Tapatalk


I think you misunderstood my most recent post. The three (3) venturi  in the small port become restrictive at 5170 RPMs. However, the port opening where the intake manifold connects to the cylinder head is not restrictive. Combined together, the AWP head still becomes restrictive at 5170 RPMs. The point here is that the venturi need to be enlarged by a few millimeters to get optimal flow at higher engine speeds. The port opening does not need to be enlarged as that flows fine. So, the venturi need to be better matched to the port opening.

The venturi are the choke point, not the port opening. I'll simplify it for you:


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> The venturi are the choke point, not the port opening.


I disagree and I rely on measured CFM nr's. Btw, that pic above has a ported inlet... Ja, das ist gut! 


I'll make it easy for you. Buy two straws, one thin and one thick and blow really hard through them and see which one makes more bubbles :wave:


Each to their own :beer:


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> I disagree and I rely on measured CFM nr's. Btw, that pic above has a ported inlet... Ja, das ist gut!
> 
> 
> I'll make it easy for you. Buy two straws, one thin and one thick and blow really hard through them and see which one makes more bubbles :wave:
> ...


Ok. You can use the Port Limiting Velocity Calculator I posted in the previous page if you want to check the flow of the port opening. You'll get the exact same results. The port opening flows just fine but the venturi are too small and choke off the AWP head. I hope I was able to demonstrate that here. I don't think we really disagree that the AWP head is restrictive at higher RPMs and the AEB head is very free-flowing.










In the above calculator, I plugged in the area of the port opening (in square inches). As you can see, the calculated port velocity at 8400 RPMs is about 60% Speed of Sound. This is considered unrestrictive.

Like your video BTW.:thumbup:


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> I disagree and I rely on measured CFM nr's. *Btw, that pic above has a ported inlet... Ja, das ist gut!*


Whoever 'ported' that AWP head ported the wrong area! Das ist no gut! LOL.


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> Ok. You can use the Port Limiting Velocity Calculator I posted in the previous page if you want to check the flow of the port opening. You'll get the exact same results. The port opening flows just fine but the venturi are too small and choke off the AWP head. I hope I was able to demonstrate that here. I don't think we really disagree that the AWP head is restrictive at higher RPMs and the AEB head is very free-flowing.
> 
> 
> 
> ...


Cool calculator, but.... where's the input for boost? We have turbo motors not NA.....


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> Whoever 'ported' that AWP head ported the wrong area! Das ist no gut! LOL.


Yeah, they seemed to think the inlet port was a restriction... how about that :laugh:

We have a saying in aviation junk-in-junk-out. It don't matter how many calculators you have or how big screens you use, if the base of your calculation is flawed everything will be flawed. To claim that a smallport flow equal or better than a larger port is an error so grave it's like thinking the earth is 6500 years old. To put that error in perspective it's like saying the distance from LA to NY is 10 inches....

I think your calculus is flawed because you don't take turbocharging into the equation. Sorry to say.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Cool calculator, but.... where's the input for boost? We have turbo motors not NA.....


That issue was already discussed.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Yeah, they seemed to think the inlet port was a restriction... how about that :laugh:
> 
> We have a saying in aviation junk-in-junk-out. It don't matter how many calculators you have or how big screens you use, if the base of your calculation is flawed everything will be flawed. *To claim that a smallport flow equal or better than a larger port is an error so grave it's like thinking the earth is 6500 years old*. To put that error in perspective it's like saying the distance from LA to NY is 10 inches....
> 
> I think your calculus is flawed because you don't take turbocharging into the equation. Sorry to say.


Whoa! I never said that!


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## Gulfstream (Jul 28, 2010)

That calculator is for NA motors. 

Also, could you address your statement earlier that the velocity don't change only density? 

Density would be boost and like I said earlier, 25psi from a K04 is not the same as 25psi from a GT35R.


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> Here is the formula I used to calculate (Limiting) Port Velocity: LPV=(.00353*RPM*S*B^2)/CA, where:
> 
> S = stroke (in)
> B = bore (in)
> ...


^

So, velocity won't change much only density/boost. So, explain why 25psi on a GT35R delivers MUCH more power than 25psi from a K04.

Maybe I'm missing something obvious here?


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> That calculator is for NA motors.
> 
> Also, could you address your statement earlier that the velocity don't change only density?
> 
> Density would be boost and like I said earlier, 25psi from a K04 is not the same as 25psi from a GT35R.


The calculations only deal with limiting port velocity. Changes in temperature and pressure (boost) won't effect the port velocity much in a closed system. But, of course, they will effect power. The calculations only deal with the basic question of 'how small is too small'.


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## Gulfstream (Jul 28, 2010)

Gulfstream said:


> ^
> 
> So, velocity won't change much only density/boost. So, explain why 25psi on a GT35R delivers MUCH more power than 25psi from a K04.
> 
> Maybe I'm missing something obvious here?


Still not clear...


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Still not clear...


Maybe someone else can chime in. It's 8:00pm here on the east coast and I have to get some work done. I'll check in later (tomorrow).


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## Gulfstream (Jul 28, 2010)

Cool beans. I think this is the problem with your math. It's for na motors and not boosted applications. 

Clearly the flow/velocity is much higher with a much bigger turbo running same boost /density as a smaller turbo and a turbo motor has great benefits of running larger ports to flow more air/fluid before reaching any compressibility problems. 

So I'll look for your explanation tomorrow. 

Sent fra min SM-T900 via Tapatalk


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## superkarl (Dec 18, 2012)

Gulfstream said:


> . To claim that a smallport flow equal or better than a larger port is an error so grave it's like thinking the earth is 6500 years old.


As a geologist I found it very difficult to resist this simile


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## superkarl (Dec 18, 2012)

Given the units a turbo is measured and rated in, pounds per minute, I'd have to agree with gulf stream that something is a miss with the calculations.

Having said that max mentioned a very valid point with regards operating state and only being WOT, or at peak boost/airflow for a small percent of the time, so I think for a road car velocity through the port should and would be beneficial with a smaller port. There has to be a compromise somewhere though, an ideal port size/shape for a given flow rate, or at least a minimum port size to maintain port velocity for a given flow rate.


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Cool beans. I think this is the problem with your math. It's for na motors and not boosted applications.
> 
> *Clearly the flow/velocity is much higher with a much bigger turbo running same boost /density as a smaller turbo and a turbo motor has great benefits of running larger ports to flow more air/fluid before reaching any compressibility problems.*
> 
> ...


Let's be clear. Yes, a much bigger turbo will flow more and be able to generate more boost at higher RPMs. However, all that flow and boost still has to fit inside a cylinder measuring 81mm x 86.5mm (or, in your case, 83mm x 92.8mm). The turbo itself does not increase velocity through the system. Velocity increases with engine speed. The higher the engine spins, the more air flows through the engine (CFM). Moderate restrictions in the intake system do not significantly effect performance until the velocity of air reaches 60% the speed of sound.



Gulfstream said:


> Cool beans. *I think this is the problem with your math. It's for na motors and not boosted applications*.
> 
> Sent fra min SM-T900 via Tapatalk


Just want to point out that your VW Head Flow Comparison on page 2 does not take into consideration boost when measuring flow through the different cylinder heads. It simply measures the volume of air (in CFM) through the cylinder head. So, the CFM results are for NA motors but can be applied to boosted applications, as you have (correctly) done. The calculations I provided in this thread really reinforce the data you already posted. The only difference is that the calculations can deal with restriction areas in finer detail. If the AWP cylinder head was ported as per superkarl's suggestion, it would flow more CFM (of course!).


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## mainstayinc (Oct 4, 2006)

superkarl said:


> *Given the units a turbo is measured and rated in, pounds per minute, I'd have to agree with gulf stream that something is a miss with the calculations.
> 
> *Having said that max mentioned a very valid point with regards operating state and only being WOT, or at peak boost/airflow for a small percent of the time, so I think for a road car velocity through the port should and would be beneficial with a smaller port. There has to be a compromise somewhere though, an ideal port size/shape for a given flow rate, or at least a minimum port size to maintain port velocity for a given flow rate.


The calculations only deal with the volume of air flow like the CFM chart that Gulfstream posted on page two. It does not deal with the mass of air through the system. That is an important difference. Also, a turbo can be measure in any units such as pounds per minute or cubic feet per minute (CFM).


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> * The turbo itself does not increase velocity through the system*. Velocity increases with engine speed. The higher the engine spins, the more air flows through the engine (CFM). Moderate restrictions in the intake system do not significantly effect performance until the velocity of air reaches 60% the speed of sound.


Yes it does and that's why you cannot explain why a GT35R makes much more power than a K04 at the same boost. Your calculator takes only into consideration the capacity of the cylinder vs rpm @ atmospheric pressure and not boosted applications. It say at such and such rpm the cylinder has this much flow and the inlet duct cannot be smaller than so and so.. It's all good for NA applications but in case you missed it the "T" in 1.8T means turbo. When you add a turbo to the equation you will suddenly have twice the airflow at half the rpm and with bigger turbos 4x the airflow. Suddenly the smallport don't look so good anymore and your calculations are not correct. 



mainstayinc said:


> Just want to point out that your VW Head Flow Comparison on page 2 does not take into consideration boost when measuring flow through the different cylinder heads. It simply measures the volume of air (in CFM) through the cylinder head. So, the CFM results are for NA motors but can be applied to boosted applications, as you have (correctly) done. .


The CFM is measured at 28in/hg vacuum and are *ACTUAL* measurements through the heads, not calculated based on rpm, and they show the potential in a boosted application. 

So, sorry to say all your calculations are only correct in a NA motor...


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Yes it does and that's why you cannot explain why a GT35R makes much more power than a K04 at the same boost. Your calculator takes only into consideration the capacity of the cylinder vs rpm @ atmospheric pressure and not boosted applications. It say at such and such rpm the cylinder has this much flow and the inlet duct cannot be smaller than so and so.. It's all good for NA applications but in case you missed it the "T" in 1.8T means turbo. When you add a turbo to the equation you will suddenly have twice the airflow at half the rpm and with bigger turbos 4x the airflow. Suddenly the smallport don't look so good anymore and your calculations are not correct.
> 
> 
> 
> ...


I have to be in Philadelphia today but I comment when I get back. Thx.


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## Marcus_Aurelius (Mar 1, 2012)

Gulfstream said:


> Yes it does and that's why you cannot explain why a GT35R makes much more power than a K04 at the same boost. Your calculator takes only into consideration the capacity of the cylinder vs rpm @ atmospheric pressure and not boosted applications. It say at such and such rpm the cylinder has this much flow and the inlet duct cannot be smaller than so and so.. It's all good for NA applications but in case you missed it the "T" in 1.8T means turbo. When you add a turbo to the equation you will suddenly have twice the airflow at half the rpm and with bigger turbos 4x the airflow. Suddenly the smallport don't look so good anymore and your calculations are not correct.
> 
> 
> 
> ...


As much as I'm trying to stay away from this discussion, the flow tests performed for our heads are done in vacuum in steady state and shows flow at various lift. These tests are great and show one thing, maximum flow through the head, nothing more, nothing else.

The turbo isn't the only thing forcing air through the motor. The turbo compresses the air that is already flowing through the motor and *helps it flow more* (it affects the flow but is not the only thing that creates it, the engine does not stall when you go off boost). The reason why a GT35R makes more power than a K04 at the same pressure is because each compressor at a fix pressure flows X CFM. You're blending two things here, ever asked yourself why our motor (independently of boost) rev at the speed that it does, not faster or slower. Once you think about it this way, you'll understand that velocity plays the same role that it does with a NA application as it does when boosted. The engine character as a pump is not a variable that changes with pressure, it sure does change with port size and velocity however.


Here is a good example, the Honda S2000 which is designed for high revs in NA form. It is a known thing in the Honda world that boosting these motors, you will see power gains by improving velocity, and get a loss if all-out flow is what you choose to go after. If flow was the only factor with forced induction, this would not be the case.
http://urgedesigns.com/?page_id=164

What you should say, is that if maximum flow in the upper revs at WOT (steady state) is what your only goal is, the big port head is the ticket. Transient conditions where all the possible air is not flowing through, it is illogical to stipulates that the BP head is still the best solution because it is behind the SP heads in terms of velocity.


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## [email protected] (Oct 23, 2008)

A turbocharger absolutely forces air into the engine. It is by design a compressor and its job is to compress beyond what the engine can ingest on its own and the act of building PSI between the compressor and valves should be a clear indication that something is being forced. An NA motor at its peak efficiency hovers around 100% VE where turbochargers can far surpass it. This means it flows more air in/out thus increasing mixture density which the engine cannot do on its own, not even close. Lets get that out of the way...

As far as port velocities, while you can make power with the smaller ports under a specific range, you suffer from wetting losses through much of the rev range. I think we get too carried away with 1.8t port sizes as AEB heads arent gigantic ports to begin with and while the port velocities are effected by the tiniest of turbos, there's not this gigantic swing either way in terms of low end response.


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## 20v master (May 7, 2009)

[email protected] said:


> A turbocharger absolutely forces air into the engine. It is by design a compressor and its job is to compress beyond what the engine can ingest on its own and the act of building PSI between the compressor and valves should be a clear indication that something is being forced. *An NA motor at its peak efficiency hovers around 100% VE where turbochargers can far surpass it.* This means it flows more air in/out thus increasing mixture density which the engine cannot do on its own, not even close. Lets get that out of the way...
> 
> As far as port velocities, while you can make power with the smaller ports under a specific range, you suffer from wetting losses through much of the rev range. I think we get too carried away with 1.8t port sizes as AEB heads arent gigantic ports to begin with and while the port velocities are effected by the tiniest of turbos, there's not this gigantic swing either way in terms of low end response.


I'm trying to stay out of this too, Max, but I agree with everything Al says, ESPECIALLY the bold!


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## Marcus_Aurelius (Mar 1, 2012)

20v master said:


> but I agree with everything Al says, ESPECIALLY the bold!


And so do I! If you look at my post I carefully worded it to add that the a turbo affects VE but is not the only thing creating airflow (when off boost air still flows through). Forced induction alllows operation above 100%, but that first 100% that the motor can achieve in NA form comes from what? Bore/stroke, head and port design mainly, and that's the point I made. The idea that just because there is compression involved, the motor stops acting like a pump and velocity is no longer a concern is what I have a problem with.


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## Gulfstream (Jul 28, 2010)

[email protected] said:


> A turbocharger absolutely forces air into the engine. It is by design a compressor and its job is to compress beyond what the engine can ingest on its own and the act of building PSI between the compressor and valves should be a clear indication that something is being forced. An NA motor at its peak efficiency hovers around 100% VE where turbochargers can far surpass it. This means it flows more air in/out thus increasing mixture density which the engine cannot do on its own, not even close. Lets get that out of the way...
> 
> As far as port velocities, while you can make power with the smaller ports under a specific range, you suffer from wetting losses through much of the rev range. I think we get too carried away with 1.8t port sizes as AEB heads arent gigantic ports to begin with and while the port velocities are effected by the tiniest of turbos, there's not this gigantic swing either way in terms of low end response.


Finally a word from a professional! I'll just hand the torch over to Arnold as he have more tools available to explain the difference between NA and boosted applications. 




Sent fra min SM-T900 via Tapatalk


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## Gulfstream (Jul 28, 2010)

Marcus_Aurelius said:


> The turbo doesn't force air through the motor.


- oh, really?


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## Marcus_Aurelius (Mar 1, 2012)

Gulfstream said:


> - oh, really?


Yeah, I see that my wording came out wrong, especially if you are only taking this part of what I was saying. If you take a look at the entire context even with the wrong statement, you can see what was being said (but I'm sure that's not we're after here). Anyway, I fixed the verbage for you.  




Marcus_Aurelius said:


> *The turbo isn't the only thing that forces air through the motor, the turbo compresses the air that is already flowing through the motor and helps it flow more (it affects the flow but it is not the only thing that creates it*, the engine does not stall when you go off boost).


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## Gulfstream (Jul 28, 2010)

Marcus_Aurelius said:


> Yeah, I see that my wording came out wrong, especially if you are only taking this part of what I was saying. If you take a look at the entire context even with the wrong statement, you can see what was being said (but I'm sure that's not we're after here). Anyway, I fixed the verbage for you.



Saul Goodman. :beer:

Turbo is a wonderful tool :thumbup:


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## Vegeta Gti (Feb 13, 2003)

lol


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## mainstayinc (Oct 4, 2006)

Marcus_Aurelius said:


> The turbo isn't the only thing forcing air through the motor. The turbo compresses the air that is already flowing through the motor and *helps it flow more* (it affects the flow but is not the only thing that creates it, the engine does not stall when you go off boost). The reason why a GT35R makes more power than a K04 at the same pressure is because each compressor at a fix pressure flows X CFM. You're blending two things here, ever asked yourself why our motor (independently of boost) rev at the speed that it does, not faster or slower. Once you think about it this way, you'll understand that velocity plays the same role that it does with a NA application as it does when boosted. *The engine character as a pump is not a variable that changes with pressure, it sure does change with port size and velocity however.*


Bingo! Thank you.


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## mainstayinc (Oct 4, 2006)

Look what came in the mail last week. Hmm... I wonder what that could be.










Oh look! It's a brand new from the factory AEB head from Issam:










Notice the nice, brand new, underside.










Large ports look nice!










And here is the project car it is going into (the black 1984 Rabbit GTI) I bought about 10 days ago from a guy in Lancaster, PA.










The interior is perfect! Absolutenly no rips or wear in the seats. New headliner etc. The exterior is in good shape but the clear coat is peeling and there are 1 or 2 small rust spots behind rear wheel well.

The plan is as follows:
1. Built AEB head capable of reving to 8500 - 9000 RPMs.
2. Built bottom end stroked out to 2067cc's.
3. Built 02C (5 speed syncro) transmission with AP Tuning Gearset.
4. FEX center differential from a Skoda Octavia to work with a...
5. Haldex rear coupler and differential.
6. Oh yeah. Almost forgot: GTX4202R turbo on E85 Ethanol.
7. Standalone engine management.

I bought the 02C transmission two years ago and intended to put it into my MK4 GTI (2.1L + GTX2867R on E85) and install the Haldex rear end using an R32 floor pan. However, I couldn't bring myself to cutting up my daily driver. So, when I saw the 1984 Rabbit GTI ("Kleiner GTI) for sale here on vwvortex, I couldn't pass that up. I got the car running last week and it just needs the brakes bleed and the exhaust attached. I intend to spend some money getting the exterior looking brand new. I will keep the stock red-on-red interior since that's perfect. Basically, the car will be completely stock looking to maintain the sleeper (Q car) look. After the outside is re-done, I will probably drive the car around for a couple of months with the original 8V 1.8L engine.

In the meantime, I plan to work on the new engine and transmission out of the car. Previously, I have paid Bill Schimmel (spturbo) to do my engine work. He has done an outstanding job building my 2.1L bottom end and many other things in my MK4. However, I might try and tackle the mechanical upgrades myself this time. This includes upgrading the valve train in the AEB head, boring and stroking the bottom end, installing the upgraded gearset in the 02C. I will have to tap into the vwvortex so-called "knowledge base" (that's you guys) for help with this part. I really don't know what I am doing but am pretty mechanically inclined and want to learn. Unlike the 02M 6 speed transmission, the 02C should drop right into the engine compartment.

Also, I bought Issam's FEX center differential last year to work with the Haldex rear end. That's going to be the really difficult part of this project: installing a Haldex system into an MK1. I know it's been done before and documented. However, the MK1 chassis was never intended to have an AWD version. Hence, the center tunnel will have to modified, the steering rack is in the way of the FEX output flange, and there is no drop in floor pan to make the Haldex work with the MK1 chassis. So, the Haldex install will have to be completely custom. The plan is to buy a wrecked MK1 Audi TT Quattro as a parts car. That way, I can see how the Haldex rear subframe is attached to the car and figure out how to implement that into the Kleiner GTI. I will have to cut and weld custom cross beams and mounting points. Not fun but doable. Also, I need the AWP engine block and other parts from the parts car as the basis for the new engine.

At some point I may start a build thread not so much to document progress, but more so to ask advice. I don't know how to weld, so that would be a good thing to learn and practice in the meantime. I can always pay the local experts to fix my mistakes (spturbo, nothing leaves stock etc.) or complete things that are too difficult for me or that I don't have time to do. After all, I run a business and have a 3rd child on the way. For example, I plan on doing much of the sanding and prep work for the exterior, but pay a local expert to spray and clear coat the car.

I can always put the AEB head on my MK4 and call it a day. After all, my valve seals are leaking on my AWP head and need replacement. That would leave me with a mechanically perfect 2.1L + GTX2867R MK4 that runs on E85 plus a nice, totally original and perfect 1984 Rabbit GTI. I already have some locals interested in buying the MK1 Rabbit. However, seeing that there are more than a few MK1 and MK2 AWD chassis in Europe making over 1000 HP using the 16V 2.0L engine, I thought it would be interesting to make an *American* version using the 1.8T as the basis (i.e.: square headlight version GTI originally built right here in Pennsylvania).

Here is throw back video some of you might remember:






My wife was pretty pissed off when I came home with a second car last week ("what do you need a second car for?"). I don't think she realizes what I plan to do with it. LOL.


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## One-Eight GTI (Jan 5, 2010)

I look forward to seeing a build thread on your soon to be haldex mk1. I would love to have an AWD mk1 with a built 1.8t


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## mainstayinc (Oct 4, 2006)

One-Eight GTI said:


> I look forward to seeing a build thread on your soon to be haldex mk1. I would love to have an AWD mk1 with a built 1.8t


Thanks. An AWD MK1 should be 1000 to 1200 lbs. lighter than an R32 or Audi TT quattro. With the GTX4202R on E85 I plan on making some serious HP. I'm in way over my head with this project. Hopefully I can pull this off with some patience.

EDIT: GTX4202R overlaid with 2067cc displacement.










I'm shooting for P2/P1 = 4.6 or about 52 psi at 8000 RPMs.


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## One-Eight GTI (Jan 5, 2010)

It's a build I'd love to do. Just don't have the knowledge to cut into cars and mend them together into one kick ass car. Losing 1000 pounds would be crazy fun 🏻


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## All_Euro (Jul 20, 2008)

mainstayinc said:


> ...Also, I bought Issam's *FEX center differential* last year to work with the Haldex rear end....


Great thread and props for the work put into the port sizes / velocities vs rpm :beer:

What is this FEX centre differential you speak of? And, yes, definitely start a thread about your MK1 project!


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## mainstayinc (Oct 4, 2006)

All_Euro said:


> Great thread and props for the work put into the port sizes / velocities vs rpm :beer:
> 
> What is this FEX centre differential you speak of? And, yes, definitely start a thread about your MK1 project!


The FEX center differential or, as Issam calls it, the angle drive, has the correct 17/27 tooth count same as the Haldex rear end. The stock Syncro center differential from the 02C has a 20/21 tooth count and will cause problems with the two systems binding. The center differential from an 02M transmission will not bolt up to the 02C either. The FEX center differential from the Skoda Octavia 4x4 solves this problem.

I really like the 5 speed 02C (02A/02J) transmission over the 6 speed 02M due to much better gear ratios. Here is a pic Issam sent me a while back showing the FEX unit:










Glad you like the port velocity analysis:thumbup:. It convinced me of the need for the AEB head for anything over stock redline.


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## mainstayinc (Oct 4, 2006)

One-Eight GTI said:


> It's a build I'd love to do. *Just don't have the knowledge to cut into cars and mend them together into one kick ass car*. Losing 1000 pounds would be crazy fun &#55356;&#57339;


To be sure, I don't have the knowledge either. I've researched a few threads about doing the Haldex conversion, but I really don't know what I'm doing. However, with enough time and patience, I might be able to pull it off. We'll see.


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## Gulfstream (Jul 28, 2010)

Another crazy build. Kinda reminds me of Boba's Mk1 awd Golf. Happy to see you went with a largeport :thumbup:

Make sure you pin the timing gear to the crank.


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## One-Eight GTI (Jan 5, 2010)

Gulfstream said:


> Kinda reminds me of Boba's Mk1 awd Golf..


 Yep exactly, pure bad ass


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## NaSMK4 (Dec 12, 2011)

I guess you could say things are getting pretty serious... over here...

Sorry to thread jack but with all this talk of awd i figured i show off something i've been working on... 

http://imgur.com/6WU6RMF










Build thread to come l8r...


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Another crazy build. *Kinda reminds me of Boba's Mk1 awd Golf*. Happy to see you went with a largeport :thumbup:
> 
> Make sure you pin the timing gear to the crank.


Yes. The Boba Motoring MK1 is the inspiration for this build. Same chassis, same turbo, same fuel. See video below: 






Although he uses an 02M 6 speed transmission. The 02C (02A/02J) is better geared IMO for higher horsepower applications (but, of course, is not a strong. Hence, the need to install a stronger gearset and bracing). I have to decide whether to use a roll cage or not. I should install just for safety since the MK1 pre-dated much of the safety systems today. But, that would take away from sleeper appearance.

Largeport FTW:thumbup:

BTW, I don't ever expect to have the overall refinement of that car. All the investment in ths build will go into the engine, turbo, drivetrain, fueling etc. The interior and exterior will be left stock as much as possible. The car will be built as a street car and I don't plan to track in the near future. But that could change.


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## mainstayinc (Oct 4, 2006)

NaSMK4 said:


> I guess you could say things are getting pretty serious... over here...
> 
> Sorry to thread jack but with all this talk of awd i figured i show off something i've been working on...
> 
> http://imgur.com/6WU6RMF


That looks like a proper AWD conversion. I don't even have an enclosed garage to do the work. Is that a custom built hydraulic jack or purchased off-the-shelf?


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## All_Euro (Jul 20, 2008)

mainstayinc said:


> That looks like a proper AWD conversion. *I don't even have an enclosed garage to do the work.* Is that a custom built hydraulic jack or purchased off-the-shelf?


Extra cred given for building without


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## ticketed2much (Feb 18, 2012)

NaSMK4 said:


> I guess you could say things are getting pretty serious... over here...
> 
> Sorry to thread jack but with all this talk of awd i figured i show off something i've been working on...
> 
> http://imgur.com/6WU6RMF




Any other pics? Going to start a build thread?


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## mainstayinc (Oct 4, 2006)

All_Euro said:


> Extra cred given for building without


Ha ha. I'll be feezing my butt off this winter in a garage tent with a heater. Hopefully, this warm weather will continue in the NE, but not likely.


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## Gulfstream (Jul 28, 2010)

mainstayinc said:


> Yes. The Boba Motoring MK1 is the inspiration for this build. Same chassis, same turbo, same fuel. See video below:
> 
> 
> 
> ...


Props to you for going balls deep with this build. You wont see anything before 6k rpm but 6-9k WILL be something different. 

opcorn:

Be prepared to double or even triple your initial budget. These builds are for deep deep pockets done right.






With a dogbox you won't be beat on the street:


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## mainstayinc (Oct 4, 2006)

Gulfstream said:


> Props to you for going balls deep with this build. You wont see anything before 6k rpm but 6-9k WILL be something different.
> 
> opcorn:
> 
> ...


Thanks. The power curve will definitely be different from my current setup (2.1L + GTX2867R + E85). I basically have insta-spool with this setup. I recently tested my new chemical intercooling setup and am getting 31psi by 3000 RPMs (see below). I held 31 psi to 5800 RPMs (before I ran out of highway) but VCDS didn't record that last data point. And I just found out yesterday that I have a massive exhaust leak due to a gasket failure between my ATP turbo manifold and my 38mm wastegate. It's blowing out hot exhaust like a hair dryer.










Good thing my 02J transmission with AP Tuning race gearset is holding up to this kind of low-RPM torque (so far, at least). I will install the same gearset in my 02C with FEX differential since I have been getting good results.

I am hoping for a 3000 RPM power curve from the GTX4202R between 5500 and 8500 RPMs (or, perhaps 6000 to 9000 RPMs). The car will be driven most of the time below stock redline (<6500 RPMs). I will either install a boost valve that is common on diesel applications that use a divided T4 turbine housing (see below) or install a nitrous controller to assist spoolup on the GTX42 frame turbo.










The nitrous controller will be a piece of cake since I already wired and installed a system on my Mk4. Also, since I am a big fan of exhaust cutouts, I will install a 3.5 or 4 inch on this new project.

Have no doubt about it. Most people who take on this kind of project don't complete it due to various reasons (career change, marriage, moving etc.). It's sad to see a lot of good build threads that are started and never completed for one reason or another. Hopefully, I am not one of those people.

Yeah. Budget-wise, this will be expensive. I was checking out IE's valve train upgrades last night. It's going to be at least $1600 to $1800 just to upgrade the valve train components. But... I plan to try and tackle a lot of the labor myself. After watching a few videos last night and doing some research, I feel optimistic about disassembling and installing new components on the new AEB head. If I get time, I'll start a new build thread so as not to threadjack other people's stuff.

Expensive, yes. The turbo will cost 1.5 times what I paid for the MK1 Rabbit.


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## ticketed2much (Feb 18, 2012)

mainstayinc said:


> Have no doubt about it. Most people who take on this kind of project don't complete it due to various reasons (career change, marriage, moving etc.). It's sad to see a lot of good build threads that are started and never completed for one reason or another. Hopefully, I am not one of those people.


Me too, it would be awesome to see one of these built locally.



mainstayinc said:


> Yeah. Budget-wise, this will be expensive. I was checking out IE's valve train upgrades last night. It's going to be at least $1600 to $1800 just to upgrade the valve train components. But... I plan to try and tackle a lot of the labor myself. After watching a few videos last night and doing some research, I feel optimistic about disassembling and installing new components on the new AEB head. If I get time, I'll start a new build thread so as not to threadjack other people's stuff.
> 
> Expensive, yes. The turbo will cost 1.5 times what I paid for the MK1 Rabbit.


Plus all the custom parts you will need to make a TT Haldex work on a MK1, nothing is going to fit. Have you thought about which controller you will use?

Looking forward to the build thread.


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## mainstayinc (Oct 4, 2006)

ticketed2much said:


> Me too, it would be awesome to see one of these built locally.
> 
> 
> 
> ...


I want to keep the Haldex system simple as possible. The wiring harness for a proper Haldex system is pretty intimidating, with accelerometers, speed sensors etc. I really don't want or need a smart AWD system. I just need a system to be able to launch and then turn off when the car comes up to speed or stay on all the time. So, the plan is to either have a simple on/off switch or have the standalone engine management (or even the nitrous controller) output 12v to the Haldex unit for complete engagement of the coupler.

I can have the standalone engine management (or nitrous controller) trigger the Haldex unit if certain criteria are met, such as TPS>50% or MAP > 1 bar. That way, the Haldex system will engage when I need it (and not when a computer decides wheels are slipping).

Not sure if this is possible. But I think it's been done before.

Nice to see you're local. The closest E85 station is in Allentown. So, I travel up there periodically.


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## sleepy1.8t (Sep 5, 2013)

mainstayinc said:


> I want to keep the Haldex system simple as possible. The wiring harness for a proper Haldex system is pretty intimidating, with accelerometers, speed sensors etc. I really don't want or need a smart AWD system. I just need a system to be able to launch and then turn off when the car comes up to speed or stay on all the time. So, the plan is to either have a simple on/off switch or have the standalone engine management (or even the nitrous controller) output 12v to the Haldex unit for complete engagement of the coupler.
> 
> I can have the standalone engine management (or nitrous controller) trigger the Haldex unit if certain criteria are met, such as TPS>50% or MAP > 1 bar. That way, the Haldex system will engage when I need it (and not when a computer decides wheels are slipping).
> 
> ...


I don't know about the space requirements, but would a Torsen setup be more what you are looking for, as opposed to Haldex?

Also, I know this isn't your thread, but I do enjoy reading your posts. Lots of good information. Cheers!


edit: ah, i answered my own question, there aren't any transverse torsen setups because legal reasons. you would probably experience less hassle doing what you're doing.


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## mainstayinc (Oct 4, 2006)

sleepy1.8t said:


> I don't know about the space requirements, but would a Torsen setup be more what you are looking for, as opposed to Haldex?
> 
> Also, I know this isn't your thread, *but I do enjoy reading your posts. Lots of good information. Cheers!*
> 
> ...


Thanks. I try and post relevant information here. I thought about doing an Audi longitudinal setup in this car since that system is more stout. But, that would be way way over my head (versus just being way over my head with the Haldex conversion) . I figure that if the Haldex rear end can stand up to R32 weight (about 3400 lbs. I think), then it should be fine with a 2000 to 2200 lb. MK1 setup.


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## ExtremeVR6 (Sep 6, 2001)

Does manifold capacity effect things in a forced induction scenario as much as it does in NA applications? It's surprised be that with all the discussion on the port sizes and runners, that there hasn't been any discussion to the air "tank" immediately preceding those runners.... But then I realized that with the level of knowledge involved, it may be an unspoken point of understanding. 

I'm also surprised that a comparison between a ko4 @25psi and a GT35 @25psi was made with a request to explain why one makes more power... Ehm... Because it's flowing tons more air at the same pressure ratio. Was that the point of the request? Again, may have been many unvoiced points of assumed understanding. 

Ps. I freaking love post like this! I'll probably reread it a number of times for digestion of so many salient explanations!


Oozed from a pustule of thought somewhere within the recesses of my mind...


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## mainstayinc (Oct 4, 2006)

ExtremeVR6 said:


> Does manifold capacity effect things in a forced induction scenario as much as it does in NA applications? It's surprised be that with all the discussion on the port sizes and runners, that there hasn't been any discussion to the air "tank" immediately preceding those runners.... But then I realized that with the level of knowledge involved, it may be an unspoken point of understanding.
> 
> I'm also surprised that a comparison between a ko4 @25psi and a GT35 @25psi was made with a request to explain why one makes more power... Ehm... Because it's flowing tons more air at the same pressure ratio. Was that the point of the request? Again, may have been many unvoiced points of assumed understanding.
> 
> ...


:beer::beer::beer:

As far as manifold capacity, I think 1.5x to 1.75x engine displacement will suffice to keep the cylinders supplied. My SEM manifold has a published volume of 2.75L which is about 1.5x stock displacement. The IE unit looks larger. Maybe others can chime in.


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## ExtremeVR6 (Sep 6, 2001)

I had read the same thing with regards to manifold volume vs engine displacement ... I'd be curious to know how the AEB manifold compares to the ATW manifold with respect to manifold volume... For some reason it's not hard for me to imagine that the volume is very similar and the only differences that are being seen are due to either larger valves or faster flow velocities when a contributing factor may be the manifold volume. In addition, it would seem like the x1.5 - 1.75% cid rule of thumb may be for gross design standards. Then mani volume would then be further adjusted with respect to runner length and valve size... after all, very few of these things are dependent on a single variable. 

From what I understand, you can offset slow flow with high velocity flow. It would seem reasonable that VAG engineers had compensated the decrease in runner/valve size with the Venturi to both maintain similar power output goals while improving emissions and fuel economy. 

I imagine this would be a part of the rest of the discussion that happened before... But a lot of it has to do with the purpose for the build and expected usable power band. If building a drag car, you really won't worry much about low end tq, you really want as much top end flow as possible. However, if your road racing, you'll want the widest power band you can get. It would seem to be the real discussion should be... Can either manifold be massaged to provide the best possible result, or where budget may be a concern, which manifold can be made to perform best given similar expenditure. Then, of course, how does that cost compare to the cost of those re-engineered intake manifolds out there (SEM, Innovative, etc). I followed IE's development thread on their manifold (which was fascinating!) but is there more engineering that can be done? I kinda doubt it given the resources and effort put into IE's project.


Oozed from a pustule of thought somewhere within the recesses of my mind...


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## ticketed2much (Feb 18, 2012)

ExtremeVR6 said:


> I'm also surprised that a comparison between a ko4 @25psi and a GT35 @25psi was made with a request to explain why one makes more power... Ehm... Because it's flowing tons more air at the same pressure ratio. Was that the point of the request? Again, may have been many unvoiced points of assumed understanding.


I can't see how all things being equal two turbos would make more power/ flow more air at the same PSI/RPM. Don't bigger turbos make more power because they keep flowing more up top than a smaller turbo? Obviously if other things are different such as intercoolers, injectors there would be a difference.



ExtremeVR6 said:


> I imagine this would be a part of the rest of the discussion that happened before... But a lot of it has to do with the purpose for the build and expected usable power band. If building a drag car, you really won't worry much about low end tq, you really want as much top end flow as possible. However, if your road racing, you'll want the widest power band you can get. It would seem to be the real discussion should be... Can either manifold be massaged to provide the best possible result, or where budget may be a concern, which manifold can be made to perform best given similar expenditure..


Good point


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## ExtremeVR6 (Sep 6, 2001)

ticketed2much said:


> I can't see how all things being equal two turbos would make more power/ flow more air at the same PSI/RPM. Don't bigger turbos make more power because they keep flowing more up top than a smaller turbo? Obviously if other things are different such as intercoolers, injectors there would be a difference.


All things being equal to the size of the turbos itself that makes all the difference. In essence you're right with respect to one size engine one displacement being considered. However when you consider the amount of airflow is that a particular turbo can provide it's more about volumetric flow as a whole. While at 1.8T engine has no trouble spooling a KO3, it would have a much harder time schooling a GT45 full frame turbo. The thing is a GT45 turbo could easily flow the same amount of air at 5psi as the K03 could at 18 psi. Now I'm kind of just pulling numbers out of air. 

Look at it like this the goal is to have enough airflow to be able to create more horsepower a smaller turbo must work a lot harder to provide the same amount of air through the engine as a much larger turbo would. So for KO three to be able to support 250 hp it has to compress The air to something like 30 or higher psi. However if you were to use a GT30R, it'll be able to support 250hp at something much more reasonable 15psi on the same sized engine. 


Oozed from a pustule of thought somewhere within the recesses of my mind...


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## ticketed2much (Feb 18, 2012)

ExtremeVR6 said:


> Look at it like this the goal is to have enough airflow to be able to create more horsepower a smaller turbo must work a lot harder to provide the same amount of air through the engine as a much larger turbo would. So for KO three to be able to support 250 hp it has to compress The air to something like 30 or higher psi. However if you were to use a GT30R, it'll be able to support 250hp at something much more reasonable 15psi on the same sized engine.
> 
> 
> Oozed from a pustule of thought somewhere within the recesses of my mind...


It's hard to compare a K03 to a BT. Most people who go big turbo upgrade to bigger intake, intercooler, aeb head, and better exhaust manifold allowing 15psi to flow more air than in a stock configuration. Plus that 15psi is usually at a higher rpm allowing more flow. It seems like 15psi at the stock manifold would be the same no matter how efficient the turbo is.


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## NaSMK4 (Dec 12, 2011)

ticketed2much said:


> It's hard to compare a K03 to a BT. Most people who go big turbo upgrade to bigger intake, intercooler, aeb head, and better exhaust manifold allowing 15psi to flow more air than in a stock configuration. Plus that 15psi is usually at a higher rpm allowing more flow. It seems like 15psi at the stock manifold would be the same no matter how efficient the turbo is.


there is no use in comparing the two k03 does not have the breath to push the amount of air needed to fill these upgrades you're talking about this would be wasted breath imagine blowing up a football field sized air mattress with just your human lungs.... thats how that k03 is going to feel with all those upgrades... this maybe exaggerated a bit but essentially it gets across the point that a k03 with all those bigger things is pointless.


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## ExtremeVR6 (Sep 6, 2001)

It may be hard to compare one build to another to determine which manifold might be better... But turbo to turbo, it's easy. Thing is though, if you've got an aim for 300 horsepower, the turbo is the best place for you to start, the rest of those mods to mentioned only make it easier to get to your target with a smaller turbo, or more efficiently. 


Oozed from a pustule of thought somewhere within the recesses of my mind...


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## ExtremeVR6 (Sep 6, 2001)

ticketed2much said:


> I can't see how all things being equal two turbos would make more power/ flow more air at the same PSI/RPM. Don't bigger turbos make more power because they keep flowing more up top than a smaller turbo?


I was replying to this question... Bigger turbos don't just flow more air up top... There's an entirely completely different dynamic in behavior between differently sized turbochargers. The turbine will make a huge difference, but it's he compressor side that gets most of the attention.


Oozed from a pustule of thought somewhere within the recesses of my mind...


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## mainstayinc (Oct 4, 2006)

ticketed2much said:


> It's hard to compare a K03 to a BT. Most people who go big turbo upgrade to bigger intake, intercooler, aeb head, and better exhaust manifold allowing 15psi to flow more air than in a stock configuration. *Plus that 15psi is usually at a higher rpm allowing more flow.* It seems like 15psi at the stock manifold would be the same no matter how efficient the turbo is.


Yes. 15psi boost at 6500 RPMs is more air flow than 15psi at 4500 RPMs and, hence, more horsepower. Below is a nice calculator that calculates peak horsepower based on displacement, engine speed and boost.

http://www.mk5cortinaestate.co.uk/calculator3.php

Plugging in the following data:

Displacement: 1781cc
Aspiration Type: Turbocharged/Supercharged
Volumetric Efficiency: 15 psi
Peak Power Engine Speed: *4500 RPMs*

*You get 191 HP*

Compared to:

Displacement: 1781cc
Aspiration Type: Turbocharged/Supercharged
Volumetric Efficiency: 15 psi
Peak Power Engine Speed: *6500 RPMs*

*You get 275 HP*. That's an increase of 84 HP.

Also, most people ignore intake temperatures. To accurately compare two different setups, you have to adjust boost to ambient temperature (21C or 70F) using the absolute temperature scale. The cooler the intake charge (i.e. the more efficient the turbo and intercooler), the more power. In other words, a maxed out K03S spewing out hot lava at 7000 RPMs has much less power than a BT properly cooled at the same boost and engine speed.

Below I re-posted my boost chart from above but added intake temperature. Notice that my chemical intercooler worked so well, that it cooled the charge temperature to -4 C at 3300 RPMs. 










Adjusting for temperature, the adjusted boost was actually about 34 psi at 3000 RPMs (see below).










Plugging in the adjusted boost and comparing it to the original boost in the above calculator yields a 14 HP increase at 3000 RPMs


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## groggory (Apr 21, 2003)

That was a very cool last post. What calculations did you use to adjust boost for temperature?


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## mainstayinc (Oct 4, 2006)

groggory said:


> That was a very cool last post. What calculations did you use to adjust boost for temperature?


Take intake temperature (in celcius) and add 273.15 to get degrees Kelvin. Divide 294.15 (21 C or ambient temperature) by your intake temperature in degrees Kelvin. Multiplyl this ratio by your boost pressure (measured in abolute pressure: 14.7 atmosphere + boost pressure). That will yield your boost adjusted to ambient temperature.


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## groggory (Apr 21, 2003)

mainstayinc said:


> Take intake temperature (in celcius) and add 273.15 to get degrees Kelvin. Divide 294.15 (21 C or ambient temperature) by your intake temperature in degrees Kelvin. Multiplyl this ratio by your boost pressure (measured in abolute pressure: 14.7 atmosphere + boost pressure). That will yield your boost adjusted to ambient temperature.


Very cool. Updated my Vag com thread
http://forums.vwvortex.com/showthread.php?5487610-FAQ-1-8t-Vag-Com-Tips-and-Tricks&p=74388884

I need to revamp that thread one of these days. It's a bit rough around the edges.


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## The Dubbernaut (Feb 1, 2010)

So after reading this, I have some questions for you experts...


Where do the different stock AWP and AEB heads like to perfom? With stand alone fuel management? Would one perform better with a 6sp? What style of performance tuning does one like over the other? (street/drag/auto-X)


I ask because Ive been out of the country for a decade in the Marines. Ive been finding parts and pieces to build a big engine MK1 rabbit over the years and Ive ended up with a 1.8t with a 2.0 crank, AWP and AEB head, and the MK1. Before I get too far into this, I wanted to read through some posts and see where the different heads liked to live, stree/auto-x/drag, and learn as much as I can. I read through this post and while some things were understandable, some debates werent and I got a little lost in the technical side of things. When I was collecting parts, at the time the 20v head was THE THING to get! So I got one asap! Then I bought a complete AWP engine minus the turbo. So there are my questions. I just want to know what different types of performance builds the two heads like. I dont mind what I build, I just want to work on VW's :beer:


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## sleepy1.8t (Sep 5, 2013)

The Dubbernaut said:


> So after reading this, I have some questions for you experts...
> 
> 
> Where do the different stock AWP and AEB heads like to perfom? With stand alone fuel management? Would one perform better with a 6sp? What style of performance tuning does one like over the other? (street/drag/auto-X)
> ...


Wooo lucky man, you have what you need to start basically _anything_. 

Maybe the more pertinent question should be, what peaks your interest the most? You can do a lot of things with what you have already collected.


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## mainstayinc (Oct 4, 2006)

The Dubbernaut said:


> So after reading this, I have some questions for you experts...
> 
> 
> Where do the different stock AWP and AEB heads like to perfom? With stand alone fuel management? Would one perform better with a 6sp? What style of performance tuning does one like over the other? (street/drag/auto-X)
> ...


^^I agree. You can do a lot of things with those parts and the MK1 platform. For a street or auto-x car, I would consider the first generation GTX2863R or second generation GTX2860R for 450 HP on 2.0L with the AWP head. You won't need to rev past 6500 RPMs to get the most out of those turbos on 2.0L's. The AWP head will give you more torque down low as compared to the AEB head as explained in this thread. I would also consider the first or second generation GTX2867R on 2.0L for 475+ HP. It doesn't take a lot to motivate the lightweight MK1 Rabbit. So, with those power levels, you will be extremely fast on the street or track. You will definitely have traction issues in first and second gear and possibly third gear if you push this setup.

If you want to go bigger, say 71mm or larger, then I would consider replacing the AWP with the AEB head. That will allow you to comfortably rev the motor to 9000+ RPMs without choking and make for a killer street setup or drag car. Even with a stock K03 or K04 turbo, the MK1 will be extremely fun to drive on the street. You can go in a lot of different directions with those parts. I just depends on what you want to do.


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## The Dubbernaut (Feb 1, 2010)

sleepy1.8t said:


> Wooo lucky man, you have what you need to start basically _anything_.
> 
> Maybe the more pertinent question should be, what peaks your interest the most? You can do a lot of things with what you have already collected.


I think thats my weakness. Having the opportunity to build anything. lol

I think Id like to build a daily driver which doesnt need special gas, something that will accept sequential shift at some point along with AWD. I understand thats is a much bigger/different build than what I mentioned earlier but Im patient, and finding those parts over the next few years is fine by me. Id like a daily driver that will essentially murder anything I come across on the road. I want to remove the rear seat set to make a bench seat for my caddy  

I know I need the trans mount to adapt the 6sp to the MK1 chassis but cant remember where to get them. Any tips on whos on top of the market for HD engine mounts?


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## The Dubbernaut (Feb 1, 2010)

mainstayinc said:


> ^^I agree. You can do a lot of things with those parts and the MK1 platform. For a street or auto-x car, I would consider the first generation GTX2863R or second generation GTX2860R for 450 HP on 2.0L with the AWP head. You won't need to rev past 6500 RPMs to get the most out of those turbos on 2.0L's. The AWP head will give you more torque down low as compared to the AEB head as explained in this thread. I would also consider the first or second generation GTX2867R on 2.0L for 475+ HP. It doesn't take a lot to motivate the lightweight MK1 Rabbit. So, with those power levels, you will be extremely fast on the street or track. You will definitely have traction issues in first and second gear and possibly third gear if you push this setup.
> 
> If you want to go bigger, say 71mm or larger, then I would consider replacing the AWP with the AEB head. That will allow you to comfortably rev the motor to 9000+ RPMs without choking and make for a killer street setup or drag car. Even with a stock K03 or K04 turbo, the MK1 will be extremely fun to drive on the street. You can go in a lot of different directions with those parts. I just depends on what you want to do.


I think 450hp was my original goal. Ive changed it up so many times with different builds Ive seen and different shifts in "scene" performance. Ive had to restrict myself from going balls deep in turbo articles and study because I was finishing school and deployed. Any suggestions on good articles that break down turbo sizing and application? I love research so share away if anyone has the good stuff! 

Like I mentioned to Sleepy, Id like to go 4mo at some point with a sequential shift/dog box setup at some point. For personal goals, Id like to build big engine BT first, and then broaden my mechanical horizons. I know that Ill have to down-tune the car at first to keep traction under the rig. Learnt that on street outlaws....Im pretty much a pro tuner now. 

Im also looking for a head that I can run on an MK1 GTI block. Will these fit that block or am I in need of some 16v soul searching? 

Thanks for the response guys!


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## ticketed2much (Feb 18, 2012)

mainstayinc said:


> Also, most people ignore intake temperatures. To accurately compare two different setups, you have to adjust boost to ambient temperature (21C or 70F) using the absolute temperature scale. The cooler the intake charge (i.e. the more efficient the turbo and intercooler), the more power. In other words, a maxed out K03S spewing out hot lava at 7000 RPMs has much less power than a BT properly cooled at the same boost and engine speed.
> 
> Below I re-posted my boost chart from above but added intake temperature. Notice that my chemical intercooler worked so well, that it cooled the charge temperature to -4 C at 3300 RPMs.
> 
> ...



Missed this back when you posted it. Were you using meth? and E85? Didn't realized lower IATs could mean more HP either. Interesting since many people don't use meth with E85.


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## sleepy1.8t (Sep 5, 2013)

The Dubbernaut said:


> Im also looking for a head that I can run on an MK1 GTI block. Will these fit that block or am I in need of some 16v soul searching?



?? thought you said you have a complete awp


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## Jeffsvw (Mar 23, 2017)

*IE Manifold*

Does anyone know if Integrated manifold will fit a mk1 on 1.8t motor? Without Hood closing issues? Don't want to purchase this and run into complications. I can't seem to find any pictures either or info on this. Ive seen the SEM Manifold in a mk1 and custom manifolds but not big like the IE one.


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## mainstayinc (Oct 4, 2006)

ticketed2much said:


> Missed this back when you posted it. Were you using meth? and E85? Didn't realized lower IATs could mean more HP either. Interesting since many people don't use meth with E85.


I was using a CO2 dry shot through a NOS injector mounted on my intercooler while running E85 through my regular fuel injectors. As you can see from that graph, I had pretty darn good results. It also gave me crazy spoolup since it reduced pressure downstream (30+ psi by 3000 RPMs!). I wanted to extend the cooling potential of the CO2 by combining it with E85 from my fuel tank through a fogger nozzle making it a wet shot. However, that experiment came to a sudden stop when I hydro-locked my engine due to the NOS fuel solenoid getting stuck open. Bill at SPTurbo is completely rebuilding that engine as we speak. I was not using Methanol on that setup (MK4 daily driver).

Yes, lower IAT's = more HP.

However, on my MK1 I plan to implement version 2.0 of this system. It will use Methanol instead of E85 in the fuel tank to make the wet shot. I plan to use the CO2 bottle to pressurize a second bottle filled with a water/methanol solution. Methanol has better cooling qualities as compared to ethanol. The system will not require a pump to pressurize the water/methanol since that is supplied from the CO2 tank. Except that pressure will be 900+ psi versus 150 psi or whatever a pump can produce. That will help atomize the W/M better. Also, the CO2 will help atomize the W/M through a fogger nozzle as before. So, this system will indeed use Methanol with E85.

After that, I plan to take the next step and start mixing in some N2O into the equation. N20 changes phase at an even lower temperature than CO2 making it an excellent chemical cooler. The final form of my chemical intercooling system might be something like 25% CO2 + 25% N2O + 40% Methanol + 10% water. The CO2 will help cool the combustion chamber and will make for a much safer nitrous shot. I can always increase the percentage of N2O if I am feeling brave and want more power.


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## mainstayinc (Oct 4, 2006)

The Dubbernaut said:


> I think thats my weakness. Having the opportunity to build anything. lol
> 
> I think Id like to build a daily driver which doesnt need special gas, something that will accept sequential shift at some point along with AWD. I understand thats is a much bigger/different build than what I mentioned earlier but Im patient, and finding those parts over the next few years is fine by me. Id like a daily driver that will essentially murder anything I come across on the road. I want to remove the rear seat set to make a bench seat for my caddy
> 
> I know I need the trans mount to adapt the 6sp to the MK1 chassis but cant remember where to get them. * Any tips on whos on top of the market for HD engine mounts*?


Check out S&P Automotive.


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## The Dubbernaut (Feb 1, 2010)

sleepy1.8t said:


> ?? thought you said you have a complete awp


Yes, I have a complete AWP and AEB head. The one I dont use Id like to put on my 1.8l caddy engine. Its a GTI motor with a 5sp I just rebuilt. If Im not using one of the heads, Id like to put it on my MK1 block if itll fit. That was my question, sorry for not being clear.


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## ticketed2much (Feb 18, 2012)

mainstayinc said:


> I was using a CO2 dry shot through a NOS injector mounted on my intercooler while running E85 through my regular fuel injectors. As you can see from that graph, I had pretty darn good results. It also gave me crazy spoolup since it reduced pressure downstream (30+ psi by 3000 RPMs!). I wanted to extend the cooling potential of the CO2 by combining it with E85 from my fuel tank through a fogger nozzle making it a wet shot. However, that experiment came to a sudden stop when I hydro-locked my engine due to the NOS fuel solenoid getting stuck open. Bill at SPTurbo is completely rebuilding that engine as we speak. I was not using Methanol on that setup (MK4 daily driver).
> 
> Yes, lower IAT's = more HP.


Wow that's awesome. That's all I can say because the rest is way out of my knowledge base! Can't wait to see your results!


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## mainstayinc (Oct 4, 2006)

ticketed2much said:


> Wow that's awesome. That's all I can say because the rest is way out of my knowledge base! Can't wait to see your results!


:thumbup: Thanks, man. Hopefully I don't blow another motor.


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