# +500 whp on a 3" downpipe/exhaust VRT?



## Lindahl (Feb 16, 2009)

How much is the flowing capability of a complete 3" exhaust on a VRT in whp?
ATP exhaust manifold, GT3582 1.06 with ATP T4 exhaust housing, Tial 38 mm wastegate with screamer pipe, and the mentioned 3" exhaust, consisting of 100 cell catalytic converter and a single muffler at the end.
The reason I ask is, that I´m considering adding a set of SP 263 camshafts to the setup, but if the upper limit of the exhaust system is around 435-440 whp, it seems like a waste to go for more aggresive cams, as this can easily be made on the present set-up. If on the other hand a 3" exhaust system will support 470-480 whp, I think I´ll opt for the SP´s.

Another quick question: Any body in here that knows the upper whp limit of the Bosch 005 internal fuel pump on a VRT? 034motorsport says around 208 lt/hr @ 75 lbs. How many whp does that approximately equals?


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## 05JettaGLXVR6 (Jan 25, 2006)

I made [email protected] 20psi on a full 3in with one muffler. Really quiet exaust. Todd Pavic's made 700+whp on a full 3in few weeks ago.

Dont bother with the cat. use the muffler tho. Any cams will help. bigger the better the 288's woke my vrt up.


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## xpalendocious (Nov 28, 2003)

ive made 575+whp with a 3" turbo back.

any reason you dont want to use a bosch 044 fuel pump? seems to be a more popular upgrade


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## Lindahl (Feb 16, 2009)

That sound good. Then I can switch to the SP 263 with good concious 
The cat. is a neccesity, as it is one of the first things the henchmen of the state looks for, and they seem quite aggresive these days 

The reason for choosing the 005 fuel pump is that this is the biggest internal fuel pump sold by Bosch where I live. After having tried several different fuel pump set-ups, I have come to the decision that one internal pump is more reliable (and less noisy) than both an internal and an external pump.
Most tuners use rule of thumb when they guestimate whether a pump is big enough, but tuners have different solutions to the math. Some say if you multiply the lt/h with 2,5 you´ll have a safe indicator of how many crank horsepower you can make. Multiply with 2,8 and you loose the safety. Others talk about multiplying with 3. In the case of 005, these numbers equal 520 bhp, 582 bhp and 624 bhp respectively.
So that´s a huge difference, especially because 520 bhp should be well within reach when using the SP 263´s with the rest of the setup.
But if neccesary, I´ll buy a 044 and mate it with the 005.


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## TBT-Syncro (Apr 28, 2001)

the max power of the pump is also going to be determined by the boost pressure it takes you to get there. there are lots of pumps that will flow 1000hp NA, but only 500-600 with Forced Induction (since line pressure raises along with boost pressure).

for anyone over 500hp, i'd also suggest going to a surge setup, with non-oem (i.e. larger feed and return lines). 

:beer:

(and i agree with the others have said about exhaust size, 3" will be fine for your goals).


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## xpalendocious (Nov 28, 2003)

use the oem intake fuel pump as a "transfer pump" and then get a 044 pump with an integrated engineering surge tank, and now you have a fuel solution that will supply 550whp, not starve in turns, keep your oem gauge sender, and be rather quiet.


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## Rheinland Technik (Apr 2, 2010)

there is plenty of potential for high horse power on 3" exhaust. A good fuel supply is key, along with proper engine management. The car below ran SDS and an Aeromotive 1000 pump.


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## kevhayward (Mar 13, 2007)

Lindahl said:


> The reason I ask is, that I´m considering adding a set of SP 263 camshafts to the setup, but if the upper limit of the exhaust system is around 435-440 whp, it seems like a waste to go for more aggresive cams, as this can easily be made on the present set-up. If on the other hand a 3" exhaust system will support 470-480 whp, I think I´ll opt for the SP´s.
> 
> Another quick question: Any body in here that knows the upper whp limit of the Bosch 005 internal fuel pump on a VRT? 034motorsport says around 208 lt/hr @ 75 lbs. How many whp does that approximately equals?



I liberated 40whp with SP 263 cams over stock profile. And that's on a 3" DP -> 3" ATP cat (Magnaflow) -> 2.5" Techtonics single Borla. With a full 3", I suspect you could find 50-60whp. Less back pressure = Less exhaust reversion = 10% more advance + more power.

Or you could go side exit and find even more.

Best way to go is 4 or 5" turbine outlet chamber = max gas expansion = exhaust bore from there not so important.


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## vrtme (Mar 29, 2009)

when i build my turbo im thinking of useing 4" all the way down the tunnel. 1 foot away from the rear axal and drop to 3" should be quite simple and shouldn't cost to much


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## Lindahl (Feb 16, 2009)

kevhayward said:


> Or you could go side exit and find even more.
> 
> Best way to go is 4 or 5" turbine outlet chamber = max gas expansion = exhaust bore from there not so important.


Can you elaborate on this? I´m not sure I understand what you mean with "go side exit"?
What do you mean with turbine outlet chamber? Is this the exhaust housing or downpipe, or something completely other?


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## charlie hayes (Jun 4, 2007)

Side exit exhaust. 










Probably not needed to see 500whp. And not that practical for street driving but it would help out. :thumbup:


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## vrtme (Mar 29, 2009)

its all there mate. the best exhaust design for a turbo car is pritty much no exhaust at all. much easyer for it to spool up and the lesser restriction in the exhaust and the lesser the backpressure the freeer the turbo is to spin up quicker and to its high rpm.. thats the way i see it anyway.

think the the perfix down pipe is like 5" getting wider and wider or somthing like that. but it just isn't possible


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## SlammedGolfIII (Nov 18, 2003)

Rheinland Technik said:


> there is plenty of potential for high horse power on 3" exhaust. A good fuel supply is key, along with proper engine management. The car below ran SDS and an Aeromotive 1000 pump.


That a T66?


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## Lindahl (Feb 16, 2009)

vrtme said:


> its all there mate. the best exhaust design for a turbo car is pritty much no exhaust at all. much easyer for it to spool up and the lesser restriction in the exhaust and the lesser the backpressure the freeer the turbo is to spin up quicker and to its high rpm.. thats the way i see it anyway.
> 
> think the the perfix down pipe is like 5" getting wider and wider or somthing like that. but it just isn't possible


That much I know. I was just unsure what the term side exit covered, but I see it´s a sidepipe in front of the front tires 
Doesn´t the one on the pic have problems with the exhaust melting the tires, or just an easy way to make them more sticky?! :laugh:
I think 4" is about the biggest downpipe that will fit the mk3, but when you talk about turbine outlet chamber is that just the first part of the downpipe, so you could start out with 5", and then narrow it down to 4" just before the downpipe exits the engine bay? The next problem I see is, that not a lot of turbos comes with a 4" or 5" outlet, but would a larger downpipe still affect back pressure in a positive way (reduce)?


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## Rheinland Technik (Apr 2, 2010)

Precision PT74


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## SlammedGolfIII (Nov 18, 2003)

Aaahhh gotcha.:thumbup:


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## _muppet_ (Aug 5, 2004)

If you have an emissions "guy" you could get one of these.

http://www.siliconeintakes.com/product_info.php?products_id=320




Rheinland Technik said:


>


Not to get off topic, but whose car is this? I would love to know more about the tune, as I am currently trying to tune my vrt on sds as well.


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## Lindahl (Feb 16, 2009)

_muppet_ said:


> If you have an emissions "guy" you could get one of these.
> 
> http://www.siliconeintakes.com/product_info.php?products_id=320


That´s pretty smart, provided that the car still keep with the emission standard.


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## _muppet_ (Aug 5, 2004)

It probably will, most 500whp vr's do :laugh: (that's sarcasm if you couldn't tell )


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## Rheinland Technik (Apr 2, 2010)

_muppet_ said:


> Not to get off topic, but whose car is this? I would love to know more about the tune, as I am currently trying to tune my vrt on sds as well.


The car belonged to 2008CC - Dave - and was tuned by Kevin Black, who is in PA and would be the best person to talk to about tuning your SDS.


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## _muppet_ (Aug 5, 2004)

I have heard that quite a few times, I saw some of his work moving down the track at last years pittsburgh classic. I missed him this year, I was in north carolina the week of the classic. Might have to wait until spring, but it seems like he is the man to talk to.


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## SoFarKingFast (Jul 9, 2003)

TBT-Syncro said:


> there are lots of pumps that will flow 1000hp NA, but only 500-600 with Forced Induction (since line pressure raises along with boost pressure).


Line pressure doesn't go up with boost pressure. 4bar NA = 4bar FI, it just flows faster.


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## charlie hayes (Jun 4, 2007)

SoFarKingFast said:


> Line pressure doesn't go up with boost pressure. 4bar NA = 4bar FI, it just flows faster.


I thought fuel pressure was a 1:1 ratio with boost. Or does it depend on the regulator you have?


And how would it flow faster without raising pressure?


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## SoFarKingFast (Jul 9, 2003)

charlie hayes said:


> I thought fuel pressure was a 1:1 ratio with boost. Or does it depend on the regulator you have?
> 
> And how would it flow faster without raising pressure?


Well, it depends on your engine management I guess. EIP used to sell some hack job tuning software with a regulator that would increase your fuel pressure as your boost went up. You are basically tricking the ECU into thinking it has a 4 bar regulator and normal air intake when in fact you are compressing the air and raising the pressure a proportional amount.

Now, since the OP didn't mention he was running this kind of management, I'm going to assume he is using the same as everyone else which is proportionally large injectors with a sized MAF housing which tricks the ECU as well. The difference is that you are still using a 4 bar regulator which lowers the chances of a high pressure fuel leak.

Pressure = Force / Area 

The pressure is constantly kept by the regulator, the area is constant (in the tubes and rail), and the force is what is varied which is exerted by the regulator spring. As a result, the actual rate of flow is constant to the rail since the fuel either goes into the injectors or back into the tank. When the injectors are open longer, it decreases the pressure in the rail, which then closes the regulator slightly and allows less fuel to return to the tank.

So, I guess it doesn't flow faster, only the return line into the tank would be changing flow rate, since the force now varies depending on the regulator spring. 

I just proved myself wrong. 

Ryan


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## charlie hayes (Jun 4, 2007)

Yeah the pressure thing made me go like  haha. :thumbup:


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## Lindahl (Feb 16, 2009)

Stand alone speed density and no maf, 3 bar regulator (to try and keep below 75 psi: 45 psi fuel pressure + 30 psi boost pressure), and 630 cc injectors. I have a 4 bar regulator and a 984 inline pump, if it starts to show signs of starvation on the dyno.


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## charlie hayes (Jun 4, 2007)

Nice what gas are you planning on running? 100 or something a little higher. You should have no problem reaching your goals. Good luck post up the results.


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## SoFarKingFast (Jul 9, 2003)

Lindahl said:


> Stand alone speed density and no maf, 3 bar regulator (to try and keep below 75 psi: 45 psi fuel pressure + 30 psi boost pressure), and 630 cc injectors. I have a 4 bar regulator and a 984 inline pump, if it starts to show signs of starvation on the dyno.


What kind of stand alone are you using? So you are going with the rising rate FPR? Why not just use a MAP sensor and big injectors?


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## Lindahl (Feb 16, 2009)

99 RON, I run a rather low compression ratio of 7,8:1 and w/m, so I guess it should be safe on ordinary pump gas.


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## Lindahl (Feb 16, 2009)

I just run a regular Bosch 3 bar regulator. The stand alone is map based (speed density).


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