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Discussion Starter · #1 · (Edited)
Ever since posting this thread, I've been curious about how much power GTiR manifolds make over Avenir's. Also, I was curious to see a comparison to a much better flowing manifold: ASP tubular VET Manifold.

Top to bottom: ASP VET, GTiR, Avenir



Top to bottom: ASP VET, Avenir, GTiR



Avenir Manifold
Installed:


Head view:


Real flow restriction:



GTiR Manifold
Installed:


Head view:


Major flow restrictions:




Found it much more painful to fit a 3" intake on the GTiR manifold, it hits the trans.



ASP VET Manifold
Installed:


Head View:


No real flow restrictions, very good merge collector compared to the other two manifolds too.




Finally the results... keep in mind these are done using Virtual Dyno on same stretch of road.
Setup: Roller Rocker, GT2860RS "Disco Potato", 3" Exhaust


I'm really surprised that GTiR manifold was not only more painful to install, more painful to attach a 3" intake to (or have a 3" comp housing), but also didn't make any real power over the Avenir.

Perhaps what surprised me the most is the fact that a much better designed ASP manifold didn't make all that much power over the other two. I think this is because of very low overlap stock Roller Rocker cams, thus T2 turbo restrictions still supersede the manifold restrictions.
 

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I did a similar test when I built those tubular manifolds. I did find the same thing at the lower HP levels. Even if you install some S3R cams the power different wont be muh. But if you cranked the boost up to say 15-16psi you will see more of a difference. I did a comparison with the GTiR and the other tubular manifold an on a DPT setup with S4's at 15psi there was a 15whp difference at full boost (3500) and about 30whp at peak power plus a smoother graph. One of the other guys that bought another tubular VET did a 2871 setup on a VE-T and had about 60whp difference I think IIRC.

Either way, thanks for the results. Throw some cams in and crank the boost
 

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Discussion Starter · #4 ·
I did a similar test when I built those tubular manifolds. I did find the same thing at the lower HP levels. Even if you install some S3R cams the power different wont be muh. But if you cranked the boost up to say 15-16psi you will see more of a difference. I did a comparison with the GTiR and the other tubular manifold an on a DPT setup with S4's at 15psi there was a 15whp difference at full boost (3500) and about 30whp at peak power plus a smoother graph. One of the other guys that bought another tubular VET did a 2871 setup on a VE-T and had about 60whp difference I think IIRC.

Either way, thanks for the results. Throw some cams in and crank the boost
You are correct at those low PSI's the exhaust to intake pressure ratio is still pretty low, but as soon as you start cranking the boost up, you start seeing the gains. I bought the VET manifold when I was on a VE, but never really tested it though.

Good work man. It would be interesting to see how a dyno compares to the virtual dyno, but I know dyno time isn't always economical to satisfy a curiosity. Still odd they were all very similar performing
Virtual dyno is actually within the margin of error for most dyno's. In this case I would give it within 10whp, but it all depends on the road.
 

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Good thread! You were @ 11-12 PSI boost right? What was the pressure ratio?
 
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