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
Real flow restriction:
Major flow restrictions:
Found it much more painful to fit a 3" intake on the GTiR manifold, it hits the trans.
ASP VET Manifold
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.