Quote:
Originally Posted by deuce_454
your headers look VERY blue, my guess, (which is only a guess) is that the turbos are on the small side, you could be at the surge limit at 10 pounds, have you done the math and checked the turbo maps?? it could be that the housings are the limiting factor.
you could be moving the same mass of air at 10 pounds thru the bigger heads as you weer at 15 pounds with the old ones.. and its the mass, not the pressure that matters, the ET 245 heads flow like a MoFo and on a 402 with your super optimal intake and hot side tubing, you could be outflowing the turbos
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The turbos were spec'd by Precision for my combo. They are T67's that flow like T76's according to Precision, and have the larger .81 exhaust vs the more normal .68 exhaust housing. They claim they are plenty big enough for 1400 hp. I actually was thinking they were on the big side as I didn't want a laggy engine, but they're not laggy at all, come up on boost nicely. They just don't make as much boost as they should.
As a comparison, I had this engine in my GTO with a pair of GT3072R turbos that made 16 psi no problem, could have made more but that was as high as I ran them. They were much smaller turbos than what I have now.
I'm going to hook a boost gauge to the outlet of one of the turbos first to see what the boost pressure is before the intercooler, just to eliminate that as an issue. If that's near 10 psi then I'm going to shim the wastegates closed so they cannot physically open and see what happens.
Jody