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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I suspect changing the cam dose not effect compression enough to change the need to boost. However, it is possible to run higher compression pistons and make the motor more efficient in other areas like ports exhaust (equal lenght) etc and be able to run lower boost for better pre boost power and the same net HP.

I had a 78 and 91 Turbo. I believe Jeff's example of the 91 turbo is and example of the opportunity of changing the muffler. I am suspect of changes in the headers making more HP, it is the wast gate circut design on the headers that bumps boost.

Getting the same peak HP .8 bar and 1 bar could happen as the K27-7200 comes in fast and hard but dose run out of boost around 380fwhp. I had the same thing happen.

If I had another 91T I would get the cat bypass pipe, keep the stock low restriction muffler, mod the WUR to a boost sensing, and put new 2-5 gears from a C2/4. After that I might look at a bigger turbo.
Old 08-03-2008, 07:31 AM
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