
Originally Posted by
SwankPeRFection
Except in both problem vehicles here, the bypass valve isn't opening, so that can't be it.
That is correct in my case. In all of my logging with crappy IAT's, my bypass valve has never opened under WOT. The only time I have seen it open under WOT is when I over-rev to 7200+ RPM on the 1-2 shift, and it opens for a brief second while the trans hangs up. We think this may be due to wheel spin, but that's just a guess. I can tell you from logs that every time my car hangs on the 1-2 shift, it is under those over-rev conditions.
I do know that the bypass valve can open with really bad IAT's, but I have not seen it. I have crept up over 80C IAT's in some of my logging. Someone can correct me if I am wrong, but I think low boost can come from a myriad of factors:
1. Elevation- higher means less dense air, and lower boost (see ambient pressure- in my case 98-99 kPa)
2. Hotter temps- same thing, hot air is less dense
3. Less air- less air=less pressure with all things equal
4. Boost leaks- pretty self explanatory
5. Bypass valve opening- either due to conditions, tuning or other factors
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