Quote:
Originally Posted by rjd_F30
It would make sense that peak HP and TQ numbers wouldn't change, but if one were to upgrade the turbo without a tune change, wouldn't the car hold boost better at high rpm after the upgrade, where the stock turbo taps out? For example, on my S2 logs, the boost target is the same 17.5 psi at 3000rpm as it is at 6000rpm, the only difference being I can hit the target at 3000rpm, but not 6000rpm. With the bigger turbo, wouldn't I be able to hit the 6000rpm boost target, thus making the car pull harder in the high rpms?
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It's all about the tune and how it's done, PS2 is able to hold a steady boost level till redline, if your tuner is able to keep 17psi till redline (with the neccesary fueling and octane) then it'll do that, but stock turbo physically cannot as the turbo just isn't big enough, and you run the risk of overspinning.
Its better to choose a good safe consistent boost and timing level with a decently low WGDC for reliability and logivevity.
I'm still debating whether I was to run PI with meth or just run a upgraded HPFP, where I currently live, my 91 octane is like 89 octane and we had to reduce boost and timing to 14.5 and 6-7 degrees, from 15.7 and 7-8 degrees.