Boost 'struggle'??

[pwpanas]

Originally Posted by winnas13

Thanks for the info. Supra is off the road at the moment while i get this wheel bearing sorted. I'll do a test run as soon as its done.

How much PSI does a stock 94' run? I have no idea if the previous owner of my car changed it at all, but when i go flat out my boost gauge shows about 12 i think.. If i did run higher psi, what's the highest that you'd want to go?

11.5psi is the oem boost spec.

If you raise your boost, it depends on the octane of fuel that you run. With an otherwise-bone-stock* 2jz-gte, running 93 octane gasoline (calculated via (R+M)/2) you should never exceed 16psi. If you do so, your engine will be damaged in direct proportion to the amount you exceed this limit. For example, at 17-19psi, your 2jz-gte may survive for several years, but your compression numbers (and horsepower) will decrease gradually. Regularly hitting 20psi and above on 93 octane fuel, your 2jz-gte will likely die within months or even weeks. Keep it at 14 or 15 psi and your 2jz-gte should last just fine. When you want to 'play hard', fill the tank (don't mix) with 100+ motor octane unleaded race fuel, and feel free to boost to about 21 psi safely (ideally you'd monitor the oem knock sensors to find the exact limit).
Disclaimer1: all this assumes proper maintenance (eg. keeping your fuel filter changed, your cooling system regularly flushed, regular synthetic oil changes, etc., etc.).
Disclaimer2: Temperature and atmospheric density are also factors. High boost on very hot days is more likely to produce detonation. Near sea level the atmosphere is more dense, so cylinder pressures may be higher...which may be more likely to promote detonation, everything else being equal.

*When I say otherwise-bone-stock, I'm primarily referring to the timing and fuel curves in the oem ecu. In general, I mean no modifications other than those specified by "BPU" (with as many plusses "+" as you want that do not affect the oem fuel and timing curves). Anything that affects these curves (eg. a 'piggyback' ecu (eg. PHR MAP ECU II) or 'standalone' ecu (eg. AEM)), your max boost with any specific octane of fuel will depend on the (extensive) tuning required to properly configure these devices.