hey every1, i no u get asked a million questions over n over.. but b/c iv just sold my 1992 3000gt SL im looking hard 2 find a 1997-99 gsx or gst and want to know all i can about these cars..by the way iv been readin all the forums and couldnt find the anwer 2 my question HONESTLY..my question is what psi is the stock turbo running and if u bought a boost controller what would b a good psi 2 run it at?? also, i want 2 keep my car a dialy driver and b relaiable.. thanx 4 any comments i REALLy do appriciate it

at 10 or 11 psi on all the ones i have put a boost controller on.

so 10 or 11 psi with the boost controller? wat is it stock??

10 or 11 stock ,but u can't boost more than 13-14 psi without the stock BOV leaking

alright thanx. and what if i bout an aftermarket bov would 13-14 psi still be a good limit 2 stop at??

yes, you can boost higher with an aftermarket BOV and a boost controler ,but with a stock car and no boost gauge, i recomended that you dont exceed 13-14 psi

I think its 9 psi with stock bov and without it...its like 12-13

yes, you can boost higher with an aftermarket BOV and a boost controler ,but with a stock car and no boost gauge, i recomended that you dont exceed 13-14 psi

Any decent bov will hold as much boost as you'll want to run on a T25. A $30 used 1g bov will do the trick up to about 19 psi, even when you upgrade turbos. As for stock boost, I boosted about 12 psi bone stock. It depends on if you have boost leaks, like your stock bov or elsewhere (mine hissed quietly all the time). Some people only boost to 10 psi stock, etc.

Once you upgrade the bov and put a manual boost controller on the car, you can run much higher boost. I run 17 psi daily on my mbc on a 1g bov and a stock T25. 15 psi is a very safe bet. Many people claim that the turbo becomes inefficient because it is spinning too fast beyond 15-16 psi, but Kevin ran his best T25 time at 22 psi, so go figure.

If you boost any higher than 17, you are looking at possible inefficiency and killing your turbo over a shorter period of time.

If you boost any higher than 17, you are looking at possible inefficiency and killing your turbo over a shorter period of time.


Not to mention fuel cut

Not to mention fuel cut

Actually it is very difficult to hit fuel cut on a T25. I believe Kevin was on the stock fuel system with just the pump rewired when he boosted 22 psi...please correct me if I'm wrong about this.

i was running 25psi on a T25 for shits and giggles with no fuel cut... i didnt have a vacuum line run to the wastegate cause i wanted to see what it would max at... hit 25 then would drop down to 17-18ish around 5500rpms

Actually it is very difficult to hit fuel cut on a T25. I believe Kevin was on the stock fuel system with just the pump rewired when he boosted 22 psi...please correct me if I'm wrong about this.

thats news to me man....if you look at all like DSM info it will tell you that after 16 psi...you get fuel cut...but i guess you have to have a bigger fuel pump?? or just have the stock one rewired?

no.. the T25 doesnt flow air for shit, it cant hold more than 17psi longer than 6k rpms so you can get away with it without getting fuel cut!

i was running 25psi on a T25 for shits and giggles with no fuel cut... i didnt have a vacuum line run to the wastegate cause i wanted to see what it would max at... hit 25 then would drop down to 17-18ish around 5500rpms

damn Jake your crazy!


lol, j/k man. 25 damn thats alot :iceslolani:

1g - Minimum boost 9-10 psi, stock ~11 psi
2g - Minimum boost ~7 psi, stock 14 psi.

The minimum is the WG spring pressure, what you would get with no boost controller. The stock figure is with the stock boost controller (BCS).

Joe, you're right on regarding my setup. Stock fuel system and no fuel control, but I did have UICP with 1g BOV and race gas.

Fuel cut has nothing to do with boost, but airflow per rev. A T25 cant really hit it. A 14b can, but I'm pretty sure I was running 24 psi on one before I had the TMO chip and never hit fuel cut. It depends on how much air you can flow at that psi. A 16g goes to a larger 7cm turbine housing, increasing volumetric efficiency, thereby increasing airflow/rev for a given boost pressure. So you are almost garanteed to get it on a 16g even at moderate boost levels.

Like Kevin said, it's all about airflow/rev. You can hit fuel cut on a T25 by boosting 20+psi at 3000rpm. If you double the rpm, you have half the 'fuel cut measurement' or whatever you'd like to call it. The fact that you can't actually get more than 15psi after 6000 prevents it, too :)