i have a 1993 twin turbo. the car has 43K miles on it. i have hks titanium exhaust, downpipe intake and a boost controller. what is the most i can boost with the stock turbos?
thank you

18 psi

you can hit 25psi but anything past 21 is way out of the efficiency of the compressors. rule of thumb is 16psi for 91 octane, 18 psi for 93 octane, and as much as you want for 100 octane.

I have always heard that 15 psi is max for the stock twins....at least for them being effective and reliable

CHRIS

please do a search =)

quote:

Originally posted by Chris Olson:
I have always heard that 15 psi is max for the stock twins....at least for them being effective and reliable

CHRIS

JDM (ceramic) turbos lose efficiency past about 15-16psi. US (stainless steel) are efficient until about 22psi.

I would do just 18. Maybe if you want to do 20 on track day or something like that then i guess that would be ok. But, extensive use over 20 would be murder on the turbos, but if you plan on going single soon then do what you want. SOU, since the jdm turbos are ceramic, do they spool up faster than the steel us ones. Also, what would be the point of not using steel turbos in the jdm supra or vice versa.

quote:

I would do just 18. Maybe if you want to do 20 on track day or something like that then i guess that would be ok. But, extensive use over 20 would be murder on the turbos,

as well as engine internals if the incorrect fuel is used.

quote:

SOU, since the jdm turbos are ceramic, do they spool up faster than the steel us ones. Also, what would be the point of not using steel turbos in the jdm supra or vice versa

yes ceramic spool faster, this is why the JDM engines have more tq and a broader tq range than the US/UK engines. however ceramic does not put up with high egts and are more prone to breaking if they are hit with debris (carbon build up). i think i read somewhere that all replacement JDM turbos are using steel blades. reliability would be the biggest reason for using steel instead of ceramic.