I just got my swap done and drove it today. Its only boosting to 6-7 max psi. I think the mechanical boost gauge is ok because its vacuum is reading 20 at idle. When I pinch off the vacuum hose on the side of the turbo the boost goes through the roof until fuel cut! Is this normal for a stock 1991 st185 with top mount intercooler to only get 6-7 psi? I thought it should be about 10-12 psi. Or is that psi only possible with modifications to the wastegate? Thanks for the help!

-toyotacrazy

6-7 psi should be running off the wastegate only...the boost controller sounds like its not doing its job

your in safe mode. something that tells the ecu that its OK to turn the vsv on isnt working right. u should be around 10-12psi. vsv is a stock boost controller sorta.

I had the same low boost mode when I got my swap done and it was due to a restrictive exhaust. What exhaust size are you running?

you cant use the top mount IC with our cars. install a font mount before trying to run anymore boost.

Im running a completely stock except the flex pipe is made to fit the dump pipe. I still have the convertor downstream of the turbo and the convertor in the middle of the car. When I pinch off the vacuum hose to the turbo the boost hits the sky. I know I need a mbc and front mount intercooler. But will this cure my low boost issue? If so whats the best front mount intercooler/size? Thanks.
-toyotacrazy

im having the same issues with my swap, but once mine runs for about ten minutes it leaves safe mode. you should put in the Knock lights in the FI stickies. they have helped me narrow things down a bit. I haven't heard the restrictive exhaust one, but that sounds legit, because my car wasn't in safe mode when i had the stock exhaust unbolted.

I also agree with Art on the TMIC, mine is burning hot after driving... which means it isn't helping cool any!

keep us updated

Most likely, it is the IC heat soaking.
The charged air is too hot and the ECU responds to that by retard timing and won't let the car boost past 7 psi by controlling the T-VSV.
Restrictive (small) exhaust is less likely to cause that unless you have a clogged cat.

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yep

I understand how the tmic is not the best setup. I am working on a fmic now. But could it really be holding back that much boost? I mean...theres st185 celicas running around with tmic pushing 16 psi of boost. I know they have the factory hood scoop though. Ill try the fmic and see what happens. Thanks.
-toyotacrazy

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A/A TMIC will not function without hood scoop.
You need airflow too cool down the IC. That is why they call it " ait-to-air intercooler"
With out scoop to feed air to it, I would call it "interheater"
Because of this setup, you are pumping hot air into the engine.
And that is the reason why the ECU won't let you boost more.

The ECU does this via the T-VSV (Turbo Pressure Vacuum Switching Valve).
Basically it is the factory boost controller.
It is just an electronically controlled bleed valve.
It regulates boost by bleeding air out of the wastegate actuator to allows more boost.
The ECU switches it on and off base on feedbacks from many sensors. (temperature, knock, etc..)

This post has been edited by Gary: Jan 2, 2007 - 8:53 AM

thank you! That is very helpful.

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I took my hood off and drove my car. Its about 40 deg. F here. After the engine warmed up it started boosting to 7-9 psi. Before I only hit 5-7 psi. A front mount intercooler is a must! Thanks for all the insight!

>

thats interesting above ^^

is this T-VSV the same on the ST205?

yes... st205 has tsvs. you can use it to monitor your cars knock response
http://www.6gc.net/forums/index.php?showtopic=41238

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Thats a great post! Thanks

wat is the max psi u guys would reccomend pumping out of the stock turbo on internals on the 3sgte?