Boost problem!!!!!!!!!!

[S2R4200_ONEVIA]

Ok, First off I have a 1990 240sx Coupe with a redtop SR20.I'm running the stock turbo, at 12psi.My engine mods are HKS FMIC, Apexi SAFC, Greddy Profec B BC, I'm running stock injectors.OK here is my problem, when I get into the throttle my turbo doesnot start producing pressure until 4,000rpm. Stock turbo should start to spool around 2,000. There is other SR's in town and they boost fine, So I ask WHY??? I'v spent hours searching the web with no results. I'v posted on forums with no real answers.

I'v Checked there is no boost leaks!!!! Do I have a wastegate issue, or a fuel issue??? I dunno I'm stumped

[SeVa-S13]

Possibly a shot/dying turbo. Did it spool quicker before the boost controller was installed?

[S2R4200_ONEVIA]

I bought the car with the boost controler installed, I know the turbo has no shaft play and blows no oil by the seals. Is it possible my boost controler is holding my wastegate open until 4,000rpm for some reason??

[S2R4200_ONEVIA]

No more ideas???

[JesusLikesKFC]

exhaust leakon the manifold or bad turbo. im guessing its not a bad turbo being u didnt post anything like exess play or smoke ect.

[srpowered240sx]

well bypass the boost controller and try just wastegate boost. see if it does any different.

[S2R4200_ONEVIA]

I tried that it just went to stock 7psi but was still very laggy!

[Rookieca18det]

pull the turbo and inspect the wastegate flapper. This a stock t25 we are talking about right, it wasnt replaced before you bought the car. Do you think you have any exhaust leaks, you should be able to here it pretty clearly if you have one thats is causing the turbo to spool that late. Well good luck my friend I hope you get it all sorted out, nothing worst than when your car is acting up.

-richard

[S2R4200_ONEVIA]

I dont here any exhaust leaks. I just removed my boost controller and hooked everything up like stock and still the lag.

[Rookieca18det]

start eliminating things...If you have a friend with a sr see if you can borrow his turbo and see if there is any difference, it does sound like some sort of shot turbo or maybe your wastegate is leaking or rather opening early and bleeding off exhaust gas. If anything else comes to mind I will shoot it your way, I hope you get it fixed.

*edit*By the way what is your boost gauge reading at idle?

-richard

[S2R4200_ONEVIA]

-20

[kermitman]

WHat psi are you pushing out before 4000 rpm?I had a guy that thought his supra was slow because it didn't just jump onto boost... but he was producing 450 hp on low boost.

Check the turbo gaskets (the metal ones that are a pain to change), the exhaust manifold gasket, cracks in the exhaust manifold, etc. What it seems like is happening is that the heat from the engine is escaping before the turbo, providing no boost. If you can get to a dyno like mine, have them log your boost pressure. Sometimes those boost controllers are not as accurate as you think.

Usually the stock turbo is unable to provide 12 psi much past 6500 rpm and if your turbo is old, then I doubt it is even close to this.

[kermitman]

Also check TPS voltage and function, there is a delay from when the computer reads full throttle and when it actually dumps full. If the TPS is bad then even if the throttle was wide open, it won't go out of closed loop mode, hence no spool and no boost

[S2R4200_ONEVIA]

My boost reads 0 before 4K, I assume my tps is ok because my afc reads perfectly as far as throttle %.

[kermitman]

test your wastegate actuator at vacuum. it should be closed until you reach 7psi and then open, see if it is opening early. I doubt this is the issue, but maybe the wastegate is not closing fully and bleeding off boost until the car is producing so much boost.

It'd be great for you to come in and I could look at the car on the dyno, the I can watch the wastegate as thge car is under load, but terre Haute is a long drive for a Dyno run iun Kansas City