Question about boost leak

[Trippnup2]

Well I bought a 99 GST A/T (don't pick on me!) about three weeks ago. I've been reading a ton of internet posts here and at DSMtalk.com and have come with a question. Loud whistling noise while accelerating? Is this boost leak or just the turbo spooling? I know the turbo is working because you can feel it kick in around 2400 RPM's. How do I check the lines for boost leak and how many places do I have to check. I'm not a mechanic by any stretch of my overreacting imagination but I get by so use LITTLE words.

 

[TurboSpyder98]

ermm well whistling is pretty normal.. does it get louder as you accelerate? my car screams at WOT.. and its not boost leak. my assumption is its just the turbo spooling

 

[Trippnup2]

Thanks for the quick reply! Yeah it does get louder as WOT starts kicking the RPM's up! I just wanted to make sure cuz soooo many people claim they are having problems with this piece or that piece! I want to start stacking the mods on but wanted to make sure the stock equipment is fine before I start stressing it out with new things.

 

[crankbender]

Get a vacume gauge and see if you pull a normal vacume (vacume leaks are easier to detect because there is no turbo to compensate for the leak). If that is good then the only place you can be leaking is the IC related stuff and where it attaches to the turbo and TB.

 

[gstspyder1998]

My car does the same when it's in WOT.

 

[Bohrn]

hey Crankbender, how much vac is normal at idle for a 91 Tsi??

I think I have a boost leak as well, as it slowly fades at over 5 grand.

 

[Formz]

Originally posted by Bohrn
hey Crankbender, how much vac is normal at idle for a 91 Tsi??

I think I have a boost leak as well, as it slowly fades at over 5 grand.

Vacuum should be around 18 (in/mg??). Mine is at about 12 right now, I really need to find that damn leak!!

 

[crankbender]

Yeah 10in isn't too good without cams or a modified TB plate.

When you say the car fades at over 5k what do you mean? is it the boost pressure fading or the car not pulling? If it is the car not pulling you may want to borrow a logger and see what your timing advance is. It may be that you are getting retard because of detonation instead of a boost leak.

 

[Bohrn]

Well, I don't have an accurate boost guage, and relying on the factory toy one, it shows almost full boost until I lift, but the car seems to not pull too hard anymore. I cleaned the intercooler and pipes, and I think maybe I didnt get one of em on right again, but all the connections are tight, so I am at a loss.

The detonation thing may be happening, but I run 94 octane(friggin expensive) gas, so that should not be an issue. Who would have a datalogger near me to borrow??

Also, I hear that it takes like 200 miles for the computer to reset from one little knock sensor input. Is there a way to speed this process up? seems like a long time to wait, and with 94 octane, it shouldnt happen again.

Should I have my base timing checked? If it is right,will the WOT timing be right or is it not really connected?

Thanx again, helpful people here...

 

[Formz]

it has been my experience that the stock boost gauge will represent boost fairly well, but it can't represent vacuum for CRAP.

One way you can feel if you have a boost leak or not, is go WOT, at full boost, then let off very quickly. If the car jerks a little bit then chances are its a boost leak.

 

[Bohrn]

Formz, what do you mean by jerk a little bit? If you let off at WOT in any car, turbo or not, its not gonna be smooth. What sort of thing am I looking for??

thanx for the help

John

 

[Formz]

it jerks a tiny bit, like its not smooth. I wish I could describe it better to you but I cant. Just something you have to feel.

 

[Mistaspakles]

The stock boost gauge is worthless, get an aftermarket boost gauge.

 

[Formz]

actually, if you compare BOOST readings its pretty accurate. its under vacuum that its horrible innacurate. Plus, it only goes to 14psi.

 

[turbo_lover]

For a 2g is 20inhg at idle normal. And at WOT 11.5 psi.