Some people I know like my friend with a DSM read like 3 more psi on his boost gauge after taking off his exhaust. Someone else I know told me they got 2 more psi out of putting a test pipe on...I dont understand this, what does this have to do with the wastegate letting the turbo boost more ?

 

It should not do that....if you take your exhaust off, it will lessen the backpressure the turbo has to work against to pump the gasses out, which will make it spool faster, but won't give you extra PSI....unless somebody knows something I don't

 

I boost 1-2 more psi after 3' downpipe.

 

Yeah I only had 5psi with a 7psi spring in my wastegate when running a stock cat, but when I put in a 2.5 inch test pipe I would run 7. Anyone know why this is?

 

Actually, you just answered it. Less backpressure = more efficient turbo.

 

I must have missed that too. When I straightpiped my car I didn't get any more boost. I just got to full boost quicker.

 

Because of the stock cat! It's such a restriction that you can't get enough exhaust through it to spool the turbo to more than 5psi!

 

What size turbo did you have? And how big of an exhaust did you have before the test pipe?

Also, what kind of boost controller?

 

T04e/3 46 trim / .48 a/r
I was and am currently running the stock b pipe with a new axleback borla muffler.
TurboXS dual stage manual boost controller.
I am currently at 10.9 lbs of boost and according to my datalogs, it hasen't creeped over 11 lbs yet.

 

Its because the stock dsm wastegate can't flow enough air. They are getting what is called boost creep. Where the boost goes up uncontrolled. With a properly sized wastegate you won't get that.

 

Has anyone noticed boosting more in these cold winter months? It was in the 20's here last night, and I hit about 7.5 psi, when normally I only get 6.5 or 7. This is a drag kit with a tial, .45 bar spring, 2.5" drag d/p, 3" thermal exhaust.

 

Cold condensed air owns you.. I usually boost at 7.5-8psi on mine. Took it to the track the first cold night of the year, and hit 9psi quick... scares ya the first time or so thinking your WG went bye bye..

jB

 

That is what I figured, but I couldnt put an exact reason to the cause. Thanks man!!

 

It's not that it's really more efficient it just that the turbo has nothing to hold it back (back-pressure) so it just spins faster and spools up quicker than normal. Turbo's (with the exception of the variable-vane variety) have pre-determined efficiency maps. That's what the compressor map is for. Come on I thought you knew this stuff people. I'm supposed to be the village idiot look at my Sig. Not trying to be a dick it's just humorous from my veiw-point that's all.


[Modified by tzsir, 7:42 PM 12/12/2002]

 

Thanks for all the responses guys !