Went to the track last night and had a strange issue.
With the stock catback it ran perfect on 5psi.
Removed the catback and couldnt keep it from goin to 8-12psi. I checked the wastegate line and its good. (referenced from the turbo housing)
My tune was setup to pull alot of timing incase something like this happened. And fuel table goes rich too.
I leaned it out and gave it some timing. Think it was blowing outthe spark then.


But we loaded up and left the track. 5psi is all it would do with the catback on and pullin the trailer with busa on it.


What gives?

The wastegate is on the driverside of the cross over and it has its own 1.75" exhaust into a 2" muffler.

Just dunno why it would run so good with the catback, remove the catback and overboost?

Somebody learn me something.

 

exhaust makes all the difference w/turbo. mine spools faster and makes more boost w/ less exhaust. some guys have two tunes. one for quiet street exhaust and one for cut out open, for that reason.

 

When you reduce back pressure after the turbo, your also reducing it before. So the WG needs less spring to lower the boost cuz it has less back pressure to help open it. I put a spintech muffler on the tail pipe of my truck one time just to knock the drown out and lost 2 psi of boost just doing that from the added back pressure.

Shows just how much back pressure that stock exhaust adds

 

Back pressure difference... Plus that wastegate exhaust setup you have probably chokes the gate some. You need a lighter spring and less restriction after the wastegate to keep you boost consistent with the exhaust removed.

 

Yep what kb said, I run throw a 3in flowmaster, when I pop the cutout open (were it's still 3.5 inch) my boost gos from 14 to 19 psi.

 

Hate to thread jack but is this reversed with a supercharger setup? Everything I have read says I will drop boost if I free up my exhaust on my setup. All I hear is i will have to pulley down some after headers and ORY

 

Yep, its the opposite with a blower.

 

Gotcha. Makes sense with how KB described it and the basic physics behind how a turbo vs supercharger works.


Thanks

 

Why did you pull the exhaust to begin with and is this the first time you did it?

 

Cool. I kinda understand. But i was under the impression that at ~5psi the pressure would open the wastegate valve, Limiting boost.

Even tho the exhaust preasure helps open.


But at the same reasoning, this is the same wastegate i ran on my STS kit. No exhaust after the turbo and no exhaust on the wastegate. It ran at 5-6psi.


I wanted to see how bad the stock exhaust was holding it back. And yea first time to remove it.
I just unbolted it and moved it over to the next hole so it wouldnt flop.
Gonna throw some BR7EF's in it and gap them a lil tight. See if it will run with them.

Im on 4 yr old TR6 that have seen better days. Theres no more V in the electrode. Just a rounded peice.

Im gonna try my other catback with a magnaflow muffler on it