Boost creep after installing tailpipe?
Thread Starter
Staging Lane
Joined: Nov 2011
Posts: 52
Likes: 0
From: VA
Boost creep after installing tailpipe? Right after installing a 4000 stall converter and adding a 3.5" tailpipe to my 4" exhaust I started getting funky boost creep. I never had a problem prior to this. Wastegate, vacuum lines and boost controller are all good. Could adding the tailpipe cause this? The 4" goes all the way back to the rear axle.
4.8 Silverado KBracing turbo kit with 4" downpipe.
I'm running 7-8psi with a 44mm gate. No catalytic converters just a 4" dynomax bullet. The boost creep doesn't stop rising until I let out, I've seen well over 15psi
4.8 Silverado KBracing turbo kit with 4" downpipe.
I'm running 7-8psi with a 44mm gate. No catalytic converters just a 4" dynomax bullet. The boost creep doesn't stop rising until I let out, I've seen well over 15psi
It could be causing enough back pressure to cause this? What size turbo?
I have a similar setup with an S-480 .96 AR 1.10 with a section of 5" off the turbo and necking down to 4" at the shock tower all the way to the rear of the car over the axle with a 4" MF muffler. I have a 2-1/2" hot side with a single 44mm gate as well. With a 3# spring it creeps to about 7# in the 1/8.
I have a similar setup with an S-480 .96 AR 1.10 with a section of 5" off the turbo and necking down to 4" at the shock tower all the way to the rear of the car over the axle with a 4" MF muffler. I have a 2-1/2" hot side with a single 44mm gate as well. With a 3# spring it creeps to about 7# in the 1/8.
Thread Starter
Staging Lane
Joined: Nov 2011
Posts: 52
Likes: 0
From: VA
It could be causing enough back pressure to cause this? What size turbo?
I have a similar setup with an S-480 .96 AR 1.10 with a section of 5" off the turbo and necking down to 4" at the shock tower all the way to the rear of the car over the axle with a 4" MF muffler. I have a 2-1/2" hot side with a single 44mm gate as well. With a 3# spring it creeps to about 7# in the 1/8.
I have a similar setup with an S-480 .96 AR 1.10 with a section of 5" off the turbo and necking down to 4" at the shock tower all the way to the rear of the car over the axle with a 4" MF muffler. I have a 2-1/2" hot side with a single 44mm gate as well. With a 3# spring it creeps to about 7# in the 1/8.
Isnt it the other way around? The more back pressure you have the less boost you'll make because the turbine can't spin as easily? That's why people add a cutout and the boost will go up.
TECH Fanatic
Joined: Oct 2015
Posts: 1,280
Likes: 28
From: Pittsboro, IN
I guess if somehow during the installation of the converter something got messed with on the boost controller.
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True. But the only things he said were changed were the addition of the tailpipe (which would add backpressure) and a higher/different stall converter. I was just throwing something out there.
I guess if somehow during the installation of the converter something got messed with on the boost controller.
I guess if somehow during the installation of the converter something got messed with on the boost controller.
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Staging Lane
Joined: Dec 2016
Posts: 82
Likes: 3
Since the wastegate valve is open and ur getting boost creep. Maybe that little bit of back pressure from the new tailpipe is just enough to backup the turbo housing and ur wastegate valve cant escape the pressure fast enough. While before the downpipe and wastegate exits were enough. U could install a little bit bigger wastegate.
I experienced exactly this on a build years ago. It was a 3.0 v6 on 21psi making 480whp with a 3 inch turbo back exhaust. When I bolted the chamber muffler onto the end of it, it would creep a few PSI.
However, usually my creep issues have been improper wastegate location and/or too small of a gate for low boost for that application.
1 thing you could try is to pull the spring out and roll into it in high gear and see what boost you make. If the gate is holding you back then you should make the same boost your making now, but just spool slower.
However, usually my creep issues have been improper wastegate location and/or too small of a gate for low boost for that application.
1 thing you could try is to pull the spring out and roll into it in high gear and see what boost you make. If the gate is holding you back then you should make the same boost your making now, but just spool slower.
I would guess that location was just on the edge of inadequate, and the addition of the tailpipe did it-on the KB Racing manifold I put my wastegate right at the bend where it goes up to the turbo.
At the very least in its current location I would have angled the pipe in the direction of the flow. Pull the tailpipe and see if its back to normal.
At the very least in its current location I would have angled the pipe in the direction of the flow. Pull the tailpipe and see if its back to normal.
Thread Starter
Staging Lane
Joined: Nov 2011
Posts: 52
Likes: 0
From: VA
Tailpipe removed but I still have plenty of creep. I noticed when I roll into WOT the boost creep is a lot worse. It only creeped 2 psi when I mashed it but 5+ rolling into it. Second gear short pulls
The size and priority (or lack thereof) of your wg appear to be what's causing the issue. If you did like mentioned above and locate it at the bend going up to the turbo, it would probably do better. Or you could do like denmah and others and locate the wg on the exhaust housing of the turbo.
