BOOST CREEP - 16psi w/o Waste Gate Spring
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gone fishin
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BOOST CREEP - 16psi w/o Waste Gate Spring
I have been chasing a boost leak gremlin for months now with no luck.
And after an over-boost that blew the head gasket... I'm gettin frustrated.
I've replaced everything shy of the waste gate (38mm tail)
Hoses.... Diaphram... Springs.... Supply.... nothin.
So tonight we did a few dyno runs trying to root cause the boost leak.
With a 7.25 lb spring in the waste gate it creeps steadily to 16psi well before redline (approx. 10K).
With no spring in the waste gate, the exact same thing happens.
What could it be?
Is the waste gate too small?
I have a stock motor with a Velocity Racing Stage 2 Dual Ball Bearing - GT25/30R (it's the red bike in my sig).
The boost feed into the waste gate is a 6mm hose coming directly from the plenum (air box)... same for the gauge.
And after an over-boost that blew the head gasket... I'm gettin frustrated.
I've replaced everything shy of the waste gate (38mm tail)
Hoses.... Diaphram... Springs.... Supply.... nothin.
So tonight we did a few dyno runs trying to root cause the boost leak.
With a 7.25 lb spring in the waste gate it creeps steadily to 16psi well before redline (approx. 10K).
With no spring in the waste gate, the exact same thing happens.
What could it be?
Is the waste gate too small?
I have a stock motor with a Velocity Racing Stage 2 Dual Ball Bearing - GT25/30R (it's the red bike in my sig).
The boost feed into the waste gate is a 6mm hose coming directly from the plenum (air box)... same for the gauge.
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Last edited by Cecil; Oct 24, 2005 at 04:38 PM.
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If its creeping with no spring in the gate I'd say it can only be a few issues:
Gate is too small
Exhaust path after the gate is restrictive, not allowing the gate to flow enough.
Poor gate location. Is the gate bleeding off of 1 cylinder? Is the gate exit 90 degrees to exhaust flow?
Downpipe is restrictive.
Gate is too small
Exhaust path after the gate is restrictive, not allowing the gate to flow enough.
Poor gate location. Is the gate bleeding off of 1 cylinder? Is the gate exit 90 degrees to exhaust flow?
Downpipe is restrictive.
Thread Starter
gone fishin
Joined: May 2004
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Originally Posted by Fordified
If its creeping with no spring in the gate I'd say it can only be a few issues:
Gate is too small
Exhaust path after the gate is restrictive, not allowing the gate to flow enough.
Poor gate location. Is the gate bleeding off of 1 cylinder? Is the gate exit 90 degrees to exhaust flow?
Downpipe is restrictive.
Gate is too small
Exhaust path after the gate is restrictive, not allowing the gate to flow enough.
Poor gate location. Is the gate bleeding off of 1 cylinder? Is the gate exit 90 degrees to exhaust flow?
Downpipe is restrictive.
A fresh set of eyes
Could there be an obstruction on the exhaust side of the housing interupting the flow of air to the waste gate?
Take a look at the bend out of the exhaust.... does it look suspecious(sp) to you?
Here's a pic of the set-up:
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One of the consequences of such notions as "entitlements" is that people who have contributed nothing to society feel that society owes them something, apparently just for being nice enough to grace us with their presence.”
Thomas Sowell (American Writer and Economist, b.1930)
Thomas Sowell (American Writer and Economist, b.1930)
i stepped on my weiner!
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problem is your header design and wasttegate positioning, not the gate itself, or the design
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10.02@149.5 Bullseye Power Turbos
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10.02@149.5 Bullseye Power Turbos
Top Dead Center Performance
Mobile Alabama 251 661 6067
owner/operator
www.tdcperformance.net
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Originally Posted by NChatch
problem is your header design and wasttegate positioning, not the gate itself, or the design
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What is the size of the wastegate hole in the turbine housing compared to your gate and its plumbing? You may need to port the hole in the housing out bigger to flow more. Positioning of the gate isn't optimal, but it works for many people.
i stepped on my weiner!
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yeah it seems as with the hole where the internal gate would go, is usually around 20-25mm, where hi is running a much larger tial. also the gate is literally AFTER the turbo where as it wont know or "see" boost till after it has gone thru the turbine. the gate should be moved to a different spot. i know there arent too many options.
__________________
.
10.02@149.5 Bullseye Power Turbos
Top Dead Center Performance
Mobile Alabama 251 661 6067
owner/operator
www.tdcperformance.net
.
10.02@149.5 Bullseye Power Turbos
Top Dead Center Performance
Mobile Alabama 251 661 6067
owner/operator
www.tdcperformance.net
Thread Starter
gone fishin
Joined: May 2004
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Big Red is home again... 
She's set up at 205hp on low boost and 300hp on high boost.
Had a major issue with boost creep, had to hone the waste gate exhaust port on the housing from the size of a nickel to the size of a half-dollar.
Thanks so much for the input everyone
Works like a champ now.
... choose your weapon ...
She's set up at 205hp on low boost and 300hp on high boost.
Had a major issue with boost creep, had to hone the waste gate exhaust port on the housing from the size of a nickel to the size of a half-dollar.
Thanks so much for the input everyone
Works like a champ now.
... choose your weapon ...
__________________
http://www.woundedwarriorproject.org
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One of the consequences of such notions as "entitlements" is that people who have contributed nothing to society feel that society owes them something, apparently just for being nice enough to grace us with their presence.”
Thomas Sowell (American Writer and Economist, b.1930)
Thomas Sowell (American Writer and Economist, b.1930)
Thread Starter
gone fishin
Joined: May 2004
Posts: 10,239
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Here was the problem... restricted flow to the waste gate.... thus major boost creep.
Here is the pipe...
Here's the header exhaust flange...
Here is the pipe...
Here's the header exhaust flange...
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One of the consequences of such notions as "entitlements" is that people who have contributed nothing to society feel that society owes them something, apparently just for being nice enough to grace us with their presence.”
Thomas Sowell (American Writer and Economist, b.1930)
Thomas Sowell (American Writer and Economist, b.1930)
