Boost Creep Gremlin

[Cecil_Stringer]

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.
<span style='color:Black'>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.</span>

What could it be?

<span style='color:Red'>Is the waste gate too small?</span>

I have a stock motor with a VR S2 DBB.
The boost feed into the waste gate is a 6mm hose coming directly from the plenum... same for the gauge.



<!--EDIT|Cecil_Stringer
Reason for Edit: None given...|1130200954 -->

 

[Cecil_Stringer]

Since its creeping with no spring in the gate, I'm thinking 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, the gate exit is nearly 90 degrees to exhaust flow.

Downpipe is too restrictive.

 

[Uncle Bob]

when you build 16 psi in the intake, you will have at least (most likely) 32 psi in the exhaust manifold. The angle that the waste gate runner is in the manifold really doesn't matter....32 psi is more than enough to vent to atmosphere no matter how convoluted the path.

If its building 16 psi WITHOUT a spring, then either the wastegate is partially siezed, or your feed line is just not doing its job. One or the other. No matter HOW small the wastegate is, I couldn't imagine a fully wide open waste gate allowing that much pressure to be retained in the exhaust.

If you want to verify, simply force the waste gate to stay wide open...or, just remove it completely. You should obviously see no boost in either situation.

 

[Cecil_Stringer]

Thanks for the input Uncle Bob!

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.

Works like a champ now.

 

[GoldenChild]

Whose kit was this????How old is it??? was the wastegate pipe off the header or the turbine housing

 

[frisbee]

Nice garage Cecil! I like all the bikes .

hey Uncle Bob , get on the northwest post so we can get together for a ride . All the wa. riders are on it .

 

[NearDeath]

wow... I beleive he states velocity...

 

[Cecil_Stringer]

yep.... it is a Velocity Racing Stage II Dual Ball Bearing....

 

[Cecil_Stringer]

Negative... sorry.

 

[STUNNAH]

Glad that you finally discovered the problem...I'm sure you've read about mine...

 

[TURBO1320]

cecil- stringer sorry about your luck at least you found out what it was. thats the problem with alot of people that make kits they dont have the time to do it right but they figure its good enough for the person who buys the kit because they set some record some where else with there own custom kit. All of our kits are all blended and all matched ported and alot of the times there coated on top of the 321 stainless. Or we use our own custom 310 stainless turbin housing with the 44mm wastgate built in to the housing so i guess if you get a turbo kit from us its custom with out the custom price.

 

[Cecil_Stringer]

cecil- stringer sorry about your luck at least you found out what it was. thats the problem with alot of people that make kits they dont have the time to do it right but they figure its good enough for the person who buys the kit because they set some record some where else with there own custom kit. All of our kits are all blended and all matched ported and alot of the times there coated on top of the 321 stainless. Or we use our own custom 310 stainless turbin housing with the 44mm wastgate built in to the housing so i guess if you get a turbo kit from us its custom with out the custom price.

You and I need to talk

That's a beautiful set up!

 

[1127 TO 1299]

cecil- stringer sorry about your luck at least you found out what it was. thats the problem with alot of people that make kits they dont have the time to do it right but they figure its good enough for the person who buys the kit because they set some record some where else with there own custom kit. All of our kits are all blended and all matched ported and alot of the times there coated on top of the 321 stainless. Or we use our own custom 310 stainless turbin housing with the 44mm wastgate built in to the housing so i guess if you get a turbo kit from us its custom with out the custom price.

from the exterior, that's a clean install

 

[TURBO1320]

You guys allways remember when you see my post Ive been there. I almost ran over my turbo at 140 mph. I had boost creep so bad it spit the crank out of the bike. I had cracks in my manifold so bad it turned my turbo to JUNK. I paid a guy when i was 16 to wire my bike and i watched it burn to the ground. I gave a guy 20k and one year and a half latter i got most of it back and 10k was not my money,Just not to long ago i had A&J performance skip out on $800.00 and i wont tell you who these people are but you guys know some of them. I could go on forever But all i will tell you is you guys are the most importent people in the world to me and your Dreams matter to me and i will go to the wall for you and when its all said and done and i bite the big one there is probably not going to be much left of me to put in a box but one thing is for sure people will say i was the most stand up and solid guy they ever met no one can take that from me.

 

[Mad`]

What turbo kit did you have that fell apart?
Mad`

 

[TURBO1320]

Bro i cant really say because it would get into a pissing match. All i can do is try to get people to buy my Turbo kits but BEWARE . If you do buy some one ealses kit and it dose not look right send it back and make them pay the shipping. Safe than sorry and always check your welds on any system.this time next year I should have a 310 stainless steal invesment cast Header that will be perfect in and out that will never crack it will be like our turbin housings.NLR/MOTORHEAD good stuff!!!!!!!



<!--EDIT|TURBO1320
Reason for Edit: None given...|1132087254 -->