not holding boost

[87GN 98GTP]

I have a wastegate with provision on a 3" downpipe and a 46mm wategate, I am unable to hold boost anything under 20psi, Im looking for thoughts if I should just have it fabbed to come right off the header to downpipe or try a non-knock off brand name wastegate?

 

[87GN 98GTP]

no one

No ideas

 

[TurboBuRick]

Can you snap a pic of your set up?

 

[GetOwnedVette]

Im sure one of the gurus will respond but its usually a bad BOV or a junk wastegate. Are you saying it will hold at 22psi but not 16?

 

[87GN 98GTP]

its the setup from TR customs right off turbo to downpipe im not sure its holding any boost, because depending on the temperature it could be up to 25 psi and I have the gate all the way down, I can tell when it tries to start holding around 13 or 14 but then just creeps til whatever

 

[we4Mateo]

If it's creep related, can some porting be done on the turbo exhaust side to help? I'm not sure how an external gate works compared to the stock style but I believe the exhaust exits the same port? So if it's too small, then you may need to open it up to slow the turbo down properly.

Good to see you working on the car. I'm looking forward to your dyno results after the BS3 tuning.

 

[87GN 98GTP]

yes and eric did match the pipe with exhaust side to wategate

 

[kidglok]

what spring do u have in the gate?

 

[87GN 98GTP]

im not sure on the spring but its not that because I can tell well it tries to hold the spring so that means the spring engages but cant hold

 

[TurboBuRick]

When running external set ups like that the wg hole in the turbo exhaust housing needs to be ported to the size of the hole in the downpipe. Also some contouring of the lower ledge so that the boost can better make it's way out.

Are you running any type of boost controller? Tuner style?


RL

 

[pacecarta]

im not sure on the spring but its not that because I can tell well it tries to hold the spring so that means the spring engages but cant hold

this statement makes no sense

the spring is rated for X psi and it holds the gate shut until an equal force is applied to compress it.
if the spring is a 15psi and you have gate setup tuner style which is a hose direct from turbo compressor to base of gate (top of gate open) than the lowest you can hope to run WOT is 15psi as 15 psi is applied to the base of the gate the spring will be compressed and allow the gate to open and boost to stabilize . if you cant maintain 15 psi (or whatever the spring is) without it creeping up than the pipe to the gate (or port) is restricted, or the gate is inadequate size for the flow (46 should be fine if it opens fully) , or the exhaust side of the gate is restricted


on those china downpipes its also possible that the pipe going back to the downpipe isnt fully drilled out at the 3" pipe causing a restriction , there was a thread here with pics

some have reported unsatisfactory control with the china gate and yes there is a better gate ...precision ,

 

[87GN 98GTP]

the boost controller is a Greddy with in cab controller all electric, the person who put the motor together said he port matched the exhaust hole to the downpipe, so im guessing the china gate is junk

 

[pacecarta]

hook it up tuner style and see where it goes . if it holds its not the gate but the plumbing controlling it

if it still wont hold below 20 see what the spring is , if the spring is 20psi thats as low as youll be able to adjust... try a lighter spring

 

[87GN 98GTP]

a tuner style??? whats that

 

[pacecarta]

a tuner style??? whats that

TUNER= run a hose direct from compressor to base of wastegate (keep the top port of the gate open) , this will allow the gate to run at its lowest possible boost with the spring thats in it

or you could read my previous post
http://www.turbobuick.com/forums/general-turbo-buick-tech/365386-not-holding-boost.html#post2913170

 

[TR Custom Parts]

Just porting it to the same size as the downpipe isn't enough, you need to lay back the exhaust housing hole towards the header. Try to envision the exhaust having to make that tight turn and you will know what I mean. Helped me control boost creep. And I even took the gate that comes with the pipe out of the equation. Bought a Turbosmart gate and still had the same problem. Once I laid back the hole got things under control. You can do it on the car as long as you are careful.

 

[earcher1]

mistake,sorry

 

[pacecarta]

ive also seen on the china pipes where the gate hole was small on the downpipe flange (smaller than 1") , so porting the turbo to that hole wont do much for the flow , you need to open the flange up to the pipe size then match the turbo port to that new larger hole

i had to port my atr pipe and the turbo and im running a 71 gtq with an old 40mm HKS gate and a 1.38" tube to the gate and i can run WOT with an 8psi spring at 8psi , its not until the last couple hundred feet at the track it will creep but still never goes over 12psi

 

[TR Custom Parts]

http://www.turbobuick.com/forums/general-turbo-buick-tech/280193-boost-problems.html This thread might help, look at the wastegate hole. You want to layback the area shown on the top of the hole in these pics towards the exhaust wheel. A Dremel tool will not "cut it" to remove that much material, you will want to use a carbide grinding tip. Lots of threads about this subject.

 

[TurboBob]

Can you snap a pic of your set up?

Yes, a pic will really help us diagnose this.

You need to simplify the system to work out the bugs.

Aside from the mechanics of the installation, porting, and such, we need to look at the plumbing of the control signal (hose from the turbo)

There are 2 "ports" on the wastegate diaphragm housing, the "top" and the "side", depending on how the gate is mounted, these get confused sometimes.
"Top" is a pressure balance port and will be the one closest to the radiator when the gate is installed on the downpipe. "Side" is the other one and is closest to the turbo.

Run a hose from the turbo compressor wastegate port to the "side" port on the gate, and leave the top port open. And then see what your boost goes to. This reduces the system to its simplest form and should be very consistent.

Bob