I need help with small boost creep issue. Picture and desicription provided.

[jwallsfx]

Hello all,

I am new to turbo vehicles and using the forums and google, we were (almost) successfully able to upgrade and intercool my turbo swapped Z.

The issue is that it overboosts(boost creep maybe?) consistently in every gear. We bought a new wastegate for it with an 8 psi spring. Boost goes up to 15+(gauge stops at 15). It doesn't hesitate to get their either. When the turbo spools, boost builds a little slow and then shoots up(at this point, the turbo spool is a lot louder) and goes past 8 psi. I bought a new wastegate thinking the other one was damaged with no different results. Car runs fine and pulls hard, I just don't want the boost going that high. It causes it to stutter and pop at anything past 13psi. My goal was 12 psi(I have 330cc injectors and a Begi FMU) I have a boost controller installed but it did this without one installed(line from compressor housing to wastegate and the line was only a few inches long ~7 or so and needless to say, the boost controller is turned down until I figure this out) The car is so great until it hits high rpm and boost and leans out.

 

The turbo is just a t3/t4 on a l28et so I don't think thats too much for the wastegate considering thats a common turbo upgrade for this motor.

I have scoured google and the Z forums and cannot figure it out so I am finally asking for help.

The quick question was about the install of my bypass valve. The previous owner installed a bosch type and we kept it in sequence to what it was before the intercooler and turbo upgrade. I had no boost issues with the previous t3 turbo but the compressor wheel seal went out and car was smoking like crazy.

Below is a pic. It goes from intercooler pipping(pre-intercooler) back to the turbo. The vacuum line behind throttle plate goes to the FMU and the line from the back of the manifold goes to the Bypass valve, like it was when I got it. Is this correct?

Thanks for any help and RTz, is that descriptive enough for you?

[Six_Shooter]

A picture of the wastegate and vacuum hose to it would be more beneficial in this case.

 

The bypass valve looks to be connected fine.

 

Assuming you are using an internal wastegate and as a test you can disconnect the wastegate actuator from the wastegate flapper and wire it open, or just leave it, since exhaust pressure would push it open at that point. 

 

There may be a tear in the wastegate actuator diaphram.

[jwallsfx]

The line on the wastegate comes from the turbo itself through a boost controller, to the wastegate. Literally about 8 inches worth of line(this includes boost controller. I would have thought this too, Six_Shooter but it did this without a boost controller and as for the the wastegate itself, The turbo came with it installed. It went from box to car along with the intercooler. When I realized it was doing this, I ordered another wastegate and nothing changed.  It could still be in the wastegate but this is the second one we put on it and I just don't see me getting two bad ones in a row(I know it could happen but Its super unlikely)

[Six_Shooter]

So did you ever try either wastegate actuator with the vacuum line connected directly from the compressor outlet to the wastegate actuator? 

 

Some boost control solenoids block flow until power is applied to them.

[jwallsfx]

I just recently added a boost controller. It was a line from compressor to the wastegate for most of the time it was on the car and did this. Thats what I just dont understand. It is still doing the same thing

[Six_Shooter]

Ok, go back to not having the boost control solenoid in the loop.

 

Go out to your car, pull the wastegate actuator off the wastegate flapper arm, and move the wastegate flapper. Can you move it? If so how far does it move. Take the car for a drive, does the over boost still happen.

 

BTW this is over boost by your description, not boost creep. Over boost happens quickly, like it sounds like you are experiencing, boost creep happens slowly and usually increases only with RPM. 

[jwallsfx]

Let say I am driving it and accelerating. Boost goes up alone with rpm's and goes up to 15+ as I near redline everytime. Thats still overboost? I also noticed that the silicone around where the bypass valve in the intercooler pipping has bubbles around it and small holes in the bubbles. Would leaking around the bypass valve cause overboost/boost creep?

Also, thank you very much for taking the time to try to help me.

[Six_Shooter]

I guess I would have to see video to see exactly how the intake pressure is rising. It sounded from your earlier description that it was a pretty immediate rise in pressure, which is over boost. 

 

No, any leaking at the BOV would reduce potential boost, also know as a "boost leak"

 

Check that wastegate flapper for movement first and take the car for a drive with the wastegate actuator disconnected, so that the flapper is open all the time and report back.

[motomanmike]

You may have to port the wastegate hole slightly,  also some guys cut a small groove up to it as well.  I've had this happen working with some miatas and the ever popular china turbo upgrades.  Wire it open like others have said and see what it does.