Boost Creep

[cjpp78]

Lately since the weather has been cool my boost has been over shooting the target level. It will rise to the target boost level and then around 5000rpm starts to creep 4 or 5 psi past it by 6000rpm.
I use a greddy profic b ebc for boost control and a 38mm tial waste gate. I wouldnt think the waste gate is to small but could that be the case?

 

[starscream5000]

Open wastegate? Or is it re-routed back into the down pipe (I'm guessing open with a small tube on it)? Is your vacume hose hooked up on the wastegate correctly and not leaking/having a hole in it? Is it clamped down tight? What turbo are you running and at what boost?

 

[cjpp78]

Noticed the creep problem last night so I havent had a chance to look for leaks and such but will do that. The waste gate is open with a small tube on it. Im runing the sp58gt HO bolt on kit with external gate that bolts to down pipe. I run 15psi but at about 5000rpm or so it has moved up to around 19psi. I have only noticed this in the cooler weather now. I tried turning boost down but it would still creep past target boost level, if set at 13psi it would creep up to 15 or so in the high rpm range.

 

[starscream5000]

I though Sound Performance turbos for supras were internally wastgated? Am I wrong?

 

[cjpp78]

sound performance also offers the HO bolt ons that I have. They have different exhaust housing from the internally gated version. The kit comes with its own divorced down pipe and external 38mm waste gate. The exhaust housing just has a waste gate hole, no flap to cover it. The hole lines up with tube on down pipe which bolts to external gate.

 

[97TSiAWD]

I don't know much about SP products, but do you know if the wastegate hole was ported out and has at least a 38mm diameter? If it doesn't, that hole in the exhaust housing will be the limiting factor, regardless of wastegate size.

 

[cjpp78]

not sure of the size of the waste gate hole on turbo housing . here is a pic I took of kit before installed. The hole on housing seems a little smaller than waste gate hole from the pic but im not sure. Its been a while since I have seen the turbo with out down pipe attached. I know the waste gate tube sounds like its flowing a lot of exaust at 15-17 psi though