I have a 1988 t2 with jdm motor fresh , block off plates ,intake , stock turbo ported wastegate, 2 and 1/2 inch pipping with stock cat .. it was hallowed out but thought might help if it was stock.. well whats happening is im just shooting upto 15 lbs by 4800 rpms and it if i didnt shift probably even higher . cant figure out why if anyone has any thought shed some light thnxs

 

Are you sure the wastegate is ported? Is the actuator connected to the swing valve? Is there a vacuum line from the actuator to the nipple on the compressor?

Boost control issues on S4 are common because the wastegate is very small and only leads to a single runner. You'll need to port it larger or restrict the intake/exhaust.

 

yea everything is connected fresh vac lines and everything ported the wastegate douv=ble the size of stock

 

I hate to say it, but it's probably just not ported large enough. The S4 wastegate port is only 13mm stock, so you'd be at roughly 26mm now. That's still pretty small. The stock S5 wastegate has more area than that, and can still creep with modified exhaust systems.

 

what if i completely open the wastegate and it still does that any other issue could i would still build boost

 

The wastegate is so small that you would still boost, and probably overboost. I tuned a car with a ported S4 wastegate wide open and it would still hit 14 PSI before 5000 RPM.

 

The stock MAP sensor to the ECU is 1 bar so 14.7 PSI right?
Can the stock ECU properly run fuel at that much boost?

 

Depends on what car you've got. What year is it?

 

thnx for info much appreciated

 

No, the stock ECU starts running the engine lean generally before 10 PSI. Some cars will start to run lean at the high side of 8, some are fine until 10.