I have the Greddy T-78 turbo and wastegate on my car. I am having a problem with controlling the boost pressure.

All settings in the Power FC are o.k. (they're set at 10 psi). I removed the wastegate and disassembeled it to check for broken or clogged pieces. Everything is fine. When boosting the car, it will boost until it hits fuel cut (18 psi) due to the factory 2 bar map sensor.

What could be wrong? Could the lines going to the wastegate be cracked and allowing boost to leak, therefore not allowing the diaphram to be pushed open to relieve extra boost?

Any thoughts would be appreciated.

 

how big is the wastegate ? (mm)

are you running a boost controller at all?

run a line straight from the turbo to the wastegate and see what happens. it shouldn't go past what the spring rate is. (do you know the rate?)