Turbo upgrade project is almost done

[Pete_89T2]

Originally Posted by 88turboii

i had that same problem with teh BNR stage 3, you can try running an extra spring from the WG actuator to the flapper to help keep it closed. I dont think the cat is causing it to open though, stock turbine is just really restrictive

I forget, is the BNR stage 3 wastegate the same as what he does for the stage 1? For the stage 1, (S5 turbo), he ports the wastegate some, and the wastegate actuators are pre-set to open the gate at 7~8 psi, assuming no boost controller is intervening to make the opening delay till you hit higher boost pressures. He also clips the stock turbine wheel some to reduce backpressure, so I doubt that the turbine wheel is the issue in my case.

Unless something wonky is going on with the stock ECU/boost control solenoid and its plumbing, I think Dave's theory that cat backpressure is causing the WG to flutter open is pretty sound. That plus the fact that the wastegate is ported would really limit boost. I might try bypassing the stock boost control solenoid and run the boost pressure sensing line direct to the wastegate actuator, and see if that gets me to the 7~8 psi BNR sets the wastegate actuator to operate at.