Turbo upgrade project is almost done

[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

you should be fine with the stock tmic, ive never seen it get above 150F on the street, and thats running 15 psi on a p-trim hybrid

[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.