awilson40

I installed an accuboost contoller today and when its fully open it will pass pressure to the wastegate instantly so I ran it like this just to test the WG spring / shims. It will boost a rock solid 5psi.
Is this a good place to have it or should I shim to a higher level?
Thanks

Danno

That's about right. You can try shimming it more, but you can't really get much more than 6psi with the stock spring. The more important issue is how flat it can hold your boost curve. The higher the max-boost setting, the more it tends to drop.

awilson40

Thanks,
At 12 psi it will hold flat to redline. At 16 psi, it will fall to 13 at redline.
This is all with the stock airbox and AFM.
After lots of reading, It seems guys with MAF or MAP setups have better luck with the stock turbo holding 15 psi to redline. I wonder if freeing up the intake 'helps' the little stock turbo hold boost at higher RPMs.
With stock injectors its probably safe to run 16 -17 psi for mid range torque and let it fall to redline so the injectors dont max out.
Just a thought.

Danno

"It seems guys with MAF or MAP setups have better luck with the stock turbo holding 15 psi to redline. I wonder if freeing up the intake 'helps' the little stock turbo hold boost at higher RPMs."

Yup, because there's less of a free-differential between the turbo inlet and the turbo outlet. With the AFM in place, you end up with a high vacuum between the AFM and the turbo-inlet. This causes a higher pressure differential between the inlet and outlet, thus requiring more power from the turbine-side of the turbo to flow inlet air. As you increase the power required from the turbine, you increase the backpressure in the crossover pipe (higher pressure differential across turbine-inlet to outlet generates more power). But this higher exhaust back-pressure also fights incoming boost. So it's a delicate balancing act.

"With stock injectors its probably safe to run 16 -17 psi for mid range torque and let it fall to redline so the injectors dont max out."

yeah, that won't be a problem. TurboS cars at 18psi on our GURU chip-upgrades that can hold flat 18psi boost are getting 260-270rwhp, which is about the absolute limit of the stock injectors at 3-bar on the FPR.

Duke

My WG is shimmed 4.5 mm and drops from about 1,2 bar to 1,1 at redline. That's with a K27.

Danno, I've been trying to get hold of you for some time, hope I hear from you soon.