968to986

I have a Tial 38mm wastegate on the way for my 87 944T. It's coming with a 0.8 bar spring and I have to admit I'm a little unclear on it's function and weight. Is 0.8 bar the pressure at which the valve in the wastgate starts to open? Some of research I did suggests that the spring weight should be around half of the PSI of boost you run, so to me this spring makes sense with the 15-16 pounds of boost I have planned. Any input? Thanks!

TurboTommy

Tial rates their springs based on roughly 1 to 1 boost vs back pressure, and no boost loss between the boost signal and diaphram and intake manifold. Sounds kinda complicated, but just means that the spring rate is the boost you're gonna get with no supplementary boost controller and a reasonably efficient system.
And yes, it also means the wastegate starts to open when IT SEES that pressure, even at part throttle; but the driver won't really sense that.
And yes, with good boost controllers one can easily achieve twice the boost, so, in your case probably up to 25 psi boost. (0.8 bar is considered a pretty strong spring)

968to986

Thanks for the reply. Looks like I'm ready to run 25 pounds of boost! Haha!
But it's good to know I'll be fine with this spring setting at my currently modest goals.

Adonay

Yup. I have a 0.8 bar spring in mine the car will build that and stop at .8 when the boost controls are off. My wastegate was holding 26psi just fine,the rest of the engine not so much..