How do you determine what mm wastegate you need?
TiAL makes:
35mm
35mm High Pressure (HP)
40mm
40mm HP
46mm
46mm HP
So if I was to run 15-17psi on a 60-1 or a GT35/40, what wastegate would suit my needs.
And I should get a 10-11psi spring?
Thanx!

 

Bigger is always better in this case...
I always recommend either the 46mm Tial or the HKS Race 50mm MINIMUM on a big power 13B.&nbsp Running too small causes boost creep which can kill your engine!


-Ted

 

Bigger is more controllable!!

 

I agree. I have a 40 mm HKS wastegate, and my boost goes a little higher than it's supposed to. I get about 2 PSI more than what I want. So I have to adjust my boost controller with that in mind. One of these days I"ll try the bigger one.

 

Woulden't you think exh manifold design would have to say something about this? Also the placement of the WG? I've seen some pretty ugly manifolds out there that placed the WG in bad spots, maybe those manifolds required a larger WG to keep boost creep under control?

 

That's possible. I'm using an HKS cast manifold, and it's designed pretty well.

 

While we're on this subject, what exactly is the effect of having a spring that's setup for much less boost than you're running?

When I first had my T-78, the spring was ~14 psi minimum (I can't remember exactly, it was a long time ago...), and I didn't have tuning for that, but needed my car drivable (I, em, lose control of my right foot, um, when it's on the accelerator, ah, sometimes... <g>). So my mechanic cut it so the gate would open at 7psi.

I'm finally starting to get the car tuned for proper (well, more proper) boost, and I remember hearing something about the negative effects of a spring that would allow the wastegate to open at significantly less boost than you were running... Chattering?