>From the Kitplanes article that Thomas J mentioned,  it seems that the turbo turbine needs to be oversized by a factor of 2 to allow for the fact that
the
airplane installation has a steady state throttle.   In a car application the throttle is never held open long enough to allow the TIT to build up to a
hotter
equalibrium value.  Therfore the "average" TIT in a car is a lot lower than in the steady state airplane application.
Paul mentioned that another way to make the turbine appear bigger is to drill a hole allowing exhaust gasses to bypass the turbine, thereby increasing
flow
rate and lowering turbine inlet pressure and temperature.
If the wastegate currently seems to have no effect on boost then maybe you could try removing the wastegate flap all together.
The flap is most likely blocking the flow even when it is open.

Regards, Erik

That is a pretty good idea. Unfortunately the assembly is welded together
so it might not be possible to restore it. I think modifying
the back cover of the waste gate to allow the flap to open 90 degrees
might be a better approach. At least a first thing to try.

I did a 3D of a steel spacer shown here.

Also a large 3 inch exhaust tube could be welded over a 3 inch hole
in the existing back cover to allow the flap more freedom to open fully.

A bit of porting on the waste gate might help.

Paul Lamar

What if you find that even with the fully open wastegate hole, the TIT and MAP is still too high at WOT?
If you have an old cracked turbo housing, you could try that on the dyno with the flap removed.
Then a least you know if you are in the ball park.

A further option is to try and fit a smaller diameter turbine to the existing stock shaft and housing.
What is Francois using in his turbo?
Erik

Well than if all else fails a hole in the turbine housing next to the waste
gate will work as a last resort.

Francois uses the stock Mazda 1991 2nd gen turbo.

A larger turbine is what you need if you want less boost.
It also dissipates more heat because it is larger.

Paul Lamar
 
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