Here is an idea that might save some money and weight. Use a stock turbo
or a TO3 and put a Inconel butterfly valve down stream from the turbine
exhaust. This could add some back pressure at high altitude and prevent
the turbine from over speeding. So far I cannot think of any downsides
other than reduced boost and HP but I am sure someone will. The exhaust is
cooler on the outlet side of the turbine so the heat environment is
not quite so bad as it is upstream.

Paul

bcgardner wrote:

Paul,

Haven't you basically reinvented the wastegate here?

Either a manually controlled one or one controlled by barometric pressure
could open up to control the boost and thus vent exhaust around the turbine.
The "big wastegate" solution also avoids introducing back pressure.

My thoughts.

Barry Gardner
Wheaton, IL

Yes you can look at it that way but waste gates are expensive and heavy and run 
very hot. This is cooler, light and cheap. Beside the stock 89-92 Mazda turbo 
has a built in waste gate that is probably inadequate for high altitude use. 
This will supplement that to prevent an exploded turbine wheel.

Paul Lamar
 
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