Aerochargers are better than (insert compressor)

[clayb]

> Date: Fri, 19 Oct 2001 06:24:09 -0700
> From: bearbvd at mindspring.com (Greg Hermann)
> Subject: RE: Aerochargers are better than (insert compressor)
> 
> Think you missed my point, Clay.

Not really.

> With this controller, the waste gate would be WIDE open at idle and cruise
> (for LOW back pressure), and only close when there was demand for boost
> (significantly opened throttle) , then begine to bleed as boost hit its
> set-point.

There is absolutely no reason to open the wastegate when the intake
manifold is in vacuum. The turbocharger is not a restriction under these
conditions. You could think of both sides of the turbo as "freewheeling"
under this condition. A freewheeling exhaust turbine has less
backpressure than a wastegate valve, under these conditions. Throttle
blades are the limiting factor, not exhaust backpressure, not the
compressor wheel. That's what throttle blades are for, right? Limit the
engine power to less than 0 psi manifold pressure.

> My concern is that the vlave poppet in the waste gate might run a LOT
> hotter than intended with so much off seat time--- but maybe not.

The most severe condition for a wastegate is under partial boost. Pretty
good power and exhaust temps, with the valve partially open all the
time. As they must operate continuously under this severe condition,
*some* wastegates are properly designed to dissipate the heat thru the
valve stem, not the seat. Garret makes a good unit. I've run them at 5
psi for 45 minutes at a stretch. Certainly a testament to their proper
design.

Your concern is addressed by a good wastegate.

- Clay
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