Variable Compression, Variable Displacement you decide

[Terrie S. Watts]

Another curious observation...

>You where claiming every bit of the energy used to drive the turbo
>was free.  That is not true. I will but the part about the heat
>being used to drive the turbo - but you did not say that - someone
>else did.  I will now buy that part of the energy (don't know
>what part - guess around 1/2 is free) All you claimed was it was 
>all free all the hp used by a supercharger could be gotten completely
>free with a turbo.  This statement is WRONG.   You could not explain
>where the energy was coming from so it could be free.   That was
>what I was trying to figure out.

The cooling of the exhaust gases surely powers the turbo but in a
non-turbo application doesn't it provide considerable scavenging?
In other words, the piston doesn't have to work so hard to push the
exhaust out because it is being sucked out by the vacuum generated
in the headers and exhaust pipes.  Therefore, tuned exhaust contribute
to the efficiency of a non-turbo engine just as a turbo improves the
upstream efficiency.  Still have tradeoffs right or wrong?


Matt Watts
University of Utah
Formula SAE Racing
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