Variable Compression, Variable Displacement you decide

[Andris Skulte]

Roger Heflin wrote:

> torque corves, therefore they aren't equivalent.    Also the number of
> compression stages and the number of expansions stages has nothing
> to do with the efficiency.  Thermodynamics says more stages don't
> increase efficiency.

I'm going to disagree on this point (from a purely theoretical
standpoint). If you have a cycle on the T-S chart (temp and entropy, I
think) a multistage cycle can get you more efficiency than just one
large single stage. 

>  The reason a supercharge is generally
> less efficient is that they compress more air than is needed, and substantially
> increase the pressure in the intake more than is necessary.

I don't understand this point. I thought more air (higher boost) was
always better. You have more air, so you add more fuel to keep the right
AF ratio, and vroom! More power :) If you are talking about this from an
efficiency point of view, I understand then :)

Andris - mech E student struggling with Heat xfer at the moment