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Don Klipstein

In article , wrote:
On Mon, 26 Jan 2009 09:17:21 -0600, dpb wrote:

mm wrote:
...
Besides power, I've always thought that a high compression ratio means
getting the most out of the gas. That every portion of its expansion
applies power to the wheels of the car.

Doesn't that seem reasonable, and how come it must not be true?
...

Efficiency and power are competing design features

Not true. Any time you raise the horsepower generated per cubic inch,
you increase fuel efficiency. You get more power from a given volume
of fuel. Take a 2 lire engine, and add a turbocharger to it. Both
available power AND fuel efficiency benefit. You are getting more
power out of the same size engine from a given amount of fuel.

A turbocharger achieves more power per unit engine volume by
cramming more air (to be used with more fuel) in the same volume.

Superchargers do the same thing but are powered in a different manner.

Both achieve an increase in power and decrease fuel economy slightly.

However, if 2 cars have equal power and one has a turbocharger and the
other has a bigger engine, then the car with the turbo could possibly get
better city fuel economy by weighing less.

- Don Klipstein )