In article , Nate Nagel wrote:
Jim Yanik wrote:
wrote in :

On 26 Jan 2009 17:59:30 GMT, Jim Yanik wrote:

wrote in
:

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.
not necessarily.

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.


no,because you have to increase the fuel delivered when using a turbo
or supercharger. They effectively increase -displacement-,meaning they
compress a larger charge of fuel/air mixture.(equalling a larger
motor) The more air you cram in,the more fuel you have to add to keep
the proper combustion ratio.
Really? So the engine will only run at full throttle?

A turbo will ALLOW you to cram more fuel in, but that is not a
requirement.

Yes,it is.
ever hear of stoichiometric ratio?
that's the proper mixture of air and fuel,for best combustion.
you must maintain the proper air:fuel ratio.
If you cram in more air,you have to inject more fuel,or go lean and burn
pistons.

At less than full throttle, you will be getting more
power per volume of fuel used.

sorry,it doesn't work that way.

Not necessarily; the expansion ratio is better on a supercharged engine.
It might actually get better economy than the NA engine, even after
the losses from driving the supercharger.

My make, model and year of car (1995 Oldsmobile Delta 88 LSS) is
available with 2 different 3.8 liter 6-cylinder engines - one
supercharged, one not.

The naturally aspirated one has compression ratio of 9.4:1.

The supercharged one has compression ratio of 8.5:1.

- Don Klipstein )