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Old May 14th 05, 05:30 PM
fbloogyudsr
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"Don Stauffer" > wrote
> Big thing here is that CR effect on efficiency is for FULL THROTTLE.
> The efficiency really depends on the ratios of actual pressures, not the
> geometric compression ratio. Large engines usually run at very
> restricted throttle for most of time. The result is inefficiency.
> Smaller engine runs larger throttle opening to deliver same horsepower,
> with increase in thermal efficiency. Of course, there are many other
> factors, but if everything else is the same, running at larger throttle
> opening results in lower specific fuel consumption. (disregard onset of
> power enrichening) So two engines putting out same power will give
> efficiency edge to smaller one with higher throttle opening.
>
> I believe this is the idea behind some of these fancy new variable cycle
> engines, as well as ones that cut out some cylinders depending on load
> and TP.


Your "explanation" is not very right, either because you can't write
clearly or because you are unclear on the concepts and science/engineering.
I'm not going to attempt to re-cast your explanation, as it would take
too much time, and all that stuff is readily available on the www.

BMW's Valvetronic engines are un-throttled (variable lift valves)
and appear to be about10% more efficient and 20% more powerful
than the ones they replaced.

Floyd
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