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Old 09-04-2009, 11:32 PM   #17 (permalink)
RobertSmalls
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Location: Buffalo, NY, USA
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Quote:
Originally Posted by winkosmosis View Post
Are engines really more efficient at their limits, or does it just happen that engines are tuned in such a way that a small engine is more efficient than a big engine, aside from the reciprocating mass difference?
Engines tend to be more efficient near their limits.

Brake Specific Fuel Consumption (BSFC) Maps - EcoModder

Pumping losses, friction, and reciprocating mass waste more energy in a larger engine, too. Downsizing the engine will improve MPG, unless it causes you to drive around at redline with your foot to the floor. See the above-linked plots. If your engine and gearbox are set up so you cruise at 2500RPM and 80% throttle, you'll do well. Though that would mean you'd have to downshift to pass, but that's worth it if it means a few more MPG.
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