Quote:
Originally Posted by alvaro84
That might be true, yet it's probably a very bad idea to cruise at that rpm: an 1200cc bike engine at 4200rpm needs ridiculously light throttle which gives very bad efficiency, even if the engine could theoretically do its best there. (May not be true at 90mph anymore, but most of its energy will be absorbed by the aero drag then, so it'll be inefficient again.)
Having it spin slower can mean a higher load which, eventually, almost surely leads to much better efficiency.
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That all depends on how the engine is tuned -- high performance engines with big cams etc are often very inefficient at high loads and low rpms. To a point both my TL1000S and XB12XT get better mileage at high rpms/high speeds (80-85mph) than lower speeds. Both engines are tuned with an eye more toward performance than efficiency. Still I'm not unhappy with 50mpg @ 80mph. If the engine were designed for optimum efficiency rather than performance you'd be right without a doubt, though if it were I'd never have bought it
