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Old 03-31-2011, 10:18 AM   #27 (permalink)
PaleMelanesian
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Join Date: Dec 2007
Location: Texas
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PaleCivic (retired) - '96 Honda Civic DX Sedan
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Quote:
Originally Posted by orange4boy View Post
In a lower gear the "lever" the engine is acting on is longer so it simply applies it's work faster. Therefore, you should shift only when you will end up in the best bsfc range of the next gear. If you shift too early and end up "off the island" then you will create that energy more slowly at lower BSFC until your RPM gets into the sweet spot.

Is that about it?

I'm just now getting my head around this. I have always thought that accelerating faster to X speed requires more energy but it really only requires more HP which is energy over time. In the end it's still the same amount of energy to get to X speed.
That's the idea. It's a fixed amount of energy to accelerate a car to the same point. The difference is how efficiently the engine converts fuel into that energy. That's where bsfc comes in.

You're right about "falling off the island" of bsfc. It varies by engine, but in most cases you don't want to be below 1400-1500 rpm for accelerating. Steady cruise is different - lower is better.
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