Quote:
Originally Posted by Old Mechanic
More gears allows you to have an engine that was designed to take best advantage of more gear choices. Low RPM high torque without top end performance. Eliminate the maximum power output and make the reciprocating masses lighter. More diesel like power band.
regards
Mech
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Or, you could have a race-car like power band from an Atkinson cycle engine (at high rpm the late valve closure aids volumetric efficiency), which gives you "extra gears" in the sense that at lower rpms you have not much power but good efficiency, and at high rpm you have more power. More gears lets you take advantage of that by giving you the option of staying in the powerband or staying in the "efficiency band".
The only thing stopping performance engines (with single cam profile) from good efficiency is really the overlap and somewhat the exhaust cam being too big. Bigger intake cam means more top end, less bottom end, more efficiency at low speed
@Frank Lee 7 is useful if your engine produces a lot of power and the car goes fast, otherwise 6 is okay.