Quote:
Originally Posted by Frank Lee
I think the best way is to find a BSFC chart for your engine and note the sweet spot.
Failing that, I've been using a 1000-1200 ft/mn piston speed theory that postulates best or near best efficiency is found in that rpm range. I am still not sure about the validity of it but I've run the numbers on many vehicles and even if it isn't perfect it isn't going to be too far off.
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Uh, NO! Going off BSFC is as wrong as cruising at the RPM of peak TQ at WOT. Try that in a '98-'02 Z28, your MPG will drop from ~31 to upper teens.
Separate from that, I've had at least 4 different vehicles where a bit more axle ratio actually helped my MPG. Ya gotta try it and see, there is no substitute.
Like with this RX-7, I'm starting with a 2.29:1 axle gear until I figure out the aero, then I'll try a 2.14:1 axle gear.