Hey Dave -
Quote:
Originally Posted by eyesoreracing
a DSFC map could really only be made after the car exists and its drag properties are known.
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You're right there, for sure.
I think there's a misinterpretation about what the BSFC map is telling you, in terms declaring an "ideal" cruising RPM.
The engine produces power most efficiently at 1800 RPM, but that's when it's making about
55 hp. In other words,
if you need 55 hp, 1800 RPM is the place to be. That's the RPM & load combo where the engine produces the most hp per unit of fuel.
Best BSFC RPM doesn't necessarily = lowest fuel consumption at lower engine loads. Since you're probably only going to need
roughly 12 hp to go 60 mph on level ground, lower RPM would be better. Tasdrouille figured the sweet spot is more like 1250.
But since, as you say, you've already stuck the tallest possible OEM 5th in there, it's kind of moot (as I admitted in my comment above); any further discussion is just so much fuel economy geekery.
Unless of course you wanted to make a new 5th ratio... like
this guy, or
this guy.
Congrats on the project, and the really good writing. Can't wait to see what you guys did in Cali with the aero doctor.
Darin