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Old 04-02-2008, 12:40 PM   #14 (permalink)
trebuchet03
MechE
 
Join Date: Dec 2007
Location: Bay Area
Posts: 1,151

The Miata - '01 Mazda MX-5 Miata
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Quote:
Originally Posted by PaleMelanesian View Post
Well, if your MPG during that acceleration stays high, there's no hit to the average. Yes, the engine is in a different, less-efficient mode than a higher rate. But overall, you're minimizing the fuel used. Just use no more than the absolute minimum. Running the engine at it's peak BSFC point is secondary.
While cruising, keeping around BSFC is secondary (unless your engine is small enough to do so)... While accelerating, it's primary.

Don't look at your average mpg while trying to figure out acceleration (effectively instantaneous) optimal. Miles/Gallon does not include a time variable - so trying to incorporate time (by watching average) will only bring false confidence. My average will stay really high if I've been driving for a long time compared to when I accelerate just after start up - but in both of those cases, it doesn't change my instantaneous fuel efficiency in the acceleration event.

Shoot for peak thermal efficiency while accelerating - then peak specific consumption while cruising (which will likely not be peak thermal). Then later, when you consider the time variable - your figure will be higher.

Quote:
I there any reason the acceleration coming off a stop should be any different than a P&G acceleration?
Nope Pulse and glide just sounds better than accelerate and coast (I guess :P).
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