Quote:
Originally Posted by mpg_numbers_guy
Lowest RPM is usually better than BSFC for cruising. Lower RPM = higher engine load for a given speed = greater engine efficiency, usually more so than at peak BSFC. Cars are most efficient the closer they are to WOT (wide open throttle). Peak BSFC is for acceleration efficiency.
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I was attempting to exploit BSFC by accelerating fairly briskly (and shifting so I'm roughly in the 2,000-3,200 RPM range at all times), and then moving into my final gear for lowish-RPM cruising (roughly 1,500). I do OK this way, but seemingly not as good as just accelerating very slowly.
While accelerating granny-style causes a long, slow attenuation in the indicated average MPG, BSFC tanks it rather dramatically. Granted, after getting up to speed then I can spend more time at low-RPM cruising and make up a lot of the difference. But -- at least with the techniques I'm applying -- granny driving appears to be slightly more effective.
The BSFC concept makes sense to me, but where the rubber meets the road (ugh, sorry), I'm having trouble realizing the theoretical benefits. More than likely I need to adjust my technique a little...and it wouldn't hurt to get my hands on the actual BSFC maps for my engine as well as something like the ScanGauge to verify that I'm hitting the intended engine load.