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Old 06-28-2017, 07:34 AM   #1 (permalink)
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Brake Specific Fuel Consumption

I am learning (or trying to learn) a whole new science since joining this site. BSFC is one of the many black arts I have come across.
I have been unable to find a BSFC chart for my Honda 1.2 i-DSI engine but I do have a Power and Torque curve for it. I have noticed on the BSFC charts I have studied that the sweet spot for fuel consumption seems to always be just below the peak in the torque curve so is it safe to assume, for a start anyway (until I have my ScanGauge), that on my engine it would be round about 2500 to 3000 rpm?

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Old 06-28-2017, 08:26 AM   #2 (permalink)
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I'd say thats a pretty safe assumption. It seems most engines are usually around that range.
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Old 07-02-2017, 10:52 PM   #3 (permalink)
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Peak torque for my engine is at 4500rpm, best BSFC is at 2000rpm.

I get the best economy by cruising with the lowest engine RPM possible at any speed.
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Old 07-07-2017, 11:47 PM   #4 (permalink)
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It's worth noting that there's only a tiny drop off if you fall off the peak island - you can go all the way to ~3750rpm with nearly the same efficiency. OEM's have already tuned our engines to be economical for the majority of real world driving.

An OBD gauge is unlikely to pick up improvements in economy at BSFC, it measures air, not fuel, and is never that accurate.

I had a pre OBD MY2000 Mercedes that had a definite dip in consumption as measured at the injectors at ~2800rpm (80km/h). My non OBD 2010 Proton will get my UT-Comp so we'll see I can pick up a similar drop again.

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Old 07-08-2017, 05:05 PM   #5 (permalink)
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Minimum BSFC is almost universally close to maximum load at ~2k-3k rpm.

Brake Specific Fuel Consumption (BSFC) Maps - EcoModder
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Old 07-09-2017, 06:11 PM   #6 (permalink)
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I still think 3000 is too high... More than 2500 is not a preference of mine, though I have no choice in first and second gear. I also avoid more than 80% load. Natuarally aspirated 1.6L non-vtec Civic gets 60-70mpg tank averages by driving this way almost ALL the time. You mileage may vary.


See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.

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