Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Move over granny, BSFC is coming through!

#SaveTheManuals · 10-02-2019, 05:47 PM

I was trying to think of an inflammatory title for this thread to lure people in, but I got lazy and settled for moderately humorous instead.

To date (i.e. my entire driving life until last week) I've only employed granny-techniques in my quest for better MPG. Except when I had a Miata...then I just drove like a maniac 100% of the time and had an amazing time wasting fuel. This forum introduced me to BSFC, and the idea appealed to me immediately -- not only because it makes sense, but also because it sounds like a lot more fun to drive that way.

For the final 1/5th or so of my last tank, I accelerated fairly hard in the 2020 Corolla SE (2.0L 6-speed MT) to get up to speed. Not pedal-to-the-metal, but pretty spirited. I was able to slowly increase the MPG on that tank toward the end, so I think I'll abandon the granny-style for a while and see where BSFC takes me.

I don't have the BSFC map for my car's engine, but Toyota published a chart that looks suspiciously similar:

I think this confirms my SOTP feel that < 2,000 is a little low for peak efficiency; in 4th gear at moderately high load it feels like it's almost on the verge of lugging at 2,000 RPM. It looks like the sweet spot is about 2,700 RPM (presumably under moderately heavy load?). I'm really not sure why everything falls off a cliff at ~3,000 RPM and the chart ends at 3,200 RPM. It looks like incomplete data to me. Peak torque on this engine is at 4,400 RPM.

Is there anything to be gleaned from the chart to help me figure out optimal RPM for shift points? My main concern is when to shift from 3rd to 4th. It seems like I need to shift in 3rd later (close to 4,000 RPM, probably non-optimal efficiency) in order to get into 4th significantly above 2,000 RPM so there's no lugging at high load.

10-02-2019, 05:47 PM	#1 (permalink)
#SaveTheManuals EcoModding Lurker Join Date: Sep 2019 Location: Northeast Posts: 27 ATOYOTA - '20 Toyota Corolla SE 90 day: 37.91 mpg (US) Thanks: 8 Thanked 5 Times in 5 Posts	Move over granny, BSFC is coming through! I was trying to think of an inflammatory title for this thread to lure people in, but I got lazy and settled for moderately humorous instead. To date (i.e. my entire driving life until last week) I've only employed granny-techniques in my quest for better MPG. Except when I had a Miata...then I just drove like a maniac 100% of the time and had an amazing time wasting fuel. This forum introduced me to BSFC, and the idea appealed to me immediately -- not only because it makes sense, but also because it sounds like a lot more fun to drive that way. For the final 1/5th or so of my last tank, I accelerated fairly hard in the 2020 Corolla SE (2.0L 6-speed MT) to get up to speed. Not pedal-to-the-metal, but pretty spirited. I was able to slowly increase the MPG on that tank toward the end, so I think I'll abandon the granny-style for a while and see where BSFC takes me. I don't have the BSFC map for my car's engine, but Toyota published a chart that looks suspiciously similar: I think this confirms my SOTP feel that < 2,000 is a little low for peak efficiency; in 4th gear at moderately high load it feels like it's almost on the verge of lugging at 2,000 RPM. It looks like the sweet spot is about 2,700 RPM (presumably under moderately heavy load?). I'm really not sure why everything falls off a cliff at ~3,000 RPM and the chart ends at 3,200 RPM. It looks like incomplete data to me. Peak torque on this engine is at 4,400 RPM. Is there anything to be gleaned from the chart to help me figure out optimal RPM for shift points? My main concern is when to shift from 3rd to 4th. It seems like I need to shift in 3rd later (close to 4,000 RPM, probably non-optimal efficiency) in order to get into 4th significantly above 2,000 RPM so there's no lugging at high load.