Quote:
Originally Posted by California98Civic
I know it might seem counter-intuitive but it seems to work well. Look at Palemelanesian's PaleCivic fuel log. He accelerates between 1500 and 2000 rpm at about 80% load. I do about the same, often 2200 RPMs. A distinction worth something might be that we're not at "maximum load" as you say, if by that you mean WOT and 100% load. We are at maybe 30% throttle and seeking about 80% load, which is generally regarded as the best region on the BSFC map for fuel economy purposes. I'm not claiming expertise, just experience. It works, and lots of guys here argue this is why.
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Oh, I understand that. I also accelerate at 70-80% load. I also understand that at lower load, the peak BSFC comes at a lower rpm. For example the S2000 has best 100% load BSFC at ~4700rpm eyeballing it off the chart, but the peak efficiency arrives at 3000rpm.
What I have trouble believing is that the efficiency at 1500-2000rpm is better than it is at say 2000-2500. Most engines have their efficiency falling off at all load levels below 2000rpm. I try to get out of first early if I don't need to immediately accelerate since 2nd gear has much more controllable power on my short geared car, but otherwise I shift at 3000 to avoid landing much below 2000rpm in 2nd.
My car can be driven if I use the 1500-2500rpm range only and I'd prefer to use that range because it makes the shifts easier, but I have a strong suspicion that at 1500rpm the engine's efficiency is already pretty crappy. Maybe my engine is just in bad shape. The only hard and fast numbers I have are 1500rpm in 5th seems to get less mpg than 2000rpm in 5th, which is my best steady state cruise speed. On a road that I know is pretty much completely flat, to hold 1500rpm in 5th requires a somewhat high load, and Torque (which can read fuel flow rate and OBDII speed) seems to suggest that 4th (1900rpm) gives slightly more mpg than 5th. My 5th gear is about the same number of revs per mile as the 6th gear on an AP2 Honda S2000, so we're talking VERY short.
I'd like to do more testing on this as I do a few more tune up things to my engine. I don't burn through gas very fast so it's hard to do tank to tank testing. Yesterday Torque said I got 33mpg on a 50 mile drive even though I was pulse and gliding most of the time on the highway below 60mph, and drafting a semi...perhaps it's just my engine needing some work.