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In my truck it's something more like 1600 or 1800 rpm at 60mph. |
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Actually, the more I think about it, I think 2,200 is about 65 mph. Will have to make a note of it tonight on the drive home. |
EPA claims you can improve mileage by 80% with no change of the engine, through better powertrain.
holycow, is exactly right, he needs about 3 more gears to lower his engine speed at higher vehicle speeds. I wish I had a 6th gear in my VX. Aero means less sustained average power is needed to maintain a given speed. Better aero combined with much higher top gear ratios (import autos are now up to 8 speeds) mean you can capitalize on better aero by using lower engine speeds at higher loads. It may be the same rpm as idle but it will always be at a greater load, therefore with a much better BSFC than idle. Cylinder filling combustion events are always most efficient (lowest vacuum), but WOT at 1000 rpm is overkill. Vacuum is the thermometer of efficiency but the old belief that sustained lower vacuum operation equals economy is basically flawed. If you want an efficiency guage take the vacuum guage and read it backwards. Your pulse should be very low (to no) vacuum. If EOC is utilized, its no vacuum. When idling its high vacuum. Most efficient is low vac High vac is least efficient EOC is no energy consumption I found driving automatics using P&G to be much harder to get dramatic improvements, unless you can fool the tranny into staying in higher gear with a decent load applied. In the old days you could adjust the kick down cable to get the desired results. Maybe the tranny shift points could be changed through reporgramming the ecu. regards gary |
I can't see how anyone would want a 6th gear in their VX. I would constantly need to downshift at the slightest hills with such a setup. Seems the gains would be very slim and not worth the constant shifting, unless you keep the final gear ratio the same and make 1st, 2nd and 3rd closer. :D :thumbup:. Also, on fe.gov a 2004 4 speed automatic Celica gets 33hwy 25 city and 5 speed manual gets 30hwy and 23 city... how does that work? The site makes no indication the engines are different.
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But I still don't really understand your example, because the low rpm would tend to be an advantage, not a disadvantage. Idle is only a wasteful state if the engine isn't moving the car forward. If your engine idles at 800 rpm, and can also propel the car at 60 mph, at 800 rpm, then the latter state isn't properly called idling. And the key question is something you haven't specified: what's the load? Quote:
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And there's no reason to assume that running idle rpm at highway speeds is inherently inefficient, in BSFC terms. If the load is high (because you've installed a small motor, for example), it's not. Since you haven't specified the load, we don't have a clear picture of the scenario you're imagining. Quote:
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edit: oops, I was a bit off with those numbers. That should say 70mph=2357 rpm. And above I should say that 75mph= 2525 rpm. |
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I made that point here: https://www.gassavers.org/showpost.ph...7&postcount=22. Click through to see a picture of a Stewart-Warner 'Motor Minder,' which illustrates the point we're talking about. |
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