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Old 11-08-2007, 12:20 PM   #1
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perfect time to shift?

I shift below 2000 rpm on my 94 civic dx, since i drive 100% city. im wondering if it would save more gas if i shifted at 3000 rpm would be more efficient, since it takes more time to get up to speed with shifting at 2000 rpm, the time wasted might consume more gas since shifting at 3000 will make me get up to speed faster and coast
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Old 11-08-2007, 12:36 PM   #2
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Well I know on my VX, which has a shift-light to tell you where to shift, it keeps pretty much all of the city shifting under 2200rpm. The VX does have more tq lower in the RPM band than the DX motor, so you might want to go up to 3k...not sure really. I would try shifting higher and compare tank mpg results to shifting at a lower RPM.
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Old 11-08-2007, 02:07 PM   #3
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My untested hunch is that you want to shift at as low RPM as possible without having it lug after you shift. Sometimes when driving a Prius I feel that fast bursts of acceleration are just as efficient as slow acceleration because of the car's predisposition for P&G. But the Prius has the continuously variable transmission that makes it easier to do fast bursts while maintaining optimum RPM. I think most people would tell you to get a SuperMID and do some testing. I find it hard to believe you get 28mpg shifting at below 2000rpm. I'm pretty sure the general consensus early shifting is better. As long as the engine isn't lugging.
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Old 11-08-2007, 02:45 PM   #4
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but shifting isn't always the answer. In my insight I've found that some times its easier to hold a higher FE average in a lower gear. I think alot depends on your speed. I can travel 45mph in 4th and maintain the same mpg as I can in 5th. It really depends on several other variables other than RPM.
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Old 11-08-2007, 03:52 PM   #5
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I had a supermid before but i sold it since i drive 100% city now, with tons of stop and go, so i dont want to concentrate on looking at it when theres alot of people and cars around me, can be dangerous

1993civicvx : i think if you had my route and lived where i live, getting 28mpg is normal haha. i used to get 44 mpg on my car before i moved to philly
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Old 11-08-2007, 04:25 PM   #6
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When I had my 2000 ZX2 with a 2.0 DOHC motor, I found better fuel mileage shifting at 2 1/2 grand
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Old 11-08-2007, 05:11 PM   #7
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I shift no higher than 1500rpm. Usually around 1300-1400 rpm.
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Old 11-09-2007, 04:18 AM   #8
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My understanding is that shifting lower and keeping a larger throttle opening reduces pumping losses. Less fuel/air mixture also goes through an engine at lower RPM. That's not to say that it's good to throw it in a low gear and stomp on it. Heavy throttle (more than 70-80%) will cause enrichment. This is how I heard it explained. Hopefully someone can confirm or correct this, as I am still a relative novice.

I generally shift around 1500 RPM unless traffic conditions require a little more umph. Then I might let it go to 2000 and skip a gear somewhere when my speed is where I want it to be.
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Old 11-09-2007, 11:01 AM   #9
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So is it better to be at 1500RPM and 60% throttle or 1250RPM and 100% throttle? Which uses less fuel? It seems to me 1500 would, but I never do it. I always opt for the lower gear if I can. I need a SuperMID super bad.
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Old 11-09-2007, 11:12 AM   #10
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Quote:
Originally Posted by 1993CivicVX View Post
So is it better to be at 1500RPM and 60% throttle or 1250RPM and 100% throttle? Which uses less fuel? It seems to me 1500 would, but I never do it. I always opt for the lower gear if I can. I need a SuperMID super bad.
Just to throw a wrench into everything..... I, for the life of me, CAN NOT get my car out of closed loop while in gear and stomping on the throttle... Otherwise, ideal would be closer to as much throttle as possible while keeping it out of open loop while also considering load (constant = better)
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