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Old 09-06-2006, 06:56 AM   #1
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When do I shift for optimal MPG/FE?

This website must be the best place to ask this question. I already know that when driving, it's best to anticipate what lies ahead (hills, red traffic lights, etc). But, even when you've sped up a bit on a downgrade....to get your mojo up for the big hill that lies ahead, you'll still likely run out of speed at some point on the hill. So my question is, once you've started to run out of speed on the incline, when do you decide to drop down a gear? If I'm in 5th gear and just about running out of steam, should I know there's a definite margin of loss if I stay in 5th gear and try to stretch it...since the engine is now working harder to get me over the hill in 5th. But if I shift to 4th gear too soon then I've increased my RPM's...which also may use more power/gas if I downshift too soon. SO, folks, where do I shift? I would imagine this depends upon the engine's power band. I have an '88(F.I.) CRX HF.

**Bonus question: where do you all typically shift when taking off? Do you typically have cars honking behind you?

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Old 09-06-2006, 08:58 AM   #2
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Given how manufacturers seem to build gasoline engines, I would think that your minimum BSFC is going to be ~2/3-3/4 throttle from ~2-4k rpm. But... the actual BSFC map would tell you what you want to know.

Originally Posted by FormulaTwo
I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 09-06-2006, 03:33 PM   #3
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**Bonus question: where do you all typically shift when taking off? Do you typically have cars honking behind you?
On my car, I have been shifting at 1500 rpm's or lower. I haven't had anybody honk at me; yet.
Horsepower is how hard you hit the wall, torque is how much of the wall you take with you.

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Old 09-06-2006, 03:59 PM   #4
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what is your speed

What is your speed on those hills? Its better not to downshift unless the hill is just extremely steep. How are you setting up for those hills? Sometimes it is better on the shorter downhills to go ahead and keep your gas pedal in the same position and gain a little speed so you can scrub off the speed on the uphill without leaving the optimium range of operation.

My shift points 1500-2000 depending on the situation.
Current Stable
GasSaver: 2000 Honda Insight Silverstone w/AC 65+mpg
Track Terror: 2002 Honda S2000 Gran Prix White- lots of mods - 28mpg
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Old 09-06-2006, 10:21 PM   #5
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flat shift at 1500
mild hill shift at 2000
steep hill 2500
mild downhill shift at 1200

if i know i can get away with some engine off then i just keep it in 3rd gear until i reach 35 to 40 mph depending on the situation then let the revs settle down before killing the engine (gotta lube it first before killing it for a wee bit!)

i try not to barely climb rpms in 1st gear, i want to get out of 1st asap but at the same time not getting creamed by some automatic behind you that doesn't need to shift from 1 to 2, I have to take my time because my car sucks when trying to sync to the 2nd gear (it loves to take its time, shift any faster and i burn too much clutch :P so I try to wait for revs to sync before shoving it into 2nd gear)

but hey that's just me, i'm sure since your shifting at such low rpms, you can quick shift and barely burn some clutch? who knows, my rpms don't drop when I clutch in (older cars do.. lucky bastards) due to the emissions system burning any remaining fuel before injecting some more.
If your reading this, then good for you, your saving some gas because your here.
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