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Old 10-07-2008, 05:59 PM   #1
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acceleration question

I have been reading that it is better to accelerate moderately with a stick shift to get into top gear faster then to accelerate slowly.

Which is better?


If you accelerate moderately what rpm should you be shifting at?
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Old 10-07-2008, 06:33 PM   #2
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In my automatic 4wd pickup I get the best economy with moderate acceleration. I usually give it about 25% throttle. In lower gears I see my Scangauge report 3 MPG or less with any amount of throttle pressure. Since I don't have much to loose I just hurry up and get into a higher gear faster.

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Old 10-07-2008, 06:54 PM   #3
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I remember hearing about revving higher to skip a gear in total for fuel economy
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Old 10-07-2008, 07:08 PM   #4
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I used to do well in my old AMC Spirit (manual 4 speed) by skipping 3rd gear and going straight to 4th.

-Jay
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Old 10-07-2008, 07:49 PM   #5
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Since you have a manual trans, use about 3/4 throttle and shift as early as you can without lugging the engine. If you're accellerating too quick using this method, shift earlier. If you need to accellerate quicker, shift a few hundred rpm higher.

Skipping gears isn't great for FE because you have to rev the engine a little higher in the low gears, which is a double hit to FE since you're spending more time in a lower gear, and you're reving the engine higher than optimal.

In my car I try to shift around 1500 rpm. This gives me plenty of accelleration for normal driving conditions, and I don't hold up anyone behind me. Accellerating and shifting this way feels odd at first, but you'll get used to it.
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Old 10-07-2008, 08:36 PM   #6
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I usually do 1-10 mph in first (there's no point doing it earlier, as it goes 1-10 in a second and a half), 10-15 second, 15-20 third, 20-30 fourth and 30+ fifth. The last gear you end up in depends more on where you are driving, stay in the highest gear you are comfortable with.

As DRW said, to change your acceleration, change your shift points rather than your throttle position. I usually change my throttle position depending on the incline (more on steeper hills) so that the gears are about the same. But that's just how I do it. I'm sure there are better ways.
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Old 10-07-2008, 10:05 PM   #7
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I have an automatic and coming from a stop I accelerate a bit 20% max throttle but I try to get in top gear and locked up as early as possible. with a manual (like my bike) I shift at lower RPM and let the torque pull me up to speed.
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Old 10-08-2008, 05:26 AM   #8
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Quote:
Originally Posted by DRW View Post
Since you have a manual trans, use about 3/4 throttle and shift as early as you can without lugging the engine. If you're accellerating too quick using this method, shift earlier. If you need to accellerate quicker, shift a few hundred rpm higher.

Skipping gears isn't great for FE because you have to rev the engine a little higher in the low gears, which is a double hit to FE since you're spending more time in a lower gear, and you're reving the engine higher than optimal.

In my car I try to shift around 1500 rpm. This gives me plenty of accelleration for normal driving conditions, and I don't hold up anyone behind me. Accellerating and shifting this way feels odd at first, but you'll get used to it.
This is great advice, and almost exactly what I do. Accel at 90% load and shift at 1500 RPM. If I need more power I just shift later.
Cars have gears for a reason. The only one I ever skip is first if conditions allow. That means downhill starts or flat starts with no one behind me.
The reason this way is better is because it keeps pumping losses lower by letting the engine have almost as much air as it can take at any given time.
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Old 10-08-2008, 05:36 AM   #9
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be careful that you don't give it too much throttle. too much throttle will throw you into open loop and your air fuel ratio changes. mine will go from 14.7 to 12.5 at WOT and where it reads WOT can be different on different cars.

this is not necessarily true if you have a wide band O2 sensor.

90% throttle might be enough to be considered WOT on some cars.
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Old 10-08-2008, 07:20 AM   #10
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I agree with the others, based on my experience. Use as much throttle as you can without triggering open loop fuel enrichment mode (which, if you don't have appropriate equipment to find out when that happens, you can just guess at 75 to 90 percent throttle opening), and shift earlier or later to adjust your acceleration.

I'm lucky, my VW doesn't need to use open loop (has something to do with having a wideband O2 sensor), so I just floor it. :P

I find myself shifting sometimes as low as 1200 rpm.

Take a look at the link in my sig about lugging, which is probably not what you think it is; definitely avoid lugging, but it's not so terrible if you're just making your engine growl a little.
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