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Old 06-21-2011, 02:26 AM   #1 (permalink)
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Best way to drive hills

Heres the situation, a road with hill after hill. Whats the best way to traverse it with the least amount of fuel?

I can only imagine several ways:
EOC from the top of the 1st hill then go slow in a high gear up the next.

Speed up down the 1st hill and then coast up the next hill.

Speed up half way down the 1st hill then EOC half way down and half way up the 2nd hill then low speed up the rest of the 2nd hill.

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Old 06-21-2011, 06:18 AM   #2 (permalink)
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When driving something ridiculously overpowered you definitely want to EOC downhill and accelerate uphill. If the inclines are too long, or not steep enough, you may split them up to more than one pulse.
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Old 06-21-2011, 07:17 AM   #3 (permalink)
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Power up the hill, but cut power at the right time to crest the hill at a relatively slow speed. Engine off coast until your speed reaches your slowest desirable speed in the highest gear. Bump start and accelerate up hill if possible, or run at economical cruising speed to the next hill. You could also eoc pulse and glide to the next hill. Always try to crest the hills at a relatively slow speed, especially if you don't know what is on the other side of the hill (a stop sign at the bottom?).
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Old 06-21-2011, 10:42 AM   #4 (permalink)
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Light acceleration downhill to pick up speed, then gradually back off the throttle after you start climbing - still letting off as you go up, [steady throttle if you have a longer climb, but not accelerating], coast over the top, then gradual acceleration on the downhill, repeat.

It takes less horsepower and fuel to accelerate on the downhills than it does to try to power up the next hill. You may have to do some testing to see what works for you. I'd skip the EOCing if you have lots of ups and downs to do.
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Old 06-21-2011, 11:25 AM   #5 (permalink)
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Quote:
Originally Posted by Floordford View Post
Heres the situation, a road with hill after hill. Whats the best way to traverse it with the least amount of fuel?

I can only imagine several ways:
EOC from the top of the 1st hill then go slow in a high gear up the next.

Speed up down the 1st hill and then coast up the next hill.

Speed up half way down the 1st hill then EOC half way down and half way up the 2nd hill then low speed up the rest of the 2nd hill.
I'm using my ultra gauge to drive with 70-80% engine load going up hills. Your car, with its power, would possibly fly at 80% load. But you want more load--within reason--for more efficient use of engine movement/power... That's my understanding and practice.
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Old 06-21-2011, 11:57 AM   #6 (permalink)
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99Metro: ive seen semi trucks use that method. Almost like they are keeping close to the same engine load instead of maintaining the same speed.

California98Civic: It idles at 11% load and 20-25% load can move it pretty well. Maybe 35%ish for a big long hill.
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Old 06-22-2011, 11:07 AM   #7 (permalink)
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In higher powered, overgeared vehicles, powering up the hill is better, as it keeps the engine closer to its sweet-spot. In the case of my Jeep, I get my best highway mpg by maintaining steady speed up a hill, and then coasting down the backside, provided it's not steep enough for me to gain speed on the descent.

The mpg achieved from that is certainly better than what I see on flat ground, or very long, steep hills (where slowing down at the top doesn't prevent me from getting above my cruise speed by the bottom).
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Old 06-22-2011, 11:36 AM   #8 (permalink)
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I agree with most of the others. Accelerate up the hill, coast down it.
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Old 06-22-2011, 11:56 AM   #9 (permalink)
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The ultimate hill approach IMHO, ignoring minimum speed concerns for a moment, is to use the extra load on the climb to get to the best bsfc spot. i.e. find the best compromise between 75% load and 2500rpm if your bsfc map looks like the following (manual trans assumed). And then kill the engine near the top of the climb so that you barely coast over the top and down the other side.



Note, efficiency tapers off more gradually to the "west" or the "southwest", so that is the side I would error on if possible.
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Old 06-29-2011, 10:39 AM   #10 (permalink)
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Couldn't someone just do a more or less reasonable A-B-A-B test of different hill climbing methods? Someone who commutes in hilly territory could try one method on even days, another on odd days, and average it out after 2-3 months.

I crawl up hills at the slowest possible speed, often reducing both gear and speed instead of keeping gear and stepping on it, but I have no idea if this is the best way to do it since 95% of my driving is in flat-to-slightly-rolling terrain.

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