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Old 08-24-2009, 08:13 PM   #11 (permalink)
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Tygen - I believe that the gently rolling hills are perfect, even for neutral coasting w/ the engine on, because you can maximize your downhill stints with only short bursts of acceleration, and even the curves slow you down a bit if you pick up too much speed.

The longer, steeper hills aren't great, because you're wasting alot of energy in braking trying to keep your speed down.

I try to time my acceleration so that I can put it in neutral and speed up to the speed limit going down a hill, so that I don't have to waste as much gas speeding up.

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Old 08-24-2009, 09:44 PM   #12 (permalink)
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Quote:
Originally Posted by Christ View Post
Tygen - I believe that the gently rolling hills are perfect, even for neutral coasting w/ the engine on, because you can maximize your downhill stints with only short bursts of acceleration, and even the curves slow you down a bit if you pick up too much speed.

The longer, steeper hills aren't great, because you're wasting alot of energy in braking trying to keep your speed down.

I try to time my acceleration so that I can put it in neutral and speed up to the speed limit going down a hill, so that I don't have to waste as much gas speeding up.
+1 for rolling hills. I have a couple good ones on my commute and coasting in N with my auto Neon helps the mileage quite a bit. I'm not afraid to speed on them either but usually I don't go more than 25km/h over. The key to hills I think is climbling them, for my cars it seems top gear is always best so even though it seems unnatural to get a run at a hill, if it helps you stay in top gear to the top I think you come out ahead.
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Old 09-01-2009, 03:43 PM   #13 (permalink)
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I have only had experience with the rolling hills of central NC so can not say about larger mountains.

It was challenging at first because the distance between hills varies and the EOC is usually much shorter than you would like. Meaning you could coast for a much longer distance than the hills allow. I learned to just go with the flow. Say I pulse to 50 mph in a 45 psl zone and EOC on top of a small hill. I coast for… maybe ¼ mile and get down to 40 mph. My choices are to pop the clutch and accelerate to 50 mph to begin the next hill climb or coast another hundred yards right to the bottom of the hill before popping the clutch going 35 mph. (These are fictitious numbers, for example only). Which one works better for total trip mpg? It really depends on the hill you are about to climb and the next EOC coast on the other side. If it is a sloooow gradual climb then I gain some momentum to DWL the hill. If it is a shorter climb I coast right up to it then accelerate more aggressively for a few second before DWL up it.

The technique that works best in all circumstances is only possible with no traffic behind you. That is to start at the psl and coast whatever the distance available is. Then DWL the hill according to your end of coast speed and EOC the next downhill at whatever speed you are at. I’ve had a few days where I tried this on my commute and the results were fantastic! I had a few EOC starts going 25 mph and coasting down to 10 mph. I also had EOC starts going 40 mph and ending at 36 mph. What screws the whole process up is that vehicle appearing in your rear view mirror and you have to accelerate to the psl before they get to you. Unfortunately this happens when you are going 15 mph right at the bottom of a steep hill!!!

Bottom line I have come to think that small rolling hills will return better mileage than large mountains like Brian climbs. There is just no way to get back most of what you put into the climb. Small hills you lose much less climbing so do not need to gain that much more coasting.
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Old 09-01-2009, 05:34 PM   #14 (permalink)
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I think hill mileage results depend largely on having a long uninterrupted runout. I got 59 mpg on my Scion (210% of EPA) over 165 miles in the mesa country on the Navajo Reservation. The long runouts going down the mesas gave me great mileage, and there was no traffic to contend with. Most of the time going down steep mountains, I end up stuck behind some slug who makes me bleed off all my momentum with my brakes. Steep long hills do allow me to get great mileage, as I DWL up them, and get my best mileage P&Ging massive miles on the way down. EOC just comes out even, with a slight loss, but P&G drags out the coasting miles and allows big mpg numbers.
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Old 09-02-2009, 12:54 PM   #15 (permalink)
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Quote:
Originally Posted by WoodyWoodchuck View Post
I have only had experience with the rolling hills of central NC so can not say about larger mountains.

It was challenging at first because the distance between hills varies and the EOC is usually much shorter than you would like. Meaning you could coast for a much longer distance than the hills allow. I learned to just go with the flow. Say I pulse to 50 mph in a 45 psl zone and EOC on top of a small hill. I coast for… maybe ¼ mile and get down to 40 mph. My choices are to pop the clutch and accelerate to 50 mph to begin the next hill climb or coast another hundred yards right to the bottom of the hill before popping the clutch going 35 mph. (These are fictitious numbers, for example only). Which one works better for total trip mpg? It really depends on the hill you are about to climb and the next EOC coast on the other side. If it is a sloooow gradual climb then I gain some momentum to DWL the hill. If it is a shorter climb I coast right up to it then accelerate more aggressively for a few second before DWL up it.

The technique that works best in all circumstances is only possible with no traffic behind you. That is to start at the psl and coast whatever the distance available is. Then DWL the hill according to your end of coast speed and EOC the next downhill at whatever speed you are at. I’ve had a few days where I tried this on my commute and the results were fantastic! I had a few EOC starts going 25 mph and coasting down to 10 mph. I also had EOC starts going 40 mph and ending at 36 mph. What screws the whole process up is that vehicle appearing in your rear view mirror and you have to accelerate to the psl before they get to you. Unfortunately this happens when you are going 15 mph right at the bottom of a steep hill!!!

Bottom line I have come to think that small rolling hills will return better mileage than large mountains like Brian climbs. There is just no way to get back most of what you put into the climb. Small hills you lose much less climbing so do not need to gain that much more coasting.

I think you hit the nail right on what I saw. The amount of effort and gas spent going up the hill can not be regained on the coast down because you can't stay at a speed high enough to please the dude stuck behind you. At least the larger hills of western PA alowed for nice long coasts above the speed limit after climbing the hill. There were a couple times I let the coast run out to 35mph and that seemed about right to regain what I lost going up, but that is just not doable on I-95.
Also, it's difficult to quantify "Gently rolling" hills. To someone in Colorado it's different that someone in Kansas....More of an opinion thing....

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