Hypermiling hills? does it matter to accelerate going up or going down?

[KyleH]

I have a hypermiling question on hills if anyone has any experience.

My speed limit is 60mph, and I have been ranging 45-65 mph when no one is around. Using "L". While on the incline, I slowly let the car decelerate (slowly release gas in "L") as low to 45. At start of the decline, I start accelerating (slowly) the car until it reaches 65, then let it regen back to 55 on the flats.

Does this conserve or benefit the overall mileages? Does gravity on the incline help with accleration where it woudl be effective to accelerate faster on the decline and conserve more by decelerating slower in the incline? Does regening energy when the wheels are spinning at 65-55 produce more energy effectively than to have a constant speed?

Or, would I have been equally off by setting the cruise control to 60 mph?

-KyleH

[jaksecret]

While the wiki gives some information, it might be helpful to use practical knowledge to answer some of these questions. at the speeds you're talking about, wind sometimes is and sometimes isn't an issue. it probably starts to become a real 'drag' on the car above, say, 50mph. So, with that information alone, you should be able to determine that, uphill or downhill, the slower you are going, the less energy will be needed to push you through the air. Uphill, you'll need alot more power just to get up the hill, so try to minimize your speed uphill above, say, 50mph. However, going downhill, you're getting free momentum from gravity and as long as you're not actively accelerating, you're getting whatever speed you want 'for free' up to the point at which the wind drag starts slowing your car down again. the steeper the hill, the faster you can go before this becomes an issue.

But your use of 'L' all the time I think bears some discussion. With a perfect command of the pedal, you should be able to drive around in 'L' all the time. Since I'm not perfect, I usually use 'L' only when i'm about to need to slow down for some reason (a car, a stop light, etc), or i'm in traffic and want to accurately control my speed in the traffic flow. But on a mild downhill or uphill above, say, 50mph, i am in 'D' because i can be sloppier with the pedal and get more 'glide' out of the transmission. I've been playing with 'N' a bit on flat ground while gliding, but a little pedal control in D probably negates having to do that.

Lets see what others say.

[saghost]

http://en.wikipedia.org/wiki/Fuel_ec...Burn_and_coast

"Pulse and Glide" for us in EV mode.

If you're still in CD (as in, the battery hasn't switched to the fuel tank,) this *will not* get you better mileage in your Volt. There's no greater efficiency to be found with high accelerations with an EV - actually, you lose more power due to I^2*R losses in the wiring from the high currents. Worse, it has a good chance of forcing the car out of two motor into single motor (only a factor at speeds over 50 mph) costing you another 2-4% efficiency in back-EMF losses due to higher motor speeds.

AFAIK, the best approach for the Volt in EV for hyper-miling is a DWL (driving with load) approach - possibly modified with increased regen if the speed builds too much. (In DWL, you pick a power output/throttle position that gets you a speed you can tolerate on the flats, and then hold it as you go up and down hills - slowing down on uphills and speeding up on downhills.)

Or you can realize that your car costs a quarter as much to drive as anything else on the road, pop it into sport mode, and have fun with it...

[MrEnergyCzar]

Put it in cruise control....even on open back roads...

MrEnergyCzar

[Slapshot28]

Put it in cruise control....even on open back roads...

MrEnergyCzar

I totally agree! Plus, it's much less distracting to you and to other drivers.

IOW, it's safer.

[Ladogaboy]

If you're still in CD (as in, the battery hasn't switched to the fuel tank,) this *will not* get you better mileage in your Volt. There's no greater efficiency to be found with high accelerations with an EV - actually, you lose more power due to I^2*R losses in the wiring from the high currents. Worse, it has a good chance of forcing the car out of two motor into single motor (only a factor at speeds over 50 mph) costing you another 2-4% efficiency in back-EMF losses due to higher motor speeds.

Yeah, I couldn't imagine that pulse and glide would do anything in electric mode.

That being said, I am interested in the deceleration difference between D and L. I'm transitioning from an AWD (so lots of parasitic loss), so I'm curious how the Volt will compare.

[saghost]

Yeah, I couldn't imagine that pulse and glide would do anything in electric mode.

That being said, I am interested in the deceleration difference between D and L. I'm transitioning from an AWD (so lots of parasitic loss), so I'm curious how the Volt will compare.

D and L only changes the way the controls behave. You can achieve regeneration that matches "feet off pedals in D" in L by feathering the gas - and you can achieve deceleration that matches "feet off pedals in L" in D by light application of the brake pedal. In both cases, the car's systems will be doing exactly the same things, with the same efficiency (well, when matching D in L the brake lights are on which they aren't in L, but that's it.)

I very much prefer Sport and L for driving in traffic jams, but I'm fully aware you can get the same results without them - you just have to be a lot more active on the pedals - hitting the gas a lot harder, and hitting the brake pedal a lot more often. In Sport and L, the car can dance.

When the traffic situation and your patience allows it, coasting is more efficient than holding speed and then using regen - which is more efficient than having to use the actual mechanical brakes.

[tboult]

You want to conserve momentum and minimize regen (unless your coasting speed would be > 60mph. I've not done the computation but I believe, from my experiments, that around 65 or so, the wind drag eats more than the regen->drive paring. So you want to drive with load an minimize regen on the downhill. I do DWL using CC in D, setting it at the minimm level I'll accept and let D accelerate on the downhill (CC in L will hold the speed tight.. D will let it get higher) and on the steeper & longer hills I may use shift to L while still in CC if I get going to fast (on some the speed limit is 45 so I won't let it get about 55). On shorter steep hills, on my more agressive hypermilling days I'll do N and really let it coast up. I've not been able to measure enough difference in D and N over a few miles to decide that N is any better.. though on a few hills it lets me keep up with traffic better.