Uphill Pulse and Glide???? Waste of time?

[Santiago]

90% of my driving is either uphill or downhill. Pulse and glide works great on level or downhill but it seems almost questionable at best or futile with any kind of uphill grade. Does anyone have any pro comments or am I wasting my time trying to do this? Going uphill seems to more than wipe out any gains in MPG from going downhill and using pulse and glide.

[Bob64]

I haven't done any tests, but I feel its best if you - depending on the hill - build up speed before the climb, and have the engine on, but shedding speed, all the way up in one pulse, if possible. If others have some better techniques that arn't pulled out from my gut feeling, then please share

[efusco]

The serious hypermilers on CleanMPG may have a different POV...but I tend to not P&G on uphill climbs.

What I do is anticipate the hills as much as possible...I may start accelerating at 2300 or even 3000rpm just prior to the start of the climb in an effort to build enough momentum that I can climb the hill while staying at/below 3000rpm if at all possible...since above 3000rpm efficiency starts to drop fairly precipitously.

A lot depends upon how much speed you're willing/able to lose to maintain that RPM...some of the long steep hills here in the Ozarks require me to push 4000-4500rpm to maintain the highway speeds necessary for normal traffic flow.

[andyprius]

You just can't get around topography and overall speed. Do an average of something more than 50% downhill, keep speed between 30-40 MPH and stress NO energy use on the MFD and I guarantee a green battery. Coming back the other direction where it's more uphill and the opposite occurs, a low charge rate and 2-4 purple bars (about) Exteme conservative driving on the drive back will not ever produce a green battery, but will drive the guy behind you crazy.

[JimboK]

I do P&G only on the gentlest of hills, where my typical pulse rate (as determined by RPM and fuel injector timing) still allows acceleration. Otherwise, in hilly terrain I'm doing more of what could be called terrain driving: ICE-on going up, glide going down. And as the others suggest, I anticipate hills and build momentum to carry me up the next one when I can.

[JSH]

I have been successful with pulse and glide on hills.

For example the 65 mile drive to my former employer was remote state highway with little traffic. With the cruise control set to 65 I got 45 mpg.

If I allowed my speed to gradually drop to 55 mph going uphill and glide or lightly regen downhill to a max of 75 mph I got 55 mpg.

[efusco]

Originally Posted by jhinton

I have been successful with pulse and glide on hills.

For example the 65 mile drive to my former employer was remote state highway with little traffic. With the cruise control set to 65 I got 45 mpg.

If I allowed my speed to gradually drop to 55 mph going uphill and glide or lightly regen downhill to a max of 75 mph I got 55 mpg.

I think that's a bit different than what I consider pulse and glide, but it's equivalent to what I do...maintain a steady/efficient RPM uphill letting speed bleed off as tolerated. Downhill I'll glide/hyperstealth as fast as conditions allow. It's clearly better than maintaining steady speed.

[Celtic Blue]

Yep, that's a different beast. I almost never get to do the classic pulse and glide because around here is mostly hills. When I have had the opportunity for true pulse and glide I've been astounded at the mileage.

I call the hill driving mentioned previously "roller coastering" and it is what I practice when I can (except for traffic and signals of course.) I only regen to keep the speed down to a reasonable level, then go back into a glide before the crest where I hit my minimum speed.

There is probably some speed/pitch/distance combination where it makes more sense to regen early rather than suffer the aero losses from higher speed. Obviously, if one ran flat out glide on a long downhill, energy that could be stored in the battery for the coming climb would instead all be wasted in aero drag. On the other hand regenning the whole way down to maintain a cruise speed needlessly converts potential energy into charge with its attendant losses. When you throw in engine efficiency and vehicle speeds on the climb it becomes a rather complex problem computationally. Picking a number out of the air I suspect the tradeoff generally becomes unfavorable above 65 mph...but I wish it was 70 or 75...

[Bob64]

Well... I have to add that I avoid using brakes when going downhill.... Especially since my uphill climbs tend to leave a rather large "buffer" zone between me in the car ahead of me, such that by the time I catch up to him, I'm matching his speed.

It's my belief that regeneration is much less efficient then losing the energy to aerodynamic drag (the prius has a low drag coefficient anyway).

Think about it:
kinetic - > electrical -> chemical - > electrical -> mechanical is VERY inefficient

I'd rather keep as much energy stored in kinetic momentum then force it though all those hoops. It also gives you time to gain a lead on that car thats tailgating you.... and a chance to start the next hill at a running start.

One other thing... my hills typically leave me at less then 40mph. So I make sure my ICE is off, then drop it into neutral (to prevent ice startup when accelerating above 41mph), and allow gravity to take me to 55+ mph (and down again to normal speeds once I reach the next hill).

[efusco]

Originally Posted by Bob64

Well... I have to add that I avoid using brakes when going downhill.... Especially since my uphill climbs tend to leave a rather large "buffer" zone between me in the car ahead of me, such that by the time I catch up to him, I'm matching his speed.

It's my belief that regeneration is much less efficient then losing the energy to aerodynamics.

Think about it:
kinetic - > electrical -> chemical - > electrical -> mechanical is VERY inefficient

I'd rather keep as much energy stored in kinetic momentum then force it though all those hoops. It also gives you time to gain a lead on that car thats tailgating you.... and a chance to start the next hill at a running start.

+1--I aim for zero regen...never get there, but that's the target.