Regen in "N" and "D", Interesting Observation

[Ladogaboy]

It seems like intelligent feathering of the accelerator can achieve everything you're trying to, with less hassle and risk.

It's possible, but there really doesn't seem to be a good coast spot for the Volt. We already know that pulse-and-glide doesn't work with this car, for a number of reasons, but feathering the accelerator might work as an alternative. Again, like I said before, the primary goal is to time lights so that you can conserve as much momentum as possible. The deceleration that occurs in D (without feathering) seems greater than ideal for maintaining momentum.

[Ladogaboy]

The past few days I have taken trips to a small town . I use 0.6 kWh to get to the top of a hill . Later I make the descend using L , and it not only keeps my speed down without using brakes , it generates 0.4 kWh so the entire trip only consumes 0.2 kh .

If I try the coating in N method , I would use more energy and braking .

Apples and oranges. There is a time and place for everything, and as I was just saying, momentum is the name of the game. Because of the regen braking system, hills are about the closest the Volt will get to mimicking the effects of pulse and glide.

[tboult]

The point you seem to be missing is that I can achieve exactly the same result - the same car speed sequence and power flows - by coasting with the accelerator not quite released in D, or moderately depressed in L. The only thing I can see that N does for me is make it easier to find that coasting spot - and throw out regen while preventing acceleration if I get forced out of that spot. It seems like intelligent feathering of the accelerator can achieve everything you're trying to, with less hassle and risk.

Intelligent feathering (compared to N) has much more hassle and more risk of wasted energy but lower physical risk (since you don't have to shift to speed up). I don't us N unless there is virtually noone around, luckily in my commute that is common ;-)

@Ladogaboy.. I do my light timing by knowing the speed at which I leave one light to time them all.. if I set CC at 38 (in my local 45mph zone) and the traffic is light, I never even have to take it out of CC. If traffic is heavy (more cars) then I drop it to 36.. Coasting means you were already going too fast -- reduce your acceleration way earlier and avoid regen if you can. In stop/go traffice I'd never use N.. someone behind me may not be stopping fast enough (because I'm slowing) and that exactly when I want to be able to accelerate.

I use N only for rolling hills (on say my local aptly named roller-coster road) where I can coast from 30 up to 55 and back down going over those hills. If I do the same hills in D I only coast up to 42 or so and don't make it near as far up the next hill.

@ sinnombre coasting on hills only helps if you have to go back up the next one... clearly not a good thing if you have to stop anyhow

[Ladogaboy]

@Ladogaboy.. I do my light timing by knowing the speed at which I leave one light to time them all.. if I set CC at 38 (in my local 45mph zone) and the traffic is light, I never even have to take it out of CC. If traffic is heavy (more cars) then I drop it to 36.. Coasting means you were already going too fast -- reduce your acceleration way earlier and avoid regen if you can. In stop/go traffice I'd never use N.. someone behind me may not be stopping fast enough (because I'm slowing) and that exactly when I want to be able to accelerate.

That must be nice. The lights here are irregular, and many side streets have sensors that will turn the main street's light red at random times. Nothing more discouraging than seeing two dozen cars come to a stop for 30-60 seconds just so one car can make a left turn.

[sinnombre]

Apples and oranges. There is a time and place for everything, and as I was just saying, momentum is the name of the game. Because of the regen braking system, hills are about the closest the Volt will get to mimicking the effects of pulse and glide.

The only time I am comfortable using neutral for coasting is with a manual transmission . I do use this method in my Jeep , but I think it's very easy and efficient to just drive the Volt in L and let the car regen some energy while slowing down .

[saghost]

very interesting conversation. Perhaps we could/should ask for a new feature that takes info from Volt vehicles (via Onstar) to interpolate optimal speeds between lights to avoid all reds and to then push that info to volts driving those same routes/times. Imagine the value of being able to have cruise control that actually knows how to time all lights wherever/whenever one goes. OMG that would be cool, and it is completely doable. And patentable. I hereby declare that I am the owner of this incredible idea and that no one anywhere can ever use it without at least thanking me profusely and with Laurel and Hardy handshake. ummm...never mind...time to take my nap now.

Interesting thought. Volts with LDA and FCA already have a video camera in the front that the car is doing a bunch of processing on... For a Nav equipped car, the car knows what light is what... If it had a database of light timings, it could tell you from watching when the light rolled in the distance when it would be yours, and/or recommend an average speed to approach the light at (or set such a speed by cruise control.) Won't catch the initial roll of a sensor light, but could tell you all about any red light you're approaching, in theory (assuming it has the light in LOS early enough to get the initial roll timing. Interesting thought...

[Ladogaboy]

There would probably be liability issues, and I'm not sure that the general public is quite ready for car features bordering on autopilot.

[Ladogaboy]

Yeah, but if I were GM, I'd worry about people running red lights (possibly causing accidents) and then blaming it on the smart cruise control. "But officer, I had my red light approach on, and it told me that the light was green!"

[Logical_Thinker]

It's possible, but there really doesn't seem to be a good coast spot for the Volt. We already know that pulse-and-glide doesn't work with this car, for a number of reasons, but feathering the accelerator might work as an alternative. Again, like I said before, the primary goal is to time lights so that you can conserve as much momentum as possible. The deceleration that occurs in D (without feathering) seems greater than ideal for maintaining momentum.

Ladogaboy, why doesn't pulse-and-glide or a modification thereof work for the Volt? How about powering off the Volt in Neutral (treating it like turning an ICE off, in Neutral) when approaching an intersection -- I'm not necessarily suggesting this as a regular practice (though I've done that in auto-transmission ICEs successfully a lot) in the Volt but just as a test....

[saghost]

Ladogaboy, why doesn't pulse-and-glide or a modification thereof work for the Volt? How about powering off the Volt in Neutral (like turning an ICE off, in Neutral) when approaching an intersection?

I'm obviously not him, but I'm going to try to answer your question anyway. The Volt Pulses & Glides for you, when it's useful.

Pulse and glide exists mainly to move the engine into more efficient operation - it's mostly useful when the car is moving at speeds that require less power than the slowest full throttle operating point - speeds where the car would throttle the engine. By accelerating and then gliding, the engine operates at a better point - and then shuts down, so you lose a lot of the bearing friction losses during the glide.

In EV operation, it isn't relevant - there's no big penalty for operating at part power to be overcome - in fact, the bigger penalty is for operating at high power, in the form of resistance heat loss in the wiring.

In extended range operation, it would be an issue below about 65 mph for the Volt - but instead of throttling the engine, the Volt cycles it, in effect performing it's own pulse and glide using the battery as a reservoir instead of the car's kinetic energy. It runs the engine harder than it needs to to move the car for several miles (much of it in "virtual 6th gear" with the main drive motor stopped and the engine providing all of the drive power and a little extra through the smaller motor to the battery,) and when it's built up ~400 Wh of power, it turns the engine off and drives a mile or two electrically (you only see the full 400 Wh on very flat surfaces, because it's much more sensitive to power demands than state of charge. Letting off of the gas completely in L will shut the engine down anywhere in this range.)

If you could hit dead on the v6th acceleration level, and a zero power coast, you might get fractionally more efficient than what the car is doing. But it's a lot more effort, and only a tiny gain - the car has already granted you 80% of the P&G benefits anyway.