To maximize mileage, I put my Bolt in neutral while coasting down a hill, with due acknowledgment of hazards of having reduced control over the car vs. when in gear. I see reference in the manual to the car shifting into Park automatically if left in neutral "for extended periods of time." Do I need to be concerned about other issues, and in particular is there any risk of a hill being long enough that the car might automatically shift into Park while I'm still coasting? Thanks.
Coasting in neutral
1 - 20 of 75 Posts
I assume they are talking about when the car is sitting. The manual also says the car won't shift into Park above a few miles per hour.
Joined
·
2,121 Posts
Are you actually sure this saves you anything? While you're driving all the car's electronics and systems are using about 1 kW, so driving in neutral you are slowly running down the battery.
Typically going downhill the car can stay at constant speed and get some regen in as well.
If you want to feel like you're doing cool things for control, I'd say stick with one-pedal driving.
Joined
·
336 Posts
I'm with you Striper. First, I had a call with some GM engineers on another matter and I asked them outright if there is any mechanical downside to using N. They were clear: No.
As I learned on this forum. if you drive so that the energy used/regenerated is close to 0 (say between -2 and 2 kwH) that is exactly like driving in N. I have confirmed this by simply driving at 0 or 1 or -1 kWh and shifting to N: there is no change. The problem is that it takes concentration and effort to keep the effort close to 0; in fact, it is almost impossible in the terrain around here. Cruise control doesn't help. So I often resort to N.
And, yes, this does save energy. One a downhill, one would often be wasting energy if one was using kWh. And if one is storing kWh, slowing the car down, that too is a waste (depending of course on the character of the hill). I live at 9500 feet in a very mountainous environment with all kinds of hills: small, big, and giant (eg, 6000 feet down from Eisenhower Tunnel to Denver). So while the car of course regenerates on downhills, if that slows the car excessively requiring energy input when the hill flattens, that is a net negative.
As I learned on this forum. if you drive so that the energy used/regenerated is close to 0 (say between -2 and 2 kwH) that is exactly like driving in N. I have confirmed this by simply driving at 0 or 1 or -1 kWh and shifting to N: there is no change. The problem is that it takes concentration and effort to keep the effort close to 0; in fact, it is almost impossible in the terrain around here. Cruise control doesn't help. So I often resort to N.
And, yes, this does save energy. One a downhill, one would often be wasting energy if one was using kWh. And if one is storing kWh, slowing the car down, that too is a waste (depending of course on the character of the hill). I live at 9500 feet in a very mountainous environment with all kinds of hills: small, big, and giant (eg, 6000 feet down from Eisenhower Tunnel to Denver). So while the car of course regenerates on downhills, if that slows the car excessively requiring energy input when the hill flattens, that is a net negative.
Joined
·
8,977 Posts
But the problem is that if you're in "N" you don't get any regen, do you? So when you have to slow for curves, etc. you're just burning your kinetic energy up as heat.
It seems to me that if you use cruise control then it would regen the optimal amount of energy without worry about minding the pedal position, and you'd also get the regen from any braking you need to slow for curves.
Joined
·
392 Posts
bingo
On long downhill mountain passes a “sweet spot” might be encountered where the force of gravity offsets opposing forces of: ( tire to road friction + motor/axle drag in neutral + aerodynamic drag). That offset situation might just keep the vehicle rolling down a long pass at a relatively constant desired speed.
Engaging N in that situation will as stanwagon mentions, could enable speed to drift up and down within an acceptable range. And in theory save energy as compared to having D engaged with cruise control. Because in D invariably a little energy will be applied from time to time and conversely a little regen but the regen will be less than 100% efficient, certainly less efficent than coasting in N. So net-net a tiny bit more energy will be used with D on cruise control. Recognizing this is really splitting hairs. And coasting in N one would need to stay on one’s toes when catching up to traffic, or going too fast or too slow, in order to know when the best time is to engage D again.
I won’t be able to experience coasting due to lack of long constant-slope downhills combined with generally horrible traffic on highways clogged with commuters and transport trucks. The only time I use N is on sidestreets near home for a short distance when I think I want to dry out the friction brakes. And in trying to engage N, mine seems balky as it takes a couple of tries to get N. Almost like the vehicle is saying “do you really want to to this?.. it does feel a little creepy as well. As I can’t help but think that the vehicle or me is going to end up accidentally destroying the parking paul in the transmission.
Engaging N in that situation will as stanwagon mentions, could enable speed to drift up and down within an acceptable range. And in theory save energy as compared to having D engaged with cruise control. Because in D invariably a little energy will be applied from time to time and conversely a little regen but the regen will be less than 100% efficient, certainly less efficent than coasting in N. So net-net a tiny bit more energy will be used with D on cruise control. Recognizing this is really splitting hairs. And coasting in N one would need to stay on one’s toes when catching up to traffic, or going too fast or too slow, in order to know when the best time is to engage D again.
I won’t be able to experience coasting due to lack of long constant-slope downhills combined with generally horrible traffic on highways clogged with commuters and transport trucks. The only time I use N is on sidestreets near home for a short distance when I think I want to dry out the friction brakes. And in trying to engage N, mine seems balky as it takes a couple of tries to get N. Almost like the vehicle is saying “do you really want to to this?.. it does feel a little creepy as well. As I can’t help but think that the vehicle or me is going to end up accidentally destroying the parking paul in the transmission.
Joined
·
749 Posts
Striper41 , Putting the car into Neutral when going downhill is not necessary, but it is a good way to dry out wet brakes without regen interfering (as stated above). You are not maximizing energy. You are wasting it.
Manage your speed with the pedal and put the car in L for maximum regen. Use the regen paddle for more.
Manage your speed with the pedal and put the car in L for maximum regen. Use the regen paddle for more.
Joined
·
8,977 Posts
Yeah, if "N" lets you roll close to the speed limit, I can see that this would be true. But that seems to me like an extremely specific situation, not likely to be encountered very often unless you happen to live near just the right kind of hill. And if you have to use the brake pedal for curves or traffic then you're going to start eating into those small savings pretty quickly.
Few years ago I did this on my suburban. Put it in neutral down a hill and blew the transmission when I put it back in drive. Left me stranded in the middle of nowhere. My emotional scars prevent me from trying this on the Bolt, even if intellectually I know it's okay.
Joined
·
749 Posts
Hmmmm. Rethinking neutral versus regen on a downhill grade.
There are always friction losses. Regen is not 100% efficient.
Therefore, regen-ing to the bottom of a hill while not exceeding the speed limit would recover a certain percentage of the energy lost.
Coasting in neutral to the bottom and using the brakes WOULD waste energy, but if the brakes do some regeneration (which we know they do), then some energy is regained.
All other things being equal, if you barely use the brakes, then you would not gain or waste any more or less energy. But the moment the friction brakes are engaged to limit the speed, you are wasting some energy that could have been recovered.
If you never touch the brakes and do not care about your speed, you will have the best energy efficiency, and you might be going 70+mph at the bottom of the hill/mountain.
There are always friction losses. Regen is not 100% efficient.
Therefore, regen-ing to the bottom of a hill while not exceeding the speed limit would recover a certain percentage of the energy lost.
Coasting in neutral to the bottom and using the brakes WOULD waste energy, but if the brakes do some regeneration (which we know they do), then some energy is regained.
All other things being equal, if you barely use the brakes, then you would not gain or waste any more or less energy. But the moment the friction brakes are engaged to limit the speed, you are wasting some energy that could have been recovered.
If you never touch the brakes and do not care about your speed, you will have the best energy efficiency, and you might be going 70+mph at the bottom of the hill/mountain.
Joined
·
749 Posts
I have read that this is a bad thing to do to an automatic transmission.
The Bolt is a different animal. Unfortunately, I do not know what kind of animal it is.
It doesn't have a transmission. It's just reduction gears. It theoretically should be Ok, but I would not try it myself.
Hi. First post. Having driven a Mitsubishi I-MiEV for the last 5 years, I'm quite experienced at using neutral to coast. I've done it several times now with the Bolt.
Since there is no mechanical change between Drive, Neutral, and Reverse, it doesn't run the risk of damaging the gearbox to coast in Neutral. This differs from conventional automatic transmissions where they physically disengage the gears for Neutral; EVs are solid-state in this regard. However, the caution with the Bolt is that you don't accidentally press the Park button. That could be bad, as Park is a mechanical lock.
To engage Neutral while moving, you have to hold the shifter forward for about half a second, pressing the shifter button isn't necessary. You also don't have to press the button to go back into Drive or Low. It only needs pushed to enter Reverse or come out of Park.
As for coasting efficiently, you don't want to excessively gain speed and use air drag to limit your speed, you'll gain more by keeping speed down with regen. "Cutting it loose" at the bottom is fine, though. You'll also want to get in the habit of dropping back into Drive or Low to use regen when you need to slow down, preventing the use of friction brakes.
There are other situations where coasting is beneficial, not just on pure downhill runs. There is a road by my house where I can coast for a few miles due to the up and down terrain with a general descent. Coasting tends to push the trend bar up pretty quickly on this road. The longest I've kept the Bolt in Neutral was about 2 minutes, clicking into Drive and back to Neutral because of the uncertainty of the car going into Park automatically (I would hope a car from a major manufacturer wouldn't do this, but I'm not taking it for granted on a first year car).
Since there is no mechanical change between Drive, Neutral, and Reverse, it doesn't run the risk of damaging the gearbox to coast in Neutral. This differs from conventional automatic transmissions where they physically disengage the gears for Neutral; EVs are solid-state in this regard. However, the caution with the Bolt is that you don't accidentally press the Park button. That could be bad, as Park is a mechanical lock.
To engage Neutral while moving, you have to hold the shifter forward for about half a second, pressing the shifter button isn't necessary. You also don't have to press the button to go back into Drive or Low. It only needs pushed to enter Reverse or come out of Park.
As for coasting efficiently, you don't want to excessively gain speed and use air drag to limit your speed, you'll gain more by keeping speed down with regen. "Cutting it loose" at the bottom is fine, though. You'll also want to get in the habit of dropping back into Drive or Low to use regen when you need to slow down, preventing the use of friction brakes.
There are other situations where coasting is beneficial, not just on pure downhill runs. There is a road by my house where I can coast for a few miles due to the up and down terrain with a general descent. Coasting tends to push the trend bar up pretty quickly on this road. The longest I've kept the Bolt in Neutral was about 2 minutes, clicking into Drive and back to Neutral because of the uncertainty of the car going into Park automatically (I would hope a car from a major manufacturer wouldn't do this, but I'm not taking it for granted on a first year car).
Joined
·
336 Posts
It -- the "right kind of hill" -- is encountered constantly here. And the idea that N "wastes energy" is incorrect if the mechanical brakes are not used. It would be unnecessarily regeneration that wastes energy. Of course if N yields a speed too fast for a curve or traffic or anything else, I don't brake, but put it in D or L.
"Couple of tries to get N" -- I don't get that. If kwH usage is low, between, say, -5 and 5, it is very smooth.
Re accidentally destroying something: I'll mention again that I asked two GM engineers point-blank if there was any issue whatever with doing this, and they were unequivocal: NO.
But really the main point is that you can simulate true N by keeping energy use at -1,0,+1. It just that that is a little hard to do for any length of time while listening to the radio, talking to a passenger, etc.
"Couple of tries to get N" -- I don't get that. If kwH usage is low, between, say, -5 and 5, it is very smooth.
Re accidentally destroying something: I'll mention again that I asked two GM engineers point-blank if there was any issue whatever with doing this, and they were unequivocal: NO.
But really the main point is that you can simulate true N by keeping energy use at -1,0,+1. It just that that is a little hard to do for any length of time while listening to the radio, talking to a passenger, etc.
Joined
·
501 Posts
Does anybody even know what actually happens in 'N'?
I mean it's not like the car's actually in neutral. 'L' doesn't
really meaning Low. It's just a shifter from a Buick or
something that actually has a transmission. Does the Bolt
apply power to simulate neutral? Does it disable the field
so there's only mechanical drag and no electrical drag from
spinning the drive motor? Who knows?
I mean it's not like the car's actually in neutral. 'L' doesn't
really meaning Low. It's just a shifter from a Buick or
something that actually has a transmission. Does the Bolt
apply power to simulate neutral? Does it disable the field
so there's only mechanical drag and no electrical drag from
spinning the drive motor? Who knows?
i don't think there's any reason to put it into neutral. if you're going downhill, you can press the accelerator enough to disable the regen (and you'll know it when you see 0 on the energy consumption meter). then you can just let up when you want to slow down.
Joined
·
8,977 Posts
I'm going to have to test this, because I don't believe you get any regen at all when the shift lever is in the "N" position. Not from the paddle, not from the brakes. My understanding is that the "N" position of the shift lever is a regulatory requirement to keep the motor disengaged from the drivetrain, which wouldn't be the case if you could regen in that mode.
The only EV I've experienced that applies regen while in Neutral was the BMW i3. It changes the behavior of the brake pedal so the first bit of pedal travel is pure regen and then blends in friction. Normally, the brake pedal in the i3 is friction only.
The Bolt is 100% friction on the brake pedal in Neutral. But still, if you need to slow down, then drop it back into Drive rather than using friction.
1 - 20 of 75 Posts
Join the discussion
