[Amberdea]

I’m surprised no one has mentioned anything about the under carriage. Adding covers to make it as flat as possible and covering all the gaps should make a huge difference, even more than removing the side mirrors.. has anyone tried this?

 

[GJETSON]

I’m surprised no one has mentioned anything about the under carriage. Adding covers to make it as flat as possible and covering all the gaps should make a huge difference, even more than removing the side mirrors.. has anyone tried this?

Somebody on here, several years ago, put up pictures of their plastic cover extending from the back edge of the battery box to the rear bumper. They also have pizza platter wheel covers.

Improving the Drag: Lowering and under car aero:

...One section left to do on the back 1/3 where it meets the diffuser and then the entire underside will be flat and smooth. Think I might also try to re-work the white side panels and maybe make a short side skirt. Didn't have enough material of the right dimensions to rework the white...

www.chevybolt.org

15" Wheels & 205/65R15 Tires

Has anyone mounted 15" wheels with 205/65R15 tires? I've ordered a 2017 Bolt that will be delivered in a month or so, but there are some great deals going on for 205/65R15 winter tires where I am right now. That tire size carries the same 25.5" overall diameter as the factory standard...

www.chevybolt.org

15" Wheels & 205/65R15 Tires

I drove 205/65R15 X Ice 3s all last winter without issue. Just threw them on again for the upcoming winter. They're mounted on steelies, don't rub the breaks. Would you mind sharing from where you purchased the steelies?

www.chevybolt.org

 

[NewsCoulomb]

I’m surprised no one has mentioned anything about the under carriage. Adding covers to make it as flat as possible and covering all the gaps should make a huge difference, even more than removing the side mirrors.. has anyone tried this?

There's actually not that much turbulence under the Bolt EV. The flat bottom might help a little, but not nearly as much as removing the side mirrors.

 

[heisian]

The Prius has slight regen with foot off the accelerator. I mostly coast by using N, and sometimes coast by applying slight pressure on the accelerator.

Regen is about 1/3 efficient at recapturing kinetic energy. For that reason, coasting to lose speed is more efficient. Since it isn't practical to coast all the way to a complete stop, regen is the next best thing.

I haven't got a clear answer on how the Bolt behaves with regard to using the brake pedal for regen. People refer to it as blended brake/regen, which makes it ambiguous as to if it uses both friction and regen at the same time, or if it only switches to friction after maximum regen has been reached. As you correctly point out, the Prius uses only regen with the brake pedal until exceeding the ability to regen, at which point the friction brakes transition in.

I was wondering if coasting in N was the way to go... thanks!

 

[Sean Nelson]

I was wondering if coasting in N was the way to go... thanks!

Coasting in N for anything longer than short stretch is a bad idea in the Bolt because it turns off the electric pump that lubricates the gear train.

 

[ARob]

I was wondering if coasting in N was the way to go... thanks!

N will not regenerate. you are wasting inertia.

 

[TFPDrive]

N will not regenerate. you are wasting inertia.

Inertia is best realized when it only slowed down by external forces. Regen is not perfectly efficient so the less you use it (and assuming you don't replace it with friction braking) then the more efficient the drive.

 

[heisian]

N will not regenerate. you are wasting inertia.

What I did in my 900mi round trip this past weekend from Oakland to LA was only put it into N on downhills that were steep enough for me to maintain or gain speed. When I gained speed, I'd let it get to 5 - 10mph higher and then put into D for the regen. Gave me some pretty awesome results according to the bar graphs.

But for flat grade driving, or shallow downhills, no N.

 

[GJETSON]

Gave me some pretty awesome results according to the bar graphs.

You mean these bar graphs? All done in L.

 

[heisian]

You mean these bar graphs? All done in L.

View attachment 32530

Yep, I got similar "off the chart" readings. From what I've read, yes, it's all doable in L, but you need to precisely actuate the pedal to maintain the 0 or 1 kWh consumption, so I just personally find it simpler to put it into N in the limited situations I described.

It may also be habit as I drove manual for a long time and would do the same in N, and then downshift to rely on engine braking if I was gaining too much speed.

 

[GJETSON]

Yep, I got similar "off the chart" readings. From what I've read, yes, it's all doable in L, but you need to precisely actuate the pedal to maintain the 0 or 1 kWh consumption,

I did this by setting CC to the speed limit, and driving downhill. You are waaaay overthinking this whole thing.

 

[heisian]

I did this by setting CC to the speed limit, and driving downhill. You are waaaay overthinking this whole thing.

I used CC for at least 90% of the time on the 900mi trip I just finished this past weekend, but I noticed that if I was on a steep enough hill, I "felt" slightly better to shift into N and let myself gain 5-10mph over the speed limit - the point at which everyone else drives anyways - and then flip back to D to get regen near the bottom of the hill where everyone tends to slow down.

Perhaps I am overthinking - I just got my Bolt two weeks ago, so I am still experimenting with it. Maybe I'll get tired of thinking about range maximization a year from now - but this IS the hypermiling forum, after all, and to my knowledge, hypermiling is squeezing every extra bit of range out of your car as possible.

My suspicion on the graph bar readings: 252 is pretty close to 255, which is the highest possible value for an 8-bit reading. So my guess is that you're not really seeing 252 mi/kWh, but a very high value that the computer can't really compute accurately. So I interpret those insanely high bars as fudge data that can't really be used to accurately determine your efficiency.

Again, maybe I'm overthinking, but again, we are on the hypermiling forum. People come to this forum to overthink range, don't they?

 

[redpoint5]

I was wondering if coasting in N was the way to go... thanks!

As Sean pointed out, I don't recommend coasting in N since the oil pump for the gears relies on the vehicle being left in D or L. Also, any efficiency boost would be miniscule.

The reason I so aggressively hypermiled in the Prius is that I had a commute that was just on the boundary of my 13 mile range during the spring and summer seasons. If I absolutely maximized my ability to preserve momentum, I could just barely complete my commute 100% electric. When I'd fall short, it would run the engine for 30 seconds or so, which is considered severe service for an ICE.

In the summer I had no problem completing my commute, even running the AC, and in the winter, I had no chance of completing it entirely in EV mode.

There's not much reason to get 1/2 mile more range from the Bolt's ~250 in the scheme of things by employing every last efficiency trick. EVs by design operate much more efficiently, even in the hands of relatively inefficient drivers. About the best one can do to extend range is to simply drive slower.

 

[heisian]

As Sean pointed out, I don't recommend coasting in N since the oil pump for the gears relies on the vehicle being left in D or L. Also, any efficiency boost would be miniscule.

The reason I so aggressively hypermiled in the Prius is that I had a commute that was just on the boundary of my 13 mile range during the spring and summer seasons. If I absolutely maximized my ability to preserve momentum, I could just barely complete my commute 100% electric. When I'd fall short, it would run the engine for 30 seconds or so, which is considered severe service for an ICE.

In the summer I had no problem completing my commute, even running the AC, and in the winter, I had no chance of completing it entirely in EV mode.

There's not much reason to get 1/2 mile more range from the Bolt's ~250 in the scheme of things by employing every last efficiency trick. EVs by design operate much more efficiently, even in the hands of relatively inefficient drivers. About the best one can do to extend range is to simply drive slower.

On some other thread, somebody claimed they had asked a GM engineer if coasting in N was detrimental and that the response was no. But it seems like the consensus is that is incorrect information?

I'd be interested in what the drivetrain looks like. In an ICE manual transmission, you have your clutch, your input shaft, your gears, and your output shaft. If you coast in N, then only your output shaft is spinning, and there is no oil pump or oil pressure for gear lubrication - the gears simply rely on the oil viscosity to coat the surfaces when in motion.

So then the million dollar question is - what does the Bolt's drivetrain look like? It's FWD, and so perhaps it has a transaxle, like ICE FWD cars. This transaxle, does it have an input and two output shafts like an ICE engine? And if you are in N, is it only the output shafts that are spinning on their bearings, while most of the differential gearing is at rest?

I suppose people here have already seen this breakdown of the drive unit: Chevrolet Bolt EV Powertrain Dissected: Video
Myself am watching the video right now.

 

[GJETSON]

My suspicion on the graph bar readings: 252 is pretty close to 255, which is the highest possible value for an 8-bit reading. So my guess is that you're not really seeing 252 mi/kWh, but a very high value that the computer can't really compute accurately. So I interpret those insanely high bars as fudge data that can't really be used to accurately determine your efficiency.

Yup. The reading is nonsense. There is a long thread about this glitch.

Measuring Energy Use: Euro vs. USA

I mentioned on another thread that the Bolt's EFFICIENCY HISTORY screen is very badly wrong. Here is the issue: Suppose you drive 5 miles at 247 mi/kwh. You used 0.02 kWh and the bar chart reads 247. Then you drive 5 miles at 3 mi/kwh. This uses 1.67 kWh and the bar chart reads 3. The average...

www.chevybolt.org

 

[heisian]

On some other thread, somebody claimed they had asked a GM engineer if coasting in N was detrimental and that the response was no. But it seems like the consensus is that is incorrect information?

I'd be interested in what the drivetrain looks like. In an ICE manual transmission, you have your clutch, your input shaft, your gears, and your output shaft. If you coast in N, then only your output shaft is spinning, and there is no oil pump or oil pressure for gear lubrication - the gears simply rely on the oil viscosity to coat the surfaces when in motion.

So then the million dollar question is - what does the Bolt's drivetrain look like? It's FWD, and so perhaps it has a transaxle, like ICE FWD cars. This transaxle, does it have an input and two output shafts like an ICE engine? And if you are in N, is it only the output shafts that are spinning on their bearings, while most of the differential gearing is at rest?

I suppose people here have already seen this breakdown of the drive unit: Chevrolet Bolt EV Powertrain Dissected: Video
Myself am watching the video right now.

I ended up watching a whole bunch of Bolt EV disassembly videos... so fascinating.

It seems like the output shafts spin in N, which means that the differential gears and rotor spin because they are always directly engaged with each other, and without any positive or negative electrical load being placed on the DC motor, we in essence get "Neutral".

Here's a really good video of the disassembled rotor turning the drive/differential/final gears and CV shafts:

I would still presume that there's enough oil viscosity, especially with Dextron A/T fluid, to keep the gears sufficiently lubricated for short periods of time, especially because the transaxle case maintains a certain level of oil, but of course this is just me guessing.

At any rate, the level of complexity of the gearing here is 1/10th of that of a manual or automatic transmission, many of which have no oil pump or pressure at all, and so I still feel the risk of gear degradation while running in N is low.

 

[Sean Nelson]

I'd be interested in what the drivetrain looks like. In an ICE manual transmission, you have your clutch, your input shaft, your gears, and your output shaft. If you coast in N, then only your output shaft is spinning, and there is no oil pump or oil pressure for gear lubrication - the gears simply rely on the oil viscosity to coat the surfaces when in motion.

As you discovered in your next post, there is no true "N" in the Bolt's drivetrain - the gears are permanently engaged with no clutch or other mechanism to unmesh them. "N" simply means no torque is applied to the motor to propel or retard the output shafts.

In terms of gear lubrication, one can only assume that GM designed the drivetrain with the electric pump (which increases component and assembly costs) because the designers deemed it necessary. I doubt you'd incur any damage for occasional short stretchs (I think of something like 30 seconds as qualifying as "short"), particularly since there will be very little load on the gears. But making a habit of it seems inadvisable.

 

[heisian]

As you discovered in your next post, there is no true "N" in the Bolt's drivetrain - the gears are permanently engaged with no clutch or other mechanism to unmesh them. "N" simply means no torque is applied to the motor to propel or retard the output shafts.

In terms of gear lubrication, one can only assume that GM designed the drivetrain with the electric pump (which increases component and assembly costs) because the designers deemed it necessary. I doubt you'd incur any damage for occasional short stretchs (I think of something like 30 seconds as qualifying as "short"), particularly since there will be very little load on the gears. But making a habit of it seems inadvisable.

So he mentions here that the oil is circulated in order to cool the stator and lubricate the ball bearings (video is set to the exact time):

So I suppose I would worry about the ball bearings being damaged if in N for extended periods of time, but Dextron IV ATF is incredibly viscous stuff, it's very hard to get off of your hands (and it stinks) and would have no problem coating the drive and differential gears as they spin through the bath.

 

[redpoint5]

I wouldn't worry much about premature wear either for short stints of neutral coasting. I'd equally not worry about getting that last 1/2 mile of range from the Bolt unless it became necessary due to circumstance.

Neutral can be very closely approximated by precise accelerator control.

 

[Capital EV]

Has anyone ever done a mirror delete modification on a Bolt EV? I'm not interested in the legality of it so no need to inform me about that. And yes, I've read the unhelpful replies in this long thread telling us to simply drive slower. Driving slower doesn't improve the car in any way.

That's got to be about the lowest hanging fruit in lowering aerodynamic drag.