Aerowhatt
Gold Member
Posts: 425
Joined: Wed Jan 28, 2015 1:52 pm

### Re: Hypermiling the i-MiEV

I thought of a quantitative test for this best gear choices for the hypermiling debate.

Using a well known stretch of highway, I used canion to compare two back to back (as identical as possible) runs. One using D and N as needed and the other leaving the car in B the whole time. Both runs I used the same efficient (smooth changes and finessed pedals) driving style. Reseting the trip at the base of the on ramp and taking a screen shot at the stop sign at the end of the off ramp. I found the details interesting. The most important data is the Mi/kWh summary achieved for each run.

Using D and N as needed the result was 9.5 Mi/kWH
Using D and N as needed
pict_2018-06-30_09-32-08.png (120.84 KiB) Viewed 240 times

Using B full time for the run the result was 7.9 Mi/kWh
Using B mode only
pict_2018-06-30_09-44-08.png (121.85 KiB) Viewed 240 times

The bottom line is that D and N as needed resulted in 9.5/7.9 = 120 % the efficiency of the same drive at the same speed under the same conditions in B mode.

On the way home I thought "hey I should have done the test in every drive mode for comparison". I'm curious, so I will go back and compare full time D, E, and B again under the same conditions.

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

Aerowhatt
Gold Member
Posts: 425
Joined: Wed Jan 28, 2015 1:52 pm

### Re: Hypermiling the i-MiEV

For completeness I went back and compared E mode and B mode on the same stretch of road. Take note that this was a different day and conditions were different than the conditions in the graphics in the previous post. In the previous post there was a pretty decent headwind. In the following results there was a slight tailwind.

,
Eco mode only
thumbnail-2.png (90.19 KiB) Viewed 239 times

B mode only
thumbnail.png (91.93 KiB) Viewed 239 times

Aerowhatt
2014 cool silver ES, acquired new 4/2015 (42.7ah at ~26K miles)
2014 Labrador Black Pearl ES, acquired new 3/2016 (41.5ah at ~15k miles)

DkubusEV
Posts: 5
Joined: Sat Jul 21, 2018 9:03 pm

### Re: Hypermiling the i-MiEV

Aerowhatt wrote:
Don wrote:'Loose efficiency?' - Better tighten that up!!

It all depends on the driver - You can 'coast' in B without shifting to N just by feathering the pedal so you're neither using power nor regenning. One pedal driving, no shifting required. The ammeter on the dash will tell you when you're in that sweet spot, but once you get used to driving this way, you can tell by the seat of your pants when you're neither using power or braking . . . . and when you need braking, just lift all the way off and you won't be swapping your foot from the go pedal to the brake

Don

The sweet spot doesn't matter because "coasting" in gear doesn't exist. When in gear the inverter is energized and supporting a rotating field in the motor which matches the rotational speed of the motor armature (which requires power to do). "Coasting" in gear is actually regening enough, to make enough power to create and support this field. It's easy to demonstrate to yourself with canion. A downslope on which you can steady state coast (in N) at 40 mph will yield an instantaneous miles/kWh in the range of 13 to 19 (in any drive gear while the amp needle is held at zero). That same stretch at 40mph in N will yield an instantaneous miles/kWh in the range of 130 to 190. It is ten times less efficient to "Coast" in a drive gear as you describe, than to actually coast in N. It's not in question, it is a demonstrable fact! Zeroing the needle in a drive gear is a very different thing than shifting into N. The second one is rightly called coasting. The first one is something else entirely.

Aerowhatt

P.S. The guy who did 97 miles recommending B as the most efficient mode for Hypermilin. He simply doesn't know any better. B mode is only most efficient for "jack rabbit driving" because it reduces friction braking in the driving style. Hypermiling is the antithesis of "jack rabbit driving" . . . so. He could do much better than he did using D and N. It's a a mathematical fact.

Absolutely what I would have thought would be the case, cheers for the confirmation. ive been driving my petrol cars like this my whole driving life and it gets me great economy. I think for my vehicle I will try to wire in some "swap over relays" so that I can just have a switch that can control a "dead man pedal" switch so that if you activate the "coast switch" then every time you lift off the accelerator pedal completely then the relays will select N right away until you re-apply the pedal....

just a theory for now as I still need to construct my aero body and install my 2010 imiev into it.