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Old 03-16-2008, 10:31 PM   #1 (permalink)
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Experiment: EV coastdown in gear vs. neutral (in the ForkenSwift)

After watching the video of shifting the clutchless transmission, I've had a few people ask me why I bother shifting to neutral to coast an EV. One would expect a complete lack of "engine" braking with an electric motor where the engine used to be. No?

Well, I've noticed that there does seem to be some drag from the motor (its brushes & bearings and drive end cooling fan being the culprits). It's not a lot, but I never tried to quantify it... until today.

So this afternoon I went out and did a very simple, and not entirely thorough test:

Coastdown from 20 km/h (indicated) in 1st gear vs. neutral.

First gear
- 58.8 m / 193 ft (average of 2 runs)

Neutral
- 70.4 m / 231 ft (average of 2 runs)

Difference
- 11.6 m / 38 ft, or 20%, or slightly more than 3 car lengths





Conditions: 1 degree C, cold car, calm winds, snow tires @ 55 psi, level road (to my eye). Oh, and the right front wheel bearing is toast. It's the source of most of the "road" noise you hear in the video in 2nd gear and higher. :-D

So I figure I'll keep popping it into neutral when I'm coasting up to stops & turns.



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Old 03-16-2008, 11:16 PM   #2 (permalink)
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Wow, that's 11+ metres is pretty considerable.

The question I have is:
Doesn't the coasting in gear trickle some energy back into the batteries? Sort of like a radio controlled car.
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Old 03-16-2008, 11:16 PM   #3 (permalink)
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Very quiet video!

I don't think I could go that long without having the radio on or talking to myself

I've noticed more than a few times(no actual measuring yet) when I coast in gear(regular ole 2HI button on) it is definately a shorter ride. I've got an automatic, so I'm still kinda leary of doing this toooooo much and I try to make neutral coasts only when coming up to a stop where I know I will truly have to stop so I can ease back into D without engine RPM's getting loopy on me.
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Old 03-16-2008, 11:20 PM   #4 (permalink)
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Nice!

It's funny to watch that vid and notice that I'm "driving-along" by noting when I'd be throwing 'er in neutral.
These new driving habits die hard.
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Old 03-17-2008, 12:03 AM   #5 (permalink)
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Quote:
Originally Posted by LUVMY02CREW View Post
I don't think I could go that long without having the radio on or talking to myself
I'm almost embarassed to admit that neither of my cars have radios. The Flea never came with one, and the previous owner yanked it out of the blue car. I stick one in my ear on longer trips. Around town I don't miss it though.

Quote:
Originally Posted by Peakster View Post
Doesn't the coasting in gear trickle some energy back into the batteries? Sort of like a radio controlled car.
Not in this car - no regen. Regeneration isn't common in DC conversions. The AC cars have it though.

Andrew: I'd have to say that the video was definitely not a demonstration of hyperwatting. I pretty much had the go pedal mashed to the floor all the time I was accelerating, and I used the brakes in the vid more than I typically do.
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Old 03-17-2008, 01:55 AM   #6 (permalink)
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Since you are the site's driving technique guru, have you ever thought of posting similar videos of driving technique in ICE cars?

I'd love to visually see when EOC is used, coasting distances, cornering speed, acceleration, gear selection choices, timing, defensive driving tactics, and other advanced driving techniques.

It would be a great resource that's unprecedented as far as I know. (If it's not, feel free to direct me to where I may find them...) I suppose the only caveat is that some of those techniques are illegal...

In any case, awesome stuff.

- LostCause
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Old 03-17-2008, 10:12 AM   #7 (permalink)
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I hadn't thought of doing ICE driving vids ... until I finished this one for the EV. You're right - particularly with the added graphics, it'd be a good way to demonstrate P&G and EOC.

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Latest mods: 3-cylinder Mitsubishi Mirage. EcoMods now in progress...
Ecodriving test:
Manual vs. automatic transmission MPG showdown



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www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
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