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Old 11-27-2007, 01:06 PM   #348 (permalink)
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Here's a thought for anyone else considering a conversion. If you're going to try hypermiling your EV, you might want to keep your clutch.

We went for a direct motor-input shaft connection. It's less complex and saves weight (importantly: rotating mass).

BUT - I've learned driving around the neighbourhood, even though the electric motor only has a fraction of the internal friction of the ICE when decelerating (only two bearings, and none of the ICE's engine braking), coasting the e-motor in gear slows the car perceptibly more than coasting in neutral.

But the clutchless setup makes coasting in neutral more difficult. Getting to neutral is easy - just flick the gear lever out of gear when not under load. The problem is getting back into gear without coming to a complete stop. It requires rev-matching the motor to the speed of the input shaft. That's tough to do cleanly (or at all) when (a) you can't hear the motor, (b) have no tach, and (c) the transmission synchros are pretty worn out.

It's open to debate whether the savings from being able to coast in neutral would outweigh the increased energy consumption of retaining the flywheel & clutch, but I'd bet an EV hypermiler would see best results from being able to use neutral easily/frequently.
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