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Old 11-27-2007, 02:26 PM   #448 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,057

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 54.01 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 73.57 mpg (US)
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09-30-2007, 09:24 Pm

Man, I'm getting weary of the hours going into this car... will be very glad when we get our plates. I need a break. This weekend:
  • made up several more cables/lugs (motor cables & other half of Anderson emergency disconnect pair)
  • mounted the ammeter shunt on the underhood platform
  • spent a long time thinking about the best way to mount, orient & wire the low pedal contactor
  • cut & installed strips of rubber for under the battery hold-down angle iron, as requested by my mechanic
  • spent most of my tinkering time Saturday adjusting the motor brush timing... again.
I was reading up on the pile of EVDL messages ripening in my inbox, and came across a message from motor guru Husted about low voltage systems & brush advance. Noted that he said "5 degrees for mild" voltages. Apparently the common "10 degrees for street use" applies to higher voltages (say 120+). So I went out and measured... and the brushes were advanced almost 17 degrees!!

Whoops. For 48v he suggested putting them to neutral.

I now have them near 2 or 3 degrees advanced. According to Jim, the closer to neutral timing = more low end torque and less top end RPM. The motor should run more efficiently too. After making the adjustment (drilled a new set of adjustment holes in the end cap ... with the motor still in the car), I can vouch for the first 2 statements. The car goes up hills better (relatively speaking), but I can no longer wind it out to 4000 rpm before shifting - it just runs out of steam.

And it still won't spin the tires on gravel, before or after the adjustment. I tried.
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