View Single Post
Old 11-26-2007, 10:23 AM   #193 (permalink)
Batman Junior
MetroMPG's Avatar
Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 21,055

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)
Thanks: 2,842
Thanked 5,702 Times in 2,946 Posts
12-11-2006, 05:34 Pm

The EV list folks seem to be leaning towards it being a brush timing issue, but the expert requested another specific motor pic, and I'll wait to do anything until I hear from him.

If you want to see pics of the motor & its guts:

What I have learned:

You can eyeball whether a series motor is using advanced brush timing by comparing where the brushes contact the commutator relative to the bolts that hold the field coil shoes in place. If it all lines up (brushes inline with the field bolts, it's neutral timing.

A quick look at our motor shows that its timing is in fact advanced for stock rotation (the field pole shoe bolt heads are the painted ones on the casing with the hex heads - the black marker lines line up with the brushes when the end cap is in place):

We'd have to move the brushes the equivalent distance to the other side of the shoe bolts to have the same timing for the direction we want to use the motor.

Also learned: for "street" EV use, 10 degree advance is good. 13 degrees for racing.

Haven't tried it yet. Will wait to hear from Mr. Husted.
Latest mods test: 15 mods = 15% MPG improvement: A-B test, 2007 Honda Civic 1.8L, 5-speed
Ecodriving test:
Manual vs. automatic transmission MPG showdown: Nissan Micra 1.6L

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget
  Reply With Quote