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After a couple of weeks I put it back to where it was. Turns out (at least with this motor / voltage / controller / vehicle weight configuration) that advancing it made it somewhat slower (7.5 seconds 0-25 compared to 7.0 standard) and less efficient (about 300 wh/mile compared to ~250 standard).
There may be a happy medium somewhere, but without drilling a few more holes (or constructing a variable ring) where it was seems to be the best position. Eventually, I may drill holes at 5 degrees advance, and 5 degrees retard to see how those positions may change power/efficiency.
On a side note, it appears that this motor may be maxed out for this 1250 lb car.
Today I put 13” tires on the Citicar to see how it would affect speed and acceleration. For baseline, my Citicar has a top speed of 32 / 36 (normal / field weakened) and accelerates from 0-25 in an average of 7.0 seconds with 145R12 tires. (R in this configuration implies an 82 aspect ratio.)
I have a pair of tires from a 1981 Comutacar with 13” rims. They have 135R13 tires with the same bolt pattern as my 1976 Citicar. For the test, I put the 135R13 tires on the back of the Citicar.
Using a GPS, I determined that the speedometer was spot on with the 12” tires. With 13” tires, the speedometer registered just under 24 MPH when the Citicar was actually moving 25 MPH.
Acceleration from 0 – 25 (actual) remained the same with the 13” tires as with 12” tires – 7.0 seconds average (5 tests).
More interestingly, the actual (GPS measured) top speed was exactly the same (32/36) with 12” and with 13” tires, although motor RPM was lower with 13” tires. This leads me to believe the main limitation with my Citicar is not in gear ratio, maximum RPM of the motor, voltage, or amps available, but in the ultimate power of the motor. Last year, I put an extra battery in series (for 54 volts) and the top speed was also 32/36.
For reference, at 3000 RPM / 6.8:1 the Citicar is going 27.74 MPH, and with 13’ tires it is going 29.05 MPH.
Looks like I'm running out of ideas to improve speed and acceleration of this motor. The best / most successful experiment so far was field weakening... (other experiments were with increased voltage, increased amperage - direct contactor - increased tire size and advanced timing. All others experiments did not shown much/any gain. But again, this is with this particular motor... If your motor is not severely overloaded as this one appears to be, you may have better success...
If you just want a higher top speed, my money would be on field weakening, and a second step would be to adjust timing a few degrees positive or negative to see where your particular setup stands.
Tom
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