[ausev] Honda DelSol Motor

[Chris Robison]

Ken wrote:
> Would a 8" motor be enough for a DelSol or should I budget for a 9" 
> motor?

This depends on your performance goals.

The difference in acceleration between these two motors won't be huge as 
long as you're not maxing out your controller's motor current limit. The 
8" will mainly get hot faster with spirited driving. So for "good" 
performance, go with the 8".  If you want to smoke the tires at the 
expense of some weight and making more of a challenge to get everything 
to fit under the hood, the 9" would smoke them pretty well without 
getting too hot, if it fits in the car at all.

Bigger motor = higher torque for a given current, higher voltage across 
the motor ("back-EMF") for a given RPM. Put another way, for a given 
mechanical output in horsepower, the larger motor draws fewer amps but 
needs more volts. No free lunch.

The benefit of the larger motor's reduced current requirement is reduced 
temperature rise and therefore higher continuous horsepower. Its higher 
thermal mass allows higher peak horsepower and longer durations of 
horsepower output that exceeds its continuous rating.

The drawbacks are higher weight, rotating mass (inertia), windage losses 
and friction (larger commutator and brushes). Larger motors also 
typically have a somewhat lower redline.

Take advantage of your car's small size. The del Sol does not need a 
large motor to run well. You're going to have a fun car with an 8" 
motor, assuming other parts of your system (controller, pack voltage) 
are up to snuff. Netgain's ImPulse 9 might be a compromise if you're a 
little heavier in the foot; it's 9" in diameter but shorter to reduce 
weight and to fit in smaller cars. I've never seen one in person but I 
understand they've been popular since they were introduced.

Whatever motor you choose, since it's a Honda, check your engine's 
rotation direction. Look at the crankshaft pulley on the end of the 
engine with the belt-driven accessories -- the pulley that's driving all 
the others.  If it turns clockwise, you can buy a stock motor. If it 
turns counter-clockwise, you'll need to order one with reversed brush 
timing. I think usually in this case the engine will be on the driver 
side of the car, which is also opposite from the standard. Checking the 
pulley will tell you for sure though.

   --chris