powering down the alternator

[suspendedhatch]

If you have a 1988 or later Honda, the alternator is already pulse-width-modulated. In essence it only puts as much drag on your crank as is necessary to keep the battery charged. If it's an American car you might see some advantage to doing this. We wont know until you post your honest results.

If your battery voltage drops below about 10 volts the injectors don't work as well and as a workaround the ECU will increase the injector times to try to keep the car running as long as possible. What happens is the air/fuel ratio goes very very rich.