We run an air cooled drag car. It has an MDS 6AL ignition system, a MSD ignition retard box, two electric "squiral cage" cooling fans, three nitrous soleniods, as well as the engine starter.

We also tow the car back from the end of the track. We run the two electric fans to cool the heads down while we are towing the car back to the pits. We use the tow truck's "trailer terminal" on the seven way trailer plug to charge the race car's battery while it's on the tow strap. This allows us to go rounds with the V8 guys when they start "hot lapping" us during eliminations.

Racing this system over time, we have found no measureable performance drop when running a small Nippendenso alternator. I believe the horsepower lost in driving this accessory is more than made up in the performance gained with a hotter spark. The MSD system is a heavy draw. My vote would be run the alternator.