Alternators, Amps, and the 818

[Rasmus]

I disassembled my OEM '06 alternator to clean it and inspect the bearings and brushes. While it was open got to thinking how heavy this thing is and if there's anyway to lighten the OEM part. By my eyes, there's not.

Rotor: 2855 g
Stator with Rectifier: 1613 g
Case halves, bolts, and larger bearing: 910 g
Pulley, mounting hardware, and brackets: not considered
Total mass: 5.378 kg (11.85 lb)


The copper rotor and stator make up the bulk of the mass in this thing and I don't think there's anyway to lighten them. So that leaves moving to a smaller alternator with a less massive rotor and stator. But that'll put you down on amps. Ideally, I'd guess, you'd want to produce about 1 more amp than your maximum sustained running draw. So for me that looks like:

Water pump for Air-Water intercooler: ? amps
Radiator Fans running at full clip: ?? amps
Fan(s) for brake ducts: ?? amps
Fuel pump: ?? amps
ECU, instrument panel, sensors, and spark-plugs (e.i. the engine) ??? amps

I don't ever plan on running full out at night so headlights/running lights doesn't factor in. I guess it might if it drew more than the radiator fans and brake duct fans. I can look up the most of that stuff but it's the engine draw I don't know. How many amps does "the engine" need to function?

Ultimately my question is: what is the lightest alternator I can get away with running that doesn't cost Formula 1? What's the smallest amp alternator I can run?