@ConnClark
Was thinking about this again recently, and I came across this after many hours of reading:
Diodes, Rectifiers - Single | Discrete Semiconductor Products | DigiKey
Product sheet:
http://www.ti.com/lit/ds/symlink/sm74611.pdf
26mV forward voltage drop, 0.3uA reverse leakage, 15A recommended continuous current diodes for $3.69 each! They can take 24A but the voltage drop increases a bit. They're synchronous rectifiers in a single package! The Microsemi chips that are the next lowest rated Vf on Digikey are said to be active rectifiers (LX2400ILG, out of production replaced with the higher rated LX2410A). Those chips happen to also be rated for 225C which is good for an engine bay.
I think my car has a 130A alternator, each phase is putting out 130A at its peak over a brief moment, so it would take 5*2 per phase * 3 or 30 of them
I don't really see this car consuming 130A but it could probably get close thanks to the electric power steering, though I've probably shaved off around 10A with LED bulbs around the car. With my MR2 and its 80A alternator, using 18 of the chips seems a little more sane.
Anyone want to try these out?