For most of us, this is Dark Territory. Taboo. Who would fool around inside a regular Alternator? Somebody did, and shaved off 4% of his fuel costs. The first post has a downloadable document (PDF) with wiring schematics. The diodes he replaces are garden variety, available from most electronic suppliers, and once you take the circuit out of an alternator, you see how simple they are, and this mod is a cheap power booster. 4% more engine power not wasted: http://ecomodder.com/forum/showthread.php/alternator-modifications-18045.html I've got a couple spare alternators for mine, and a replacement kit for rebuilding the innards, so I'll do this over the winter months. On my 85 HP, Inline Six, that's another 1.7 HP found without much pain. Might do the Electric Fan trip, now, and save some more.
[Wet blanket] I didn't see anyone in the thread linked claiming 4% fuel efficiency increases. He is claiming a 4% increase in the alternator efficiency which doesn't necessarily equate to 4% increase in fuel economy. I'm also dubious of people claiming percentage gains or losses. The alternator takes however much power it takes to turn. Same car/engine you can use percentage gains/losses, but just because I take the alternator from your 85hp engine and put it on my 170hp engine doesn't mean I'm now saving twice as much power as you. [Wet blanket]
