Quote:
Originally posted by gsxr
Hi all,
...
The 143A unit could put out roughly 100 amps at my ~600rpm idle speed, and appeared able to put out max current at barely above idle, not even 1000rpm!  The highest load I could generate, including some current to charge the battery, was 125-130 amps. At 1000rpm, it put out the 130 amps and did so at 14.1 volts! And at idle, same thing, 14.1 volts (with a smaller load, under 100 amps.) The only time voltage dropped was with VERY high load at idle and I don't think I ever saw it go under 13 volts, and that was with an "artificial" load that is unlikely to occur in normal use.
My "normal" load is low beams (90Wx2) and ACC fan, plus whatever the chassis electrical stuff pulls (EDS, gauges, etc.) This appears to be roughly 40 amps, plus some current to charge the battery. The good news is, with my "normal" load I get a solid 14.1-14.2 volts, even at idle! VERY nice. I'd like the voltage a bit higher (14.4-14.6) but there is not an adjustable regulator available for the 143A unit (AFAIK). No big deal, I'm happy with the setup as-is. The stock unit badly needs an adjustable regulator, and I'd highly recommend one for those of you not interested in the full big-alt swap. Set it when stone cold to 14.6v or so, it will drop a bit as it gets hot, and you want to set the HIGHEST point.
The only down sides are extra weight and horsepower loss. The 70A unit weighs about 11.5 pounds, the 143A unit is 16.8 pounds. Not a big deal. But when you spin the shaft of the 70A unit, it feels light and spins easily. The 143A is MUCH heavier (massive) and definitely takes some extra crankshaft power to spin, even with no electrical load. I'd guess it could easily sap 3-5 HP more compared to the original. Still worth it, IMO.
Regards,
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Excellent Mod, thanks for the info. I once did something very similar to my old RX-7.
BTW, Don't worry about the voltage at 14.1. That is exactly where you want it and the voltage regulator seems to be working perfectly. Any higher and you'll generate excess hydrogen gas and sulfate up your lead plates in your battery. 14.1 V is exactly the right voltage for charging batteries for best life, especially since you'll have very little voltage drop between your alternator and the battery with your new cables.
Also, to figure out how many ponies are robbed, lets do some math: Since Power = Volts * Amps, Power = 14.1V * 130 Amps = 1833 Watts. 1833 Watts = about 2.5 hp. Assuming about 80% effeciency for converting mechanical energy to electric energy (fairly conservative estimate), and that's 2.95 hp.
Hmmm, I'm a mechanical engineer, not electrical...how do I remember this crap?