Could this work? temp cutoff of altenator?

[bennettsweb]

I didn't find it anywhere, so I though I better ask:

Could you wire a relay to turn off the battery-to-alternator path? From what I understand about electro magnets I figure if the alternator no longer had the battery load putting torque on it, that's got to be at least a noticeable power gain. If you don’t believe me, hook up a spare alternator to a battery and try to turn it!

This would only work temporary. I guess my real question is can the ignition, ECU, lights and all get enough power form the battery for a little bit (talking like 15 secs for max acceleration) or is that just not possible. Is it wired that way or does ignition only come from the alternator?

Let me know what you think -- including if you think I'm stupid.

-Ben

[redwagon]

I think back to the race bikes I used to work on that ran total-loss ignitions for a whole race day... but that was two or four coils, the tach and a computer the size of a deck of cards, and it was all designed to run at 12V. Your ECU and fuel pump use a lot more current and they are used to seeing 14.4V. I think you'd see a drop in both ignition voltage and in fuel pressure at the pump.

[vrg3]

The battery could certainly handle running the engine for 15 seconds. In fact, if your battery is properly charged you could probably drive for an hour or so without an alternator.

The ECU isn't a problem; it's designed to work at much lower voltages than normal because it needs to work while cranking.

The fuel pump and ignition, though, might suffer from lower voltage. If you're only running off the battery for 15 seconds, though, I can't imagine it being a significant problem for the fuel pump. It might be smart to use some kind of MSD DIS ignition or something to keep the sparks strong though.

I don't know if I agree that it would be a noticeable power gain, given how hard the engine has to work to turn everything else rotating under your hood, but I do agree that in principle it'd free up some power.