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Re: Alternator/Charging theory question Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 24 Jul 2003 14:06:44
In Reply to: Alternator/Charging theory question, JJ, Thu, 24 Jul 2003 13:05:56 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I assume that we're talking about an idling car. You turn on the headlights or the blower, and the RPMS drop.
When the engine is running, the alternator provides all the current requirements of the car. If you turn on an electrical load, that's an increase in the amount of energy needed. That energy needs to come from somewhere, and the only somewhere available is the engine. The increased load on the electrical system actually makes the alternator a little harder to turn. This puts a bigger load on the engine, and engines don't produce a lot of power at idle. This is the same load as if the A/C compressor kicks in - the engine has to work harder to turn an engaged A/C compressor than one that's not.
Now, the engine control system should keep the idle constant - it'll use the AIC to add a little air, and the extra air comes with a little more fuel, so the engine should compensate. But the ECU isn't perfect at keeping the idle at the same speed (a Saab with a good idle, Ha!) so unless the ECU compensates, the revs will drop.
Make sense?
posted by 192.249....
, Fri, 25 Jul 2003 05:44:34, Thu, 24 Jul 2003 14:06:44 <-- Viewing This Message
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