Forgive the question because it is truly out of my skill level. But, could an oem regulator theoretically be used in an aftermarket alternator so the higher amperage alternator be used? If not, I wonder what regulator could be used to fit our needs?
The regulators control the output of the diodes. To get higher output, one uses a stator that has more windings, sometimes a rotor with more windings, and diodes that can handle higher currents.
With a simple control method, the regulator doesn't
necessarily need to know too much about the parts - it's an immediate feed-back loop. The regulator controls the field current, which alters the field strength, which changes the output. Output voltage above the reference point? Lower the field current. Output voltage below the reference point? Raise the field current.
With the LS, the PCM is controlling the regulator. If the PCM doesn't understand that the performance parameters of the alternator have changed, then it can't control it properly. The PCM may be trying to do something witty, like estimating power loads instead of a straight voltage reference.
If you pair a larger stator/rotor with a stock regulator, the diodes can fry from the extra output.
Given what I've (and others) have seen from the DB alternators, my guess is that the modified alts need a higher field current at idle than the stock alternators. The LS PCM just isn't adapting to that change, resulting in the lowered output.
*note* this is from my experimentation and someone tenuous grasp of EE. I destroy a lot of parts before I get any circuit correct (see my fan controller thread...). Hopefully Joe can toss in his viewpoint and correct my mistakes.
For further reading, check out
http://www.rowand.net/Shop/Tech/AlternatorGeneratorTheory.htm
That guy's pages are really good on a wide variety of topics.
Also,
http://www.alternatorparts.com/understanding_alternators.htm has good diagrams and digs into the electrical aspects a bit more.
As to the other notes, I
think the internals of the V8 regulator have the same physical dimensions as the typical 6G "small case". When you shop for those, the aftermarket doesn't like them. The small size limits output potential greatly. The 6G "large case" tend to go much higher.
So one experiment would be to find an aftermarket 6G small case high output alternator with PCM control, and swap the guts over the the LS case. That still assumes that all PCM control is created equal. And that some other manufacturer besides DB has gotten the PCM control correct at idle.
Here's a good description of the PCM control:
http://www.napaechlin.com/Ford-PCM Controlled Charging System/Content.aspx - and a specific note is the PCM calculating load at idle and regulating the alt to the hairy edge. That reduces engine load giving a smoother idle. And if the alt performs exactly as the PCM expects, then you're fine. If it's modified and the PCM can't adapt, then, well, too bad.
Another option would be to put a traditional internal regulator into an HO alt. The PCM will probably throw codes when the alt apparently ignores its commands, though. The "alt load" wire is unique to PCM controlled regulators.
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