So, i think the least understood part of alternators is the regulation. So i'm going to touch on it a little bit.
With todays pcm regulated alts things have gotten a little more complicated. Vehicles turning the alt down to 13v and garbage similar to that. Sure it may help fuel economy, but we want loud
Unfortunately pcm regulation can often limit the alternators output greatly as well, as if it wasn't bad enough already. We recently tested 2 differing alts on a similar stereo setup. 1 alt did 260a(250a rated) on the bench and the other did 295a(270a rated) both using internal regulators. The 250a model went on the car using a internal regulator 1 wire add on we offer for 25$, which you just have to run a switched wire to it. it effectively bypasses the pcm regulation. The 270a was switched to using pcm regulation. The 250a model is doing 250a all day long, the 270a unit is struggling to do 200a fresh.
Mike did some tracking down on this. Turns out the pcm regulation setup just can't handle the draw from a HO alt. The pcm maxed out barely over 1a. He then switched the same alt to a external regulator, which is a 129$ upgrade when purchased with an alt. The alternator gained 50a of output during the switch, and the alt was drawing around 2.5a from the external regulator. so we can see that the pcm can't even provide half the field current that the alt needs to put out its full potential. You likely will only see a 5-10a or so difference between the internal and external regulators. Not near as big of a jump as going from pcm regulation.
The catch. Unfortunately some vehicles will throw a check engine/battery/charging system light when not using the pcm regulation. Many vehicles don't, but i can't say a percentage on how many will. Just be prepared for the possibility. I've heard some performance programmers can turn the charging failure lights off.
Will your vehicle gain from going from pcm to internal/external regulator? definitely. How much? 20-100a. We really can't say how much amperage your pcm can supply. Will you get a cel? unfortunately we can't determine that either.
Post any questions on the topic you might have. I'm going to make a clamp video this weekend taking my 270a 6-phase alt from pcm regulation to external regulation, to show how big the jump in output is.