Pcm VS Internal VS external regulators

[profundus-sanus]

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.

[k3n12ock]

I'm just wondering why My voltage won't hit 14.0 05 xB PCM controlled.

[Radioactiv]

I'm guessing the PCM can actually seem to cut the alternator out put out also? My friend has a 07 Toyota Tacoma and it seems to randomly cut out at times. I'm guessing he would have to go to externally regulated?

[profundus-sanus]

yes. the pcm can limit field current as well as back the voltage down.

in my grand prix i can get full power for the first couple minutes of driving the vehicle, after that, when my voltage backs down, current is cut as well.

[phatryan69]

good to know.. gonna look at externally regulating my alt now

[sho412]

ok so I just got a 07 yukon denali and I notice my voltage will only stay @ 14 for the first few moments of driving then drop to 13.xx I have a dc 320 in the garage im gonna put in but do I need the 1 wire deal to get my voltage rite and if so will it work with the dc alt? (shoulda got a singer)

[dirtrider]

Nick my alt is doin work!! Always goes right back to 14.8v

[tony30cl]

external reg on my cl for a few months with no Battery or Cel! honda owners need external regulation. with the eld that turns the alt off is worse than a pcm ever could be

[profundus-sanus]

Originally Posted by dirtrider

Nick my alt is doin work!! Always goes right back to 14.8v

i know man!

the massive difference between yours and mine, then a long talk with mike, inspired this post.

Originally Posted by tony30cl

external reg on my cl for a few months with no Battery or Cel! honda owners need external regulation. with the eld that turns the alt off is worse than a pcm ever could be

oh i think my grand prix is right up there with your honda, lol. gm copying honda, imagine that, lol.

i regularly see 14.6-15.1 cold and within 30 minutes of driving 12.8, lol.

Originally Posted by sho412

ok so I just got a 07 yukon denali and I notice my voltage will only stay @ 14 for the first few moments of driving then drop to 13.xx I have a dc 320 in the garage im gonna put in but do I need the 1 wire deal to get my voltage rite and if so will it work with the dc alt? (shoulda got a singer)

i would go 1 wire yes. your regulator controls your voltage completely.

we're really just trying to get away from plug and play setups in general. they're convenient but their such an unknown variable.

[Jeffhulbert50]

Just ordered my alt with the new tech, hell ya