Alternator delete with regen braking modification for better MPG

[Loren]

So, its back to the drawing board for version 2 for this modification.

One of the other wires from the ECU is providing power to turn on the voltage regulator. What if you put your switch there?

Oh, and for the record, try to make your cuts at least 6-8" away from that ECU connector. If you end up with a wire that's too short to comfortable crimp or solder, you'll understand why! Give yourself some room to work with.

[stevedmc]

If you're really old, you remember when alternators were simple 2-wire devices, and the voltage regulator was a separate part. And so was the starter solenoid. And fuel pumps were mechanical, bolted to the side of the engine block. I don't miss any of that stuff.

You forgot to mention the dimmer switch on the floor.

[stevedmc]

Once I revved up the engine a little, the voltage jumped up to 14.4V. Boo! So, it is self exciting somehow. This simply won't work. It started exciting (powering up) at probably a little over 2k rpm. Its not like I can just 'not go over 4,000 rpm' and make this work. So, its back to the drawing board for version 2 for this modification.

Stinking computer. I'm just glad you didn't fry your ECU.

I haven't had to mess with the alternator on my car yet, but I can't imagine there being more than one or two wires hooked up to it to trigger charging. Why not clip the trigger wire(s) on the alternator and temporarily put electrical tape on them instead of a switch?

If it works, then go back and install a switch. If it doesn't work, solder those wires back together and then go back to the drawing board.

[Loren]

You forgot to mention the dimmer switch on the floor.

Yes! And carburettors and distributors with contact points, manual chokes, and... 3-speed automatic transmissions.

Sorry, way off-topic.

[Eggman]

One of the other wires from the ECU is providing power to turn on the voltage regulator. What if you put your switch there?

Would residual magnetism cause this too?

Now for the testing. I fired it up and it surely appeared to be working. My scanguage said a wonderful 12.6V which is right where it should be. However, I did run into a bit of a snag. Once I revved up the engine a little, the voltage jumped up to 14.4V. Boo! So, it is self exciting somehow. This simply won't work. It started exciting (powering up) at probably a little over 2k rpm. Its not like I can just 'not go over 4,000 rpm' and make this work. So, its back to the drawing board for version 2 for this modification.

I wonder if:
1. Grounding the circuit would keep any residual magnetic energy from exciting the field and energizing the alternator, and
2. If grounding the circuit would cause any harm. If so, would a low-current fuse protect against damage?

[Eggman]

Oh, geez. There are several levels of information going on here.
...
With the internet at our fingertips, learning stuff like this is easier than it's ever been!

Interesting research, thanks. I was hoping for a link to where you got your info, but I understand your explanation.

So, in your scenario, how would an ECU manage regenerative braking?

[Loren]

Would residual magnetism cause this too?

I'm going to bet that the fact that the alternator comes on with that input open is by design. It's a fail-safe. If you lose that connection, you'd WANT the alternator to default to charging to keep the car running. It would be slightly less efficient, but it would keep running.

I wonder if:
1. Grounding the circuit would keep any residual magnetic energy from exciting the field and energizing the alternator, and
2. If grounding the circuit would cause any harm. If so, would a low-current fuse protect against damage?

I like the way you're thinking, and I think you're onto something with #1.

What we've done by putting a switch on that wire is create an OPEN circuit. That might very well be it's normal condition when the ECU has commanded the alternator to be "off". Rather than just opening the circuit. GROUNDING the circuit might very well turn off the alternator.

As for #2, I don't think there's any current on that control circuit. It's just a control circuit. As such, it is very likely that it never gets a 5 or 12 volt signal. It just switches between ground or not ground. Easy enough to test... if one were so inclined.

Interesting research, thanks. I was hoping for a link to where you got your info, but I understand your explanation.

Yeah, no real easy answer in this case.

So, in your scenario, how would an ECU manage regenerative braking?

The newer a car is, the more sophisticated the ECU is. They have all sorts of inputs, and control damn near everything. So, for instance, if you were going for "regenerative braking", then the ECU would simply keep the alternator "off" except for those specific conditions where the engine is decelerating. You could use the brake pedal input (but, that's probably not going to give you enough charging if you're "hypermiling"). More likely, they'd do something like enable the alternator when the car is in DFCO. You're coasting down and you're foot has been off of the accelerator for more than x seconds. (but, they can't bet that you're going to drive that way, either... so, it's surely more sophisticated than that) But, then... what if you're on the highway cruising for 3 hours? Surely, it needs to initiate some charging then? Which would mean that the ECU itself would need to sort of act like a voltage regulator (which is what I thought it was doing, but apparently it is not). Not a true voltage regulator, not handling the current of the alternator and switching that big load... but, just a simple switch that ENABLES the actual voltage regulator when it senses that the voltage is too low. (and the ECU already monitors voltage, you can see it in an OBD reader)

I still think the simplest solution here would be to grab a Euro ECU and see if that works on our cars (it should), and if that alternator control works like it should. I'm all for modding things to death if there is no other option. But, if an easy factory option exists...

[Daox]

Alright, lets talk about version 2.0. I looked through the PDF Fummins posted earlier in this thread. It said if you cut the sense wire, most alternators default to shutting off. So, lets see how to get to the S (sense) wire.



The 'relay box' is the fuse box in the engine bay. F15 is the location of the fuse that runs to the S wire. So, testing this one out will be as simple as pulling fuse #15 under the hood. Yay, I like easy.

So, I tested it. I pulled the fuse, fired the car up and... 15V! Haha, the opposite of what I wanted. If the alternator can't sense the battery voltage, it just blasts out 15V. Sadly, this doesn't get us any closer to killing the alternator at will. However, it does tell us how to turn the sucker on full blast! This was part of phase 3 of the project, so we will file that information away for later.

So, it looks like we'll have to figure out a version 3.0.

[Eggman]

I find it humorous that it's called an IC VOLTAGE REGURATOR.

Maybe that's why we can't figure this out.

[Loren]

I guess pulling the sense wire might shut off the regurator output. In pure theory, it shouldn't. Low voltage should enable the regulator. But, if you lost the sense wire (or blew that fuse), that would cause the regulator to go nuts and give you "all of the voltage", which can be up to 18v. You don't want that kind of output for very long, it would cause system failures, overcharge your battery, and ultimately fry the alternator. So, it's probably designed to automatically shut off when it senses an open input on the sense wire as a fail-safe.

Easy enough to test. Even easier since there's a fuse. And if it works, you can get one of those "add-a-fuse" things to fit into the fuse slot and probably do your mod without even splicing into a wire.