Thread: One Wire (self energizing) Alternator?

Good info to know. I'm actually going to be be checking out my B15's QR25 alternator when I get some time, now that I know it has this type of alternator, and try to do some measurements without taking it off, and see what it might take to bolt up. I know that the lower mount piece is shorter than the B13's, it would be easy enough to grind it down to fit, as long as the upper pivot point can work. My only other concern is the output post is further forward, which puts it more towards the fan shroud. As long as that clears, it would actually be a plus as those wires are now further away from the header.

I'm thinking that a clutch type pulley would actually be a benefit on a track car where you are constantly changing RPMs.


Back on the topic of 1 wire alternators... The common GM ones that I've been coming across are by and large lower output than what we have. On older cars, that worked OK. But I don't think I can afford to go with a lower output, especially since the radiator fans I'm putting on are going to draw more power when they are running than stock, add headlights (for night races), and the amps add up fast.

I've done some googling on 1 wire regulators to see what was available, and from that checked what alternators those went into. Most were for older series or lower amperage alternators, and none that I saw looked even close to being able to fit.

I figured this was a long shot, but everything seems to be a dead end short of paying big $$ to find a suitable racing alternator or have one modified by a rebuilder, assuming they can even handle that task since there doesn't seem to be that many parts available for models that fit our cars easily.


So now I'm back to figuring out how to best deal with the sense line for the alternator, which would probably best be a topic for another thread.

Why not ask an alternator/generator rebuild shop to see what they can do to mod an SR20 alternator for race duty?

Haven't had time to do that yet, and I figured that they might need to actually have a sample unit on hand to verify parts. It's on my list.


One thing that I've been mulling over, that I've read that a lot of people in the GM world have done with their alternators is to jumper the alternator output over to the Sense wire. This will (should?) fool the alternator into thinking that the battery voltage is exactly what the alternator is putting out. That means that the alternator isn't going to be able to respond well to changes in electrical load, but that's no different than a 1 wire alternator would be anyway. But I think this would still lead to problems when using a kill switch, if the sense line is reading alternator output, as the alternator is spinning down, would it still try to ramp up the voltage and burn itself out?


On a different topic, I checked out some B15 cars at the junk yard this weekend for the clutch type alternator mentioned above, which is also used on the 2.5 Altimas of that time as well. From my limited checking, it seems that those clutches don't last that long and are a definite failure point. I checked out two of them, gave them both a spin by hand and then grabbed the pulley to stop it. On both of them the internals stopped turning immediately, meaning the clutch had failed and that it was acting as a simply pulley (as it should when those fail). The 3rd car (an '06 Altima I think) had an aftermarket Duralast alternator (interesting that they needed it replaced so soon?) and when I gave that one a spin and stopped it, the internals kept rotating for a few moments, so that clutch was actually doing what it was supposed to. I went ahead and picked that one up, since I've got a B15 at home, now I've got a spare alternator even if I don't use it on the B13.

Mounting that one is going to be a challenge, the bracket that it mounts to on the 2.5 engines is part of an idler pulley, and no part of that will fit the SR20 engine. The lower mount on the alternator seems to be a different length than the B13, shorter, so it may be a simple matter of grinding down the stock alternator bracket to let that fit. It may be a bit before I can play around with this idea.

I honestly don't know the exact cause of our issues, however we seemed to have resolved the problem. We did this by replacing the ground wire for the alternator, as well as cleaning the body contact spot. We replaced the alternator plug coming off the wiring harness, which was loose. And we also coated the header and then wrapped it, to prevent over heating. Oh, and post importantly, we acquired an OEM Nissan alternator instead of using the Duralast garbage. Just went through a weekend at Watkins Glen without a problem.

^ Did you have a cut-off test done? Rev to 3000 RPM and then turn off with the kill switch and what happens? <-- That is what is needed to pass NASA Tech and both ours passed without issue at Road America last weekend and since being built actually.

Yes, same protocol for Lemons and Chumpcar.