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I just ran my car at the 1/2 mile drags and saw some unfortunate behavior out of my alternator. I have an antigravity lithium that is fully charged at 13.1V. Anything below that is discharging the battery. I need this thing to survive on 20 minute track sessions. I can't have the alternator cutting out like this. As soon as I get to WOT in 1st gear, 1 second later the voltage has tanked.
This is a brand new powermaster one wire alternator with a 3" pulley.
Engine is an LS7 making 590whp. Turning ~7200 rpm. Standard diameter ATI pulley, 3" alternator pulley, and manual tensioner. Alternator RPM stays below 18,000.
The alternator stops charging when I'm at WOT. Voltage spikes back up on my shifts, and comes back up as soon as I lift. Driving part throttle back to the pits it charges fine.
What could possibly be different about WOT that makes it fail to charge? I cannot believe the belt is slipping. I have the tensioner quite tight and the belt condition looks good.
I once had an alternator that would stop charging at high rpm. It turns out that the rotor had a flat spot on it, and the brushes couldn't keep contact at high speeds; basically, it was experiencing "valve float,' only it was the brushes.
Are you sure that the belt is keeping in contact with the pulley at WOT?
I once had an alternator that would stop charging at high rpm. It turns out that the rotor had a flat spot on it, and the brushes couldn't keep contact at high speeds; basically, it was experiencing "valve float,' only it was the brushes.
Are you sure that the belt is keeping in contact with the pulley at WOT?
Can’t say I’ve heard of that before.
I can’t imagine I have belt slip. I’m following OEM belt routing and have a manual tensioner that is nice and tight.
I believe the Powermaster alternators have an 18k rpm limit. You can Google how to determine your alt rpm, but I’d bet you’re right there at it, if not over it. A larger alt pulley will fix it, if this is the case.
I believe the Powermaster alternators have an 18k rpm limit. You can Google how to determine your alt rpm, but I’d bet you’re right there at it, if not over it. A larger alt pulley will fix it, if this is the case.
18,000 alternator rpm is 7200 rpm, and highest it went in the datalog is 7100 rpm.
It seems to be engine load based which makes no sense to me with a 1 wire alternator. When I shifted the voltage jumps back up and then when I’m back in gear accelerating it drops back down.
18,000 alternator rpm is 7200 rpm, and highest it went in the datalog is 7100 rpm.
It seems to be engine load based which makes no sense to me with a 1 wire alternator. When I shifted the voltage jumps back up and then when I’m back in gear accelerating it drops back down.
Could simply be that it’s not “Swiss timing” in the alternators ability to detect when to cut load.
I poked around with a volt meter and found the back of the alternator putting out 14.2-14.3, and at the end of the charge cable it is only reading 13.7. I think I found my problem! Would also explain why my voltage was dropping significantly with a hot engine bay.
Glad it looks to be something simple. I'll make a new cable and expect to be fixed.
I poked around with a volt meter and found the back of the alternator putting out 14.2-14.3, and at the end of the charge cable it is only reading 13.7. I think I found my problem! Would also explain why my voltage was dropping significantly with a hot engine bay.
Glad it looks to be something simple. I'll make a new cable and expect to be fixed.
What size is your charge cable now? I go ridiculously big on my Powermaster charge cables when I do them. The heat soak is a thing, like are seeing. If the wire size is on the marginal side, heat will exacerbate the issue like what you are seeing. Pay attention to the cable ends too, the input/output need to be on par too.
I had a similar issue with my Powermaster alternator. Turned out I overspun it initially and fried the regulator. They fixed it for free and sold me one of their new 3.5" pulleys at cost. Works great now.
Do you have part number for the 3.5" pulley "
Is the pulley steel or Aluminum?
I'd like to equip (several) of my fleet with slower speed alternator pulleys.
I don't have a part number, as they hadn't even released it when I got it. I know it's out now, I am sure Powermaster will sell you some direct if you call.
Do you have part number for the 3.5" pulley "
Is the pulley steel or Aluminum?
I'd like to equip (several) of my fleet with slower speed alternator pulleys.
Motion Raceworks or Hawks has multiple sizes of alternator pulleys. I've got a Motion 3" and Hawks 2.85"
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Powermaster alternator not charging at WOT 
