Alternator dropping voltage at WOT only?
TECH Enthusiast
Joined: May 2010
Posts: 558
Likes: 1
Did we ever get a resolution on this issue? My CTS-V is killing alternators left and right. I made a bracket to mount 145a AD244 alts on the car (stock truck alternators) and I killed one on friday street tuning it for a half mile drag race event, then killed the new advance auto alternator on sunday when i cranked the redline up to 7,200. The "Battery not charging" was flashing before every shift when racing, but going up to 7,200 from 7,000 finally killed the thing.
I'd love to not have to put a new alternator in the car every time I go racing
I'd love to not have to put a new alternator in the car every time I go racing
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Killing them sounds more like a wiring issue. Usually from applying too much voltage and no resistance to the field wire. Might try a self-exciting “1-wire” replacement. Or look your wiring over well and ensure your style alternator is wired properly.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Did we ever get a resolution on this issue? My CTS-V is killing alternators left and right. I made a bracket to mount 145a AD244 alts on the car (stock truck alternators) and I killed one on friday street tuning it for a half mile drag race event, then killed the new advance auto alternator on sunday when i cranked the redline up to 7,200. The "Battery not charging" was flashing before every shift when racing, but going up to 7,200 from 7,000 finally killed the thing.
I'd love to not have to put a new alternator in the car every time I go racing
I'd love to not have to put a new alternator in the car every time I go racing
Is there decent airflow to the unit ?
When I had issues some years ago, old 01 Camaro unit that worked for years eventually packed in. I had it repaired locally and again it served for another few years.
However this time when I got it repaired...it would stop charging at 6500rpm.
I bought a cheap alternator off ebay and it did the same bloody thing.
I then bought a 170A unit off these guys, along with a slightly larger pulley and it's been fine since
https://alternatorparts.com/ad230-ad...ternators.html
I did buy new regulators for the old alternators as spares...but never did try them again and I hope I never need to. Because again it would be a gamble as to whether they would work or not, and nowhere local would ever have the means to spin the alternator up to working speeds to test !
Alt Pulley Size Hi, I would FIRST installer a LARGER ALT Pulley.
It could be a RPM Problem ?
Let us all here know.
I manufacture many "ALT" and can inspect one for damage.
Lance
It could be a RPM Problem ?
Let us all here know.
I manufacture many "ALT" and can inspect one for damage.
Lance
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Just to revisit this for anyone it may help. I used a boost a pump to stop my pump worries, but never fixed the root of the problem.
The issues is alternator RPM, pure and simple. They typically stop charging around 18k RPM. You may get lucky with a nice new factory alternator over a cheapie reman, but they all do it. Buying a super BA alternator or slowing them down is the only way to fight this I'm aware of. Take your crank diameter divide by alt pulley diameter and multiply it times your max RPM. I have a 3.10" pulley. 7.5/3.10=2.4x7200= 17,419 rpm. I should be good. Haven't tested it yet, will report back.
The issues is alternator RPM, pure and simple. They typically stop charging around 18k RPM. You may get lucky with a nice new factory alternator over a cheapie reman, but they all do it. Buying a super BA alternator or slowing them down is the only way to fight this I'm aware of. Take your crank diameter divide by alt pulley diameter and multiply it times your max RPM. I have a 3.10" pulley. 7.5/3.10=2.4x7200= 17,419 rpm. I should be good. Haven't tested it yet, will report back.
I’ll look forward to that.
I have that issue on a car I tune. Turbo car.
It however has a 25% UD Summit balancer. I haven’t done the math.
He finally bought a fancy Powermaster truck alt. Same issue.
Engine is now in a different vehicle, so much simpler wiring to deal with. I’m hoping it was the car!
I have that issue on a car I tune. Turbo car.
It however has a 25% UD Summit balancer. I haven’t done the math.
He finally bought a fancy Powermaster truck alt. Same issue.
Engine is now in a different vehicle, so much simpler wiring to deal with. I’m hoping it was the car!
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Believe most of those 25% UD are 6.14". If stock is 2.25" on alternator.... 2.72 X RPM. Will likely still drop off line a bit over 6600. Summit has the 2.75" part # ASP-540084 (can get cheaper on ebay) That'd get ya over 7500.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo 9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
If they all did it, there would be far far more people complaining about it
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
And doesnt everyone datalog ? They should. Although on a road car...if it was at night, the drop in voltage should be very obvious on dash lights and the headlights.
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Everyone surly doesn't! lol. Hardly any of the carb'd LS guys do. There are tons of those at our track. Most daily driving folk... etc. I think they just don't know what to look for, it doesn't hurt them, so they don't pay attention. If its not broke, no need to fix it. It's not like the drop in voltage for 2-3 seconds is super noticeable. Only reason I noticed is my fuel system was done and my pressure was dropping off. It's gotten better with the 160a 1 wire alternator, but still does it. Partially due to the thing overcharging at 14.7 all the time I'm assuming. So when the Alt. drops offline the battery is still near 12.9-13.0 for a brief time. Where as a normal system will likely regulate you closer to mid 13's as it should.
Sure with the factory diameter pulleys 7.5 and 2.25... You're looking at 20000 rpm at 6k. I'm not sure if the factory alt pulley is really 2.25... but anything around 6k plus is pushing it. My bone stock 2005 GMC truck does it at well. 109k on factory orig alt.
Sure with the factory diameter pulleys 7.5 and 2.25... You're looking at 20000 rpm at 6k. I'm not sure if the factory alt pulley is really 2.25... but anything around 6k plus is pushing it. My bone stock 2005 GMC truck does it at well. 109k on factory orig alt.
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Its a crap shoot man, I was told the more true the commutator the brushes ride on is, the less the brushes bounce and the more RPM friendly they are. They are all rated for "X" RPM range though. So if you spun one to 24,000... it must have been a really good one!
Here is a decent article on the subject... basically stating 18k is the limit for most.
https://www.hotrod.com/articles/0206...ur-alternator/
Here is a decent article on the subject... basically stating 18k is the limit for most.
https://www.hotrod.com/articles/0206...ur-alternator/
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Its a crap shoot man, I was told the more true the commutator the brushes ride on is, the less the brushes bounce and the more RPM friendly they are. They are all rated for "X" RPM range though. So if you spun one to 24,000... it must have been a really good one!
Here is a decent article on the subject... basically stating 18k is the limit for most.
https://www.hotrod.com/articles/0206...ur-alternator/
Here is a decent article on the subject... basically stating 18k is the limit for most.
https://www.hotrod.com/articles/0206...ur-alternator/
After I had the unit repaired one time..it started dropping out at around 6k. I too at the time read some BS articles about the brushes so I took the unit apart and added stronger springs to the brushes. Didnt make a bit of difference. Electric motors can spin much higher with brushes....so I do not believe they are the issue here.
Get that test rig sorted !! lol
Thread Starter
Joined: May 2011
Posts: 8,485
Likes: 1,032
From: Wichita, KS
Believe the run-out on those is like 30 micron max... or something crazy. And none of the remans are that good. Thats according to the little alt shop in my town. They basically said slow it down. So 3.10" pulley it is! That'll be my test rig! Alreadyhave it, just need to get it installed and get a new belt.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
voltage isnt critical to engine operation/safety at idle....it is at 6k and beyond.
But even at idle...it's not like the alternator isnt spinning like **** in either case.
Just get a good alternator, and it isnt an issue though. Or if really stuck, underdrive crank pulley and/or larger alt pulley if you were turning some very high engine rpm's and sustaining them