So the 160a alternator definitely fixed it. Went to the track tonight. Drops from 14.1v to 13.5v, but stays steady at 13.5 the whole run. the BAP must be doing it's thing as well. I'm logging 44 psi at idle... and 76.6 at 20lbs of boost so jumping 32ish psi with 20lbs of boost. Probably what is suckign down the voltage so much.

 

Bump for an oldie to see how folks are making out. I'm about to drop $$$ for a Powermaster I think. Can't have this unpredictable voltage situation at WOT.

 

The 160a 1 wire deal fixed all my issues. I really think I was just overrunning the original alternator.

 

Sweet. Just an old-school one-wire deal huh? What kinda rpms are you turning?

 

Pics back in the thread, but it was a $140 ebay deal. It self excites so it doesn’t need the plug on the back. Just a solid lead to the battery/bus. 6800 on the shifts with steady voltage. I do have the ebay $28 alum pulley that’s slightly larger. OEM diameter crank pulley.

 

IMO there is no rhyme nor reason as to why they do it.

I've had some that do, some that dont..and they look the same externally.

But you definitely want stable voltage at all times

I got my 170A from here a few years ago now and it's been faultless. I did ask for a slightly larger pulley too

https://alternatorparts.com/ad230-ad...ternators.html

 

I added a 2.75" alternator pulley to my parts counter alternator, 1/0 gauge cabling & Superdamper in July 2015. That took care of the upper end problem... it used to start failing mid 5000, but now it's stable to redline (6400, which is all I need). I still had charging problems so I did the math and bumped my engine idle from 850 to 915 so it turns the alternator shaft at the same RPM as stock idle. If I needed to spin the motor to 7K, I'd need a 3" alternator pulley and set the engine idle to 1K for factory charging. No problems since then.

 

Stock LS7 Corvette redline is 7200rpm...just saying. I'm still convinced that problems occur because of improper installation and wiring. MHO...

Andrew

 

It'd be pretty damn difficult to install or wire one wrong, when it's a simple bolt and plug.

I had one alternator stop charging at high rpm after a repair. Same unit, same windings. Not 100% sure what was replaced although defo a new regulator. And thereafter it would always stop charging around 6k.
I checked/replaced the brushes in case there was some sort if issue there, but didnt make any difference. I did buy another regulator for it and fit it, but as I bought the AD244 based unit, I've never actually needed to try the old one again to see if that fixed it.

The same unit had been repaired some 6 years prior to that by the same person and it had worked fine until it failed.

A cheapo unit bought off ebay also refused to charge in most cases above around 6k ( but not always )

 

Not sure how you can mess up the installation of this.

Regarding a new car's alternator performance...I wouldn't doubt a brand new alternator, not rebuilt, would perform better. A reman unit could have a shaft that has run-out on the high-end, questionable components. But from what I can see almost all alternators are somekind of reman????

 

What does a new LS7 alternator from GM cost? What are the specs on it? It wasn’t the installation in my case, as the original alternator that came with my used engine worked for many years prior with no voltage issues. I think it’s the crap remain alternators myself. I really doubt most of them put out their rated amperage. I spoke with one of the guys at autozone about this. He says if you get a year out of one you are doing really well. Also said sometimes you get lucky and get a “good one”. They are the most returned item they sell. Zero quality control since they have a “lifetime” replacement warranty.

 

A quick search on rock auto shows this being the OEM replacement alternator for a LS7 Corvette:

http://www.rockauto.com/en/moreinfo....442777&jsn=446

Andrew

 

If that's truly a NEW alternator that's not a bad deal. I think the amp rating may be a little low for a fully-equip boosted car though, maybe not. Also not sure if that alt would fit the truck acess bracket.

Reason I use the word "truly" is b/c even though GM uses the word "new" there is instances where the alternator was a factory reman.

 

For $325 you can get a nice aftermarket “built” alternator. “Power Bastards” stuff is great I hear. Rated at 220a at 1200 rpm in a stock case truck alternator for $350. Texas speed also sells a billet 150a Mechman for $300 that’s nice.

 

I always wondered if the aftermarket units were better than a new OE unit.

The vette alternator is interesting. Perhaps that is a higher-quality unit as it is assumed the rpms will be higher vs say a truck unit???? I doubt they would have a separate manufacturing process for one alternator though.

 

The Vette alternators are not interchangeable with the truck alternator. The mounting points are different.

Andrew

 

I have an autozone gold AD244 I was losing voltage at high rpm on my data logs so I tried checking the voltage from my alternator post and it was fine reading 14 volts to redline with my multimeter. But my data logs showed voltage dipping to 12v. In WoT runs
I added a wire from terminal S to the battery stud in the back of the Alt and now my data logs read 13v at high RPM, long story short if you are Data logging voltage let's say with Hptuners, you are seeing 12v ign voltage on logs, which is what your coils and injectors run on. So if its dipping that's definitely not wanted.
so then out of curiosity I thought well why not wire the S terminal to a 12v ign source since that's were my voltage is dipping. FIXED MY ISSUE. 13.5 steady to redline. But at high rpm my battery hit 15v due to the alternator compensating for the voltage dip. Other than the battery is usually at 14v. It will hit 15v for a couple of seconds while I'm flooring it. But I dont think its damaging. Maybe the 2.75 pulley can help there?.
also my tune changed dramatically at wot throttle 15psi boost, started running really rich which makes sense since I had to dump fuel there in my OLSD tune to compensate for the voltage dip

 

I had a similar issue with my off road truck, I had to switch the alternator pulley to a bigger size. At about 5500 rpm it would stop charging then would come back on until you turn off the car or battery for a about 5 min.

 

I'm willing to bet you have the alternator output wire run "straight to the battery".

If that is the way you are set up instead try running the alternator output to some intermediate point. From that junction run a large gauge wire to the fuse panel than a smaller gauge wire from that to the battery. Do it right and that should keep you from overcharging your battery.

Batteries can suck up 100's of amps. No reason having a large chunk of your alternator output cycling needlessly through the battery, because that is what is happening when you put that much voltage on it.

 

I know this is ancient, but had a thought. Could you use a $30 2 farad audio capacitor to fix the voltage drop issue? Would work like an oil accumulator to supply voltage during WOT high RPM conditions only? For me at least It would be easier and cheaper than under driving my alternator. I use an "exact fit" belt with no tensioner of any sort from crank to alternator. (elec water pump)