I read another post some where on this same thing.. I know that my power master 130 AMP will work to 7200 , Have you tried gettin in touch with CS ??? maybe there is something that prevents over charge or voltage spike if you spin the unit too many RPM's.. I am running march serpentine pulley kit so nothing crazy there..

So it would seem that a much larger pulley is going to be needed or something to lower the rpm of the alt itself.
ROTATION SPEED
Alternators spin at approximately 2.5 times that of crankshaft RPM,
so an engine at a 700 RPM idle would spin the alternator at 1,750
RPM. Note that the maximum RPM of any Tuff Stuff alternator
should not exceed 15,000 RPM’s (6,000 engine RPM’s). There is
no need to worry about use of an underdrive pulley system or an
ignition regulator turn on with Tuff Stuff alternators. All Tuff Stuff al
-
ternators charge at very low engine RPM’s. No other manufacturer
in the industry has an alternator that produces more amps at low
RPM’s than Tuff Stuff.Also note that Tuff Stuff 1-wire alternators are
bi-directional and will charge when spun in either directio
Here is some info right off the that site ..

 

CS is the style of alternator, not make. But I am looking into a larger pulley - again

What kind of car are we talking about ? Some oem computers turn off accesories over a set rpm. could this be a possiblity

This is a 96 Mustang with an LS motor, but I have a separate computer running the car. Alternator is wired separately. I ran another wire to the L terminal just to make sure that wasn't the issue, and it wasn't

Most likely it is brush bounce. The slip rings are out of round most likely and the brushes bounce at high rpm. Seen it A LOT!

Short of changing alternators, are slip rings replaceable?

 

What kind of car are we talking about ? Some oem computers turn off accesories over a set rpm. could this be a possiblity

 

Most likely it is brush bounce. The slip rings are out of round most likely and the brushes bounce at high rpm. Seen it A LOT!

 

Put an underdrive pulley on the crank, or get a drive mandrel like I did. I'm sure you are still over speeding it

 

In General... Underdrive Pulleys are a bad idea...
they may make a little bit of power on some engines...but in the long run they hurt the motor more than its worth...
smaller crank dampers mean less vibration control...which means you beat the engine up from the inside out...


many alternators are only good to 14k-16k Alternator pulley speed....

likely you are spinning it faster than it can handle... the brushes basically lift off and you no longer get any contact...

change the Alternator pulley out to a bigger one so it spins slower...
it just simple math to figure out what size you need

RPM * Crank pulley size / Alternator Pulley size = Alternator RPM

RPM / (Desired Alternator RPM / Crank Pulley Size) = Needed Alternator Pulley Size

 

Well Scott, the issue is the lack of available that pulleys that are large enough

 

Have one Cut by somebody like Bob at AEICNC (plumbbob)

its not that expensive and he will cut any size you want and any number of ribs you need or any style of grooves or shape you need.

almost ANY decent machine shop can cut a pulley for you if you bring them one as a reference so they have proper dimension for spacing.

 

KRC makes a nice 3.5" pulley priced right. I think a 3" might not be enough, 3.5" borderline too big but I'll try it.

http://www.krcpower.com/ecommerce/a...ators-and-accessories/alternator-pulleys/3-50-6-rib-delco-alternator-pulley.asp

 

I currently use a 3.5 on my alternator
spin it 7800.....nets me 17k at the Alternator...but my alternator is designed to handle that..
I have no issues, still have plenty of amperage at idle as well

 

Whats your idle speed Scott?

 

When i set mine up the place I bought the alt from was adamant I did not spin the alt over 6k. I plan on shifting at 8,500 so my Alt in now under driven

 

BTW There are some good underdrive Dampers out there. they are full size with the pulley area cut down and the AC part full size. I run one on my wives car but i only shift it at 7,400

 

Here are some readily available alternator pulleys.

http://store.alternatorparts.com/alternator-pulleys.aspx

 

Its amazing more people aren't having this issue as most people are spinning stock alternators/pulleys way past 6000 rpms. My guess is they arent tracking voltage and seeing it happen. Probably isn't a big deal for a carb'd car.

 

I went with the larger AMp to handle all my NOS solenoids fans pump etc. I have never seen a drop as I can track it with the grid..

 

I had the same problem ended up being belt slippage@ higher rpms.

 

This is something that I havent really thought about. I'm running the factory serpentine system from a LS truck motor. Its a new 6 rib belt and a new factory tensioner. The tensioner does move quite a bit at idle, I assume that thing is moving even more at speed. The alt. does have at least 50% belt wrap. Wondering could be an issue???

 

Put an indicator on the slip rings and getting .002 of run-out. That can't be good when the alt. is spinning as fast as it does. You can also see an uneven wear pattern on the rings, in fact it looks like the brushes are making limited contact on some areas.

Do these aftermarket alt. manufacturers tighten up these tolerances?

 

Do these aftermarket alt. manufacturers tighten up these tolerances?

They should. Considering the diameter of the slip ring, 2 thou is pretty bad in my opinion.

I've had conversations with both East coast auto electric and Powermaster. Both have tech guys that can answer thatquestion about their products.

 

I run a East Coast alternator for 16 volts.

They recommend a 2:1 ratio.

I run a 5" pulley on an ATI damper and a 2 1/2" alt pulley. It sees 7800 RPM on the top end.

 

We'll, hooked-up the 145a ad244 that I had laying around, and couldn't close the hood completely due to clearance, but it was latched. Ran the engine up to 6100 and voltage stayed solid at 14.2 even though alternator shaft speed was over 20k (had the factory 2.25" pulley on there). This is with a well worn used alternator too! Looks like I just didn't have enough alternator after all.:emb:

Looks like I'm pulling just over 100 amps at WOT b/c usually its ok in 1st gear but then voltage drops off in 2nd and 3rd as things get loaded down. Pretty interesting actually.

Thanks for all the tips!!

 

spinning the Alternator 20k ...is too much

its not that the alternator is not enough.... its that its not able to transfer the voltage at that High rpm


it needs to be in the 14k-16k range at the most...

put a larger pulley on the alternator.

 

I dropped the $550 for the Mechman and haven't had an issue since. Hot idle drops to 13.8v. 14+v all the way down the track.

 

I ran into this issue years ago, after lots of reman and new off the shelf alternators I went back to junkyard pull offs that were OE. Come to find out the OE alternators use a higher amp rectifier. 50 amp vs 35 amp. The remans and new off the shelf cant keep up at high rpm. Every build that comes out of the shop has a junkyard alt and haven't had voltage issues in years.

 

Damn, I forget the guys name that was the resident pro here for alternator shit. I think it was Rayyyyyyyyyy or something like that. Anyway, as you can see in the pic below, my alternator gets a major workout shifting as I have currently been shifting around 7700 rpm. Hasn't skipped a beat. That ray guy is the guy who got this alt for me. If he is still here, hit him up. He apparently has his ducks in a row.

Can you say "22k+ alt speed"? lol I spin the fuck out of this bitch and it has never skipped a beat.

 

I think he passed away.

 

I run a dB electrical cs130 d awesome alternator never drops below 13.9 hot with every thing on at idle. Puts out 110a at idle and 220a max.

 

I know Rayyyyyyy had a stroke or heart attack, but I am not sure if he passed away

 

Scott,
We would you happen to have part number of alternator?
Max rpm 7k ,
What size cranks pulley do you recommend.
Thanx, chays