WhiteIrocZ

iTrader: (3)

I just had a local alternator shop beef up my alternator to 160 amps. They told me that when they put in the higher amp stuff, it makes it charge more up top (higher RPMS) but less on the bottom (low RPMS). Now at idle the voltage drops to about 13 ish, but bump the gas and it shoots up to about 15 volts. I need a smaller alternator pulley to spin it a little faster so it will charge really well at idle. Any suggestions???????

Orr89RocZ

iTrader: (20)

March power and amp series underdrive pulley set has a smaller amp pulley. You can buy that kit and run just the amp pulley.

that way your amp is overdriven and should charge well if it does suffer at idle

WhiteIrocZ

iTrader: (3)

Do you have those pullies? Would you happen to know the diameter of the pulley from the peak of the inside rib? I have a friend that has a LT1 car and he has a set of March underdrive pullies for it and his pulley is exactly the same size as the one that is on my car now. I measured mine with a caliper and it is exactly 1.910".

88iroc52387

iTrader: (2)

13 volts should be fine. An actual car battery when fully charged is between 13-14 volts. It should be fine to keep it charged or if its draining at all it should be very small amt. try it i don't think you need to waste money on pully

Orr89RocZ

iTrader: (20)

yes i do have that pulley and it measures about 1.55-1.6 inch between the ribs. rib to rib peak is 1.67 or so

stock was significantly larger, i dont know where i put the stock pulley tho. its laying around the garage somewhere

WhiteIrocZ

iTrader: (3)

That may be just enough to help me out. I don't want to let it just keep doing that because the air, blower fan, electric fans, lights, stereo, etc aren't on when it goes to 13 volts. If all thats on, it goes to less than 12. I will order that pulley probably monday.

Orr89RocZ

iTrader: (20)

have you verified voltage via a ALDL scanner or some other method? The stock gauge isnt always accurate. My car has run in the mid 13s voltage wise and its been fine

WhiteIrocZ

iTrader: (3)

I can hear it in the fuel pump and see it in the lights and stuff. I like the way it charges when it is at about 750 rpms or more. The lights are bright and the fans and blower fan don't slow down. But at 600 rpms, the lights are dim and the fans slow down.

Klortho

You should be around 13.8-14.1 at idle and also with the motor at speed, if you are going above this, the you need to have the voltage regulator checked at the place that done the work on the alternator. An increase in amperage should not have made the voltage move up like that.

Take a digital volt meter put it on the terminals of the battery and see what you are at idle and then with the car running like 2500-3500rpm if there's a huge difference have that regulator checked.

Voltage is what is used to run the accessories....amperage is what charges the battery basically.

WhiteIrocZ

iTrader: (3)

I just logged the car and the voltage drops down to about 12.8 at idle and about 14.6 at anything over 750 rpms. With the air on and the fans on, the voltage drops to 12.1 and the lights dim. I can't play the stereo with a cap when the voltage goes that low, it makes the lights get really dim. I will order that pulley monday, its worth a shot. If that doesn' t work, I will just buy a new alternator or have the old one converted back to stock.

Does this look like your pulley Orr89RocZ???
http://store.summitracing.com/partde...5&autoview=sku

TTOP350

iTrader: (8)

I'm running on off of a Fox body mustang. helped a bunch.
Just take your stocker to a junkyard and compare sizes..

Orr89RocZ

iTrader: (20)

yes that looks like my pulley and i didnt know you could get it seperately like that

as long as the bore diameter will fit our stock alternators that pulley will work gooood

WhiteIrocZ

iTrader: (3)

I just got the pulley in today from Summit along with the new Detroit True Trac and 3.42 gear...hehehe. Pulley works great!!! I had to take a sanding wheel on the dremel and clean off the paint inside the hole for the alternator shaft so it would slide onto the alternator. Charges great at idle and now with the fans running, Ac on, stereo blasting, and the headlights the voltage doesn't even think about going less than 14!!

Orr89RocZ

iTrader: (20)

good deal man i figured you'd like that pulley. It works great on underdrive setups as well.

KYLE87

iTrader: (5)

Can a pulley have that much effect on it? How hard is it to change?

WhiteIrocZ

iTrader: (3)

That pulley was 3 tenths of an inch smaller in diameter than my stock pulley, so yes it did make a difference. Its easy to change, just unhook the battery, take off the alternator, use an impact gun to take the pulley off, change it, and put everything back together again. Took less than 30 minutes with grinding the paint out of the pulley too.

Orr89RocZ

iTrader: (20)

i didnt have an impact gun and couldnt get the stock pulley nut off... so i took the alternator to a local alternator shop to have the smaller pulley put on for 16 bucks....they raped me for 2 minute job haha

KYLE87

iTrader: (5)

HAHA, im afraid I will have the same problem as well. Did you notice much difference with pulley as well?

Orr89RocZ

iTrader: (20)

i ran March power and amp series underdrive pulley on my crank and the kit came with a smaller alternator pulley to match. Since i couldnt get the nut off, i used the stock alternator pulley for awhile. At night with the lights on, they would dim alot at idle and voltage dropped to 12 volts or so... not very good

Swapped the smaller pulley on and bam, back to normal operation. Seeing almost full 14 volts now. Good deal. Lights dont dim at all even with the stereo on and fog lights on

British Rich

I am about to do my pulley so my new alt will run properly at idle.

You say you just used an impact wrench?

So if I do not have an impact would you recommend I def get the pulley "puller" tool to do it?

Any help is appreciated

British Rich

Anyone?

The_Phoenix

iTrader: (3)

Sorry for resurrecting this thread but would a 2.5" UD alternator pulley be suitable for my engine compared to my stock pulley? Its part of a set of UD pulleys from Canton racing that I'm looking to purchase soon and was wondering if it would charge correctly along with the other pulleys in the set here are their diameters:

Crank - 5" Dia.

Water Pump - 4" Dia.

Alternator - 2.5" Dia. with .688" shaft

Power Steering - 6" Dia.

The Crank to Accessory Ratios are:

Water pump 80% of crank speed
Power steering 62% of crank speed
Alternator 160% of crank speed.

There is also a 4" alt. pulley available for 15mm shafts.

BTW my car is an '89 GTA with the L98.


Thanks in advance,

Ruben M.