Alternator question?

I've asked about an overdrive pulley before with no response, so I just went and found one original was 57mm this one is 54mm so slightly smaller. My questions am I going to burn up my alternator? On the older alternator I'm sure its not a prob. but with my 99 nippodenso unit will it be a problem? Please advise?

Considering ND is Japanese, and used on a number of Japanese vehicles as well (and you know how those guys can get...) you probably won't have a problem. Besides, it's not like your pully is half the size of the one it's replacing.

54m/m dia = ~170m/m circumference
57m/m dia = ~179m/m circumference

Difference? About a 5% overdrive, should be.

Why for are you overdriving your alternator? Trying to get more output, or trying to get full output at a lower RPM? If the latter, you're on the right track. If the former, you're going to want a bigger alternator anyhow (voltage output can be as much a matter of the alternator's armature and field windings as anything else - higher current units have more windings, usually using a slightly smaller gage of wire so it fits in the same case.)

like most everyone on here I spend alot of time at idle or low rpm (crawling and such) and need higher output at idle. Thanks alot...., I was scared to go to small so when I did the math, I thought 5-10% would be a good test run on the idea

mgreen84 said:

like most everyone on here I spend alot of time at idle or low rpm (crawling and such) and need higher output at idle. Thanks alot...., I was scared to go to small so when I did the math, I thought 5-10% would be a good test run on the idea

Click to expand...

Yeah - if you go too small, you're going to accelerate bearing and brush wear. I'd figure a 10% overdrive to be about the limit - maybe 15% for us, since we live at low RPM anyhow. Maybe.

I don't figure you want to go through alternators like popcorn, tho... The ND is a reasonably hardy unit (although I still prefer Delcos) and will handle some abuse.

where can I get a smaller pully? Ive wanted to do this but havent seen anyone selling them

I used micorgauges to measure my OE and went to the junkyard and found one slightly smaller.

I know it's been a long time but what did you pull that pulley out of?

I have a 96 with a nippodenso also? 90Amps I think???

The srt8 grand Cherokees have alternators made by nd and redline at 6500 rpms. Pretty sure that's about 50% overdrive from anything my xj is ever going to see?

Thanks, but I'.m trying not to get into a new alternator....especially one for a NEW SRT

Not the point I was making. A similar designed alternator can be spun safely at nearly 7000 rpm, pretty sure your alternator will be fine at 10% overdrive.