With most underdrive pulley sets:
Crank is smaller than stock (spins all acc slower)
Water pump is larger than stock (spins slower)
Alt pulley is SMALLER than stock (spins a little faster to keep low RPM charging)
A stock 3G pulley is LARGER than the stock 2G and much LARGER than the under drive pulley. This is why most underdrive alt pulleys will not fit on the 3G.
What I've done is use the stock 2G pulley on the 3G with my underdrives. This is still spinning the alt slower than it would be with the underdrive pulley. Since it's a 3G, there are no low RPM charging issues.
I know people who have used the stock 3G pulley with underdrives. Spinning the alt even slower than the stock 2G size. Still no charging issues.
In both cases, you can still use the factory belt length.
Crank is smaller than stock (spins all acc slower)
Water pump is larger than stock (spins slower)
Alt pulley is SMALLER than stock (spins a little faster to keep low RPM charging)
A stock 3G pulley is LARGER than the stock 2G and much LARGER than the under drive pulley. This is why most underdrive alt pulleys will not fit on the 3G.
What I've done is use the stock 2G pulley on the 3G with my underdrives. This is still spinning the alt slower than it would be with the underdrive pulley. Since it's a 3G, there are no low RPM charging issues.
I know people who have used the stock 3G pulley with underdrives. Spinning the alt even slower than the stock 2G size. Still no charging issues.
In both cases, you can still use the factory belt length.
I use an OVERDRIVE alt pulley on my 3G. It's a 1 7/8" pulley smaller than the stock 2G pulley.
When driving pulleys, (crank), the smaller you go, the slower everything turns. With driven pulley, smaller pulleys equals more rotations per crank rotation.
Reason i use the O/D alt pulley is to speed the alt back up at idle.
When driving pulleys, (crank), the smaller you go, the slower everything turns. With driven pulley, smaller pulleys equals more rotations per crank rotation.
Reason i use the O/D alt pulley is to speed the alt back up at idle.
Yes...some kits come with smaller alt pulleys for this reason. The stock 2G is bad enough at idle. Spin it with a smaller crank pulley and the problem is magnified.
Yes. As Mustang5L5 said, reducing the size of the driving pulley (crank) turns everything slower. Increasing the size of a driven pulley (water pump), also turns that accessory slower. Conversely, reducing the size of a driven pulley (alt) will increase the speed. Ever had an 18 or 21 speed mountain bike? Same principle.
Yes. I use the 2G alt with my 3G and ASP underdrive pulleys. With all accessories on and electric fan on high speed, I'm at 13.1 volts at idle. A friend is using the stock 3G pulley with ASP underdrives. 12.8 volts at idle.
Unless you have electrical loads out of the ordinary (I consider an electric fan ordinary), the 2G or 3G pulley should be fine.
Or an AOD, as they tend to idle lower than 5-spds while sitting at a stop light in gear. That is why i ran an OD alt pulley. When i had the AOD in my car, the difference in RPM from Nuetral to Drive was enough to bring the volts to under 12V. I needed the OD pulley for that extra RPM at low idle.
Now that i'm a 5-spd, i'll prob toss the other underdrive pulley on for the sake of having matchning pulleys.
Yes, but with underdrive pullies, an SN95 electric fan and an AOD.
The OD alt pulley fixed that issue, just needed a few more RPM.
I'm gonna take it off now
I can't remember, it's been 6 years or so. I wanna say 600 or so RPM but that's by the stock tach and who knows how accurate that is. But the 100-200RPM jump fron neutral to Drive did make a difference in charging.
I don't need it now with the 5-spd, so i'm gonna take it off so i have matching pulleys.
I don't need it now with the 5-spd, so i'm gonna take it off so i have matching pulleys.