A different alternator question
I think you misunderstood my sentence. It was just an observation of what appears to be the general design characteristics.
I'm telling you its very hard to make generalizations with alternators. You have to get a performance curve for each specific alternator. Then you have to be able to convert them to the same voltage. Assuming both are reported in alternator rpm, then you can compare knowing the pulley ratio on your engine. Then you'll know whether the output at idle will meet the loads for your car at idle.
When I write specific alternator, I mean exact model, and if from a big rebuilder, the exact unit. For example, this one
Here's some examples of performance curves from Remy or ACDelco remanufacturing that used to be on their website.
The 15 SI was an older design but the '70 amp' has higher output at 1000 alternator rpm than even the '94 amp' 12 SI.
Notice these curves were generated at 12 Volts, not 14.2 which is the actual setpoint of the regulator it will be run with in the vehicle. The curve shape will be the same, but the actual potential amps out will be different.
Measuring the pulley ratio on my Jeep's engine, I could then add engine speed to the 12 SI graph. Doing that showed the output at 1000 alternator rpm was less important than first appeared.
Its a fully smogged engine with idle speed of 600-650 in drive. At that rpm, the 94 amp 12 SI and the 70 amp 15 SI are about equal. The 15 SI may run cooler. The 12 SI was the standard alternator, whereas 15 SI uses different brackets.
Sorry I dont have the equivalent info for even factory Chrysler and Denso alternators.
I think you misunderstood my sentence. It was just an observation of what appears to be the general design characteristics.
I'm telling you its very hard to make generalizations with alternators. You have to get a performance curve for each specific alternator. Then you have to be able to convert them to the same voltage. Assuming both are reported in alternator rpm, then you can compare knowing the pulley ratio on your engine. Then you'll know whether the output at idle will meet the loads for your car at idle.
When I write specific alternator, I mean exact model, and if from a big rebuilder, the exact unit. For example, this one
might be better than some denso models at low rpm.
Here's some examples of performance curves from Remy or ACDelco remanufacturing that used to be on their website.
The 15 SI was an older design but the '70 amp' has higher output at 1000 alternator rpm than even the '94 amp' 12 SI.
Notice these curves were generated at 12 Volts, not 14.2 which is the actual setpoint of the regulator it will be run with in the vehicle. The curve shape will be the same, but the actual potential amps out will be different.
Measuring the pulley ratio on my Jeep's engine, I could then add engine speed to the 12 SI graph. Doing that showed the output at 1000 alternator rpm was less important than first appeared.
Its a fully smogged engine with idle speed of 600-650 in drive. At that rpm, the 94 amp 12 SI and the 70 amp 15 SI are about equal. The 15 SI may run cooler. The 12 SI was the standard alternator, whereas 15 SI uses different brackets.
Sorry I dont have the equivalent info for even factory Chrysler and Denso alternators.
