So cold and on a test bench. Again, I'd like to see real world measurements installed in a vehicle as things heat up from the engine and the current it is generating.
The biggest reason to recommend a 240-270a alt for a true daily is output at idle is almost always better than the larger 320a+ units ... other than that, there is not much of a reason to go with a lower output alt. if you can afford a higher output alt.
How has that alternator held up for you ??
I just ordered a Brand X Alternator - 250 amp - $287
I am surprised nobody mentioned the following:
we recommend 250 amps as a maximum for stock idle rpm, anything over 250 amps may require an idle rpm adjustment, or larger crank pulley installed. 300+ amp alternators on the newer cars can cause bogging at idle and low idle Voltage because of this. The stock output on these cars is only 100 amps, going much over 2.5x the stock output can cause this. This is due to the very weak factory spring tensioner on the car, and not an alternator problem. For the most reliable options we suggest 250 amps or less and no modification is required for those options.