Originally posted by mangler:
1. I am worried about the 20% underdrive on the alt, for the stereo wielding people...
2. anyone know how many amps are produced by the alt at idle? I'd like to see what 20% less would be, and check for amperage requirements (can anyone say rear defroster?)
1. Yes at idle with your noise pollution thumping it may pose a problem.
However with all the extra weight of the equipment & subsequent tremendous strain on the electrical system maybe you shouldn't be worried about underdriving your alternator for performance or alternator longevity in the first place.
I would not recommend one to anyone with a large stereo setup. For that matter I would also recommend you upgrade a few or your current components as well (battery, alternator, extra capacitors, etc) You know; the normal stuff needed on any vehicle pushing any serious wattage. Not doing so is just inviting component failure.
2. It doesn't work that way. 20% slower revolutions does not equate to 20% less amperage output.
The stock alternator puts out 50-70amps at idle. (load dependant of course) At ~2000 rpm it can exceed 100amps.
It's rated at 140amps, but definitely can exceed that under heavy load and enough rpm to sustain it. (10-20% safety factor) Regularly exceeding it's "rated" amperage with shorten it's life. (why large stereos eat alternators & batteries)
With this pulley the only time you
may notice a draw on your electrical system is at idle with everything running. The battery plays a large factor in this as well since it is used as a backup supply when the demand exceeds the alternator's output.
Personally I never saw a problem with a ~13% UD alternator pulley and the stock battery. With the dyna-batt (40% the reserve time) I have seen the headlights dim. However only when the idle drops below 700rpm (basically when coming to a stop with the clutch in) & I have everything (head & driving lights, radio, blower, brake lights, etc) running. With the driving lights & blower off it never does it. Above 700rpm (or
at idle) it never does it regardless.
