View Full Version : Underdrive Pulleys and Car Stereos....
09-23-2007, 01:33 PM
Whats up guys-I have UUC Underdrive pulleys in my M3. I recently ordered a 2 12'' subs and a 1400W mono block amp. Friends are telling me i am DEFINITLEY going to have a problem...does anyone have underdrive pulleys in the car with a high output stereo? any problems? Solutions? Please help me out..
BMW 1997 E36
09-23-2007, 08:38 PM
what brand of amp do you have?
tom @ eas
09-24-2007, 11:38 AM
You shouldn't have a problem - most UDPs don't touch the alternator pulley. If so, you can always get a capacitor for the amps as backup.
09-24-2007, 12:06 PM
Thanks for the replies...it is a JBL 1201.1 MONO Block amp (1200 Watts)
And, I do have a 2.5 Farad cap.....
So what do you think?
tom @ eas
09-24-2007, 01:18 PM
Should be fine - choose a set of UDPs that do not replace the alt pulley.
09-24-2007, 02:00 PM
well thats the thing, the car does have UUC underdrive pulleys on the altenator.....
tom @ eas
09-24-2007, 02:18 PM
The cap you are using should be sufficient.
09-24-2007, 04:49 PM
If your alternator can't keep up with your amplifier then a capacitor isn't going to make an ounce of difference. I'm surprised to see Tom recommending one...
Think of it this way - why didn't you just add a larger battery? All a capacitor is is an extension (and a very small one, btw) of the battery. The reality is that if amperage required (ie. amplifier + all other accessory draw) is > amperage provided (from alternator) then you will end up with a dead battery.
Having said all that, unless you run your amp at high volume very frequently, it should not be a problem. My point was simply that adding a cap is a waste of money and does not address the root issue.
09-24-2007, 07:07 PM
Thanks Doug, I have heard the same thing about the farad cap from friends.....well, i guess i just wont pound bass all the time.....I am hoping with the underdrive pulleys in the car (if in fact they are on the alternator) i wont have an issue..
DOES ANYONE KNOW HOW MUCH IT WILL COST (BALLPARK) TO RETURN TO THE STOCK UNDERDRIVE PULLEY ON ALTERNATOR?
09-26-2007, 04:46 PM
According to RealOEM, a new alternator pulley is about $20 (at least for my car (http://www.realoem.com/bmw/showparts.do?model=DE93&mospid=47592&btnr=12_0984&hg=12&fg=22)!).
09-26-2007, 05:08 PM
yupp....if there is a problem though i think im going to upgrade to a 140A Alt.
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