I don't know whats wrong, but since I installed an underdrive pulley kit in my car, the battery keeps going down on power. To be specific, whenever I'm not pressing the gas, the lights outside and the interior lights start to dim. I dont have a high-powered sound system so at least i know its not that. But still, I don't know what else it could be and wanted to investigate this problem. THanks

 

Now you know the problem with underdrive pullies. They are NOT worth the charging problems on a daily street driven car. Also forget those so called gains by the Mfg. There will be Pro & Con's on this subject. I for one vote take them off.

 

The underdrive pulley is making your alternator spin too slowly, and cause elctrical problems. They should only be used for a car that does not spend too much time in traffic or idling.

 

Try finding a bigger pulley for your alternator. Once you do that you will get it to spin faster, but you will have to get a bigger belt too and then you will probley lose any power gains you got from the underdrive kit. Maybe not though...who knows...

 

You really need a smaller alternator pulley so that it will spin faster for the same amount of belt travel. Or you can go back to the stock pulleys and have a reliable car. If you want to save power, forget about the pulley stuff and put in an electric water pump.

 

In theory, wouldn't replacing the original alt. pulley and just buying a shorter belt have the overall same effects but without the electrical problems? Just wondering because thats what one of my friends said I could do, but I don't trust him enough to just go with just his advice. Thanks

 

The lenght of the belt has nothing to do with alternator speed, it is the diameter ratio between pulleys. What you plan to do will give you the same problem you are already having. Besides, the alternator does not cause much of a load on the engine. A 100 amp alternator, under full load, will draw 4 HP at most. The big power loss takes place by spinning the water pump too fast at high RPM. Your pulleys will make it spin slower, but it will be spinning to slow for proper cooling in traffic on a hot day.

 

I had UD pulleys on my 2001 v6 and took them off. They are not worth the hassle on a daily driver. Look at other mods for the horsepower gain you are looking for.