Explain Underdrives?

[dkhl]

I'm thinking about installing new undrive pulleys, but after searching up the forums I'm a bit confused...

How does changing my underdrive pulleys affect my alternator? What exactly can I get rid of in the whole pulley setup without sacrificing too much? Basically, I'd like to run full accessories, like air conditioning, power steering, and what not.

 

[TrickStang37]

pullies still allow you to run your accessories, just that the pullies make all the accessories spin less because the crank shaft pulley is smaller and all the accessory pullies are bigger. this makes it so more belt is needed to spin the accessory but less belt is spinning since there is less belt actually moving because the crankshaft pulley is smaller. **** it, i dont know how to word it, im sure someone else could do a much better job at it. And underdrives killed 2 of my stock alternators and i wasnt runnin anything electronics wise that wasnt stock, other a cd deck, but with no subs.

 

[TrickStang37]

and basically if you want to run full accessories, there is nothing you can get rid of, except for the smog pump which will net you about 0 hp, +-.01 hp. you will save a little weight though, but not much.

 

[90mustangGT]

The engine accesories take power out of you engine to operate. Underdrive pullies gear the accesories down so they move slower so more power can be directed to the wheels. The downside to this is when the accesories are moving slower, they are not working as well. The alternator takes the biggest hit since it is so weak anyways. Underdrives were the first mod I ever did to my car, definatly a good mod. If your running other accesories and an electric fan you might want to upgrade the alternator or hold off on them.

What underdrives you get has a big effect on how "streetable" they are. I have the standard ASP underdrive kit, but I also run the 3" crank pulley and maby it would be a little hardcore for a D/D. Just regular u/d's won't be a problems, most people on here are running them w/o problems.

 

[dkhl]

I'm going to be upgrading the ignition system, which would include the battery, alternator, and what not.

I would like to run full accessories, as well as an audio system which will require quite a bit of power...

Basically, I shoudl have rephrased it this way. What can I do with aftermarket pulleys that will increase my HP/TQ while maintaining my current amount of performance for my accessories?

 

[ECU5.0]

get the pullies and get a 130 amp alternator from PA performance and you will be set