So i am looking at getting a underdrive pulley and one of my buddies says that i will need a new alternator if i get one, any thoughts? He says that because i have a system in my truck that i wont be able to run both the system and the pulley w/o getting a new alternator. If i should get a new alt, do you guys have any recomendations (brand, ect)? it will be a few weeks before i do this so im not in a rush just want a heads up. want 2 put my e-fan and superchips in first, hope next weekend (hate seeing them in the house and not in the truck!) but im stuck in crutches now so the pulley install may get pushed back even further. Gonna search the forum for pulley recomendations but im looking at the motoblue gen x pulley.... thanks for any info you guys got

 

your friend is full of chit. it will find fine with a smaller pulley. The point of a smaller one is to wind the alt faster and get it to give more charge.

 

My reccomendations....Stay away from underdrive pulleys.

For starters, they are NOT the same quailty as the factory Harmonic balancer. Most are piggyback style which are crap. others don';t have the harmonic damping capabilities of OEM.
Second, the gain to be had is minimal. Talkin like 1-2rwhp.
third, You will starve your accessories. Your alt. will not charge as sufficient at idle(driving will be fine). Your A/C compressor will slightly suffer and your Powersteering will slightly suffer.
Basically you slow down all of your accessories to free up a measly couple HP of drag.
You Cannot gain without loosing with U/D pullies.
Harminic balancers are what keeps rotational vibrations away from you crank journals so your bearings will last longer and your engine will run smoother.

Do whatever you please, but just be aware of the whole situation before hand. Most U/D pullies are sold in sets. Larger crank Pulley and smaller Alt. pulley to acomodate for the less rotations of the larger crank pulley...***Weed, what's the deal???

On the Alt. issue, I have the Tow package with the 160A alt. I am running a True 2,000w RMS stereo with a simple Batcap300 and I don't need an upgraded alt. My lights do not flicker or dim at all.

 

im running about the same with 2 amps and too many lights, no problems or dimming with all my lights on and my 3 12'' subs and 2 rockford amps running simultaneously

 

Sorry Dirty, do i have it backwards? Smaller pulleys spin faster. So which one are we talking about here. Bigger or smaller?

 

An under drive pulley is a smaller crank pulley not larger. Larger would make the belt travel farther per rotation, hence speeding up the belt. A smaller Drive pulley(crank) causes the belt to move less distance at the same rpm's(slower belt speed).A larger driven pulley(accessory, alt, pwr steering, a/c) would cause the driven component to spin slower.

Taken from wiki:

An Underdrive pulley refers to an aftermarket crankshaft or accessory pulley (such as an alternator pulley) that is designed to drive a vehicle's accessories at a slower rate than stock. Underdrive in general means the input rate of rotation in a system is greater than the output rate of rotation. However, an underdrive pulley is considered to be an accessory pulley that is larger than the stock pulley or a crankshaft pulley that is smaller than the stock crankshaft pulley, even though the accessory may not necessarily be underdriven with respect to the crankshaft pulley.

 

oh so i got it backwards? My fault guys.

 

Be very careful about what you decide to do on this issue. Like 'dog said, all of these underdrive pulleys are not the same. If you get the wrong one you can have major problems. These things have been known to literally allow engines to blow apart. There was just a thread about bad underdrive pulleys over on DT not that long ago.

 

There should be a LONG list of performance mods done before its worth it to get the underdrive pulley. I agree with dirtydog...dont do it

 

Does anyone know what amount of power one of these pulleys are supposed to free up?