What exactly do they do? I heard they didn't do s**t for the Camaro, but they help out a Mustang pretty good. I never had the pulleys explained to me, so what's their purpose and what kinda gains have people gotten out of them? I don't plan on buying any, but I've always wondered.

 

Underdrive pullies slow down engine accessorys ie. A/C, alternator, and anything belt driven. WS6.com did a dyno test with them and got something like .5 HP, and 5 ft/lbs torque (peak), with higher average gains. They don't do much for our cars, but every bit helps .

 

To slow down the belt driven accessories...does that hurt the car at all?

 

You are slowing down the alternator - and in many cars, if you slow it down enough (U/D crank pulley, plus U/D alternator pulley) you can get into charging problems at idle. The power steering and A/C don't seem to have a problem with turning slower. That'sall that runs off the serpentine belt.

In many cars with belt driven water pumps and belt drive AIR pumps, you will see some more significant savings, but with the electric AIR pump and gear driven water pump on the LT1, there's not much to be gained.

 

you slow the speed at which the accesory turns

 

Wouldn't another "plus" be that the engine revs quicker since the crank pulley turns faster and should weigh less than the stock one? I guess only if you get an integrated version and not a piggyback pulley.

 

I have one and I dont like it. Liek someone said, the alternator doesnt like it. It came on the car, so I dont konw if I got any gains...but when im sitting in traffic, battery voltage drops into the red area...like 10 or less volts. I might take it off.

 

I have March Pulleys in my car. Didn't notice a difference but I got them free so I can't grumble. I've had them for 4 years with no battery problems. Charging might be less but never had any adverse efffect. As for what they do. To put it siimple is they just put less drag on the motor by turning the other stuff less.

 

I also have a piggy back UD pulley. I don't think I wil be reusing it only because of the extra weight on the crank. I doubt an underdrive would be worth enough HP to put that weight right where we don't want it....on the rotating assembly.

Brad

 

If I were to get an o/d alternator pulley to keep charging up, would that defeat the purpose of my u/d crank pulley? Also would I have to get another new belt for the o/d alternator pulley? Sorry might be a stupid ? but im kinda new to this, thanks.

 

"Alpine Receiver, 2 12" Eclipse Aluminums, 1200 watts."
That's why it's giving you trouble....


Didn't notice a thing with the pulles they're lame.