please give opinions on underdrive pulleys. What they do good and what have you seen or heard bad about them. thanks

 

Lighter weight first off, so they turn easier. Some are slightly different sizes, which in turn can also make the motor turn more efficiently. I know there is a whole pulley kit you can purchase, but if I remember corretly they will cancel each other out if a certain one is install, cant remember which. At any rate though, they should be lighter which helps the motor turn easier. good for maybe a few more horses.

 

you only want to use one of two lightened objects, either the pulley set up or a lightened flywheel...heres why, when a piston actually comes TDC and crests its peak and the plug fires, it actually tries to stop the crank, if you lighten the crank too much this has a play on how efficiently your motor runs, also with the driline lightened too much you lose torque, from AEM

 

The flame speed doesnt travel instantly to the piston top. And if it did spark where you say it does, and reached peak cylidner pressure there, you would detonate.


Underdrive pullies are mostly for spinning accessories such as a/c, alternator, and power steering slower so they rob less power from the crank. The problem with this is, at idle, the alternator can spin too slow, causing voltage to drop, lights dim, etc etc. You shouldnt need to spin them slower because the alternator has a voltage regulator on it so it only robs as much power as it needs. The a/c has a clutch on it that disengages when not in use. The p/s prolly does rob power all the time, but spinnign the pump slower will make it harder to turn. The pulley itself is lighter than stock, but usually lacks harmonic balancers which hodna builds into the pulley which can be potentially detrimentl to your crankshaft.

To make a long story short, if you want less roating mass, just get a lighter flywheel.

 

makes sense about the crank pulley, but what about an AEM p/s pulley and alternator pulley kit, I think its called the tru power pulley set . how much if any power can that make you for 100.00 bucks?

 

less than 1 hp more than likely. if yo uare that anal about it, just remove your p/s and a/c belt and receive mroe of a hp gain for free

 

aftermarket pulleys