A stupid pully question

[mjsn1]

I want to know what is the different between normal pullies and underdrive pullies

 

[IJ.]

The size

 

[Nick M]

The underdrive pulley which you shouldn't use on a car where the pulley is integrated into the damper, spins the accessories slower. This lowers parasitic drag on the engine.

 

[IJ.]

The underdrive pulley which you shouldn't use on a car where the pulley is integrated into the damper, spins the accessories slower. This lowers parasitic drag on the engine.

Come on Nick, that's hardly a "stupid pully answer"

 

[jetjock]

Got neither the singular or plural correct but based on his location I guess he can be forgiven...

 

[mjsn1]

Thanks for your forgiveness jetjock, sorry about the spelling mistakes but i was in a hurry when i wrote this thread.

 

[CyFi6]

Got neither the singular nor plural correct but based on his location I guess he can be forgiven...

FTFY :yikes:

 

[te72]

You spelling Nazis crack me up... For further reading though:

http://www.atiracing.com/products/dampers/damper_dinan.htm

http://www.atiracing.com/products/dampers/101/index.htm

 

[CyFi6]

You may be wondering what that has to do with HP? Remember from above what is also at the front of your motor - your camshaft drive. If the front of your crankshaft is twisting, then your camshaft drive is being pulled and relaxed and pulled as the snout of the crank twists. If your camshaft position is being changed or varies, then the engine cannot properly induce, combust and remove the fuel. That means a loss in power!

That makes me a little skeptical, how much twist are we actually talking here? They are claiming there is enough twist to alter the cam timing enough to affect horsepower...sounds more like marketing. I haven't done any actual textbook reading on the subject, but from what all the experts around here say, it sounds like a dampened pulley is always better. Of course if you go to Unorthodox Racing's website you will find an article almost as long stating why solid pulleys are safe (they claim modern pulleys are rubber bonded strictly for NVH reduction, not to counteract torsional vibration).

Anyways until doing some actual reading I still wouldn't be confident in saying one or the other is necessarily bad. I will stick with OEM for now, but no telling if that even does any good above stock power levels.

 

[IJ.]

Going way back here for anecdotal evidence on another engine, 283 Chev Small blocks ran a solid hub, a lot of guys used them on 327's to improve response but found they would trash the main bearings in a short amount of time when pushed hard, an I-6 crank while having better inherent balance is a long wet noodle (ask a crank shop what they think of Nissan RB cranks) and will deflect a LOT end to end, the dampers purpose is to catch this whip much like a shocker on a wheel.

I'm guessing there will be a frequency where if unchecked it will cause damage, after market dampers are usually bigger and have a thicker bonded section as the harder you push an engine the more the crank will deflect so the greater the forces that need to be absorbed.

 

[mjsn1]

So i guess that i well stay with the stock pulley

 

[hvyman]

Money is better spent else where. Unless you just want shiney pulleys for the bling factor.

 

[te72]

Strictly speaking, I would only go with stock sized pulleys, and would only change out accessory pulleys for lighter ones (as in the DM kit, sans crank pulley swap).