why remove underdrive pulleys when supercharging?

[lightblade]

like title says, why does everyone say remove them, and what would happen if u left them on?

 

[sgarlic]

To get the accessories spinning the right speed again (to make the right amount of boost for your pulley.)

 

[lightblade]

but why would you want the assesories spinning faster again? i understand you will lose 1-2 psi maybe because of the smaller dampener, but all you would have to do is run a diff size supercharger pulley that makes more boost to make up for the loss right?

 

[lightblade]

so if i wanted to see 10lbs of boost and i had underdrive pulleys and an intercooler, a 14 lb pulley would net me 10lbs of boost right?

 

[jasonh_86]

thank u for asking that.. i've been wondering that myself

 

[Gearbanger 101]

The problem with it is, that as sgarlic stated, the smaller (under-driven) crank pulley is going to slow down all of your accessory pulleys, including your blower pulley. And yes you’re right….it may be as little as 1-2psi, or it could be more in the line of 3-5psi depending on the type of blower you’ve got and how high strung you’ve got it running. If you’re making in the 8-15hp range for every pound of boost, does it really make things better freeing up 6-8hp running under drive pulleys, just to lose 8-50hp because now cut the blower speed dramatically?

Now, the problem with just making up the boost with a smaller blower pulley, is that as it is with most systems running within the 8psi+ range, the 6-rib pulley design provides very little grip on the belt to start with. Going with a smaller blower pulley, to increase blower speed also decreases the surface area in which the blower pulley has contact with the accessory belt. This will lead to some serious belt slippage at even 8psi….and it only gets worse the harder you spin the (even with a true grip pulley) when the blower is under load.

To increase belt contact again, you could convert to the truck 8-rib pulley set up, but this tends to be an expensive venture for most street set-ups. Especially when it costs you nothing to just revert back to the stock 6.85" crank pulley.

Does that clear things up for you guys?

 

[lightblade]

makes sense, but what about someone who doesn't have teh stock pulleys anymore?

 

[sgarlic]

makes sense, but what about someone who doesn't have teh stock pulleys anymore?

Well, you can either deal with the HP loss by having a blower pulley spinning more slowly, or PM RandyStinchcomb and order new ones

 

[DBMSTNG]

do it right. get stock pulleys on the car. you're going to want the water pump to pump as fast as stock when adding in addition to not wanting to lose boost.

 

[White Stang]

Sell your power pulleys and get new stock ones

 

[aparker813]

Sell your power pulleys and get new stock ones

example...my stock plus some cash for your power pulleys
(oops this isnt classifieds is it)

 

[Gearbanger 101]

Go look on Ebay for a used stocker. They usually last forever and people are getting rid of them for peanuts.

 

[Jakes]

do it right. get stock pulleys on the car. you're going to want the water pump to pump as fast as stock when adding in addition to not wanting to lose boost.

Heat is the enemy of an SC'd motor. It causes DETONATION. Very very very bad. Besides that blower is going to more then make up for the little 2-4 hp those pulleys get you. Go back to stock.

 

[lightblade]

looks like im going back to stock then, pm me if you are interested in steeda underdrives, about a year old