Hey guys. I dont mean to sound dumb but whats the disadvantages from a smaller pulley? I mean i know when you have a S/C and if you get a smaller pulley your boost increases. But there has to be a down side to it. What do you lose with a smaller pulley? And is there anyway to offset that?

 

As you mentioned the smaller the pulley the more boot you will get. There are a number of things that could be negative.

-If you put to small of a pulley you could over spin the SC and shatter the impeller.
-To much boost could equal blown engine.
-Belt slippage

The first mentioned problem can be easily solved by simple math and calculating maximum impeller RPM at redline. The second problem is solved via a built motor. The thrid problem can be solved a number of ways. A cog setup is one way but it is a huge investment if you plan on running the cog belt off the crank pulley. Un-anodized pullies tend to help prevent slippage. Some people use a spray that is used for farm equipment that coats the belt and makes it tacky and can generally last 6-12 months. Or there is the option of a special pulley that has cross machined grooves that is supposed to bite into the belt more but I am not too sure about belt life with that.

hope that helps.

 

SMALLER pulley on the SUPERCHARGER boost will Increase...

If you put a SMALLER pulley on your CRANK then your BOOST will DECREASE since the smaller pulley will turn anything it is attached to at a lesser rate...

Example...

Install Smaller Crank PUlley (UNDERDRIVE Crank PUlley) will UNDERDRIVE anything it is attached to... Power Steering pulley will be UNDER driven... Alternator will be UNDER driven... etc etc..

 

Thanks all for your response's. Helped out

 

While were on the topic... disadvanages of underdriving power steering and alternator via crank pulley? From what I've read it' not all that noticable but I was hoping to get addt'l insight.

 

The only pulley mods that I consider to be worthwhile are for boost increases. Crank pulleys etc. I always looked at as a fad with no real purpose of any significence. But we are talking Apples and Oranges.
If u want to increase boost ---re-pulley ur Charger. If u want more response---re-flywheel ur drive train. They work well together. And $$$ well spent as opposed to Bling

 

But for NA I remember reading that there were noticable gains on just going with the crank pulley (about 4 whp if I remember correctly).

 

Unlikely --But, if so, Is the cost of the pulley worth 4 HP ? U want a gain --spend twice, or less, as much on a plenum spacer ---Motor Dyne

 

Got the motordyne setup... just trying to further the N/A bolt-on build. There's a groupbuy going on right now and the price is pretty low. If the HP gain above is correct, the $$ per HP is about the same as the MREV2 + Spacer.

Anyone with proven HP gains?

 

I did some web searches since this site didnt turn up much... one person claimed 8 whp with the crank pulley (no dyno sheet though). Also, found this old article with dyno results and a peak gain of 9 whp for the whole pulley set. From what I've read elsewhere the majority of the gains is from the crank pulley so there does seem to be something there to gain.

Heres the article
http://www.turbomagazine.com/tech/04...set/index.html

 

you only get gains from the crank pulley.. I personally felt a great gain after the pulley install.