ASP underdrive crank pulley larger than stock??

I've been told to get a hold of some people at ASP to find out the crank pulley dimensions, larger-underdrive crank pulleys seems counterintuitive, can anyone verify this before I call them up on monday to find out the scoop?

The underdrive crank pulley is larger in diameter. In your case, since you do not have a jackshaft pulley, a larger crank pulley will spin the blower faster (and anything else on that belt).

----- Original Message -----
From: Dark Man X
To: 'Paul'
Sent: Saturday, August 09, 2003 2:06 AM
Subject: RE: The 2.75" pulley from the 10 rib pulley set

Ok sorry for that delay.


I don’t understand though, why would I want an underdrive crank pulley though when we were talking about getting a larger one to allow for more boost even with larger SC pulley (for grip). I already have a stock supercoupe crank pulley.



I think you lost me lol

Click to expand...

Click to expand...

Does anyone have any input before I call there? I just know its going to be a big run-around trying to explain my project to them and why I need a LARGER crank pulley (something like 8-8.5 or even 9" )

A bigger pulley takes more time to complete a revolution (spins slower) so it consumes less of the engines power -- not sure if this is what you are asking

A bigger pulley means a longer circumference. The longer the circumference the more it takes to spin the pulley once.

Vice versa, a smaller pulley would mean smaller circumference and it would take less to spin it.

So, a large pulley slows it down, while a smaller pulley speeds it up. Under and over-drive.

In the instance of discussion here, if the crank pulley was 5" in diameter and was replaced with a crank pulley 10" in diameter while each system used a 3" blower pulley, the speed of the blower would be 2x faster with the 10" crank pulley. Remember, in this system being discussed, there is no jackshaft pulley, the blower is being driven directly off the crank. When ESM overdrives the blower 10% via the jackshaft pulley, it is done so by using a larger jack pulley. Given that the crank and blower pulley remains constant, the speed of the blower is increased by the larger jack pulley. The best visual comparison to this would be a 10 speed bicycle.

Paul

A stock crank pulley, the back part of the pulley that drive the blower.
This circumference is about delete in.

The circumference of my aluminum crank pulley that drives the blower is
about deleted in.

I would like to know what it would be with a 10% OD blower pulley.


Any mathematician out there.

Randy