Ok might be a stupid question BUT I'm a 5.0 guy so I have an excuse lol. I noticed the other day that my stock crank pulley is mounted to my underdrive. Is that normal? To me it defeats the purpose of the weight reduction aspect of the new pulleys
What you have there are "piggyback" pulleys. These are intended to provide underdrive to the accessories but to preserve the factory damper on the crank snout.
The "gain" from pulleys don't come from lightness (i.e. reduced moment of inertia) as it does from simply reducing the speed at which the accessories are turned. For any rotating machinery, shaft HP = RPM*T/5252 so by reducing RPM you reduce the HP it takes to drive the accessory.
Preserving the dynamics of the factory crank damper inertia ring mass and elastomer link (either by using piggybacks or using a damper specially designed to mimic the factory damper) is seen by many (myself included) as being very important to protecting the oil pump gears from crank snout harmonics.
ah ok. I was just confused cause on my 94 I took the stocker completly off and this just seemed odd.
I know that it's smaller pulleys make the stuff spin slower. I was just saying like smaller being lighter, Cause most of the U/D's are lighter than the stocker stuff.
Thanks for clearing that up for me. I didn't wanna be hurting things having more than one on there. I was thinking crap if this is wrong I wonder how long it's been like that
What you have there are "piggyback" pulleys. These are intended to provide underdrive to the accessories but to preserve the factory damper on the crank snout.
The "gain" from pulleys don't come from lightness (i.e. reduced moment of inertia) as it does from simply reducing the speed at which the accessories are turned. For any rotating machinery, shaft HP = RPM*T/5252 so by reducing RPM you reduce the HP it takes to drive the accessory.
Preserving the dynamics of the factory crank damper inertia ring mass and elastomer link (either by using piggybacks or using a damper specially designed to mimic the factory damper) is seen by many (myself included) as being very important to protecting the oil pump gears from crank snout harmonics.