VMP's 5% overdrive 8-rib "AC pulley" for the ATI balancer (fits ATI PN: 918047 or 918047N) adds 1lb of boost and allows for future 8-rib conversion.
You need an SFI balancer anyways, our pulley coupled with an ATI balancer gets you more boost! The 5% OD balancer pulley is small enough that it fits with no other modifications.
It's referred to as the AC pulley because it normally drives only the AC compressor, but on VMP, Roush, and Whipple 2.3L supercharged Coyotes it also drives the supercharger. This was done to load the crank shaft as close to the front main bearing as possible and make the SC belt as short as possible.
Works with both 6 and 8 rib systems (6-rib belt uses middle six ribs).
As part of VMP's 8-rib conversion system for the Coyote, we've designed an overdrive pulley that bolts in place of the "AC pulley" on the ATI balancer. These positive displacement supercharger systems use the rear shiv for best possible crank loading.
5% OD = +1psi boost increase
Equivalent to a 3mm (1/8") smaller upper pulley
Full 8-rib conversion recommended when running over 16psi.