It actually works backwards with a smaller crank pulley. The Moroso is smaller than the factory pulleys, thus slowing the alternator speed. I think my factory crank pulley was almost 7 inches. (makes a good wheel chalk now) I kept tossing the alternator belt at 7000 RPM. The moroso pulley helped my case a bunch. My alternator is a 140 amp aftermarket. haven't had idle charging issues since swapping to the moroso.
