96BlackSE,

OK - I'm convinced that YOU are convinced that just because the pulley is underdriven - the losses are less.

But that is NOT true.

Think about it. If the battery is fully charged, the alternator will NOT draw a load (or take HP to turn).

Even if the alternator is slowed down (underdriven by using a larger pulley), the load on it is stil determined by the voltage regulator.


Dead battery = large draw & load
Full battery = no draw

Underdriving a coolant pump may save a little power at first, but I'll take all the sustained cool water I can get to my engine.