Underdrive pulley recommendations?

[JFP in PA]

Originally Posted by Topless

I am not sure if any benefits would be found here. Having a mechanical WP that varies with engine speed is a good thing. Higher RPMs = higher heat = higher coolant velocity. Also electricity is not free. With an electric water pump, first you must convert mechanical energy to electrical energy with the alternator (maybe 20% loss) and then convert it back to mechanical energy at the pump (maybe another 20% loss). By this very rough calculation an electric pump would consume 40% more energy than a mechanical one for the same coolant velocity. The mechanical pump looks better to me. What am I missing?

There are significant advantages to an electrically driven water pump:

1. Reduced mechanical drag on the engine (frees up HP); the higher the engine revs, the more power is saved (drag goes up with engine speed).
2. Slows down the circulation of coolant to a constant speed (higher RPM’s actually reduce the ability of the coolant to exchange heat with the air at the radiators because it is moving too fast).
3. Compact; no pulley or belt is required, so it takes up less space.
4. Works if the belt fails.

By-the-by, electrically driven water pumps are commonly used on race engines for the above reasons……………

Te primary reason that more aftermarket manufacturers are not involved with making them for the M96 engine is the small population size of the application.