Quote:
Originally Posted by t vago
As you know, the trouble is that the water pump load will change only as a direct result of engine speed. At that point, it becomes a debate whether to continue to mechanically drive the pump at a 1% loss due to the drivebelt, or electrically drive the pump at anywhere between a 30% to 45% loss from conversion from mechanical energy to electricity, but gain a net 1% to 3% increase in fuel efficiency at the same time.
This Hot Rod magazine article has a rather interesting take on electric water pumps.
Baseline Testing - Do Water Pumps Suck Power? - Hot Rod Magazine
I gathered, from reading the article, that it might be best just to get an underdrive pulley. |
Worth remembering that at high rpm, the eddy current losses of the alternator are very high and the efficiency is usually under 50%, so that cuts the peak power saving down a bit.
At idle the mechanical pump is almost certainly more efficient than the electrical pump. However 50% greater pump speed = 1.5^3 = 3.375x as much power, so any time the engine is more than just barely above idle you're saving power with the electric pump.