Electric Water Pump

Pressure

Neil: The Stewart website addresses a seldom- considered problem with electric fuel pumps- coolant pressure in the cylinder heads. One of the functions of a water pump is to circulate coolant through the engine to the radiator and return it to the engine. The other function is to create additional pressure in the coolant passages in the cylinder heads, over & above the pressure generated by the coolant temperature. The additional pressure minimizes nucleate boiling around the hot spots in the heads and maintains good heat transfer from the heads to the coolant. A high flow/high pressure pump requires quite a few horsepower to generate that flow & pressure. Since 1 horsepower requires 746 watts to a 100% efficient electric pump, and @ 13.7 volts, this draws 54.5 amps... per horsepower! Electric water pumps simply do not have enough power to cool a high horsepower engine efficiently.

Tecomotive: Pump pressure is not the same as the system pressure. The pumps can of course be used in normal automotive cooling systems with system pressures in the range of 0.8 to 1.2 bar for instance. The pump pressure or differential pressure expresses the ´resistance´ of which the pump has to work against. Tip: A mechanical thermostat is responsible for about half of that resistance. (in most cars)