Electric Coolant pump conversions

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Most people do not understand that electric water pump kits generally do not supply sufficient peak flow to adequately keep the temperature rise across the the engine similar to stock. OEM coolant pumps are designed to keep the total temperature rise across the engine to about 10 degrees C at full-power across the engine speed range. That means a certain number of GPM or L/min per HP. 10 C temp rise is good number to prevent boiling and thermal stress in the hottest parts of the cylinder head. It is all about managing internal surface temps. A good example is that a 200 HP engine needs about 60 GPM peak flow to achieve this. I do not think you are going to find an electric water pump kit that is able to supply 60 GPM.

So how do folks get away with EWP conversions? In normal driving, and even most track driving, you don’t stay very long at full load. So when the coolant flow rate does not match what is required for an ideal temp rise across the engine, the engine-out temp get higher, peak metal internal temps peak and you get local boiling, and average coolant temp goes up, but as soon as you back-off on the throttle, the temps settle-down and you don’t boil-over. The problem is that you are adding thermal stress to the hottest high heat-flux arts of the cylinder head. I would not expect a high-output cylinder-head with an electric coolant pump to last as long as one with a properly-sized mechanical pump. You might expect head cracks or head gasket failures.

In terms of efficiency, an electric pump is generally pretty efficient as a pump, but you lose all of the efficiency in getting the electricity to the pump. Typical car alternators are only about 60% efficient, and the electric motor is only about 85% efficient. Of course an OEM pump wastes energy at light loads because it is pumping enough coolant for full-load at any rpm. I will not use an electric pump conversion in an engine that I want to last for a long time.

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