[thedarave]

Originally Posted by Christ

The cool part about water pumps is that they don't actually need to be driven at a variable speed, and they really don't need to be driven all the time. Sure, the electric pump is slightly less efficient, because of the conversions that need to take place. Unfortunately, there are also losses in belt-driven pumps, since it's more mass that the engine has to accelerate, and that mass is under increasing load, making it even harder for the engine to accelerate that mass.

With an electric pump, it's a bit different. Once the mass has been accelerated, it's up to speed, and can now be driven under constant load at constant speed, without variation. Constant load, of course, takes less energy than acceleration and deceleration, which means that the electric water pump is actually more efficient, if you view it as simply being less "lossy".

I see. This actually makes sense to me. You might be able to drive that off a separate electric circuit that charges off of a solar panel if you don't drive more than a few hours a day. You could also put in a relay failover to power it off of the alternator if the power source discharges.

Originally Posted by Christ

Someone will disagree with me on this, but the water pump DOESN'T need to run all the time. The cooling system was designed for "worst case scenario", remember? That means the OEM water pump flows more than is actually necessary, which is a waste of energy in most cases. Slowing the speed of the water pump, or leaving it off and running it on a thermostatic control will actually decrease warm-up times, and you can turn it off for short periods of time while driving on the highway, as well.

I don't think I'd necessarily turn it off, but I would love to have one set up on a thermostatic speed control that would slow down to keep coolant flow, but as the engine got warmer, it would speed up to increase cooling capacity, reaching full speed at something like 205*, still well inside the "danger" zone. (I'll run as high as 212*, never over 215*). With the OEM cooling system on Cara, it takes my driving up a mile long hill in 1st gear floored, approaching/maintaining high engine speed and nearing redline several times to get to 215*, and then only after heat soak takes effect.

A thermistor with a cut off relay might do what you're looking for. Do you have an idea how much current draw the electric water pump would take? Or is there a running thread somewhere I just missed?

-S-