never replace water pump again?

[atomicEGT]

For us, I don't think it makes a whole lot of sense... but there are cases where it would be useful/necessary.

[coleman]

Energy is not free. Your alternator will create additional drag that is proportional to the old water pump drag since it now needs to power the electric pump.

Barring the fact that all that could be easily controlled with a simple logic circuit, I think there might be a significant thing to say for the states in which a mechanical versus electrical pump operate even in dumb mode (permanently engaged with engine on). Most importantly is that the relationship is not at all proportional.

Electrical pumps operate at one speed and consume nearly constant rate of power. The impeller and the electrical pump are matched for maximum efficiency to run at that one speed to provide a steady flow without transient loads or fluid loadings during acceleration. They are just as good for driving around as for racing because they are flow limited by the voltage given to the motor, with the thermal control being the thermostat to control the direction of that flow. Controlled flow rate, controlled efficiency.

Mechanical pumps operate at one ratio with respect to the speed of the engine and vary greatly in power consumed. That belt drive ratio must be matched to be optimal at the condition when the engine is supposed to be operating the most or expecting the peak thermal load, usually that is near the peak torque range. This means they are not good at idle, and not too hot at high RPM at all. The flow rate is limited by engine RPM, and the thermal control is also related to the flow rate as well as the thermostat. Flow rate and efficiency vary largely.

I will be installing an electrical pump for my engine swapped 1981 Trans Am. I expect better fuel economy, better thermal control, and ultimate reliability. Related to how reliable electrical systems are; many new smaller cars have gear driven rack-and-pinion electrical power steering. Imagine driving down the road and the motor shorts. Car turns left NOW! They are designed to be redundant, predictable, and with safetys involved. It's a water pump that can be isolated from the engine's harsh temperment, and they are far better at being leakproof as they are typically fancy machined units (better be worth the swap to make people do it at all!)

correct, the increase in HP is only present in cars running soley on battery(ie drag cars) when using an electric water pump.

I think lots of folks associate horsepower solely to peak horsepower and ignore the full operating band of the engine (there's horsepower at idle, too). At any rate this is not a necessarily true statement like I started saying before. Electrical water pumps have a wide array of control options, you could easily control the power draw of an electrical motor at any time with the engine running. You can even run the pump with the engine off to cool off the engine in the pits, or even have the pump off for minimum warmup time in winter. These are not so easily done with a belt drive, so you can see why some people would want them in street cars as well as race cars.

Though I could be grossly overthinking it and it's really just the "shiny accessory" factor that drives us

[projectmx]

wow that is one of the most well thought out and informative posts i've read in ages... and yes i'm still keenly interested in doing this, especially knowing that i can run this after the car is off to cool the engine more while i'm waiting in line at the autox track

[coleman]

...to cool the engine more while i'm waiting in line at the autox track

Autocross has to be the situation when my intuition (but not my experience, I've not tried) leads me to believe you will see the maximum benefit from an electrical water pump. Because there is a fixed drive ratio between the crank speed and the pump speed, and your crank speed fluctuates so very much when autocrosing, that's an incredible amount of impeller speed and flow rate fluctuations for nothing when using a belt drive system. With an electrical pump your alternator will still fluctuate speed because it is still belt-driven, but the voltage limiter will keep the loading relatively constant despite the speed changes. Again, experience with other systems and just general intuition has me convinced but I've never actually tried it.

Remember that a good thermostat or an excellent logic control circuit is critical if you trust an electrical pump. A water pump does not control cooling, it controls motion of coolant which is related to the rate of cooling but is not necessarily the defining factor. Your thermostat and radiator control cooling by directing that flow and expelling heat at a rate consistent with the flow rate and thermal load - a matched system. Most problems people have with electrical pumps are due to a mismatch in cooling system components. More power usually means more heat, many people match to stock components intended for stock heat ranges, and this is the reason most people have problems.

I'm gonna stop being a huge geek now

[projectmx]

so coleman when can you come help with my car? cause you really sound like someone that could help me accomplish alot on that thing in a weekend