Electric water pump effect on warm up times

[Daox]

I've seen it mentioned several times now that electric water pumps reduce warm up time. I think I asked this question in another thread somewhere else and never really got a good answer.

Can anyone explain in detail how an electric water pump can reduce warm up time?

[mechman600]

I will argue that an electric water pump will NOT reduce warm up time. If your thermostat is working correctly, your coolant should circulate only in your engine. Stirring a pot of water on your stove will not make it heat up slower. Without coolant flow (aka electric water pump turned off), you will create hot spots in your engine which is not good. The only advantage will be an increase in efficiency by not having to spin a pump and move a bunch of water. If you can run an electric pump though a resistor to severely slow it down during warm up, this could be beneficial. But stopping the pump altogether? Eep...I would be scared of that.

[Phantom]

I agree with the above statement the only way it could help is by flowing slower when the temp is low but if it only has one speed it will make no difference, I guess if it flows less that stock overall it could do that too.

[IsaacCarlson]

I would be hesitant to use an electric water pump. Electric is not as efficient as direct drive. If the motor burns out, you are stuck. Me tinks de ol fashun wai is bet.

[dcb]

there are some opportunities to save a bit of energy with an electric water pump.

if it is brushless then it can be made very reliable.

you can delete the thermostat with the right control scheme, thermostat is basically a large pumping loss most of the time. The mechanical pump has to work against the thermostat most of the time. An electric pump only has to pump hard enough to keep the temperature correct.

install a more efficient / smart alternator and the electric options get more efficient overall. Direct drive vs belt driven would also help.

options like adding a thermos bottle to store hot coolant for later get much simpler with an electric pump.

[Daox]

I agree there is probably room to improve efficiency with an electric pump.

However, will it help with warm up?

So far I would agree with mechman. You can stir a heating pot faster or slower and it still warms up in the same amount of time.

[Old Mechanic]

With a bypass hose and properly operating thermostat, you will get a thermosiphon effect with warming coolant.

Early model T Fords used a thermosiphon system with no water pump.

I think you would get a better efficiency return if you regulated the temperature of the coolant entering the engine after leaving the radiator.

The temperature difference between coolant exiting at a 180 degree thermostat and that same coolant entering the engine after going through the radiator can be over 120 degrees.

A combination of a bypass and radiator exit thermostat that keep incoming coolant at the temperature difference experienced in the summertime would (in my opinion) significantly improve overall economy.

Combine a WAI and WCI (warm coolant entry) and you could maintain most of your summertime mileage into some fairly colder temperatures.

Remember the old Packards with the adjustable radiator fins.

regards
Mech

[Frank Lee]

Originally Posted by dcb

you can delete the thermostat with the right control scheme, thermostat is basically a large pumping loss most of the time. The mechanical pump has to work against the thermostat most of the time. An electric pump only has to pump hard enough to keep the temperature correct.

install a more efficient / smart alternator and the electric options get more efficient overall. Direct drive vs belt driven would also help.

options like adding a thermos bottle to store hot coolant for later get much simpler with an electric pump.

I dunno... pumps and fans draw the most power when they are moving the most fluid. Yes, it seems counterintuitive. Try running a box fan, then throw something against it that blocks the air- it speeds up! If it speeds up, the motor is seeing less load. Do the same thing with a shop vac. Or a sump pump. They all react the same way. So if there's a restriction in an auto cooling system, it should serve to reduce load.

I've long wanted direct drive for accessories though. And a thermos bottle.

[mechman600]

Originally Posted by dcb

thermostat is basically a large pumping loss most of the time. The mechanical pump has to work against the thermostat most of the time. An electric pump only has to pump hard enough to keep the temperature correct

Nope. When the thermostat is closed, a bypass is open to allow full coolant flow back to the water pump inlet. It takes absolutely no more power to pump through the bypass when the engine is cold than it does to pump through the rad when it is hot. The thermostat is two valves: rad closed/open and bypass open/closed.

[autoteach]

Electric does work. It is efficient, and uses less power than a mechanical pump. Many cars cannot eliminate the mech. pump because it is driven in the serp. belt system or the timing belt system. Building an idle within these systems would be difficult. Also, some pumps use the block as part of the back of the pump, this provides some difficulties as well. as for speed, for $200 you can buy a pwm to control the speed. I would not use a resistor.