Inspired by the cooling fan thread, I was wondering about the pros and cons of electric water pumps. Intended application would be a street driven domestic V8, more specifically, either a 4.6 or Windsor in either a mustang or cobra replica. How does the hp draw of a conventional water pump compare to the increased electric load on the alternator? Are there any longevity issues for street use vs being intended to free up a few hp for 1/4 mile passes?
You May not Catch an electrical Problem right away on the Street. On a drag run you may get away with a malfunktion,but they really are Very reliable,and on a dragster the battery charge will run it for that duration so no alt.needed.also the flow is always the same with the electric pump but the manual goes up and down with RPM.
I've been running a Davies Craig electric unit in my RX7 hillclimber for several years without issue.
Really good for cooling down after a run without having to have the engine running.
Pros: Much faster warmup, more consistent cooling, no cavitation, slight energy savings.
Cons: Engine cooling now depends on electronics working, and your wallet will be severely lightened.
Some production cars are coming with them now, so you might be able to get a good deal on one from the junkyard.
GameboyRMH wrote: Pros: Much faster warmup
How? You still have to heat the same amount of coolant and metal to reach thermostat temp.
As mentioned, for a drag run (or any shorter timeframe) you can run the pump off the battery only so it is taking no load from the engine or alternator. In fact, I bet you can rig up a quick dash switch to just shut off the alternator and let it freewheel.
I have also noticed that many sportbikes run a modular water pump with essentially a shaft drive, so it would be easy to use any cheap electric motor combined with one or two pumps for a DIY junkyard system. Here's an example: https://www.ebay.com/p/?iid=360529223753&lpid=82&&&ul_noapp=true&chn=ps
rslifkin wrote:GameboyRMH wrote: Pros: Much faster warmupHow? You still have to heat the same amount of coolant and metal to reach thermostat temp.
You don't have to run the pump with a cold engine. So, overall you are right, same amount of water and metal to heat, but you have better control of what water and metal comes to what temp first.
The other benny is you no longer need a thermostat.
Robbie wrote: You don't have to run the pump with a cold engine. The other benny is you no longer need a thermostat.
Eh... You could handle things that way, but IMO, it's a bad idea. No coolant flow until things are warm enough means the heads get much hotter than the block, which is harder on the head gaskets, etc. IMO, it's better to circulate the coolant all the time and just have a bypass for when the t-stat is closed that way the temps stay even throughout the engine.
rslifkin wrote:Robbie wrote: You don't have to run the pump with a cold engine. The other benny is you no longer need a thermostat.Eh... You could handle things that way, but IMO, it's a bad idea. No coolant flow until things are warm enough means the heads get much hotter than the block, which is harder on the head gaskets, etc. IMO, it's better to circulate the coolant all the time and just have a bypass for when the t-stat is closed that way the temps stay even throughout the engine.
So - you have a mechanical water pump and the engine is cold so the thermostat is closed. What coolant is circulating, and where is it going? Let's assume the heater control valve is closed too. Does the water pump actually move water around in that case? or is it just pushing water against a closed door?
Robbie wrote: So - you have a mechanical water pump and the engine is cold so the thermostat is closed. What coolant is circulating, and where is it going? Let's assume the heater control valve is closed too. Does the water pump actually move water around in that case? or is it just pushing water against a closed door?
A lot of engines have a bypass circuit to allow circulation in that situation, especially if they have a heater control valve. And a lot of modern cars don't use a heater control valve, so the heater circuit provides bypass flow as well.
OP, I have a Meziere electric water pump in the 4.6 DOHC in my 57 T-Bird. I've been using it maybe 7 years now with no problems, and I like that it can circulate water well at low engine RPM--or even after the engine is turned off.
Meziere advertised an 11 hp gain from this pump, but like any manufacturer claim, you should probably take that with a grain of salt.
Cons: mine was an older style. It went through bearings about twice a year, or every 5k miles ish
You hear people talk about unreliability which is scary. I used mine for 3 years no issues.
So which was it? 
A variable speed electric pump is childs' play !!
Low speed during warm up to provide a low flow to avoid hot spots, then the speed required to
maintain the optimum running temperature for conditions.
Can run even after motor shutdown to prevent heat soaking.
Isn't Mercedes who's using electric pumps now? Are there any other manufacturers?
Audi turbos used supplemental electric water pumps back in the day. Some of them leaked.
GIRTHQUAKE said:Isn't Mercedes who's using electric pumps now? Are there any other manufacturers?
Ford, Toyota, BMW...
Electric water pumps are nice because coolant flow is not tied to engine speed. Just the thing for if you want to build max boost at 1500 rpm. Or, if you want an engine that revs to 9500, and want a water pump that can flow at that engine speed without cavitating AND still flow anything decent at idle.
I replaced an electric coolant pump for the hybrid electronics on my old 07 Prius at ~250k. 
My Impala SS club did a group buy of Meziere pumps for their LT1s. Half of them didn't show up to the next meeting, and none of them bought one again.
Two guys rolled in puking coolant. I'm sure there are some that are great and reliable, but in general they are used for eeking out that last couple HP for 1/4 mile at a time. Engine driven pumps are amazingly reliable, and they tend to give you ample warning if they are failing. Electrics just die and one mile later you might need head gaskets.
Like most performance add ons, they come with drawbacks. Unpredictability is one of them. They might last a long time (and I'm glad you guys are having good luck with them) but for me, I would only use one if it was race-only and I desperately was hunting down those last few ponies.
Reliability of parts used by OEM is orders of magnitude better than 'just stuff'.
Especially if it has anything to do with meeting Federal 50K emissions certification (like water pumps do,
since maintaining coolant temperature is critical).
In reply to clshore :
Which is why I want to adapt a Ford Fusion Hybrid water pump, using Megasquirt's PWM controls, rather than aftermarket stuff.
Even an electric motor to drive the old mechanical pump is a better idea than some of the aftermarket pumps.
PWM motor controls are commodity items nowdays, and you can use the motor fault detection feature to put the ECU
into thermosiphon 'limp home' mode. A water pump is not so important when you are making only 5-10 HP
In reply to Brian :
Yawn!! Three horsepower saved?
What for? A Tesla doesn't need a water pump ( not for the IC engine anyway!)
Wanna go faster? Buy a newer car.
GIRTHQUAKE said:Isn't Mercedes who's using electric pumps now? Are there any other manufacturers?
3g+ Priuses have no belt drive at all.
I would love to hear/see more on this. One of the biggest issues with my H-Prof Fiat 880 was cooling. I looked into the Davis pump in th 2000s but it was just too expensive to justify. If there are production cars now with electric pumps I would look again. The pic is of an 850 motor - the pump is the device just ahead of the starter.
If it also gained me a few hp I would be quite happy.
frenchyd said:In reply to Brian :
Yawn!! Three horsepower saved?
What for? A Tesla doesn't need a water pump ( not for the IC engine anyway!)Wanna go faster? Buy a newer car.
It's not for horsepower, it's so you are not tying water pump speed to engine speed. A mechanical water pump that flows well at idle will stall before redline, leading to overheating when kept at high RPM. Or if you slow the pump down so it flows at high RPM, it will make insufficient water pressure in the engine at idle.
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