Electric water pump

[Glenn M]

My two pence worth. I'v got the smaller of the Davies Craig pumps and their electronic controller. Works well for me.My engine is a 331 sbf, 11:1, and just over 400 bhp.

Went down to the Le Mans classic this year and boy was it hot - approaching 100 degrees. Stuck in traffic getting in there were 40's boiling left and right.Yes mine ran a bit hotter, but only 90 instead of the normal 80. At times like that, ie at tickover with maximum ambient heat, that is when you want the pump to be working hard to keep it cool, which the controller does.

My car has done over 8k miles on this combination, including many hard track miles, and I would heartily recommend it. The anti heat soak run on feature is really good too.

Not sure if this is thread drift or not - if it is I apologise.

Glenn

 

[Seymour Snerd]

Can the digital controllers handle the current load requirements of the larger pumps like mine (55 GPM) ??

My recollection is that the 55 GPM Meziere pump draws 7A max.

 

[Seymour Snerd]

At times like that, ie at tickover with maximum ambient heat, that is when you want the pump to be working hard to keep it cool, which the controller does

That's true as far as it goes, but isn't the issue I'm concerned about. Maximum heat generation occurs when the engine is producing maximum power output. That's the scenario in which Meziere expressed reservations about their 55 GPM pump because in that scenario the electric pump moves far less water than the mechanical pump it replaced.

Tickover at maximum ambient is a problem because, although there is relatively little heat generated, there is little air movement (and with a mechanical pump, little water movement). In that scenario the elecric water pump is a long way from being the limiting factor as long as it is turning reasonably fast.

Meziere did not recommend variable voltage, but the person I spoke to did not have a clear explanation for why. Possibly it was just because they don't see that it solves any particular problem.

 

[Bob Putnam]

That's true as far as it goes, but isn't the issue I'm concerned about. Maximum heat generation occurs when the engine is producing maximum power output. That's the scenario in which Meziere expressed reservations about their 55 GPM pump because in that scenario the electric pump moves far less water than the mechanical pump it replaced.

I'm not sure whether that's completely accurate. I suspect that it's the load that generates most of the heat, and the rpm only adds a marginal amount of friction energy.

Meziere did not recommend variable voltage, but the person I spoke to did not have a clear explanation for why. Possibly it was just because they don't see that it solves any particular problem.

Some motors work with reduced voltage, some don't, but real speed control requires a special motor with speed feedback.

 

[Ian Anderson]

Hi I don't run an electric pump but looked into them.

Cooling the engine requires sufficient flow of water through the engine and radiator to allow the heat from the engien to be dissapated by the radiator.
This in turn needs a good flow of air through the radiator.

In stop start the airflow is seriously reduced - even with radiator fans running it will equate to approx 15mph of road speed.

Over this (15mph or therabouts) the airflow through the radiator means the water leaving the radiator is at a much lower temperature, which then in turn would mean the amount of heat it can extract fron the engine is that much higher.

As such from all my reading around the subject the smaller units appear to be sufficient to move enough water to cool the engine -so long as the car is moving and the radiator doing it's job efficiently.

Ian

 

[Seymour Snerd]

....from all my reading around the subject the smaller units appear to be sufficient to move enough water to cool the engine -so long as the car is moving and the radiator doing it's job efficiently...

OK, but when confronted by a comment from a pump manufacturer who says that is not true, how do you reconcile that with your reading?

 

[Ian Anderson]

What I read was that it takes a period of time for the water to absorb the heat from the engine.

Increase the flow rate and there is less time available for the same water to absorb the heat

The outflow from the engine is then cooler than it could be and this in turn means the engine will heat up through too much flow

As I said I do not run an Electric pump but read up a lot around the subject during the build

Ian

 

[Bob Putnam]

What I read was that it takes a period of time for the water to absorb the heat from the engine.

Old wives' tale. Only true if the water has zero flow velocity and/or is perfectly laminate. Water flow through an engine or radiator is turbulent enough so that convection or conduction within the water itself is not much of a factor. This myth probably came about when a water pump cavitated at high speed, thereby losing its ability to push water, or air pockets formed in the engine/radiator because of a similar phenomena.

Of course, there's diminishing returns as far as the ability to remove heat is concerned, but that's a result of lower efficiency because the radiating surface temperatures approach the cooling fluid temperatures.

Crankshaft-driven centrifugal pumps are a poor way to cool an engine, since their output pressure rises by the square of the speed, and there is enough resistance in a typical cooling system for the pressure to be the major factor in the flow. In order for the water pump to be adequate for low speed flow, it must be quite over-driven for high speed. A waste of power and a source of potential cavitation.

 

[Bill Musarra]

Ian,
I just got my engine cranked the other day(will post a video soon) and with my little flowing 19 GPM unit, I didn't experience any overheating. My engine is a 392(351 bored and stroked with internal balancing) and big AFR aluminum heads. Granted I am still on the rack, but I ran the engine for over 20 minutes with most of the time at 2K revs. I am also running without a thermostat. I had the fans and pump on for at least 15 minutes. The temp didn't get over 160 and when I turned the fans off, it only got to 170. I would have run it longer, but I had an old belt on the alternator and it snapped. I realize this is without a load on the engine as well, but I think it shows that you don't need a high flow pump to dissipate the heat, nor do you need to be moving all the time with a small one. I am running a Griffin radiator which measures 3" thick, & 18"h x 26"l with top entry and bottom exit. When I get it on the road in a couple of weeks, I will report how it does.

Bill