Electric coolant pumps
coyoteboy - 10/2/13 at 12:13 AM
I've done a bit of googling but wondered if anyone had experience of them as a replacement for the main engine pump. Need to do a timing belt
and pump on the v8 so thought it is probably the only time I will consider it!
spiderman - 10/2/13 at 12:38 AM
I'm picking up a GT6 tomorrow with one fitted. I am told they are very good, reduce load on the engine and the controller supplies the correct
amount of flow that the engine requires even after switching off the engine. I should know more tomorrow if you want to pm me for more details.
snakebelly - 10/2/13 at 09:48 AM
Presume your talking about the Davies Craig pumps? Been using one for years, good bit of kit, on our zetec I just had the impeller removed from the
pump so it did nothing and plumped the pump in line, never used the controller just run it constantly as the original one would have.
daniel mason - 10/2/13 at 10:04 AM
from reading on line,it seems they should be run constantly to prevent hotspots. seems like a good idea to me as it wil circulate the coolant at the
same rate when sat in traffic as it would when general driving
britishtrident - 10/2/13 at 10:07 AM
If they were so wonderful do you not think big car manufacturers would fit them across the board.
controlled by a thermostat the coolant temperature at the cylinder head outlet on modern petrol engines stays pretty constant ..
It is false to think they reduce the load on the engine because when the engine is working hard and requiring coolant flow the alternator has
supply the power to power the pump, if you take into account the efficiency of the pump electric motor and the alternator this is more power than
required to turn a mechanical pump.
Where they have an application is where a fairly low revving tintop engine is converted to a high rpm racing unit, in the old days we used to gear
down the rotational speeds of water pumps on racing imp engines because a water pump designed for running at 500 to 6000 rpm would become very
inefficient due to cavitation when spinning at 9,000 odd rpm.
[Edited on 10/2/13 by britishtrident]
froggy - 10/2/13 at 10:37 AM
I run one with a controller as the stock pump couldn't push the water to the front of the car at idle properly , the pump is supposed to last
several thousand hrs and I have seen the dc drop once the car is moving so the controller does do its job . Mine is the small version and once set up
the controller will carry on running the pump after shutdown which is useful on a turbo set up . Can't find the box but I'm pretty sure the
pump is supposed to last 8000hrs which should be good for a few years .
Think the small one is more suited to running alongside the factory pump and the larger one on its own
britishtrident - 10/2/13 at 10:38 AM
quote:
Originally posted by daniel mason
from reading on line,it seems they should be run constantly to prevent hotspots. seems like a good idea to me as it wil circulate the coolant at the
same rate when sat in traffic as it would when general driving
On any car engine built in the last 60 years a thermostat by-pass circuit prevents hot spots, it circulates coolant when the thermostat is closed
to keep the temperature reasonably constant from the bottom of the cylinders to the top of the combustion chambers. The wax capsule thermostat on
modern engines is not an off-on switch it gradually opens to control flow to/from the rad to blend cooled coolant from the radiator with hot by-pass
flow.
It is very important to avoid over cooling.
coyoteboy - 10/2/13 at 11:02 AM
quote:
If they were so wonderful do you not think big car manufacturers would fit them across the board. controlled by a thermostat the coolant temperature
at the cylinder head outlet on modern petrol engines stays pretty constant .. It is false to think they reduce the load on the engine because when
the engine is working hard and requiring coolant flow the alternator has supply the power to power the pump, if you take into account the efficiency
of the pump electric motor and the alternator this is more power than required to turn a mechanical pump. Where they have an application is where a
fairly low revving tintop engine is converted to a high rpm racing unit, in the old days we used to gear down the rotational speeds of water pumps on
racing imp engines because a water pump designed for running at 500 to 6000 rpm would become very inefficient due to cavitation when spinning at 9,000
odd rpm.
I never said they were wonderful, to be honest, but I do clearly see some benefits to be had depending on a few things. It is indeed important to
prevent over-cooling and in a normal system the stat does that just fine. But there's the option here to maintain high flow after high output use
(sitting in traffic after a blast) where a normal pump would struggle to push enough (seen this with my tin-top, temps reaching mental levels and
boiling in my turbo housing until revs raised). High flow isn't necessarily needed at high revs, so that's a waste of energy there too -
ultimately the electronics provide a nicer solution. FWIW some modern cars have electronic thermostats and some have aux water pumps for after-run
continued flow but I'd suspect they won't go to electronic pumps just yet because 3000 hours isn't a lot and failure of it is a fairly
major breakdown for a commuter/businessman in london - horses for courses.
I don't think it's unreasonable to make the assumption that the impellor on a mech pump is a compromise. I don't believe that the power
use of an appropriately sized electric pump system would be particularly large. Many quote values of 5-10kW use from a larger engine mechanical pump
at full revs. While I suspect this is excessively high for sales purposes, I don't suppose 1kW is far off the march. Most elec pumps run at about
8A, which is about 100W, to run the same pumping capability. The alternator would have to be 10% efficient to make that even a close call. Most
alternators are 80-90% efficient.
But I do take the point about increasing complication.
My questions really were more about did anyone have any experience with particular products/suppliers and any issues with running them, rather than is
it better or worse than a mech pump - I'm well placed to make those assessments myself, but I appreciate the thought process 
After a quick search there's PLENTY of academic and industrial research going on and pretty much all of it points out that fuel economy can be
notably improved, radiator size can be significantly reduced and coolant temperature can be far more accurately controlled using electronic pump
control (and combinations of electronic pump/valve control). These research projects include authors who are from OEM suppliers and manufacturers.
Don't forget many modern hybrids are now using electric coolant pumps too - I have a feeling the mech pump is a legacy hang-over that won't
be around long.
FYI I was just reading one interesting thesis of someone who had set up both an OEM pump, fan, rad, stat etc system off a large engine and run it
through a set of tests on a dyno measuing power input to all of the parts, then replaced the stat, pump and assumed airspeed with a fully controllable
fan, pump and stat system. The conclusions were that their system was able to meet the cooling needs of the engine in that testing with 60W, where the
OEM system took 538W (in certain operating regimes of course, not all the time). They also noted that thermal mass of the engine was vast in
comparison with the thermal effect of the coolant so reducing coolant flow at startup had little effect on warmup times, but that coolant flow on
turn-off greatly reduced the hot-spot generation inside the engine due to heat soak, as you'd expect.
[Edited on 10/2/13 by coyoteboy]
froggy - 10/2/13 at 12:06 PM
The longer pipe runs might be your issue as that's what I found with mine although I do run a very large radiator up front
coyoteboy - 10/2/13 at 06:10 PM
What pump are you running? I'd expect a very large radiator to have lower restriction (assuming it wasn't just really long!)