Electric water pumps re-visited

**Hen** · 14-11-2009, 12:30 AM

Mr Cressida, I think Timbo has answered your questions clearly regarding how modern alternators are controlled. And he has direct hands-on knowledge of this stuff (at least last time I knew, he worked in the field). Please read it again and see if it makes any more sense.

Hen

**timbosaurus** · 14-11-2009, 08:02 AM

Thanks Hen. I just can't be bothered explaning the difference betweena selectively controlled alternator and regenerative braking

**Billzilla** · 14-11-2009, 09:26 AM

I know it's possible to turn off the alternator with the belt on - The Gemini race series boys sometimes hide a switch under the dashboard of the car to do that when racing, to get a tiny bit more power.
(or so I've heard .....

)

**Mr89Cressida** · 14-11-2009, 09:40 AM

Hen thats fine not disputing anything, just curious, but also he is in the field, and so am i...thats why im asking....

**Sam_Q** · 14-11-2009, 12:30 PM

I was thinking a normal horn relay to cut the feild wire of the alternator would stop it charging? or would it sustain itself once going?

CrUZida: yeah pretty much trying to screw every last bit out of what I have without spending hard cash as it's just not something I can do anymore.

**CrUZida** · 14-11-2009, 12:52 PM

Originally Posted by Sam_Q

I was thinking a normal horn relay to cut the feild wire of the alternator would stop it charging? or would it sustain itself once going?

I would expect the same, although it does bring about the problem that your car is probably not tuned to run on 12.5 volts, which *may* bring spark and fuel delivery issues.

Originally Posted by Sam_Q

CrUZida: yeah pretty much trying to screw every last bit out of what I have without spending hard cash as it's just not something I can do anymore.

I reckon an oversized pulley would do a better job.
With an EWP you are converting mechanical energy to electrical, then back to mechanical again, each time with a % loss in efficiency.
Where as with a standard water pump, its mechanical to mechanical, at probably a very high efficiency. And with an oversized pulley, that efficiency should be a bit higher still.

**Sam_Q** · 14-11-2009, 02:21 PM

well I think I will do a bit of an experiment. I will floor it a few times on an empty road, unplug the alternator and then do the same again to see the result.

Then try the same again by taking the accessory right off the engine and taking it for a short drive. I am sure my engine will be just fine for 2 pull power runs in 2 gears only.

I tried an oversized pulley but the max you can really go is a 15% under-drive and I suspect it can go a whole lot slower. The result of that? well lets just say I will have it for sale soon I think.

It's like the whole thermofan thing, it only takes what it needs and no more so it's more the energy regulation through the price of some innefficiency

**timbosaurus** · 14-11-2009, 02:36 PM

Yup, you disable the field, and the alternator stops charging. You'll get a charge light on our older cars obviously.

Cruz is right when saying that running a car at 12V can impact the req'd duty cycles/coil charge times etc, but fortunately most ECU's have a battery voltage multiplier tables related to this, which compensate for this sort of thing.

No idea what car you're talking about Sam, but I still think we are moving far away from the original water pump question

Also, as Cruz said, I would expect any significant power difference through converting from mechanical to elec water pump. It could potentially be more reliable (can be lucky, can be unlucky with D/C EWP) especially at higher revs and if you are having issues getting the right thermostat/pulley diameter/radiator size/etc for you car, a well setup elec pump and controller can give you a better result. I'd only do this if your existing system is failing you though.

The motor I'm building now had the water pump blanked off by a previous owner, presumably to use an EWP to ensure good flow over the full RPM range (1000 - 10000rpm) so i'll probably use one anyway.

**wa5** · 14-11-2009, 02:50 PM

I think B & M make an electric pump to suit small block Chev (amongst others) ...
just found one for a Plastic motor (308).

http://www.a1hiperformance.com.au/do...hp?prod_id=461

looks like it would be adaptable to other things, with a bit of tinkering.... and draws 5.8 amps according to the add.

**DX20VT** · 15-11-2009, 07:12 PM

Put my 2c worth in here,

sure a car may need next to no water flow to the radiator at times,
but most modern cars including the 20V 4AGE need water flow around internally in the block to prevent hot spots, which is why the have a double acting thermostat.

so you still need a good flow of water at all times.

And Alternator charge interuption has been done for years.
older model Honda's had a 4 terminal voltage regulator with a C terminal which when earthed cuts the chagre rate down from 14.4V to 12.4v at Full throttle.

I fitted one of the regulators to my corolla race car as the actal alternator is the same type as 4AGE ones,
and tried it on the dyno while we were tuning, but the low voltage started to cause issue's with spark, and there was no increase in power so I abanonded the idea.