Hey guys,
I am working on putting an electric water pump in my little Fiero project. It isn't an LS1, however the concepts relate to the LS1 or any other automotive engine. Here's my dilemma. I bought a Davies Craig Electronic Water Pump with the controller off eBay. I've heard plenty of bad things about them since that, but let's not go into that, as I can easily swap a CSR pump in at any time.

I am more interested in finding the best way to control the pump. The idea and intent of Davies Craig (D-C) is to use the controller to control the pump, and vary voltage to the pump to act as the thermostat at a preset temperature. The function is this, before 176*F, the pump does nothing, and does not flow any water. Between 176-203*F, the pump pulses/ramps flow to attempt to keep the temperature at this level. Above 203*F, the pump operates continuously at full voltage. This sounds all fine and dandy, and a great way to operate the pump. However there are some concerns:

1) Heater. From the factory, most if not all cars constantly circulate water to the from the heater core. Coolant bypasses the radiator, and flows to the pump, through the engine, to the core, then back to the pump, whilst being mixed with the rest of the coolant system in the pump and engine. The problem here is that NO water will flow to the core at all until it reaches 176*F. Thus your heater won't work at all until your car is completely warmed up, which is not ideal for a street/strip car like mine, especially in Colorado.

2) Coolant to the turbocharger. My turbocharger, like most on the market today, utilizes engine coolant to cool itself. My plan is to place the turbocharger inline before the heater core. Thus water flows into the turbocharger, then to the heater core, then returns to the pump. Problem here is that the turbocharger heats up quick, often the first time you spool. I had a turbo DSM for a while, and even in 20* weather, the heater would be blowing warm in one block. I pulled out of my driveway, got it to full boost for a couple of seconds through first gear, then again in second to the speed limit, and my heater was warm. Well with the EWP, the coolant at the turbo would get really hot, really quickly, but not be circulated because the pump would not be flowing. So it could very easily boil before the heater even gets warm. This creates big problems.

3) Coolant flow though the engine, even when cold. From the factory, even when your engine is cold and your T-stat closed, it still flows water though the engine. Fist via the heater core as explained above, but second through the bypass line, which often includes the throttle body. This serves 3 functions as far as I know. First, the throttle body de-icing that we all know is not a big deal and of no consideration here. Second, the bypass. This is to protect the heater core when the engine is cold, T-stat closed, but you run the car hard and at high RPM. RPM goes up, coolant flow goes up. So much that it will build up to pressure levels that the heater core wasn't intended for, and it will destroy the heater core. So the factory has the bypass line, so that pressure doesn't build up. It's last affect is to prevent hot spots in the engine, which could boil and create air in the system. The water directly around each cylinder heats up much quicker than say, the water at the top of the head, or in the galley between the heads right before the T-stat. So the factory flows a small amount of water, just enough to keep coolant temperature constant throughout the engine. The EWP wouldn't do this, and with a turbo and such high specific outputs (132hp/l in my case), a lot of heat is created very quickly in my case, and boiling the coolant before the water temp at the probe is high enough for water flow is a possibility, and will create more big problems.

So this is why I can't see my EWP working with the controller, as D-C had intended. So does anyone here use a EWP? How do you control it? I do not want full flow all of the time, it draws too hard on my already stained alternator, and it cuts pump life. I also do not want a switch to tun on the pump when I need it, that's what electronics are for, to do my work for me.

 

Before anyone says go back to the stock mechanical pump, that is out of the equation because I ran fuel lines and the wiring harness where the serpentine belt would be.

Here are two solutions I've come up with, please give me feedback and/or any other ideas:

1) Use the pump and controller as they were designed. However, where the power feed wire goes from the controller to the pump, splice in a new wire. This wire goes from my 12v supply to the current power wire, but has a resistor in it that will cut current enough so that the pump's flow is minimal, but adequate, to alleviate the above situations. I would still have to run a traditional thermostat, that way the restricted flow would only flow through the bypass and heater core lines, but that is ok, so long as the T-stat opens before the pump goes to full operation.

2) Disregard the controller altogether. Run 2 separate power lines, one for full flow, the other with a resistor for the cold flow, as above. Have an in-cab switch on the full flow wire. Then I'd leave the full flow wire closed, so the pump would only get a restricted amount of current. Then, once the car reached operating temperature, I would flip the switch and it would provide full current to the pump. Then the ordinary thermostat would regulate temperature. This is simple, but it involves my interaction every time I run the car, and I don't want that. Is there any way to have a thermo-switch that opens the circuit when a probe reaches a certain temperature?

Ideas? Thoughts? Comments? Suggestions? How are you all doing it?

 

I talked with a good friend of mine who knows his stuff. He's the one who pointed out the potential problems in the first place. He liked the first idea, and said it was perfect. Now I need to find out what size resistor to use. I am completely clueless. Here are the draw specs on the pump:

Technical Specifications:
Operating Voltage 4V DC to 14.5V DC
Maximum Current 7.5A
Flowrate (Max.) 80 L/min, (1300 US gal/hr) at 13.5V DC
Operating Temperature –20°C to 130°C (–5°F to 270°F)
Pump Design Clockwise centrifugal with volute chamber
Motor Life 2000 hrs continuous at 80°C (180°F) and 12V DC
Pump weight 900 grams (2 lb)
Pump material Nylon 66, 30% glass filled
Burst Pressure 350 kPa (50 psi) Minimum
Max. Radiator Cap Pressure 200 kPa (29 psi)

 

I can't believe the pump does not rotate at all when the controller is at minimum... Are you certain on this? For the reasons you've mentioned I believe the pump has a minimum flow it will go down to, but not stop.

http://www.racerpartswholesale.com/elecpump.htm

Reading the info about the pump on that page it says the pumps operate from 4V on up and the controller output varies from 5V and up. I think you should install as per instructions and see what happens, it probably works as you require!

 

I was surprised too, but everything I've read leads me to believe this. I may just install it how it's intended to be installed and see for myself. It does say operating voltage is between 4 and 14.5, so maybe it never stops, and when the engine is cold just runs the pump at 4v? This seems much more logical to me, but contradicts the other data I have seen. I think I will hook it up outside the car to test it, I'll do that tomorrow if I get time.

 

If the pump doesn't run at all until 176, wouldn't you have at least the possibility of hot spotting and possible detonation until then?

Especially if you do this (crazy IMHO): That sounds suicidally stressful on a turbo motor, again IMO.

Jim

 

That's exactly why I'm trying to find a way for it to turn on, and run at low voltage, until it warms up. That's problem number 3 that I had mentioned.

It is stressful, but no more than doing it when the engine is warm IMO. The oil was not warmed up yet, but I wasn't exactly stretching the engine to redline, just to 4-5,000rpm.

I am mounting and wiring the pump today, all according to D-C's setup instructions. I am going to see for sure if it runs below 176 or not.

 

Could you use a system of relays to flip-flop between a hardwired 12 v source to the WP and the WP controller? 10A diodes would isolate the two sources. Yes they do make 10A diodes.

Intergrate the inverted output from one of those temp sensors you push into your radiator and you got a system that puts 12 volts to the WP at key-on until the car warms up.

I won't do the wiring diagram for you though

 

That sucks, because that was the only part of your post I understood...lol

I want to test the WP first, see if it does run when cold. If not, then I will figure out how to make it do so.

I'll be testing it in a few days, I got tied up building equal length headers

Thanks for the help!

 

Well, with some good automotive relays you should be able to toggle between those two power sources: The controller and straight 12 volts. I have done it before. Just tired and can't think ATM.