Author Topic: In-line electric water pumps.  (Read 9594 times)

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Offline 1leg

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Re: In-line electric water pumps.
« Reply #15 on: December 01, 2014, 11:47:21 PM »
Most of the 12volt electric water pumps used mainly in drag racing application will not make more than 6psi of pump pressure. They Flow a great amount of water and would work fine in most LSA with N/A motors under 1000hp, A good belt driven pump will only use about 10 hp or less and will give you the added assurance that you are getting enough water flow and pressure.

Pump pressure and system pressure are two very different things.

You can get remote mounted belt driven water pumps that are about the size of an alternator that will give you more cooling options if you cannot get a highflowing stock pump. Stock pumps are prone to cavitate that will lead to loss in HP not just water flow.

http://www.summitracing.com/parts/mez-wp430s





 
Jerry
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Offline SPARKY

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Re: In-line electric water pumps.
« Reply #16 on: December 02, 2014, 08:36:35 AM »
 Stewart told me not the turn the pump over about 5000-5200 at WOT --- so I geared it down to turn 5200 at 8200 eng speed  used Gilmer belt so I do not have to worry about slipage
« Last Edit: December 03, 2014, 11:37:41 AM by SPARKY »
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Offline SteveM

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Re: In-line electric water pumps.
« Reply #17 on: December 02, 2014, 05:03:56 PM »
Tons of good information here, guys.

The reason I'm looking for a remote type WP is for packaging reasons.  If I can ditch the OEM water pump, it saves valuable space on the front (crank pulley) end of the engine.

I've always been told that pumps make flow, and that a restriction is needed to generate pressure.  The Davies Craig pumps are what has been suggested for my application (Mercedes Diesel).  If they can flow enough for a stout Duramax, they should be enough for this MB engine.

Unfortunately, the class (DT) requires a stock or larger radiator mounted in the stock location.  I suppose this doesn't preclude the use of a "radiator in a box" setup mounted somewhere else, but some semblance of a factory style radiator needs to reside in the factory location.

The discussion is excellent!

Steve.
1/2 of the Rampage Brothers

Offline Stainless1

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Re: In-line electric water pumps.
« Reply #18 on: December 02, 2014, 05:33:14 PM »
Steve, the radiator has to be there, it does not necessarily need to be used.  You could do a tank in the bed or one of the radiator in a box, in the bed.
Stainless
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Offline Rex Schimmer

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Re: In-line electric water pumps.
« Reply #19 on: December 02, 2014, 08:22:16 PM »
Steve said:

I've always been told that pumps make flow, and that a restriction is needed to generate pressure.  The Davies Craig pumps are what has been suggested for my application (Mercedes Diesel).  If they can flow enough for a stout Duramax, they should be enough for this MB engine.

You are right "kinda" most if not all water pumps for engines are of the centrifugal type, they make pressure by accelerating a mass of water to a high speed and this provides a high flow rate. When a restriction is encountered with a centrifugal pump it does cause pressure but because the impeller on the pump has to have clearance between itself and the housing, any increase in pressure means that amount of slippage between the water and the impeller increases and the actual amount of water that flows out of the pump drops. If you can get the flow vs. pressure curves you will see that increased pressure means reduced flow. Engine driven pumps typically turn at much higher speeds 4-5000 rpm, which means the water leaving the impeller is at a higher speed has more inertia and can sustain higher outlet pressure with out as much slippage (loss of flow) I think that most electric pumps probably don't spin much over 2000 rpm, (correct me if I am wrong here) you might try to double the input voltage which would double the speed, in theory, and maybe sustain higher pressure.

The high flow rate is needed to insure that the water flow through the engine and the radiator is turbulent, the more the better. When Yamaha brought out they killer 750 two stroke road racer in the 70s it had a cooling problem. The fix was Yamaha sent everyone a new set of drive gears for the water pump to increase its' speed and flow rate. Problem solved. High internal water pressure from both the radiator cap pressure and the flow resistance to the water from the pump increase the water boiling temp and the high flow rate reduces or eliminates hot spots around the exhaust valve, r.e. Sparky's experience with his big block. If you use the Davis Craig pumps you need to see what the actual flow rate is when it is connected to your engine and cooling system. I will bet a cup of coffee (retired that's all I can afford!) that is is way under what they rate it for.

Rex




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Rex

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Offline Rex Schimmer

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Re: In-line electric water pumps.
« Reply #20 on: December 03, 2014, 03:12:44 PM »
If you are considering an electric driven water pump I would highly recommend you go to the Davis-Craig web site and look at the application information that they have for each of their pumps and also their tech data. They certainly appear to have done their homework on their units. Each pump technical description includes a flow vs. pressure graph, which is certainly something you can not typically find from other electric driven water pump manufactures. Super interesting info and web site!  www.daviescraig.com.au

If you need tech or application information contact John Benson at Davis-Craig.
johnb@daviescraig.com.au .  I am not a proponent of electric driven water pumps but if I were to use one it would have to be the Davis-Craig units they certainly appear to be high quality and also know their limits.

Rex

Rex

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Offline John Burk

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Re: In-line electric water pumps.
« Reply #21 on: December 03, 2014, 04:51:52 PM »
If the problem with an electric water pump hot spot boiling put a screw in schrader valve somewhere in the system and add 10 or 20 psi of air before the run .

Offline Rex Schimmer

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Re: In-line electric water pumps.
« Reply #22 on: December 03, 2014, 05:08:33 PM »
John, is correct that adding some air pressure will "pre-load" the cooling system to a pressure that will raise the boiling point and help prevent hot spots and pump cavitation. Skip Pipes uses a CR Racing "air spring" which is a container that has a schrader valve and acts as an accumulator for the cooling system.

"I'm with Sparky, run a mechanical pump, and a sophisticated cooling system to drive cooling system pressure up and keep water up into the cylinder head. I do this using a CR Racing, Air Spring. YMMV

Skip Pipes"
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Rex
Rex

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