Electric Water Pumps (EWP)

Electric Water Pumps (EWP®) FAQs

Question No. 1
Which Davies Craig Electric Water Pump will best suit my vehicle’s engine?

Generally, we recommend the use of the EWP®80 (Part No. 8005) on engines up to 3.0 litre capacity and the EWP®115 for larger engines. Both EWP® Electric Water Pumps fit most makes and models and mount into the bottom radiator hose and are complete with all the necessary components required for easy installation, with a comprehensive DIY instruction booklet.

Question No. 2
What benefits will the Electric Water Pump give my engine over the existing belt driven mechanical water pump?
Both the EWP®80 and EWP®115 are performance accessories that increase power sent to the drive wheels, while improving cooling capacity and fuel economy and eliminating engine heat soak after a hot shut down. Old mechanical, belt driven water pumps run directly off the engine and sap engine power. The engine cooling is improved with a EWP® by having a higher flow rate at idle and low engine speeds when there is little or no ram air, and when the engine is switched off. But the important improvement for a race vehicle comes from the fact that the power the mechanical pump takes from the engine increases as the cube of its speed - so when the pump speed doubles from idle speed say 600 rpm to 1200 rpm, the power it takes increases by 8 times. Then another 8 times going to 2400 rpm and so on up top 10,000 rpm. It is this extra power and torque you are releasing by disabling the mechanical pump, that goes to the drive wheels. Both Electric Water Pumps can be hard wired into your electrical system or you may opt to use the Digital Controller (Part No 8020) which will greatly enhance your control of coolant flow and engine temperature.

Question No. 3
What do I do with the engine’s existing thermostat?

If you choose to use the Davies Craig Digital Controller you should remove the engine’s thermostat – the Controller is the new “thermostat”. The Digital Controller allows you to electronically set the engine target temperature and it adjusts the rate of coolant flow, hunting for, and then locking onto the temperature you set. You have five (5) options; 70c, 75c, 80c, 85c and 90c for either economy or performance, unlike your thermostat, which  is set at one temperature by the engine manufacturer.

Question No. 4
How and where do I fit the Electric Water Pump?

Both EWP®80 and EWP®115 Electric Water Pumps fit most makes and models and mount into the bottom radiator hose. You just cut out 100mm (4 inches) of hose and let the EWP in. The existing water pump housing is still required as an inlet into the engine block, or a blanking plate can be manufactured to bolt up to the block with an inlet for the radiator house to replace the old pump. It is recommended that you do not ‘hard mount’ your Electric Water pump. When firmly fixed to the chassis or engine, the EWP® may bow which disturbs the shaft seal and may cause a leak and not reseal when the EWP® cools. The EWP®115 weighs only 980 grams, therefore the radiator hose is more than capable of holding your lightweight EWP®. Should it be necessary to mount the pump we recommend you use rubber ‘cotton reel’ type mounts to help cushion the pump against vibration and you can use the extra holes around the perimeter of the base of the EWP for this purpose. A supplementary mounting plate can also be used for mounting purposes. Both kits come complete with all the necessary components required for easy installation and a comprehensive DIY instruction booklet.

Question No. 5
Do I have to remove the existing mechanical water pump?
If you want extra power and  fuel savings you will need to remove or disable your existing mechanical belt driven water pump . Alternatively you may wish to keep your existing mechanical pump and use the Electric Water Pump as an auxiliary pump. 

Question No. 6
Where do I mount the Electric Water Pump?

Both EWP®80 EWP®115 Electric Water Pumps fit most makes and models and mount into the bottom radiator hose. It is recommended that you do not ‘hard mount’ your Electric Water pump. When the EWP® heats up the body of the pump will expand slightly. If the EWP® is located in the hose only, the expansion is no problem. When firmly fixed to the chassis or engine, the EWP® may bow which disturbs the shaft seal and may cause a leak and not reseal when the EWP® cools. The EWP®80 weighs only 800 grams and the EWP®115 weighs only 980 grams therefore the radiator hose is more than capable of holding your lightweight EWP®. Should it be necessary to mount the pump we recommend you use rubber ‘cotton reel’ type mounts to help cushion the pump against vibration. 

Question No. 7
Is it possible to fit two EWPs to my engine?
Customers with large race engines are having great success with two EWP®s mounted in line. One is controlled by a Davies, Craig Digital Controller (Part no 8020) set to its target temperature and wired to the ignition. The other is run by a standard on/off thermal switch (part no 0401) wired direct to the battery, and set to cut in at a few degrees hotter than the Controller target temp. When the Controller is running the first EWP® at full speed and the engine temp still increases, the Thermal Switch kicks in the second EWP® and runs it until the engine temp drops 4◦C. in the same way an electric fan is controlled. When the engine is shut down hot, the second EWP®, being wired direct to the battery, will run until the engine cools. The same Thermal Switch used to run an electric radiator fan can be used for the second EWP®. In this case, make sure the fan and EWP® are wired directly to the battery. Both the fan and the EWP® will run on hot shut down, typically for as little as 20 seconds, to cool the engine.

Question No. 8
Will I need to fit the Electric Booster Pump?
Davies Craig recommends you fit an EBP® Electric Booster Pump part no 9001, to engines equipped to run on LPG where a constant flow of coolant is essential to ensure the LPG regulator does not freeze up on a cold start. This very compact unit fits in the engine’s heater hose lines and offers up to 20 litre/min of coolant flow.

Question No. 9
Will the fitment of an Electric Water Pump be a drain on my electrical system?

The extra current is very little. About 90% of total motoring time the EWP will run at 10% of its maximum speed using about 2 amps. Being in nylon, the impeller can have aerofoil cross section and the tip clearances can be very small. A mechanical pump has to perform at 600 rpm and 6,000 rpm and it cannot be efficient at both these speeds and all speeds in between. Furthermore, as the power the pump requires to operate increases as the cube of the speed - when the mechanical pump is operating at the higher speeds, as it does, as a car passes through its gear range, its ‘robbing’ engine power in the order of 6 to 10kW. The EWP® which uses at maximum speed 9 amps x 13 volts gives 120 watts at say 30% efficiency from the alternator to hydraulic power means about 0.4 kW to drive the EWP®, when it does operate at full speed.

Question No. 10
I would like to place the Thermal Switch (Part No. 0401, 0402, 0404) unit in the vehicle’s cabin rather than under the bonnet. Is this possible?

No, Davies, Craig Thermal Switch (Part No. 0401,0402 & 0404) must be mounted in the engine compartment near the radiator. The EWP/FAN Digital Controller (Part No. 8020) should be mounted inside the vehicle cabin to access the controls and feedback information away from direct sunlight and should not be exposed to excessive heat.

Question No. 11
Is the idea that coolant can pass too quickly through a radiator true?

The "pump too fast lose less heat” notion is very popular and many experienced mechanics are very attached to it but – it is a fallacy. Davies Craig has been carrying out research and development for over a decade on a number of projects and has never been able to pump genuine liquid coolant faster and lose less heat. In all car engines, when the mechanical pump reaches cavitation speed, coolant turns into a gaseous state which is compressible,(liquid is not) and the real flow rate of liquid coolant drops even though the mechanical pump has a higher rpm,  and so heat loss drops. The engine temp then rises. And it only seems like the flow rate is too fast, and the coolant is spending too little time in the radiator to lose its heat etc. etc..

Question No. 12
My vehicle is fitted with a thermostat bypass what should I do when I wish to replace the existing mechanical water pump with an EWP®?

Where there is a thermostat bypass in some engines including those produced by BMW & ROVER, there may be a bypass from the thermostat housing back to the water pump chamber so when the thermostat is fully closed, coolant passes directly from the engine block to the thermostat housing and then straight back to the block without passing through the radiator. When fitting your EWP® to an engine which uses a bypass valve style thermostat, after you have removed the thermostat, you will need to block off the bypass passage (with a core plug or similar), to prevent flow from your EWP passing directly back to the radiator without passing through the block.

Question No. 13
Why is the power used by the EWP® much less than the mechanical pump?
The EWP® is designed for maximum efficiency at its maximum speed of 2250 rpm. Being in nylon, the impeller can have aerofoil cross section which gives lift and the tip clearances can be very small. The mechanical pump has to run at 600 rpm and 6,000 rpm and it cannot be efficient at both those speeds and all speeds in between. Furthermore, as the power the pump takes increases as the cube of the speed - when the mechanical pump is operating at the higher speeds, as it does as a car passes through its gears; it is taking power of the order of 6 to 10 kW. The EWP® uses at maximum speed, which is usually less than 20% of total motoring time, 9 amps x 13 volts gives 120 watts at say 30% efficiency from the alternator to hydraulic power means about 0.4 kW to drive the EWP®. The EWP® never needs to run at very high speeds where the mechanical pump is consuming high power and torque. In addition, with the old mechanical pump and a thermostat set up, the thermostat is partly closed most of the motoring time and in a cool climate at highway cruising, it is about 90% closed. As a consequence, the flow and pressure being generated by the mechanical belt driven pump and paid for with power and torque, are choked at the thermostat and wasted. This system has worked reasonably well for a long time but it is not smart. With your EWP and digital Controller, power and torque is never wasted as there is no choking (no thermostat) and only as much flow and pressure as is required is produced. We are starting to see the allowance of EWP® s in racing mostly for the extra power but also to prolong the life of engines with the run on after hot shut down to eliminate heat soak. In any case we cannot stop progress, nobody in racing runs drum brakes or cross ply tyres these days!!
Question No. 14
Can I fit the EWP to the top radiator hose?
With respect to the EWP fitment in the top radiator hose, there is no negative effect, reduced EWP motor life etc.
What is critical however, when the EWP is fitted to the top hose the system MUST be FULLY bled and NO AIR is to be left in the system at any time. The EWPs are not self-priming pumps and as such, should the EWP be operated dry, premature failure of the seals may occur. The reason we nominate the bottom radiator hose is this very good reason as listed.
Question No. 15
Does the EWP fit my engine?

As the EWP is positioned within the bottom radiator hose, the EWP is a universal fitting pump. The EWP kit comes complete with a range of adaptors to fit hose sizes 32mm to 50mm or 1 ¼“ to 2”. 

Question No. 16
At what temperature does a normal engine run?

The ideal operating engine temperature is dependent on the type, size, capacity, workload and environment the engine is working in, however the best engine temperature is usually between 85-105°C or 185°F-221°F.

Question No. 17
How much current does the EWP use?
The max current draw to operate the EWP80 is 7.5A and the EWP115 is 10A. However under average operating conditions the current draw is approx. 2A and 3A respectively. 

Question No. 18
Do I really need to have the Digital Controller?
The Digital Controller (Part No. 8020) is Davies Craig’s recommended method of operating both models of the EWP. However it’s not the only method of control. If the EWPs are to be used in motor racing or drag racing, you can run the EWP continuously, due to the extreme amount of heat produced under those conditions. If your race engine runs too cold, upgrade to the Controller. The EWP may be used with a Davies, Craig Thermal Switch (Part Nos. 0401 and 0402) as an auxiliary pump.  If the EWP is the only pump in the engine it should not be run with an on/off thermal switch like a radiator fan. Your engine needs some flow all the time or hot spots will form outside the cylinders.

Question No. 19
How much power will I gain?
Davies, Craig performed a number of tests which concluded that a normal water pump uses up to 10kW of power to operate at its high speeds, therefore if it is removed this power is saved and sent to the drive wheels. Not all the power gained will be transferred directly to the wheels as a small percentage will be lost through the drive-train. Each engine is different and the size, capacity and performance of the engine will determine how much power will be gained. Generally higher revving engines such as small capacity and rotary engines will have the biggest percentage increase in power and torque. With the extra power, maximum engine speed will increase so you should be careful that other engine components can handle the extra rpm. A Dynamometer test on the 5.0L V8 VT Commodore measured a 10kW improvement at high rpm and overall increase in torque particularly in the lower rev range.

Question No. 20
How does the Digital Controller work?
When the ignition is first turned on, the Digital Controller will 'system check' the EWP and it will run the pump for approx 10 seconds. The Digital Controller supplies a six volt PWM- pulse width modulation, (10 seconds on – 30 seconds off) to the Electric Water Pump from a cold start until the engine temperature reaches 20◦C below the target (set) temperature. At this point the Digital Controller then supplies a PWM (10 second on – 10 seconds off) till 5C less,  then the Controller will ramp up to full system voltage as and when required searching for and locking onto the target temperature.

  • Electric Thermatic Fan/s will deploy at +3◦C above target temp.
  • If the engine cools below the target temperature, the Controller will step back from full system voltage down to 6v if necessary and generally it will go back to pwm when highway cruising.

The Digital Controller will indicate when;

  • The EWP® is running
  • The target (set) temperature is reached
  • The supply voltage is too high or too low
  • The EWP® is running at full supply voltage and is not holding the target temp (Thermatic Fan/s need to be turned on)
  • There is no power to the EWP®
  • If you wish, you can look at what the Controller is supplying the pump by connecting a voltmeter to the EWP® motor leads. But remember when the Controller is in PWM mode, the meter will flicker.

Major advances in the new Digital Controller:

  • Temperature settings are now electronic in that the SET temperatures are now easily set digitally at the touch of a button.
  • An automatic time-out has been built into the Controller to run the EWP to the target temp or for a maximum of 2mins after ignition OFF, to eliminate the effects of heat soak on engine shutdown. Generally the EWP® will run for less than 2mins because heat soak washes out in about 20 seconds.
  • A suite of self diagnosis functions has been built into the Controller which will identify cooling problems enabling easier trouble-shooting.
  • The Controller has a number of monitoring features to keep the user appraised of system operation conditions at all times e.g. Controller on, pump operation mode, cooling system temperature etc.
  • A new option for mounting the temperature sensor into the top radiator hose is offered in lieu of placing the sensor wiring between the hose and housing or into the thermostat housing. Part no is 0409.
  • The current carrying capacity of the Controller has been increased from 7.5 amps to 12 amps in conjunction with a significant weight reduction.
  • A 'Test' function has been adopted which gives the user a visual warning -- on the Controller and remotely -- if a system problem is evident.

Question No. 21
What is the flow of an old fashioned mechanical belt driven water pump?
Davies, Craig P/L conducted tests which showed that each capacity engine had different coolant flow rates i.e. V8 was more than a 4-Cyl. One common V8 has a flow of 24 l/min at idle (600 rpm) and so about 240 l/min at 6000 rpm. That is 240 kilograms of coolant being rammed through narrow radiator tubes every minute. It takes a lot of power to do that. However it was shown by the CSIRO that in a standard engine, flow above 80L/min increases heat loss by very little. Once the flow has reached a rate where all of the heat being produced by an engine is being dissipated in the radiator there is no benefit from pumping faster.

Question No. 22
Why does my mechanical pump have a higher maximum flow rate then my EWP?
An engine requires a certain flow when it is idling and the vehicle is stationary in high ambient temperatures - say 15 L/min. The flow rates at higher engine speeds are a consequence of the idle flow and are roughly proportional to the increase in engine speed above idle. Invariably the flow rates at high engine speeds are much more than is required given that high engine speeds are transient, as the engine passes through gears, or the vehicle has high road speed and so there is high ram airflow through the radiator. Heat loss is a function of coolant flow and air flow and you do not need both to be at their maximum as the system is designed to maintain engine temperature with both at their lowest values. But you have to have those high coolant flow rates because the mechanical pump speed is a slave to engine speed and if you have 15 L/min at 600 rpm, then at 6000 rpm you will have about 150L/min. That is 150 kilograms of coolant being rammed through the radiator tubes every minute – it takes a lot of power to do that.

Question No. 23
How is the engine cooling improved with the fitment of a EWP?
The cooling is improved with a EWP by having a higher flow at idle and low engine speeds when there is no or little ram air, and also when the engine is off. But the important improvement for a race vehicle comes from the fact that the power the mechanical pump takes from the engine increases as the cube of its speed - so when the pump speed doubles from idle speed say 600 rpm to 1200 rpm the power it takes is 8 times. Then another 8 times going to 2400 rpm and so on up top 10,000 rpm. It is this power and torque you are releasing, by disabling the mechanical pump, to go to the drive wheels.

Question No. 24
Can I install my EWP very close to an exhaust pipe?
The Davies Craig Electric Water Pump, material specifications; Standard PA66 GF30. Thermal properties, continuous working temperature = 135°C, Peak Temperature = 160°C.

Question No. 25
Can I use the EWP & Fan Digital Controller to run my Thermatic Fan Only?
The EWP & Fan Digital Controller (part no. 8020) is primarily designed to run the EWP with the added function to switch on and off your Electric Fan, which saves you the cost of having to purchase an additional electric fan switch. If you are not using our EWP then we would recommend against purchasing the EWP & Fan Digital Controller as you primary fan controller as you can't independently set the cut in temp for the fan. The EWP & Fan Digital Controller is programmed to switch on the fan at 3°C above the EWP temp setting. For a fan only application we would recommend using either our Mechanical (part no. 0401) or Electric (part no. 0402) Thermatic fan switch and wire direct to the battery so the fan will run on after engine shutdown. 

Question No. 26
Can I mix water wetter, glycol and/or anti freeze products in my cooling system when fitted with your Electric Water Pump?
Yes, the range of Davies, Craig Electric Water Pumps are precision manufactured using Nylon 66, reinforced with 30% fibre glass capable of withstanding various types of inhibitors widely available on the automotive market. This same tough material has been tested and approved by many automotive manufacturers and is the same material designed into the manufacture of radiator side and header tanks adopted by a good number reputable automobile manufacturers worldwide. 

Question No. 27
Do you supply an EWP115 with the old style bolt up fittings?
We don't make an EWP115 with bolt up fittings, however we are due to release our new EWP115 Aluminium pump most likely around early April 2010 (Part No. 8040 for the Pump & Part No. 8050 for the Combo Pack). The Alloy version is identical to the original with the addition of an internal 1" NPT thread on both the inlet and outlet to allow for dash style fittings. 

Question No. 28
I am looking for a water pump or booster pump that will fit a one inch hose, do you have anything for this size hose?

Our EBP (Part No.9001) will adapt to 1" hose. While the inlet and outlet is only 19mm (3/4") many of our customers have used this very efficient pump on 1" heater hose lines.
If you have access to adaptors you can order Part No.9002 which is our 'short' EBP, supplied with the wiring loom and without the fittings. 

Question No. 29
Can I run the EBP (9001 & 9002) on a 6V system? 
You can run the EBP at constant 6V, some early cars had 6V systems. Obviously it will only deliver 10 litres per minute instead of the usual 20 litres per min. All our EWPs can be operated at any voltage up to 15 volt, although the 15 volt operation is not recommended for long periods.
On the other hand, not so the Digital Controller, it MUST be operated at 12 volt and if an over-voltage situation occurs the unit may malfunction.

Question No. 30
Can I run the Digital Controller on a Vintage Car without suppressed ignition leads?
No, your old wire leads will cause the ccntroller to play up. You will need to install new leads to allow the controller to work.

Question No. 31
If I buy an EWP without a Digital Controller, should i remove thermostat?

This depends on the vehicle and what the vehicle is used for? Generally for short circuit race/drag applications and engines used under extreme conditions we recommend removing the thermostat to provide the greatest cooling capacity. It is always recommended to use the controller for other applications, however if you have decided not to then we recommend to drill a small 5mm hole in the thermostat to allow some flow and release of back pressure when the thermostat is closed. You may find in these circumstances that the engine temperature is not managed effectively and also the pumps life will be reduced if the controller is not used. 

Question No. 32
Can I use your pumps in a Positively Earthed vehicle / application?

Our EBP (Part No. 9001-9002) and our Digital Controller (Part No. 8020) can not be used for a positive earth vehicle.

However our EWP80 & EWP115 models can be used in positive earth applications / vehicles, you have to simply reverse the polarity of the pump wires.

  • For our 12 volt EWP80 and EWP115 the wires are Blue (positive), Black (earth), simple reverse this wiring in your applications thus Blue wire becomes Earth and Black becomes Positive.
  • For our 24 volt pumps, the wires are Red (positive), Black (earth), simple reverse this wiring in your applications thus Red wire becomes Earth and Black becomes Positive. 

Therefore you can run these pumps constantly on from ignition or you can use them with our Mechanical Thermal Switch (Part Number 0401 & 0404) which will switch the pumps on and off at the desired temp. You do lose some functionality in not being able to use the Digital controller (Part 8020). 

Question No. 33

The Digital Controller ‘Fan’ light comes on just over the ‘targeted/set temperature’ but the Thermatic Fan is not switching on?
Please check the wiring of the fan relay. The green wire with the black trace from the Digital Controller to the fan relay is a negative switching wire. Therefore from relay pin 85, this wire should be connected to the positive battery terminal either directly or through pin 30. See attached diagram. 

Question No. 34

Can the EWP Digital Controller Handle 2 x EWP's in Parallel?
This is dependant on the type EWP being used or your set up. The EWP Digital Controller can't handle the total current of 2 x EWP115 in parallel but it will handle 2 x EWP80's. However if you run the second EWP115 off the fan output through a relay it will run both, but the second pump will only switch on and off 3°C above the set point, not via PWM.  

Question No. 35

I need to have the Digital Controller temp set to 75 degree or the temp gauge pulses occasionally to ‘Overheated’ - I would prefer to run it at 85 degree?
I would strongly recommend to relocate the EWP Controller sensor to the same location or as close as possible to the vehicles temperature sensor so the 2 sensors are both reading from the same location. It is not uncommon for temperatures in different zones of a cooling system to vary by 10-20 degrees C and this temperature difference between the two sensors may be what's causing all your issues. Relocate the sensor and if you still have issues please let us know.

Question No. 36

I am trying to choose between a EWP Alloy and Nylon plastic pump, what are the advantages or disadvantages of each one?
There is no performance difference between our EWP115 Nylon and EWP115 Alloy.
Only the outer housing is in different material.
EWP115 Nylon
Pros: - lightweight (980 grams or 2.16 lb.)
Cons: - No thread on the inlet or outlet to fit screw-in style hose or AN fittings.
EWP115 Alloy
Pros: - Cast alloy housing can be polished for a shiny look. 
          - Has AN -16 thread on the inlet and outlet to enable the fitment of screw-in style hose fittings.
Cons: - Heavier than nylon version (1151 grams or 2.56 lb.) 

Question No. 37

Have a question is more about the Quality of the dc supply on EBP. I know the voltage limits, of course - but when you convert the ac output from a transformer into dc via a bridge rectifier the dc voltage is quite rough (unsmoothed), and the question is really - how much smoothing is required for the pump to be happy and operate reliably long term?
This EBP has its own built in voltage regulator to regulate & smooth the input voltage. As you mentioned earlier that the customer is using a AC to DC transformer & a bridging rectifier circuit, indeed he need to use an appropriate capacitor. I cannot give you any values for the capacitor which he need unless I see the full circuit. But as an example if he is using a bridge rectifier of 1N4148 then 220uf capacitor will do the job.

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