The standard water pump on your engine is bolted to a belt, so it pumps hardest when the engine is spinning hard and barely pumps at all when you are sitting at a light with the temp gauge climbing. That is the wrong way round for a boosted street car, a track car in traffic on a hot day, or anything that spends time idling after a hard run.
An electric water pump swaps that relationship. The question most people ask us is which Davies Craig kit to buy, and whether the controller is worth the extra. Here is how we answer it.
The short answer
- The EWP150 Alloy and Controller Combo is the default pick for most builds. Pump and controller together, so you get temperature control rather than a pump that just runs.
- Buy the bare EWP150 alloy pump kit only if you already have a controller or your ECU is going to handle it.
- The common mistake is fitting a pump to cure an overheating problem that is really a blocked radiator, a wrong thermostat or a lazy fan.
- Budget for the wiring at the same time. A relay, a loom and a sensor mount are what turn a good pump into a system you can trust.
How an electric water pump works and what the numbers mean
A belt driven pump is geared to the crank. Flow rises and falls with rpm, which suits a highway cruise and does very little for you in stop start traffic or during the two minutes after you pull off a track. It also takes power to turn, and that load is there whether you need the flow or not.
An electric pump runs on 12V and does not care what the engine is doing. Flow becomes something you control, which is why they turn up on drag cars, drift cars and street builds that idle a lot. The model number tells you the size of the pump: the alloy EWP150 kits are the ones we stock for performance engines, and the alloy housing is the version worth having in an engine bay that gets hot.
The EBP kits are a different job. The EBP23 and EBP40 are booster pumps, which means they add flow to a circuit that already has a pump rather than replacing it. Heater circuits that never quite work, long coolant runs on a swapped engine, and secondary loops are the usual reasons people fit one.
Control is the other half of the story. On its own, a pump moves coolant whenever it has power. With a controller, it moves coolant to hold a temperature, which is the part that changes how the engine actually behaves in traffic and after shutdown.
Picking the right one for your build
Street cars and daily drivers
Take the combo kit. The alloy pump with its matched controller covers the pump, the control and the sensor side in one order, and a controlled pump is what stops the temp gauge doing laps on a summer afternoon.
Track and drift cars
Same pump, more attention to the install. Mount it out of exhaust heat and run the wiring properly with a relay. Then think about the cool down lap and the ten minutes in the pits afterwards. This is where the control side earns its money, because the pump can keep working when the engine is not.
Swapped and custom engine bays
A swap usually breaks the factory cooling layout. Alongside the pump, look at where the coolant is going to sit and how you will bleed it. Radium make a range of expansion and header tanks in our engine coolant reservoir kits collection for exactly this problem, and Davies Craig list block adaptor kits for some engines, including the GM Holden 253 to 308 adaptor.
Older V8s and club cars
The same argument applies, with the added bonus of taking a belt driven load off a tired front end. Check hose sizes and mounting room before you order, because clearance is what usually decides which way the pump goes in.
| If you want | Go for | Why |
|---|---|---|
| One box that does the whole job | EWP150 Alloy and Controller Combo | Pump and controller matched, nothing else to source |
| A pump for a setup you already control | EWP150 alloy pump kit | Skip the controller if your ECU or existing switch is doing the work |
| More flow through a circuit that is already there | EBP23 or EBP40 booster pump | Adds flow without replacing the engine pump |
| Fan and pump on one temperature reading | Digital gauge thermatic fan and EWP switch kit | One sensor, one controller, no arguments between systems |
What to buy with it
The controller and switch gear come first. The Davies Craig digital gauge thermatic fan and EWP switch kit drives both the fan and the pump from a coolant temperature reading. If you only need the fan side handled, there is a digital thermatic fan switch with a 1/4 inch NPT sensor, and a mechanical thermatic fan switch for a simpler setup. A 1/4 NPT thermal sensor adaptor kit gets the sensor into a hose or housing that does not have a spare port, which is the detail that usually holds up an install.
Then the wiring and the fan hardware. A 12V fan wiring loom and relay kit saves you building one, and the universal single and dual fan mounting kits are the tidy way to hang fans on a radiator. All of it sits in the Davies Craig cooling products collection.
Do not skip the rest of the cooling system. A pump cannot fix a radiator that is past it, so if the core is original and the car is making a lot more power than it used to, look at a Koyorad radiator for your chassis at the same time. Fresh coolant matters too, and the Motul coolant range covers what to fill it with.
Two install notes worth repeating. Mount the pump so it stays full of coolant rather than sitting at the highest point of the system, and bleed the system properly afterwards. Air pockets read as an overheating pump when the pump is fine.
Where NZ Performance fits
We hold Davies Craig stock in New Zealand and dispatch from Palmerston North, so a pump, a controller and the fittings to install it turn up together instead of arriving in three parcels over a month. The wider Davies Craig range covers the fans, switches and sensors that go with the pumps, and the Koyorad radiators page lists what we carry by chassis. For everything else on the engine, start at engine components.
If you are working through the whole heat management side of a build, our water and methanol injection guide covers charge temperatures rather than coolant, and the Link vs Haltech ECU guide is worth a read if you would rather have the ECU switching the pump and fan than a standalone controller.
FAQ
What does an electric water pump actually do for a car?
It separates coolant flow from engine rpm. A belt driven pump moves the least coolant when the engine is idling in traffic and the most when you are already at speed. An electric pump can run flow where you want it, including at idle, and takes its drive load off the crank.
Do I need the controller as well as the pump?
You want one. Without a controller the pump runs at a fixed state whenever it is powered, so you lose the temperature control that makes the swap worth doing. The EWP150 Alloy and Controller Combo bundles both, or you can add a Davies Craig switch kit to a bare pump.
What is the difference between an EWP and an EBP booster pump?
The EWP kits are a water pump for the engine. The EBP23 and EBP40 booster pumps add flow to a circuit alongside the pump already there, which is how most people use them on heater circuits and secondary cooling loops.
Will an electric water pump fix an overheating car?
Not on its own. If the radiator is blocked, the thermostat is wrong, the fan is too small or the head gasket is leaking, an electric pump moves the problem rather than solving it. Fix the cause first, then fit the pump for the control it gives you.
Can I run the pump and the fan from the same controller?
Yes, that is what the Davies Craig digital gauge fan and EWP switch kit is for. It reads coolant temperature and drives both, which is tidier than two separate systems fighting over one sensor.
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