Talk to me about electric water pumps

This is probably worth a look, an aftermarket controller used to run stock OEM Pierburg pumps. Many different pump sizes available to suit different needs, and you could go and get a pump from a breakers yard if you want to save money over the new ones. It is the "fancier" end of control, pump is controlled by PWM but the controller does all that for you, so not necessarily complex from a user perspective.

tecomotive.com/store/en/

No personal experience myself btw, just looked good to me. And I think I'd personally have more confidence in an OEM designed pump than aftermarket in general.

I like the idea of using a second hand OEM pump (most of the other parts I'm using are repurposed OEM), but I couldn't really find anything other than small auxiliary pumps on eBay for reasonable money. Maybe I need to look better. In my mind the advantage of a Davies Craig pump over OEM ones is that they're nice and compact, and the flanges and be turned in any direction. I thought Davies Craig pumps had a pretty good reputation?

Would there be any merit in using a controller on a non-performance engine? As for setting a target running temperature, can't the same be achieved with a simple in-line temp sensor? I'm probably overlooking something!

The ones around the £30-£50 mark I saw were all small auxiliary pumps, but I've probably not used the correct search terms. What types of BMW use the Pierburg pump you mentioned? Is the controller a stand-alone thing?

The heater on my car is part of the cooling system, not sure I would want anything other than a pump that runs constantly like the original mechanical pump? If I'd fit a temperature controlled pump I'd need to fit an auxiliary pump for the heater as well? The Davies Craig pump I linked in my opening post draws max 7.5A at 13V and has a flow rate of 80L/ min.

'BMW electric water pump' brings up plenty on ebay.

The Tecomotive controller is standalone. In a BMW, the waterpump is controlled by the ecu.

With the Tecomotive, the pump always runs at a low speed even when the coolant is cold, otherwise you would get hotspots around the cylinders. Therefore there will always be some flow through the heater circuit. If you find the flow is not enough, to some extent you could manipulate it by setting the target coolant temperature lower. The pump would then run faster as it approaches the target temp. Another feature of the Tecomotive is that it can continue to circulate coolant and run the fan after you've switched off the engine, to bring the temperatures uniformly down after you've finished driving.

I would think that the DC one works in a similar fashion.

I always had cooling issues on my Lancia engined Minor. I had already fitted as big a radiator as I could. Someone suggested two smaller electric fans instead of the one big and a Davies Craig electric pump. I never had a cooling issue again. From memory the electric pump and controller takes over the job of both thermostat and mechanical pump. You remove the wax thermostat and the guts of the old water pump body - if it needs to remain - to provide something for the existing hose to attach to.

With the fans and electric water pump running I could watch the water temp drop quickly from too hot to too cold. I _think_ I added a connection to the Megajolt so fan and pump activated automatically from 5500 or 6000 revs.

Before:




After:




Not much to see. I had this setup for about a year without problem then the car was nicked. Hence the aforementioned thoughts of a V4 engined Minor down the line.

The pump hangs off the two hoses and is not mounted to anything else.

I've never had any issues with mechanical pumps on V4s, but I need the space for something else, hence I need a pump that doesn't need to be in line with the belt. A bonus advantage of an electric pump on a V4 would be that it no longer puts any strain on the balance shaft bearings, which are the engine's main weak spot.

It's really easy to completely remove a mechanical pump from a V4, just hacksaw it off the timing cover. I'll modify one this weekend if I have time, I'll also delete the fan bearing in the process, which is a common mod when electric fans are fitted.

I did a bit of development work on electric water pumps for an OEM back in the late 90’s. I would definitely run a controller rather than leave it constantly running. A lot of engine wear is created when an engine isn’t run at the designed temperature so if you pick the wrong set point on your pump you’ll either run the engine too hot or too cold. The controller will optimise flow so that you have rapid warm up and optimum running temperature without having to worry.

One thing we did learn is that on the vehicle we used was that with the engine pump not working the car overheated as original pump had more than just an inlet and outlet to it. This meant that one port that was originally low pressure now became high pressure so the head had no flow. We had to block one port off to prevent this. This was a relatively new engine so older engines may not be afflicted with such problem.

Before fitting one though I would ask myself is it really worth it. If it’s for an engine with an inherent weak spot like you say, that’s great. If it’s for cooling issues I would generally think the issue is elsewhere as in the world of cooling it’s airflow, engine condition and in the realm of engine conversions,circuit design that’s the major factor.

Google just answered my question (he uses a bigger pump, but the same principles apply I suppose):