Driving an electric water pump from DTA S80

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mefmotorsport
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Driving an electric water pump from DTA S80

Post by mefmotorsport »

Just to share an idea with you all/for info:

I bought a Davies Craig electric water pump for my BMW engine but I was loathed to spend the extra £150 on their controller, the pump was expensive enough for a poxy little plastic toy like thing!

Originally I was going to design a stand alone pump controller myself using a PIC but then I thought about using the ecu to control the pump. The problem is that I wanted the pump to continue running after the engine was switched off. Of course that's not normally possible as when you switch off your engine it's normally by killing the ecu power.

After some thought I decided to rewire the power to the ecu such that it's permanently powered from my battery once the master switch is on, then control the engine by applying power to the coil, injectors etc via an ignition switch controlled relay.

I configured the unused AUX6 output on the ecu to drive a relay to power the water pump. The settings for the control of AUX6 can be selected from the DTA menu, I selected "Water Temp" and then entered the temperature that I wanted to start the pump running, ie "on at" = 65 degrees (so the pump doesn't start circulating the water until the engine is starting to warm up). In the box for "off at" I put 150 degrees (if it ever gets that hot the engines scrap anyway!) and for "Hysterysis" I put 3 degrees so once the engine has switched off the water pump will continue running until the temperature of the circulating water reaches 63 degrees. (this is so the relay doesn't chatter when it reaches 65 degrees when cooling down)

Of course this also means that the electric fan controlled by AUX2 will also keep running now until the water temperature drops below it's own setting, say 87 degrees.

Hopefully this will mean that the engine will cool in a nice controlled manner when I come off a stage into a service area/pits etc with a red hot engine (as normally if you switch off the engine the ecu cuts the fan and of course normally the mechanical water pump will stop circulating the hot water so the water in the engine stays very hot for ages)

Of course it also means I can keep an eye on the X dash which, as it gets all its info from the ecu, it's normally useless with the ignition off!

The only downside I can think of is that when I come to restart the engine after its all cooled down, I wont get the "start fuelling enrichment" that is normally applied when it's first switched on, or maybe more importantly the initial power up of the fuel relay to prime the fuel system. maybe I need to think about that?

Maybe it's all overkill or even too simple to mention on here but I thought I'd post it and see what your comments are!

Martin
VR6Turbo
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Re: Driving an electric water pump from DTA S80

Post by VR6Turbo »

Run the mechanical water pump, get yourself down to a scrap yard and find a Golf VR6. They have a fan control module that not only runs the fans after shut down, but also a secondary water pump. :D

After run water circulation is been something I've been trying to achieve myself, as simply and cheaply as possible, but that VW box seems to be the only way for me.
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mefmotorsport
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Re: Driving an electric water pump from DTA S80

Post by mefmotorsport »

I've removed the internals completely from the S50B30 belt driven water pump so that's no longer an option, anyway I wanted to get rid of it, mainly due to clearance problems with the pulley and the electric rad fan! (I had to move the engine 15mm forwards due to the lack of sump clearance on the steering rack which has made things a little tight up front)

I've also modified the thermostat so it's always fully open, I'm hoping the DTA S80 set up as above will do the job quite nicely.

Martin
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Re: Driving an electric water pump from DTA S80

Post by VR6Turbo »

True, if you don't mind leaving the ECU on a permanent live. But as it's a race car, I don't suppose it matters that much :D

I used to run a Meziere water pump. A lot more manly than those Davies Craig jobbies, but it should be up to the job though.
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mefmotorsport
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Re: Driving an electric water pump from DTA S80

Post by mefmotorsport »

VR6Turbo wrote:True, if you don't mind leaving the ECU on a permanent live. But as it's a race car, I don't suppose it matters that much.
Well it gets switched off by the master cut off switch which in my car actually acts as my normal on/off switch since there's no steering column key, only a toggle switch for the ignition.

I must admit I'm not over impressed with the Davies Craig pump, it doesn't look like a serious competition part but I suppose I'll give it the benefit of the doubt, they're supposed to be reliable and designed for competition use.

Martin
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Re: Driving an electric water pump from DTA S80

Post by welshpug »

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mefmotorsport
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Re: Driving an electric water pump from DTA S80

Post by mefmotorsport »

welshpug wrote:use something like this?

http://www.cbsonline.co.uk/product/Adju ... ostat_STAT
I don't think so! That's a rather antiquated system using a capiliary sensor!

Martin
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ignitionautosport
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Re: Driving an electric water pump from DTA S80

Post by ignitionautosport »

Just get the davies craig controller, they work well. Overpriced, yes, but they work well.\

I have seen guys fit thermostats then wonder why their pump blows apart from cavitating against it. The Davies-Craig pump controller works fine. I leave the fan connected to the ECU and the pump controller from IGN usually, so it doesn't run after engine off anyway - if I say it's off, I want it OFF!
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lumley32
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Re: Driving an electric water pump from DTA S80

Post by lumley32 »

what i have done is put the pump on one of the aux (cant recall witch number but the highest amperage one) and used PWM to control the pump so as the temp goes up the pump speed dose, no relays or controllers!

it works very well, so now i dont run a thermostat at all, but it wouldn't work after the engine has stopped.

i dont no witch Davis Craig pump your using but i tried there smaller one years ago and it lasted about 2 races, since then i have used a Bosch pump (used for inter-coolers i think) and never had a problem with one!
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mefmotorsport
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Re: Driving an electric water pump from DTA S80

Post by mefmotorsport »

OK, thanks for the input, I'll give my idea a try first and see how it goes. If it works out I'll be pleased as I cant see the point in having a stand alone controller if the ecu has the capability of doing the same job.

Martin
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