Fitting Digital Thermo fan switch to DS

Greenpeace

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Hmm Yes there is a reason and I suspect it is not what you think. I do not know of any car with an electric water pump ?
Many of BMWs later model cars have dedicated electric water pumps. I know some MBs have supplementary ones, not sure if any of their models have dedicated electric water pumps though?

I do agree though that you need to be sure all the factory parts function as intended before inventing a better mouse trap.
 

faulksy

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In theory you can replace the engine driven fan and pump with electric parts. Pottsy tried ages ago on his rally car with limited success. The thread is here

https://www.aussiefrogs.com/forum/index.php?threads/ds-cooling.31751/


I suspect the reason it didn’t end well was to do with how it was set it up. There is little to no ram air effect on a DS so the cooling system is designed around a fairly hefty fan constantly pulling air through the radiator and engine bay. I reckon the electric fan needs to spin up before the coolant gets to the thermostat opening point not after. If it doesn’t spin up till the coolant hits 90 then you not only have to cool the radiator but you also need to displace the volume of 100deg plus air that has built up in the engine bay.

Davies Craig fans can pull 30A, add to that 7.5A for their smallest 80L/min pump and you’ve got a fair load of 440W, plus conversation losses, on the electrical system. That power has to come from somewhere, i.e the engine. Whether it presents as less of a load than the mechanical pump/fan combo I can’t say.

It’s not to say it’s a bad idea but it is important to be aware of the realities.

The Engine Guard previously mentioned does have the ability to sound an alarm or trip a fan relay at a user defined temperature. Back to Glenn’s original question, you can leave the original thermo switch in place and just use the probe inserted into the radiator. All the original switch does is turn on a relay.
 

Rally

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I seem to remember a longish thread on here about fitting electric water pumps, electric fan, removing the engine driven fan and extra sensors. All Davies Craig. The conclusion was that it was a waste of time and reverted to original.
My rally car has had a Davies Craig electric water pump for the last 15 years with zero problems .
I have the controler cable tied to the dash were I can see the engine temp and what mode the pump is in by a quick glance at the row of different coloured LEDs , I would rate it as one of the best upgrades I have ever undertaken.
 

PeterMol

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This from the Natrad web site

All there is to know about water pumps for cars. Did you know that your car's water pump is responsible for circulating coolant around your engine's cooling system? This is an extremely important feature. ... Modern vehicles typically have electric water pumps due to the range of performance benefits they have.

As you say though each to their own
 

PeterMol

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Many of BMWs later model cars have dedicated electric water pumps. I know some MBs have supplementary ones, not sure if any of their models have dedicated electric water pumps though?

I do agree though that you need to be sure all the factory parts function as intended before inventing a better mouse trap.
I understand your point and it is a fair one. Unless the modern option is more efficient. I’ve just been looking for low impact ways of squeezing a bit more power from my DS. The fan option does provide more power but for me getting rid of that roar from the pulley driven fan on acceleration is a very good outcome. The water pump appealed to me because it has a controller that works together with the fan to manage the most efficient outcome between the two with the added advantage of no more thermostat as the controller completely stops the flow of water allowing for a faster warm up

All that being said the original set up worked fine and there is a lot to be said for originality. I just like this option because, like a123 it is almost completely invisible and will improve fuel economy. The economy claim has been independently tested many times

So, each to their own. Whether original or tweaking, anything that keeps our cars on the road gets a vote from me
 

Greenpeace

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I understand your point and it is a fair one. Unless the modern option is more efficient. I’ve just been looking for low impact ways of squeezing a bit more power from my DS. The fan option does provide more power but for me getting rid of that roar from the pulley driven fan on acceleration is a very good outcome. The water pump appealed to me because it has a controller that works together with the fan to manage the most efficient outcome between the two with the added advantage of no more thermostat as the controller completely stops the flow of water allowing for a faster warm up

All that being said the original set up worked fine and there is a lot to be said for originality. I just like this option because, like a123 it is almost completely invisible and will improve fuel economy. The economy claim has been independently tested many times

So, each to their own. Whether original or tweaking, anything that keeps our cars on the road gets a vote from me
Don't get me wrong I have/have had some drastically modified vehicles. I'm all for anything that will improve power and efficiency.

But as you would have read, one person says a certain mod is sh#t and another will say the same mod on the same model car is the best thing since sliced bread!

Unless there is an obvious fault or failure in a cooling system component, modifying it to "fix" an overheating problem is a bit of a stab in the dark.
Unless your sure your original components are performing as designed, it is impossible to judge the value of any modifications you make.
An electric water pump will obviously out perform a standard one where the impeller has half rusted away. But will it equal or out perform a new standard component? Clearly you if you have an overheating issue and the standard pump is performing to spec it is unlikely that swapping it for an electric one will resolve that problem.

When I bought my 3 wheel Reliant it had a pretty wild cooling system, as the previous owner had overheating issues. The Reliant is similar to the DS in that the inlet air is channelled through a large duct (in the Reliant's case up and over the front wheel) back to the radiator.
The Reliant used a Mini radiator from the factory. It had a new Mini radiator and thermo fan in the stock position along with the factory engine fan, and it had another new Mini radiator and thermo fan mounted up under the LH front guard. They were all interconnected with a swathe of hoses and monitored by a digital controller, it still got hot! I poked my head down in the engine compartment and there were huge gaps where the ducting met the radiator (the one mounted in the standard position), the gap over the top of it was 3" wide. I eliminated all the gaps, overheating problem solved. Removed the extra radiator and it's associated paraphernalia, still ran fine (it was just sitting up in stagnant air anyway). Added a Rootes style supercharger making 10psi of boost, which along with some other mods doubled its power output and it still ran cool.🤷‍♂️
I ended up replacing the copper/brass radiator with an equivalent aluminium one for the sole purpose of reducing weight. It still runs the standard 3 blade unshrouded plastic fan and it still stays cool regardless of the weather.

Old matey could have saved himself of a lot of time and $ if had made sure everything functioned as intended before he embarked on trying to build a "better" mousetrap.🤷‍♂️
 

JulianEdgar

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It's a long time ago now, but having tested a Davies Craig water pump, and then had detailed conversations and interviews with the company engineer as a result of that testing, I would never buy any Davies Craig item. Hopefully, they've improved since then.

Re triggering a radiator fan, these days digital temperature controllers are so cheap that it can be done for literally under $20. You can even monitor the original temp sensor.
 

brian woodcock

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Tell me if I,ve got this right! Using an electric water pump, which I assume will be stationary when the engine is cold, then there will be no circulation in the head. This is normally provided by the bypass circuit. This will cause uneven heating of the head!
Woody
 
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