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Electric water pump conversion


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This is something I thought people might be interested in, so I am sharing it with you all.

Please understand that I am not suggesting that anybody else should try it or that it is better than a standard Lotus water pump, I am just showing you a project that I  wanted to try out.

OK, hope that clears the air! :)

Here is the BMW water pump I decided on.

 

waterpump bmw

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I had a think about the original water system and decided that the original water pump flows water into the front of the block and out of the top of the head, it then returns along the inlet manifold to the thermostat case where it is bypassed back to the water pump, if the thermostat is open it goes to the top of the radiator then travels down through the radiator core and back to the water pump.

There is then the heater which is basically another bypass circuit from the back of the head to the front of the water pump.

Plus the expansion swirl pot which takes water from the top hose back to the water pump inlet.

See I told you it was simple!

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Front of the pump showing the heater return pipe which will now be used as the bypass circuit from under the thermostat.

This will allow heated water from the engine to flow under the thermostat so it will still open as the engine warms up.

IMAG1962.jpg

Second hand BMW water pump.

IMAG2008.jpg

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Intresting project, and a tidy looking conversion.   What will you be using to control the coolant flow ?   Will be intrested to see how this system works out. 

But personally have never liked the thought of electric coolant pumps after seeing so many fry rover v8 engines after failing.  Less flow at certain speeds will overheat the engine and thin oil viscocity too much,  Too much and it will over cool and oil will not get up to temp causing premature engine wear.  Very fine balancing act.  :)

A

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Next job was the heater return pipe, another T hose between the inlet manifold and thermostat case (this does work but the flow isn't great so I might just pipe it to the front of the new waterpump).

I have also added the extra blue water temp sensor to the inlet manifold...more of this later

IMAG2014.thumb.jpg.aa78cb716a4ffc08de2beb126c868aa6.jpg

IMAG2031.jpg

3 minutes ago, silverfrost said:

Intresting project, and a tidy looking conversion.   What will you be using to control the coolant flow ?   Will be intrested to see how this system works out. 

But personally have never liked the thought of electric coolant pumps after seeing so many fry rover v8 engines after failing.  Less flow at certain speeds will overheat the engine and thin oil viscocity too much,  Too much and it will over cool and oil will not get up to temp causing premature engine wear.  Very fine balancing act.  :)

All will be revealed!

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Ok so water flow sorted.

I already have twin fans fitted in front of the radiator thanks to a scrapped Peugeot 306!

I decided to keep the thermostat right from the start to give a known working temp to the main cooling circuit, and also keep the original otter fan switch linked to one of the fans as a fail safe system.

Now to control the pump I needed either a bastardised bmw ecu or something else custom made, lots of head scratching and internet surfing and I found this little item made in Germany by a small electronics company.

http://www.ebay.de/itm/332062708402

The Tecomotive-tinyCWA is a small ecu with 16 different pre set programs to run the Pierburg CWA water pump usually used by BMW racing teams.

It can hold the water temp at a pre set target by reading the temp from the new blue temp sender I fitted to the inlet manifold, either speeding up or slowing down the pump or operating the second fan on the radiator, very clever little thing.

I have just propped it up on the dash for now to keep an eye on it but over the last few months of use I find myself watching the indicated water pump speed too much!

I will hide it under the dash and just watch the temp gauge in the future.

So far all seems to be working fine, temp is set to 90 deg and thats where it stays come rain or sunshine.

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THis is a neat conversion but what are the benefits. I understand that the coolant flow will be dependant on temperature and not engine rev's and this will maintain a more even temperature through the whole engine cycle and reduce the risks of over heating. I guess new car manufacturers use them to maximise fuel efficiency and reduce emissions by keeping he engine in a finer operating window where things can be optimised but what is the benefit on an old car other than the over heating risk?

 

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Hi Mike,

There are some benefits for an old car and a few drawbacks but this is why I wanted to try it out, only by giving it a go would I find out if it is a worthwhile conversion that may benefit other Lotus owners.

Among the benefits are a much quicker warm up time as the oil gets to working temperature much quicker for those short trips to the pub, so less wear on the bearings, the pump just ticks over until it reaches the pre set target temp.

It is a reactive system and uses one of the fans early depending on the rate of rise of the water temp instead of only when it is nearly overheating.

The pump can be mounted anywhere (thinking about Esprits here).

The pump speed is independent of engine speed so runs fast when stuck in traffic and slow when you have airflow over the radiator at speed, reducing power loss.

It also has a delayed shutdown of the pump and the fan after the ignition is turned off, running the pump and fan until the water temperature drops to a safe level to prevent hot spots around the block.

The main down side is the need for a larger battery and a more powerful alternator but that's not a bad upgrade anyway.

Its a bit early for me to say if it was worthwhile yet but It was nice to find that it does actually work and the cost was not much more than a rebuilt Lotus water pump, and it can be put back to original if needed.

 

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  • 3 years later...

Hi Rick,

Yes it's still working well!

My initial thinking was that it would be a great conversion for the Esprit due to the lack of room with changing the water pump.

The original water pump is fine if you are using the car daily but the seals tend to go off if the car is sat for periods and then used hard.

The BMW electric water pump is just so reliable, the only small hitch I have had is with the cheap chinese relays that I bought for the back up fan.

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I bought the same pump and controller many years ago to do the conversion however due to the fact I had to finish the europa before brexit (it's easier to make an EU car legal in another EU country) the esprit went back into storage, now that I have started on the esprit again I am digging out al the conversions I wanted to do back in the days.  the pump will go in the front close to the rad, only downside is I need to figure out how the heater and expansion tank need to be connected as I understand that it is best for the heater outlet and expansion tank go to the cold side of the rad before the waterpump.  (sucking side of the pump) I'll need to find out the hot side for the heater, do I plump in the main tube to the rad or a take off from the head?  i'll like to keep hose as short as possible but I do not want to compromise on function. 

lots of reading to do....  thanks for your feedback, much appreciated

Rick

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For Esprit I suggest pump should be located aft, near the engine, in order to circulate coolant within before thermostat opens and maximise velocity through the jacket in order to scour idle pockets against local boiling.

Cheers 

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