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Post by Rob Bell on Mar 5, 2004 6:36:28 GMT -5
Okay chaps - here's a question for the electronic gurus amongst you... As mentioned elsewhere, Dave and I have been involved in an electric water pump project whose purpose is to circulate water after the ignition has been switched off. The idea is to tackle the real problem of increasing water temperature in the small water ways in the cylinder head that occur especially after a hard run (be that on track or on fast roads) where the coolant can boil and damage the alloy head casting. The control circuit would, therefore, have to have a separate power supply - and power a water pump for a given period after the engine has been switched off (say 15 minutes). There ought to be a reporter LED so that the owner knows that the pump is switching on and off as it is supposed to. A more sophisticated version could employ the temperature sender for the instrument gauge - switching the pump on at 110C and off again at 80-90C. The front radiator fan could also be switched. For details on how the Lotus electric water pump installation works, see below  We've got quotes for the first system that works out to be around £100 per unit on a small run of 5. This pushes the whole kit over a prohibitive level of £300-350  So the question is - is it possible to design a system that would cost significantly less? Could the MEMS power down circuit - as used by Carl for the window delay circuit - be used (more details on Dieter's site: www.mgfcar.de/power_delay_by_carl/index.htm)? Over to you guys! ;D |
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Post by Bruce on Mar 7, 2004 13:44:50 GMT -5
Doesn’t the MEMS unit switch the front cooling fan on if the temperature in the engine water is too hot? And with the ignition off? If so this circuit could be used to supply the water pump for up to 9 minutes or so after the ignition is switched off. If the temperature that the fan operates at, is too high for your liking, then this could be altered by having a relay, switched by the ignition, introduce some resistance into the water sensor circuit. This setup, assuming it works, would mean that the fans would run as well as the pump. Surely this would be ideal apart from the current consumption!
Anyone know for certain of the front fan works with the ignition off, like the engine compartment fan?
Bruce
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Post by Dieter on Mar 7, 2004 17:25:31 GMT -5
Hi Bruce, welcome to the club. ;D I think we don't have this feature with front fan coming off. It's common with nearly any front engine car though. However, I like the idea. www.mgfcar.de/schedules/sb13.jpgIf it doesn't then the next question is.... Why doesn't it and can this feature get activated with mod to the existing wiring ?? Under Bonnet Fuse #6 and compartment fuse # 15... Do they get powered with ignition shut down ? Does the ECU pull to ground the blue-slate wire with ignition shut down ? How can this be modified and will the signal from the ECU coolant temp sensor (processed by above mentioned circuit) meet the requirements for switch modes of the additional electric water boost pump. |
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Post by Rob Bell on Mar 8, 2004 7:23:29 GMT -5
Unfortunately, the front fan is not powered after ignition switch off Bruce (and welcome to the board! ;D) - but your mention of the powered engine bay fan is interesting... I wonder whether the relays employed in the current ECU could be deleted in preference to powering from the engine compartment fan?  |
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Post by Bruce on Mar 8, 2004 8:39:41 GMT -5
Yep, have to agree with you now I've studied the circuit diagrams. However, the front fan relay coil can be powered from a permanent supply by removing the light/green/slate wire from the relay and connecting that terminal on the relay to another 'always on' supply line such as the brown wire on the relay?. This would allow it to work. It will still only work for 9 mins or so because the MEMS powers down after that time and switches the relay off. I guess the current taken by the pump would be similar to that taken by a rad fan. The relay is designed to carry the current of two rad fans so if you don't have aircon then it should be sufficient as it is. If not then just put another relay working in parallel witht he first one.
I'm assuming the MEMS will still switch the rad fan circuit with the ignition off (during the nine minute delay). I can't test this on my car at the moment as it is immobilised with the battery out. I don't do any mileage during the week as I now work about 40 seconds walk from home!
Bruce
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Post by Bruce on Mar 8, 2004 8:42:40 GMT -5
ALSO, Is this website in a different time zone?  Bruce |
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Post by Rob Bell on Mar 8, 2004 8:51:14 GMT -5
ALSO, Is this website in a different time zone? Bruce LOL - yes it is! To correct, in your personal preferences, if you enter the time zone correction of +4.67 you get approximately the correct time. Although why you have to do this, I don't know!  Good thought regarding altering the power feed to the rad fan Bruce. " It will still only work for 9 mins or so because the MEMS powers down after that time and switches the relay off."I think I am being dense - but how does this work Bruce? |
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Post by Rob Bell on Mar 9, 2004 7:50:00 GMT -5
Okay folks, clearly the MEMS is the cheapest 'timer' that we have - namely it switches off after about 5 minutes. So the cheapest, simplest circuit would be a relay, taking power from the purge valve, and an LED to report when the pump is on or off.
How difficult would it be to introduce a degree of temperature control from the blue temperature gauge temperature sender? And just as importantly, how expensive?
And one more very important question: how consistent is the MEMS power down duration? Always 9 minutes/ sometimes more/ sometimes less?
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Post by Bruce on Mar 10, 2004 10:42:28 GMT -5
<<And one more very important question: how consistent is the MEMS power down duration? Always 9 minutes/ sometimes more/ sometimes less? >>
I did the Carl power delay mod for my windows some considerable time ago and at the same time fitted an LED which shows up while the MEMS is powered up after switch off. The time the MEMS is powered seems to depend on the temperature of the engine. I have never had more than 9 minutes but a stone cold car will only keep the MEMS powered for a second or so after switch off. The LED is really usefull in that I can check from my house if the MEMS relay is stuck on. Of course, since I fitted it the d**n thing has never played up again!
Sent you a separate e-mail on the Water Pump electrics Rob. Is it possible to insert a Word Doc on these pages?
Bruce
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Post by Rob Bell on Mar 10, 2004 10:55:14 GMT -5
I'll convert it to html Bruce, and put the link here shortly...  |
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Post by Rob Bell on Mar 10, 2004 11:13:33 GMT -5
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Post by Bruce on Mar 10, 2004 13:41:57 GMT -5
My manual states on at 102 and off at 96 degs C
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Post by Rob Bell on Mar 10, 2004 14:00:49 GMT -5
My manual states on at 102 and off at 96 degs C Which is identical to the Lotus cooling circuit! [see above] |
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Post by Rob Bell on Mar 24, 2004 7:38:14 GMT -5
Bruce, a little update. I've contacted Roy regarding your cunning plan regarding the water pump controller. He's still got some contacts at Longbridge, so he's going to try and find out a little more about the MEMS power down - namely what were the design parameters of the set up - particularly, how long it was designed to remain on and what tolerances were applied...
I think that this is the way forward - let's hope that someone at Longbridge can help us out with some more information! ;D
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Post by dave on Mar 24, 2004 7:50:38 GMT -5
Good work Rob.
The last time I spoke to Roy I suggested that we potentially test this method out at Silverstone with the green car, if Marvin's agreeable. This would help us move forward a little more quickly. Can you give that idea another push when you talk to Roy again?
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