Cooling fan

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Discussion

trackerjack

Original Poster:

649 posts

183 months

Monday 1st September 2014
quotequote all
Can anyone help me please?

I wish to have my cooling fan run on after switching the engine off as the MK1 1.6 engine has an HSK turbo and I want it to continue blowing until the thermo cuts it off, I would rather use the cars inbuilt thermo than add another but how can I energise the switch with out the ign circuit?
Obviously I am not a leccy man!

VladD

7,853 posts

264 months

Monday 1st September 2014
quotequote all
In simple terms I think you need to run the positive wire from the fan thermotsat straight to the battery, rather than having it part of the ignition circuit. A bit of a pain when the battery is in the boot. Better people than me will tell you if you need to add an in-line fuse or other such safety measures.

Google for a wiring diagram, as that would probably be useful.

trackerjack

Original Poster:

649 posts

183 months

Tuesday 2nd September 2014
quotequote all
You know I never thought of that, so simple its so obvious and I love simple cos its all I understand!

Yes just a fuse and live wire.
The car is a special so I have the battery in the front so not far away.

MX-5 Lazza

7,952 posts

218 months

Tuesday 2nd September 2014
quotequote all
Do you really need it? How often will you be parking up after a good hoon with sky high temperatures without having driven for a while at more moderate speeds which would cool everything down anyway?

I'd say it would be better to concentrate on keeping coolant & (more importantly) oil temperatures down while running i.e. fitting an oil-cooler and better rad. Keeping the fan running after switching off the engine doesn't help much anyway as it will only be cooling the radiator. The water pump won't be running so it will be doing nothing to cool the engine and the oil pump won't be running so it also won't be cooling the turbo.

skinny

5,269 posts

234 months

Tuesday 2nd September 2014
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as above, you'll only be cooling the radiator.

VladD

7,853 posts

264 months

Tuesday 2nd September 2014
quotequote all
You could get a turbo timer that keeps the engine running for a while and then shuts off when the engine has cooled?

Demon Tweeks

MX-5 Lazza

7,952 posts

218 months

Tuesday 2nd September 2014
quotequote all
Or just drive sedately for a couple of miles before parking up...

skinny

5,269 posts

234 months

Wednesday 3rd September 2014
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or fit an electric water pump

trackerjack

Original Poster:

649 posts

183 months

Thursday 4th September 2014
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Its in a seven type kit car and as this type of car is narrow I have an alloy rad which is non standard.
It has a fibreglass bonnet which is close to the turbo (which is lagged) but still gets mighty hot and the fan is to keep air running over the engine to avoid a hot spot.

The car does not run hot but I have not put it on track yet.

Thanks for the replies and all I have to do is replace the ign live with a battery live with a fuse protecting and it will continue as it does on most modern cars.

skinny

5,269 posts

234 months

Thursday 4th September 2014
quotequote all
ahh if it's more for air circulating round the engine bay than water cooling necessarily, then carry on! smile

trackerjack

Original Poster:

649 posts

183 months

Thursday 4th September 2014
quotequote all
Yes thanks it has really been helpful picking you guys brains, the car is a hoot to drive and quite the quickest car I have had as it weighs just 650kg with an output of approx 170bhp so 60 comes up in 4 sec or so and took me 3 years to build.
The boss has an immaculate Mk1 so technically we are a 2 MX family but hers is a standard 1.6 and though very nice to drive and be in its not fast but fast enough.

VladD

7,853 posts

264 months

Friday 5th September 2014
quotequote all
trackerjack said:
Yes thanks it has really been helpful picking you guys brains, the car is a hoot to drive and quite the quickest car I have had as it weighs just 650kg with an output of approx 170bhp so 60 comes up in 4 sec or so and took me 3 years to build.
The boss has an immaculate Mk1 so technically we are a 2 MX family but hers is a standard 1.6 and though very nice to drive and be in its not fast but fast enough.
Fancy posting a picture?

MX-5 Lazza

7,952 posts

218 months

Friday 5th September 2014
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VladD said:
Fancy posting a picture?
Or a series of pictures? biggrin

Arbs

143 posts

174 months

Friday 5th September 2014
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Wouldn't switching the feed to a perminant feed just mean the fan runs all the time? As I see it, the ecu reads the coolant temp determining when the fan kicks in and out. If you turn the ignition off at the key the ecu will shut down and the fan will just run till the battery dies?

VladD

7,853 posts

264 months

Friday 5th September 2014
quotequote all
Arbs said:
Wouldn't switching the feed to a perminant feed just mean the fan runs all the time? As I see it, the ecu reads the coolant temp determining when the fan kicks in and out. If you turn the ignition off at the key the ecu will shut down and the fan will just run till the battery dies?
I assumed that the fan switch had a built in thermostat, but if that's not the case, then you're right, it's a lot more complicated.

cwinterb

82 posts

180 months

Friday 5th September 2014
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Relay with a built in switch off delay and a push button on the dash to start it off, or if you're cleverer trigger it on the ignition switch off?

Something like this:

http://www.autoelectricsupplies.co.uk/product/836/...

Edit: This sounds like what you need, if you can find one in the UK:

http://www.wolstentech.com/products/timedelayrelay...


Edited by cwinterb on Friday 5th September 16:52

trackerjack

Original Poster:

649 posts

183 months

Monday 8th September 2014
quotequote all
Picture request is a yes and the old fart in the car is me.
The original donor was PPC magazine owners brother and the quest was to get as much power as they could. The car was a 1990 Mk1 and reputed to kick out about 170bhp and I reckon it certainly feels like it does.
First picture is the other toys with my wifes superb 1991 MK1 import my 944 (big brother to the MX5)and on the right is my track Quantum 2+2 RS turbo.
I have learnt that the fan operates without ECU intervention by means of the thermo earthing out to create the relay trigger. I can merely supply the relay seperately with a live wire and hey presto it will run all the time the thermo earths the relay.









trackerjack

Original Poster:

649 posts

183 months

Monday 8th September 2014
quotequote all
cwinterb said:
Relay with a built in switch off delay and a push button on the dash to start it off, or if you're cleverer trigger it on the ignition switch off?

Something like this:

http://www.autoelectricsupplies.co.uk/product/836/...

Edit: This sounds like what you need, if you can find one in the UK:

http://www.wolstentech.com/products/timedelayrelay...


Edited by cwinterb on Friday 5th September 16:52
Special thanks to you sir for finding these products as the rear heated screen in my Porsche 944 has emptied my battery twice now!
Both can be used for the fan and I may still do that.

Someone had to buy the 1980's MG Montego and I was that man as it suited the family then and was one of the first cars to keep its lights and interior lights on as you left the car, I remember several people saying "Oh you left your lights on", however the quickest thing on an MG Montego was the trip to the scrapyard in the sky.

VladD

7,853 posts

264 months

Monday 8th September 2014
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Great car collection Jon. Thanks for the pictures.

pewe

648 posts

218 months

Monday 8th September 2014
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As mentioned above keeping the rad fan running will not cool the turbo when stationary.
Problems arise by not allowing the turbo to spool down (given it's spinning at 100k + revs) before switching the engine off.
Simplest solutions:- a) use fully synth oil - much less likely to break down when subjected to turbo heat,
b) allow at least one minutes idle after a high speed run (aren't they all?)
c) introduce a secondary oil pump on the oil flow to the turbo controlled by a thermo switch.
The last one has been contemplated by tecchie son and I for some time but seems a bit sledge hammer compared to allowing spool-down time.
HTH.
Cheers, Pewe
Mk1 s/c 161