Fan operating temp?

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trolleybus
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Fan operating temp?

#1 Post by trolleybus » Sun Jan 31, 2016 10:53 pm

OK lets try again.

If one fitted an electric fan with the option of an on temperature and an off temperature setting, what would these settings be?
Bernard (Australia)
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johnconradlee
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Re: Fan operating temp?

#2 Post by johnconradlee » Mon Feb 01, 2016 9:13 am

My electric fan thermostat broke a while ago so I've been switching it on and off with the override switch for the last year and a half so this has reminded me I ought to fix it before the summer! :idea:

Anyway the standard thermostat opens at 82°C plus or minus 2°C, so the fan needs to come on after this (as up until this point there won't be any water going through the radiator) and is fully open at 95° so I'd suggest a somewhere in the middle. On at 87°C off at 82°C might be a place to start.

As I said I need to buy a new one at some point soon I'd be interested to see what other people say.
John Lee

1966 Triumph 2000 Mk1 "LuLU" (the Lee family Triumph) - various shades of Green and rust - The engine runs, she's alive!!!!

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trolleybus
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Re: Fan operating temp?

#3 Post by trolleybus » Tue Feb 02, 2016 3:03 am

Thanks John,
This proves when one asks the the right question one gets the right reply.
Cheers,
Bernard (Australia)
1977 2500 TC Auto EFI
1956 TR3 since 1980

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Re: Fan operating temp?

#4 Post by Dazzer » Tue Feb 02, 2016 2:45 pm

Hi John

Thanks for that John. I to have ran my rally car for the last five years with no thermostat switch. But I have a problem with over cooling.

When I put the cooling system back together as a belt and braces job I had the standard rad re cored with an extra row of off set cores, I also fitted one of the rather expensive racestorations high output water pumps.
I dont run a manual fan just a kenlowe electric pusher. But its very rarely on.

It cools OK just a little bit too well!

Basically the fan is only on when stationary for any length of time or when thrashing on tight tests.

The car runs at temp when stationary but get moving on the open road and it drops down to 70s and below.

When I rebuild it this time round I'm going back to a standard rad and will implement an electric switch at the temps recommended.

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Re: Fan operating temp?

#5 Post by Mike Stevens » Wed Feb 03, 2016 1:03 pm

I think it's important to control the fan with temperature for a number of reasons -

1. You want to keep the engine temperature at 'optimal', somewhere around the thermostat temperature as that is trying to control the water temperature too.

2. The fan draws some power (maybe 50-100W) and this power comes from the engine - you want this power to go to the wheels really!

3. You will lengthen the life of the fan.

There are plenty of ways to control the fan, both manual and automatic. Manual requires a constant eye on the temperature gauge - which you don't really want to do on a stage! There are also lots of automatic methods too.

Good luck!

Cheers,
Mike.
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Re: Fan operating temp?

#6 Post by leesellars » Wed Feb 03, 2016 2:54 pm

Hello friends

On my Rally car it has an 82* in and that is where it starts to open. Its fully open at 90*. So I have an 92* fan switch with Manual override. As you know its only on when in traffic. But I use the manual Overide as soon as we come off stage to stop residual heat build up. Until we have a road section where I put it back to normal. I use a 14" revolution fan in front of the radiator.

Lee
Triumph Mk2 PI 1975
Triumph TR6 PI 1973

Clifford Pope
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Re: Fan operating temp?

#7 Post by Clifford Pope » Thu Feb 04, 2016 11:45 am

I think this debate tends to forget that the purpose of the fan is to control the radiator temperature.
The engine temperature is not regulated by the fan, but by the thermostat.
The purpose of the radiator is to dump into the air the heat that is passed to it by the thermostat.

So as long as the radiator temperature is lower than the engine temperature, heat can flow from the engine to the radiator. On a hot day or when the engine is working hard, the radiator/fan needs to have enough capacity to dispose of the excess heat.

It doesn't matter how low the radiator's temperature is, because it will only cool the engine to the extent that the thermostat opens to allow flow. But it is inefficient if too low because that means the fan is needlessly absorbing energy.

So the conclusion is that the thermostat ideally responds to engine temperature, but the fan responds to radiator temperature. Hence the debate about whether to mount a Kenlowe thermostat in the top hose, bottom hose, or radiator surface.
A thermostatic fan does none of these, but responds to the temperature of the air passing through the radiator - not necessarily the same as the temperature of the radiator itself.
And controlling the fan cut in by reference to the engine temperature would be the worst of all, because they are not related.

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Re: Fan operating temp?

#8 Post by Mike Stevens » Thu Feb 04, 2016 12:47 pm

Hi Clifford,

While I agree with you in principle and that (your last sentence) while it is true that while the engine temperature is lower than the thermostat temperature the radiator and engine temperatures are not related, I'm not sure that's true when the thermostat is fully open. At that stage, the engine temperature is no longer being controlled by the thermostat so the radiator and engine temperature will be closely related! In this state, controlling the fan from the engine temperature is therefore probably OK.

In fact, this is an engine over-heat condition (as Lee describes when in traffic or just off from an energetically driven stage!) which is just when you want the fan to come on!

When the thermostat is in control, it is regulating the coolant flow through the radiator and as long as it is not fully open, there is no need for a fan, only when the 'stat becomes fully open and when the temperature is rising is when you might want the fan to increase the heat dissipation capability of the radiator - just as Lee has it set!

Just some thoughts while sitting eating my lunch!

Cheers,
Mike.
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1973 2.5PI Saloon rust some Honeysuckle
1973 Stag French blue
(1949 LandRover was blue should be light green!)

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Well.....

#9 Post by sprint95m » Thu Feb 04, 2016 3:15 pm

Clifford Pope wrote:And controlling the fan cut in by reference to the engine temperature would be the worst of all, because they are not related.
Using the measurement of the coolant temperature as it departs the engine is pretty much how manufacturers do this now I believe,
whether it be for setting the petrol/air mix ratio in an EFI or determining when the fan should come on.
With the latter, the fan is triggered at that certain point because it is reasoned that the coolant leaving the radiator has not been cooled enough.


Rather than using a constantly driven water pump, a more efficient alternative is to use an electric pump.
The EWPs (in conjunction with a controller) only run when needed. The controller can also be used with an electric fan. No thermostat is employed.
The chief advantage of such a system is its ability to deal with excess heat efficiently when the car and engine is slowed, e.g. sitting in traffic having
just departed the motorway.
The EWP can be wired to continue after the ignition is switched off.


Another valuable tool is a header tank. This should be positioned higher than the engine.
It has an intake for venting from the engine's cooling system high point and
an outlet plumbed into the bottom hose before the water pump. This plumbing arrangement is to prevent pump cavitation.

Having just said that though,
given that T2000s have cast iron blocks and cylinder heads and are blessed with a decent water pump, cooling fan and radiator,
an EWP or a header tank offers no real advantage here reference the actual cooling.


The need or otherwise for an engine oil cooler is a whole new discussion :D .......
Owner of a 1979 Dolomite Sprint (EFI),
previously ran for nine years a Dolomite (1850), a 2500S (for 4 years), a Dolomite 1500HL (for a few months),
a Dolomite Sprint (for 10 years) and a second 2500S (for 5 years until 2007).

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Yes......

#10 Post by sprint95m » Thu Feb 04, 2016 3:25 pm

trolleybus wrote:OK lets try again.

If one fitted an electric fan with the option of an on temperature and an off temperature setting, what would these settings be?
I concur with John....
http://www.carbuildersolutions.com/uk/f ... c-m14-x-15

There is a but however,
normally these are fitted into a joiner within the top hose but a T2000's top hose is not conducive to this.
You may have to fit a T-piece into the temperature gauge sender's tapped hole for this sender and said temperature gauge's one instead?
Owner of a 1979 Dolomite Sprint (EFI),
previously ran for nine years a Dolomite (1850), a 2500S (for 4 years), a Dolomite 1500HL (for a few months),
a Dolomite Sprint (for 10 years) and a second 2500S (for 5 years until 2007).

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