Temperature gauges - ROBIN
I have been reprimanded for suggesting that these may not be necessary.
I must make it clear that they are essential,like clocks are essential.
But like clocks they are only of any use if they are accurate..which is my point.
I want to know the temperature in the cylinder head of my engine in real time.Thats coolant exit temperature,by the way.
I would also like it expressed in some internationally standardised unit of measurement.......degrees centigrade will perfectly well suffice.
I have several thermometers about this place for various purposes even the inexpensive ones manage to be accurate to less than one degree,so this is hardly a matter for another million dollar development programme.
Re: Temperature gauges - David W
As the only person to post after you on that thread I feel I must take responsibility for the "reprimand".

My point was simply that having a temperature gauge could save an engine.

I would like to speak more broadly of car temperayture gauges but will stick to one car where I know several examples well.

On the Citroen Xantia TD the coolant temperature gauge is marked (as you require) in degrees centigrade between 60 and 110 degrees. The markings are such that it is possible to see a movement of as little as 2.5 degrees.

From the many times I have changed the coolant, filled, bled, heated up, tested thermostat opening temperature and finally coolant fan cut in temperature on these engines I can confirm the gauge is accurate enough and certainly reacts in seconds rather than minutes.

In the real world driving experience this enables you to see a potential overheat situation and take appropriate action to increase cooling or reduce engine load. This improvement is soon shown by the gauge.

What more do you want?

David
Re: Temperature gauges - ROBIN
I dont know which engine this is,exactly,but I DO know that on some xud applications the engine is seizing before the guage reacts.
The one in my 405 seems to be quick enough,although it is totally uncalibrated,the one in the petrol Mazda appears glued to the same spot whatever you do to the engine.This one I disbeleive!
My ,possibly erroneous, view of pressurised cooling systems was that you could run them several degrees above boiling point to improve heat dissipation to the coolant and reduce coolant volume and weight.According to every gauge I've looked at the engines are nowhere near normal boiling point,so we are still driving around with loads of unecessary coolant,poorly distributed,at too low a pressure.They didnt run piston aero engines like this....
Re: Temperature gauges - andy bairsto
The piston engine in my friends plane is a common Subaru car engine with normal car cooling.It is quite possible for an engine to cease up and the temp gauge stay put,this due to simple fact the water temp did not increase as in a piston or crankshaft failure it would happen to quickly.If you want all this accurate info fit sensors all over the place connect to a modem and then to your lap top and measure trends or what you will.In essence you will have Grand Prix car telemetry
Re: Temperature gauges - peter
One common failing is where the sensor is placed at a high point in the coooling system. Coolant level drops, sensor no longer immersed, reading is very doubtful thereafter.

If it is a significant drop in level even those sensors in the top hose eg Kenlowe Fan switches are short of accurate information.
Re: Temperature gauges - honest john
Andy and Peter are dead right. The temperature sensor in the old Jaguar straight six is at the front of the block. But this is a mixed metal block with a marked tendency to corrode internally if the coolant is not changed before the corrosion inhibitors degrade. The internal corrosion turns to sludge which blocks the waterways at the rear (gearbox) end of the engine, so overheating can occur there even though the sensor is reading a relatively normal temperature at the front of the block.

HJ
Re: Temperature gauges - Stuart B
Well I am siding with David W here in that why do you want a coolant temperature gauge to read an exact number of degrees?

Cars have quite different design thermostat opening temperatures for all sorts of reasons. so if you drive a car where the thermostat is set to open at say 80C and then leap into one which opens at 90C and you have an accurate temperature gauge, what do you do in the second car, panic cos you think its running hot? Personally its a case of keeping an eye on the normal situation and reacting when it is different.

Having said all that those who comment that because of a number of factors eg sensor positioning an indication of coolant temp is not that helpful I totally agree with. In any car I have had which had an oil temperature gauge, eg 205GTI, OK so it was not possible to get an accurate reading, but if the engine was working hard one could see the rise in oil temp and react accordingly.

Also it was surprising to see how long it took for the oil temp to register anything on a cold winter morning and again I used to adjust driving accordingly.

Bit like oil pressure lights, when it comes on its too late, but with a pressure gauge and a bit of intelligent interpretation its fine.

Dare I suggest the problem is the lack of intelligent interpretation these days.
Re: Temperature gauges - David W
Yep I'm saying they are near enough and useful Stuart.

Regarding HJs comment supporting Andy and Peter, it goes back to my comment about the Citroen /Peugeot engine on the other thread...

"The XUD engine isn't prone to problems, it's prone to operator induced failure..... helped by many not having temp gauges!"

David
Re: Temperature gauges - Bill Doodson
Hummm,

I have to agree with all of this. As an "engineer" I like to know whats going on with what ever it is I am trying to deal with. To pick on Robins point I want to know what the temperature is EXACTLY in oC. But David W is also right that for the car "or bike" as long as the indication is within the set limits of the manufacturer, well what does it matter if its 80, 90 or 100 as long as its in limits. HJ's, Andys and Peters points are the most valid, if its not reading correctly, no matter what the gauge indicates its as much use as a chocolate chisel.

I have spent the last couple of days trying to get a steam powered water heater to control correctly. The heat exchanger uses steam to heat water (radiator) and is rated at 600Kw (900HP)for the water and steam flow conditions involved. It has to heat about 10 litres/sec of water from 15C to 85C in about 2 seconds and then shut down and maintain 85 for between 1 and 100 seconds at varying rates for 8 hours per day. Once we have sorted the control loop out it will do it. We have to have the thermometer in exactly the correct position and it has to react in 10/s of a second. But it makes the thermostat in your car or bike look a bit sick.


Bill
Re: Temperature gauges - ROBIN
For the life of me I cannot see what the thermostat has to do with this.
It is a revoltingly crude and inaccurate device which merely stops water from entering the radiator until such additional cooling is necessary.
Unless I have not been keeping up with developments it is either open or shut,which cannot be right.It is prone to un-noticed malfunction,and has no bearing whatever on the normal running temperature of the engine or the recording of the magnitude thereof.
I repeat.this is a no-brainer,we need to know the coolant exit temp. from the head and we might as well have it in degrees C as anything else.
Re: Temperature gauges - Stuart B
ROBIN wrote:
>
> For the life of me I cannot see what the thermostat has to do
> with this.
> It is a revoltingly crude and inaccurate device which merely
> stops water from entering the radiator until such additional
> cooling is necessary.
> Unless I have not been keeping up with developments it is
> either open or shut,which cannot be right.It is prone to
> un-noticed malfunction,and has no bearing whatever on the
> normal running temperature of the engine or the recording of
> the magnitude thereof.
> I repeat.this is a no-brainer,we need to know the coolant
> exit temp. from the head and we might as well have it in
> degrees C as anything else.

Well excuse me for misunderstanding how cooling systems work but the purpose of a thermostat is according to my education
A) To control the flow of coolant into the radiator so as to ensure the engine reaches design operating temp as fast as reasonably possible, and
B) Once design operating temp has been reached to release sufficient coolant through the radiator to ensure the engine CONTINUES TO OPERATE AT IT'S DESIGNED TEMPERATURE.

If one has a stat which is stuck fully open for some reason the usual symptom is that the engine runs too cold with all the consequent ill wills that follow if that situation is left too long. Therefore one should realise that in normal operation the stat is part open and alters its opening according to the temperature of the coolant flow across it. It is not just an open or shut case. Engine heats up it opens a bit more, engine cools down less cooling is needed so it shuts a bit and cycles around this point.

Clearly there are two schools of thought, those who want an accurate reading in degrees C, and those who don't particarly want to know the absolute number of the temperature reading but want a gauge which reflects the situation with reasonable reliability. One opinion is not right and the other wrong its just a different opinion.

Quite agree that it might not be too difficult to sort out, so if I am in the minority I presume Robin will put inventiveness to good use and we can expect to see an after market kit produced so those who wish can see an accurate calibrated coolant temperature readout in real time. I wish you every success in your venture.
 

Ask Honest John Right column

Value my car