Measuring engine temperature with an infrared thermometer
Discussion
They all change, as the stat opens/closes, fans come on & thats just a steady(ish) state tickover. Applying throttle at standstill, whipping up the bonnet after a fast run all yield quite interesting differences.... Measuring all round the engine also gives quite diverse readings (even only considering where you are close to the water jacket). Hence my scepticism over temp sensors & gauges, if it gives you an idea of hot/cold running and overheating its fine IMHO, people recently seem to be developing a paranoia about some kind of accuracy?
Dave
idling (+occasional revs): 75-85C stat housing, 73-90C SwirlTank, 70-84C rad top hose, 60-70C rad bottom. Thats in garage pretty cool weather.. 82C winter stat, but low otter switch in rad outlet. Think they vary rather a lot. I tried once to make a spread sheet of all the temps, but the basis is changing all the time, and I could only measure 1 point at a time so it became a bit pointless, you can only accurately compare a couple of measurements at a time I reckoned.
Dave
idling (+occasional revs): 75-85C stat housing, 73-90C SwirlTank, 70-84C rad top hose, 60-70C rad bottom. Thats in garage pretty cool weather.. 82C winter stat, but low otter switch in rad outlet. Think they vary rather a lot. I tried once to make a spread sheet of all the temps, but the basis is changing all the time, and I could only measure 1 point at a time so it became a bit pointless, you can only accurately compare a couple of measurements at a time I reckoned.
The interesting thing with these measuring devices is “Emissivity” which can make different materials of the same temperature register a different result. An example of this would be to bring two samples of aluminium one polished and one black anodised to the same temperature. The Emissivity would be different and therefore the remote sensor (measuring the infra red light radiated) will produce a different result to a pair of contact sensors. For that reason they are better for comparative measurements of the same material, like temperature across the tyre tread.
Having said that they are very useful and with the engine up to temperature the general thermostat area tends to agree quite accurately with the dashboard gauge on my car.
Having said that they are very useful and with the engine up to temperature the general thermostat area tends to agree quite accurately with the dashboard gauge on my car.
The reason I've got one is due to (what I believe is) an over enthusiastic temp gauge.
It reads at 90 when travelling at speed, i.e. motorway and about 100 when in traffic. The PO has confirmed that it's always done this since he owned the car. The fans cut in and out as they should. I just want to check that it is over reading first before forking money out on thermostats, senders, etc
It reads at 90 when travelling at speed, i.e. motorway and about 100 when in traffic. The PO has confirmed that it's always done this since he owned the car. The fans cut in and out as they should. I just want to check that it is over reading first before forking money out on thermostats, senders, etc
I Think that the issue here is feel good factor.
There seems to have been many posts re temp and over heating including myself. As has been previously stated the gauges are not very accurate and should be a guide. If we had green, amber and red on our guages we would look at what is normal for our particular car and not worry too much as long as it didnt go into the red.
What seems too make this worse on our P&Js is that sender seems too have a wide range or temp readings due to its siting either in the cold air flow or where it is in the coolant flow.Which shows a wide range of temperature readings depending on outside weather temps or if sitting in traffic. I think the best we can hope for is for a consistant reading and it appears that using the 'UNUSED sender with a resistor may provide this.
As long as you dont have an over- heating issues and I am sure we would all know the best we can do is too set to a consistant reading somewhere in the middle of the dial. As long as it doesnt move too much then all should be OK.
I think it is unrealistic to get the guage to read exactly what can be read using a external reader across the range
I haven't done this mod as I am trying not too get paranoid about engine temp .
It is early days in my TVR ownership though!
Trev
There seems to have been many posts re temp and over heating including myself. As has been previously stated the gauges are not very accurate and should be a guide. If we had green, amber and red on our guages we would look at what is normal for our particular car and not worry too much as long as it didnt go into the red.
What seems too make this worse on our P&Js is that sender seems too have a wide range or temp readings due to its siting either in the cold air flow or where it is in the coolant flow.Which shows a wide range of temperature readings depending on outside weather temps or if sitting in traffic. I think the best we can hope for is for a consistant reading and it appears that using the 'UNUSED sender with a resistor may provide this.
As long as you dont have an over- heating issues and I am sure we would all know the best we can do is too set to a consistant reading somewhere in the middle of the dial. As long as it doesnt move too much then all should be OK.
I think it is unrealistic to get the guage to read exactly what can be read using a external reader across the range
I haven't done this mod as I am trying not too get paranoid about engine temp .
It is early days in my TVR ownership though!
Trev
Just thought I'd give you an update after taking the temp readings.
I checked the temperature of the thermostat housing a few times on Saturday when the car had been sitting in traffic with an indicated temperature of 100 on the gauge.
The readings were 86/87 degrees everytime.
The thermometer is from Maplin and cost me about 20 quid. Well worth the money if you have any doubts about the accuracy of your gauge.
I checked the temperature of the thermostat housing a few times on Saturday when the car had been sitting in traffic with an indicated temperature of 100 on the gauge.
The readings were 86/87 degrees everytime.
The thermometer is from Maplin and cost me about 20 quid. Well worth the money if you have any doubts about the accuracy of your gauge.
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