The Mitsubishi Pajero Owners Club®

[peteinchad]

It is well known that the temperature gauge in Pajeros is quite naff so I decided to make a better one.

Now, I know that loads of people have fitted extra temperature gauges by fitting an adapter into the top radiator hose and screwing in a temperature sender and connecting it to a gauge.

There are two problems with this (1) it measures the water temperature and (2) it cannot measure the temperature if you lose your coolant because the top hose will not have water in it and the sender will be in air.

This method measures the actual temperature of the metal in the cylinder head - known as a CHT (Cylinder Head Temperature) gauge. It also allows you to set an alarm temperature to sound a buzzer if the cylinder head temperature rises above the chosen temperature.

The CHT gauges I have seen are quite expensive to buy complete but are reasonable easy to make.

Firstly you need a THERMOCOUPLE (a K-Type one because it has a measurement range suitable for cylinder head temperatures) with a washer fitting on one end. This one is on fleabay at about a fiver. You will need one about 3 metres long - you cannot extend the thermocouple wire with ordinary wire because it will not work properly so make sure the one you buy is long enough.





You will also need a PID ( Proportional Integral Derivative) controller - don’t worry about the ridiculous name - it only needs four wires connecting. About £20 from fleabay.





Bolt the end of the thermocouple to a bolt on the cylinder head.





Run the stainless steel braided thermocouple cable along the engine and through the bulkhead.








Now it is a simple matter of connecting the power wire from the ignition terminal and an earth wire to the terminals that are marked on the back of the PID.

Connect the two thermocouple wires to the marked terminals on the PID - making sure you connect them the correct way round (one is positive and one is negative)

There are menus in the PID to set the type of thermocouple (set it to K type)

Other menus allow you to set the alarm temperature - I set mine to 90. I was surprised that the PID remembers the alarm temperature you set even when it is turned off. Once you have set up the PID then it doesn’t need setting up again. When I was testing the PID, I set the alarm temperature and then switched it off for over a week and it still remembered the temperature I set.





The menus seem confusing but just follow the instruction manual that comes with the PID and it’s fairly easy to set up.

There is a light on the PID that illuminates when the alarm temperature has been reached and there are two terminals on the PID to fit a buzzer if you want an audible alarm.

Now you know what temperature your cylinder head is and an alarm if it gets too hot. It works even if you have lost some of your coolant.

I hope someone finds this useful and that it saves another cylinder head from cracking.

[Google]

[peteinchad]

I forgot to mention:

Make sure that you buy a PID that works on 12V.

They come in all sorts of voltages from 12V up to 415V and they all look identical - obviously for our trucks we need a 12V one

[Allrounder]

Hello.

Nice looking and useful. I'm wondering, what kind of temperatures do you get, while driving?

I mounted an EGT (also K-Type), which is kinda same system, just not fitted it directly to cylinder head, but through EGR blank plate.
From the reading on the net, It should measure the temperature of the last two cylinders, before the gases go to the exhaust.

But never got temperatures under 90, while driving. 90 is when you idle it in the morning, that it heats up...
So it sounds interesting to me, why this difference. Different sensor, or just different mount for measuring...

[peteinchad]

I only got it working yesterday and went for a drive round the block - it got to high 60's centigrade and the original gauge was showing half way up to normal.

Maybe yours is reading correctly - perhaps the temperature of the inlet gases is that high because it has to go through the turbo which I assume is very hot (looking at the number of heat shields on it!)  and I doubt if the intercooler actually cools it that much.

If we are both using K-type thermocouples then I would have thought that they would both be accurate and maybe it is because you are reading the inlet gas temperature whereas I am measuring the temperature of the metal head (and I am measuring it on the opposite side of the head from the manifolds)so mine should read less than yours.

What type of meter have you got connected to the thermocouple? - I decided on a PID because it compensates for the different junction temperatures at each end of the thermocouple.

Also - did you extend the thermocouple cable? I'm not sure if you know that they cannot really be extended unless you use identical wire because it introduces another junction which throws the accuracy out of the window (apologies if you know this already)

I will take the truck out for a longer run and see what temperature it reads and let you know

[peteinchad]

I only got it working yesterday and went for a drive round the block - it got to high 60's centigrade and the original gauge was showing half way up to normal.

Maybe yours is reading correctly - perhaps the temperature of the inlet gases is that high because it has to go through the turbo which I assume is very hot (looking at the number of heat shields on it!)  and I doubt if the intercooler actually cools it that much.

If we are both using K-type thermocouples then I would have thought that they would both be accurate and maybe it is because you are reading the inlet gas temperature whereas I am measuring the temperature of the metal head (and I am measuring it on the opposite side of the head from the manifolds)so mine should read less than yours.

What type of meter have you got connected to the thermocouple? - I decided on a PID because it compensates for the different junction temperatures at each end of the thermocouple.

Also - did you extend the thermocouple cable? I'm not sure if you know that they cannot really be extended unless you use identical wire because it introduces another junction which throws the accuracy out of the window (apologies if you know this already)

I will take the truck out for a longer run and see what temperature it reads and let you know

[peteinchad]

Sorry for the double - post! - not sure what happened there!

[Allrounder]

Interesting.

As I was talking with the others, mostly Toyota HDJ 80 drivers, that are using same EGT, they have normal temperature at idle between 90 and 100 degree Celsius, when warming up. Normal warmed idle around 150C, driving on highway, flat, 100 km/h (60mph) around 300-350C. I'm having almost the same results. And they are still saying, that 2.8 Mitsu engines are designed for cool working.

To compare with 5.9 V8 4x4 engine, they almost double numbers. But you can't compare it properly (petrol, different compression ratio...)

Test it and let me know.
Were there any instructions next to the PID and sensor, where to mount it?

P.s. - I' using auberins kind of K-type sensor with weld in end.

Have a nice day!

Nejc

[davembp]

I have an infer-red thermometer and reads 99dC when pointed on exhaust manifold at idle.

[peteinchad]

I think the best way to go is to run the car and just take a note of the temperature - if the car is OK then it doesn't really matter what temperature it is showing. If the maximum temperature rises more than it normally shows then maybe that will indicate a problem.

I am going to run my truck until the original temperature gauge shows normal and then set the alarm on the PID to 5 C above that - hopefully that will give me some notice of overheating. It's a matter of trial and error I think.

I would like to invest in one of those Infra Red thermometers to check that the thermocouple is reading correctly - but other things need sorting first.

The PID came with instructions but the thermocouple was just in a bag. I got the bolt-on one because there are a couple of Aussie firms selling the same sort of system and they use the bolt-on ones. The PID is designed for operation with kilns and ovens and will take different types of thermocouple - I opted for a K-type because it's temperature range is suitable for the temperatures found in a car engine.

I would have thought that your readings are correct - I would expect the inlet gases to be much hotter than the metal of the cylinder head because the head is water cooled.

[peteinchad]

So it seems like Allrounder's temperature measurements are about right.


This is the problem with this project - it is easy to measure the temperature - either the gases in the manifold or the temperature of the actual head metal. It is not so easy to know what a "normal" temperature should be!!!

[Simon_W]

Brilliant!    
I like that a lot.  There's something very similar called Engine Watch, an Australian product. It's about £80 in UK money, and yours looks like it offers almost the same functionality for a fraction of the cost.

[Allrounder]

The normal temperature probably is known only for the Mitsubishi development sector staff.    I couldn't found it in any engine manual, instructions or on the web.

[jimmyw]

Thats a very good idea,but do you know does the coolant heat up quicker or does the outside of the engine? No harm in knowing what is going on with regards to temperature either way though. I learnt that the factory gauge is rubbish the hard way also  

You can buy thermocouple wire in a fairly big spool fairly cheap,and make your own,it's kind of fun too. Something on the long finger for me at the minute is to have an LCD on the dash which gives a readout of just about everything,brake temps,tyre pressure shock temps,coolant ,egt and all that fun stuff,just for a bit of fun and to see what is actually happening. However that will never get done  

[peteinchad]

The Aussie "Engine Watch" gave me the idea but it seemed physically a bit big to fit in my dashboard - I think mine does most of what that does but iirc it also has an oil alarm. I have oil pressure and temperature gauges fitted - but once again I don't really know what "normal" readings for these are.

I don't know whether the water or the metal heats up more quickly but I just assumed that the metal is the bit that warps - so that is what I am hoping to measure. I've had one cracked head and it was really expensive to get fixed!

I would love an all-in-one display to read everything but my little brain seems only to be able to manage meters that only read one thing at a time.

I think Allrounder is correct - the "normal" temperatures are probably only known by the people who designed the engine. I have searched but cannot find any definitive answers.

[peteinchad]

Next thing is a mpg meter!

I sometimes wish these trucks had OBD2 !!!!


But then again - do I want to know how few miles I get to a gallon of diesel?