Thread: EGT 300Tdi

Originally Posted by rangieman

As in short probe i mean about 5mm which is the one ive fitted that came with the kit
The longer probe well i scored two different lenghts , one which is 50mm and the other is 150mm in length
So im thinking the one at 50mm would do the job just right

From memory, 50mm is not going to get even close to the gas stream if mounted on the egr blanking plate.

A 5mm probe is only going to measure the temperature of the manifold, not the exhaust gas. A 50 mm probe will be a bit better but is still shield from the gas stream.

Tests comparing 3mm probes to 6mm probes for measuring exhaust gas temps in a 300Tdi have shown 6 mm probes don't record the peak temps because they don't respond quick enough.

The false results from not measuring the temp in the exhaust stream could lead to engine/turbo failure - especially if you put a load on (such as a trailer) and think that 700 - 750*C is ok for a short duration, or do not notice the temp. I assume you have installed a thermocouple with the intention of turning up the fuel - you will find the max temps reach with an empty vehicle are much less than with a load on.

The thermocouples that Ian supplies in the thermoguard kit have a straight length of 65mm and I believe they only reach to the opening into the pocket.

Like Azza, I don't like to straighten them to gain longer reach.

I have been involved with installing many thermocouples into pipelines in industrial plants. Normal practice is to set them up so the end is at the centreline of the pipe.

Hi Guys,
From the MADMAN EMS view your should not exceed 740 (from memory) on a 300tdi. What kind of thermo are you using, can you post a picture. Also if you are unsure double check that the earthing is done best place is engine block or back to battery.
Cheer
TheEntertainer

Originally Posted by TheEntertainer

Hi Guys,
From the MADMAN EMS view your should not exceed 740 (from memory) on a 300tdi. What kind of thermo are you using, can you post a picture. Also if you are unsure double check that the earthing is done best place is engine block or back to battery.
Cheer
TheEntertainer

What earth are you talking about?

Thermocouples won't work properly if either lead is earthed - the instrument measures the voltage difference between the leads - the voltage is created when the junction of dissimilar metals is heated. Doesn't matter about the casing of the probe - it just protects the vital internals.

Accuracy/calibration can be affected by adding an extension to the leads - special thermocouple leads/connectors must be used, but the leads on the thermocouple should have been long enough in the 1st place.

Originally Posted by Bush65

<snip>

Tests comparing 3mm probes to 6mm probes for measuring exhaust gas temps in a 300Tdi have shown 6 mm probes don't record the peak temps because they don't respond quick enough.


<snip>

John, any idea how much a difference between the 3 and 6mm probes in peak temp readings ?
I'm starting to think this may account for some dodgy oil tests (I'm guessing high aluminium and silicon = hot piston)

Having said that, the probe Ian supplies is pretty sensitive, the slightest feather on the throttle gives an instant reaction on the readout.

Hi John,

It is best to earth the unit back to the battery or engine block, well that is one the EMS units and I would think that this unit works in the same way, this way you can be certain the earth is a good solid earth. Does that add up?

I have longer Pyro probes, 100mm so if you would like a longer one let me know, they can be cut down to size.

Cheers

The Entertainer

Originally Posted by TheEntertainer

Hi John,

It is best to earth the unit back to the battery or engine block, well that is one the EMS units and I would think that this unit works in the same way, this way you can be certain the earth is a good solid earth. Does that add up?

I have longer Pyro probes, 100mm so if you would like a longer one let me know, they can be cut down to size.

Cheers

The Entertainer

The 100mm probe should be about the right length , I have a 50mm and 150mm probe , ill be using the 150mm probe and just bend it out of the way
Ive been told you can not cut the probes down
Ill put pics up in the next few days of the probe install

Originally Posted by rick130

John, any idea how much a difference between the 3 and 6mm probes in peak temp readings ?
I'm starting to think this may account for some dodgy oil tests (I'm guessing high aluminium and silicon = hot piston)

Having said that, the probe Ian supplies is pretty sensitive, the slightest feather on the throttle gives an instant reaction on the readout.

The problem is the response time and missing high peaks when the temps are rising quickly.

This thread on LR4x4 has some useful info - see John Barge's (Red90) posts and the various tests by Tony C. (white90).

Originally Posted by rangieman

The 100mm probe should be about the right length , I have a 50mm and 150mm probe , ill be using the 150mm probe and just bend it out of the way
Ive been told you can not cut the probes down
Ill put pics up in the next few days of the probe install

When bending the probe, use something large in diameter as a former to bend it around. Otherwise you can kink the sheath and damage the insulation/leads inside.

Thermocouples work on the principle that a small voltage is induced at the junction of dissimilar metals when heated. In my experience, thermocouples have the junction very near the tip of the sheath.