High EGT ?? & New Crankshaft.

[Boydie]

Okay, my engine is back in the Beast and once again its fully mobile, on a test run to the Mudgee wine festival the engine performed faultlessly and even going up Cherry Tree Hill (1075 meters above sea level and a 750 meter winding climb) the water temperature as indicated on my VDO guage never went above 95 degrees C, the EGT however did, right up to 780 C - I checked the thermocouple probe and is was'nt in contact with any part of the manifold and was fully within the exhaust gas stream. Prior to the new crankshaft going in it has never gone above 700 C.

The engine went to a second garage to be dyno'ed and the mechanic there commented that the probe should be immediatly downstream of the turbo and NOT before it as is in my installation and that it will give a higher reading by some 100 degrees over what the turbo is actually experiencing --- any comments on this?

So, question, given that the probe tapped into what would have been the exhaust gas recirculation blanking plate and therefore BEFORE the actual turbo is 780 C an acceptable temperature ?

Other readings were great, oil pressure 50psi hot and 15psi at idle. Boost running at 15 psi (14.7 actually) water temperature measured at the thermostat housing was 85 to 95 C.

Secondly, the new crankshaft, - a genuine LR part that caused a lot of consternation with the team of mechanics who were doing the job of installing it into the engine, the dowel on the crank flange was in the wrong location, that is it was in the dowel hole for a flywheel, not a flexplate, my Disco being a ZF auto.

Getting it out was a nightmare with the team settling on gringing it down and drilling it out, nothing would shift it so we can only presume that they are pressed into the hole with a massive hydraulic press.

A new dowel was turned up and pressed/tapped into the correct blank hole on the flange plate once a 0.75mm air bleed hole had been drilled through the flange to allow it to be pressed in.

The second consternation was once this had been done and the guys tried to fit the engine up to the ZF they found that the crank had a bronze bush pressed into the crank as if for a manual gearbox, so the engine had to lifted out --- again --- and the bush pressed out by filling the end of the crank and bush with bearing grease and using a suitable sized bolt that was a tight fit in the bush, one wack with a hammer and out it came. LR recon that there is ONLY one crank part number and that removal of the dowel and bush is a standard procedure so be warned.

[dirtydiesel]

Pre-turbo egts can be up to 150 degrees higher than post Turbo.

780c pre Turbo is near the top end of what's safe.

I'd worry about the proficiency of your mechanics if they failed to spot the spigot Bush after spending time messing around with the dowels.

[Nigelw]

I have spoken in depth with a guy I know who used to work on dyno test beds and yes that is normal to drop 100 degrees through the turbo, but 780 is bloomin high!!! He recommends no higher than 720 maybe 750 as it hits the turbine much over 760 you can get a problem with turbine blades loosing their strength and starting to stretch.

[Rangy35]

Yes the EGT is suppose to be after turbo, the turbo is still restricting air flow so there will be a build up of heat, move it to after the turbo and the reading could drop by as much as 80 degrees. I would say a 650-680 degrees is where you want to be, my personal preferred range. There will be someone more wiser than me along to give more info.

[Boydie]

Dirty, you could be forgiven for coming to that opinion but the guys who did the engine change are fully conversant with 300TDi and two of them are not only LR trained but were employed as service crews for the Camel Trophy trip in PNG, on top of this they used to partisipate in desert bashes in Oz until one smashed up his knee, they know their engines,

[Boydie]

^{I'll get the thermocouple checked}

[benthng]

Perplexing, supposing FIP and other settings is same old same old then performance and egt should not run out.

Maybe the fuel injection timing may have move a bit (retard) due to wear on the previous crank shaft keyway etc or if you have had it timed exactly per previous with piezo then ... different quality of fuel or engine oil?

Best regards, Ben

[Boydie]

The problem may be resolved, the guys who dyno'ed my Disco admit that they increased the fuel supply at the FIP, so as of tomorrow I'll close it off by 1/8 of a turn until its gets back to its former temperature, I tested the probe / thermocouple and it was-is spot on so if I gat it abck to its previous high of 720 degrees C at 14.7 psi boostat full throttle I'll be a happy chappie

[David Sparkes]

Doesn't thermocouple position rather depend on what you want to measure?

When used in high performance petrol engines I understood the concern was combustion chamber temperature, the life of the pistons being the prime concern.

With a diesel engine, especially a tuned diesel engine, I'd expect piston life to be the same prime concern, with possibly exhaust valves being the second concern.

Thus I'd always put the thermocouple EITHER as close as possible to a single exhaust valve (non turbo Petrol) or at the manifold outlet (Turbocharged diesel) where the thermocouple tip is wiped by every pulse of exhaust gas from all the cylinders, as the gasses enter the turbo.

It being understood that the manifold on a turbocharged diesel is short and stout, so once up to temperature, very little heat is lost in transit from exhaust valve to manifold outlet.The fact that the thermocouple is heated 4, 5, or 6 times per complete engine power cycle probably gives a higher overall reading than if it was being heated only once in the same power cycle, which is what would happen if the tip was placed closest to one exhaust valve.

I can see every advantage in measuring the highest possible temperature, which is pre-turbo, wiped by every exhaust pulse.

I can see NO advantage in measuring the temperature post turbo, unless (cynically) you wanted to display a lower temperature so your Customer would not know how hard the engine is being pushed, and believe he is getting good power at 'low' temperature readings. It is entirely coincidental that the specialist mechanics had to be 'coerced' into admitting that they had increased the fuelling.

I'm not familiar with 300TDi engines, so cannot say whether 780C is good or bad. If I was concerned I'd try opening a dialogue with the piston manufacturers, although you need to always ask yourself the question, 'are they telling me what they think I want to hear', as well as 'are they being too conservative, leaving an unrealistic safety margin, when stating what a 'safe' temperature is'.

HTH

[Boydie]

David, I was more concerned with the recomendation of Garratt who do not recommend that the exhaust turbine blades are not operated above 750 degrees C for more than 15 minutes, the blades can distort if they are.

Since I reduced the fuel by 3/4 of a turn the problem is resolved, EGT are back to normal around 650 C at full bore up hills with 15 psi boost, in case of the cylinder and pistons the pistons have been painted with a heat paint good for over 2000 degrees C, these were done when the pistons were new and prior to installation, it was a precaustion that was probably unnessersary but you never know.

[David Sparkes]

David, I was more concerned with the recommendation of Garratt who do not recommend that the exhaust turbine blades are not operated above 750 degrees C for more than 15 minutes, the blades can distort if they are.

Fine, thanks for adding that clarification. I also have a preference for recommendations from the Manufacturers.

I also appreciate that Australia isn't the UK. Here we would struggle to find a road where we could hold an engine at 650C EGT for 15 minutes. Just 1.5 minutes would be a significant achievement.

My own 'personal best' was climbing Shap Fell, four adults in the car, full throttle all the way, until the hill ran out.

This was handy, as my nerve was also running out, to say nothing of the passengers :-)

Regards.

[Boydie]

LOL, try running up from Lapston Hill to Katoomba a rise of 970 meters over 15 kilometers of unending UP and on a day like today - 38 degrees Celcius - my EGT never goes below 500 and normally sits on 630 and thats a "home run" for me, the joy of living in the Blue Mountains.