Thread: 300tdi disco EGT

Originally Posted by dullbird

JC you know that we WILL come to the great south island but it will be with the defender......

Remember I can still offer you free board and food/beer when you come to the big island for a stay...

...Thats OK, the Puma won't even notice the Disco on the trailer when it gets the Tombie treatment.... And thanks, I will take you guys up on the offer one day, if you have room for a camper trailer to be set up we'll try and drop in on our way to FNQ next

JC

of course I have room for a camper trailer....depending on when this drop in will be I also have 3 bedrooms as well

So I drove the disco today as Ian needed to do things on the defender...

so cruising at 110kph the temps sit around 380 to low 400's and going up hills I see around 470 to 550 (depending on the hill) this drops instantly when the hill has finished.

going down hills off throttle 110kph it sits between 210 and 320..

So I'm guessing a have a little temp le-way for adjustment because even when I pushed it a bit hard on the way home (hills are steeper and longer) I was only seeing 550 at 110kph. The car does feel like doing 110kph is an effort it certainly doesn't do it as easy since it was wound back....

Now one thing I did want to ask

coming off the highway and to a junction where I have to stop the slip road is probably around just under a kilometre when I reach the junction (slowing gradually as I come off the slip road) the temperature instantly jumps up.....now I would fully expect this to happen as I have come from highway speeds of a 110kph all the way down to stop and as the car slows so does the cold air forced over the radiator.

however would a 60 to 90 degree jump be normal? and its only when the car has come to a halt that it suddenly rockets up! (obviously because there is a lot of residual heat in the engine that it cant get rid of or cool quickly).

the reason I'm asking this as I was wondering whether this would give an indication to the viscous fan not working efficiently...if it was not normal.

and before anyone says it I'm not being paranoid just simply wondering one if its normal and whether it would be possible to pick up on a faulty viscous using this method

I think there is sometimes a bit of an error in the distinction between coolant temperature and "combustion" temperature (perhaps not the best word to describe what I'm referring to).

Once the engine has warmed to operating temperature you're unlikely to see changes in coolant temperature exceed a range of about 20 degrees. Changes in EGT are of a different order of magnitude.

My understanding is that if it's reasonable to say the combustion process is near adiabatic, then changes in EGT can be attributed to changes in the quantity of air and fuel entering the engine - for the most part. Changes in coolant temperature are unlikely to have much of an influence on EGTs once at operating temperature. For this reason an EGT gauge is probably not the best tool to use to diagnose a problem with the cooling system.

If you've driven along an exit with no throttle or a trailing throttle then all the extra air that's gone through on the overrun has a cooling effect. A jump of 60-90 degrees seem pretty normal once you've stopped because the air fuel ratio is going from potentially over 100:1 to whatever it is at idle.

ok fair enough and thanks for putting me straight..

I thought that the coolant cooled the engine.....and when cold air ran over the radiator that cooled it further.

I just made a silly assumption that buy not having effective cooling would add to the heat of the engine that is already being created by combustion any additional heat helping to heat the EGT's further.

you see that's why I have to ask these silly questions its helps me learn

Dullbird my defender EGT's are similar to yours,anywhere from high 200's to low 500's overall. Pat

Mine are similar also, they do spike when pushed with load(trailer) up some gradients.
My highest recorded is 692, I backed off because I did not want any damage.
I do run D-Gas which does make it run 20-40 degrees more.
I know that because I tried same hill, same load, same day, same carpet impression by right foot.
It is amazing however how quickly they drop once the pedal is slightly released or a lower gear selected.

yes I did that to Ian today actually when I was explaining to him what to look for etc....going up a very long hill the temps started climbing it hit 600, however while he was driving I said "watch" I pushed the auto lever back to 3rd and the drop in temp was amazing at how quick it was, well instantaneous actually.