victoria to montreal and almost back again... :(

[White Mule]

The Delica Community is truly a lovely family, we each help others so our karma stays good in case we need help.

Well put Christine

Please let met know if I can provide some help.

I may only know so much, but what I know is yours to have.

[Mr. Flibble]

I want to see the Deli running again more than I want to see a flamewar, so while this might be better suited to a different thread I put it here (if all my conjecture is correct) to help the Deli community better understand Pyros and why they are important.

So.. explain how the 2 could be unrelated then? it's only 1 engine! the heat can't be directed in to one and not the other!

The readout of the engine coolant and EGT is only partially related in an L300 - this is going on my understanding of how an L300 works and a Diesel works, so I could be out of line here, but I will give it my best shot.

I believe that the L300 turbo is only oil cooled (the L400 is oil and water cooled I believe) thus the EGT temps can spike long before the actual coolant has increased in temp because the turbo gets very hot - but can only be cooled to a certain degree by exhaust gas and oil. Since the turbo is now extremely hot, and the heat carries over to the engine coolant mostly by the oil that is flowing through the turbo, the oil must heat up and pass that excess heat onto the coolant before the engine temp guage begins to climb.

This would cause a noticeable lag in the actual temperature of the turbo versus the engine coolant temperature. The advantage of an EGT is that you get an immediate readout of the actual exhaust gases causing the overheating. Thus, it would be possible to get your turbo cherry-red with heat, and then have it cool off by dumping the waste heat through the exhaust system (as you slowed down, or the wind dropped) and some of the waste heat passed from the oil to the radiator, and by that time the turbo would have cooled down and not caused a significant rise in the overall engine temp.

So, my understanding is, that EGT and overall temperature are related - but not directly correlated. That is, your overall engine temperature will climb the harder you work your turbo. But, it is possible to have your turbo get extremely hot and not dump all the waste heat directly into the engine and cooling system for some time. So, if you ran your turbo full out, over time your engine temp would climb - unless your radiator was capable enough of pulling out the heat that was not dumping into the exhaust, say from a cool oncoming headwind. Thus, you would not see the coolant temperature rise because the waste heat would be dumped by the coolant before it could register on the engine temperature gauge which only actually monitors one side of the coolant flow. If the engine temp gauge is monitoring the "wrong" side of that coolant flow, the heating of the turbo won't be as noticeable through the engine temp gauge.

(EDIT, in my rambling I forgot to put my point in here)
So, in summary, you could have a condition where the majority of waste heat is being removed from the turbo via exhaust gases and the tailpipe - and a small amount is removed by the oil flow, say 10%. But, since this small amount of heat removal is not enough to overwhelm the radiator, the engine temp readout does not climb as much as the EGT reading would.

The L400 should be better at this because the turbo is both water and oil cooled, but it still makes a good case for installing an EGT so you don't get your engine damaged by the "lag time" that it takes a heated turbo to start dumping large amounts of heat into the engine itself.

[crushers]

since you are giving this thought process decent posting maybe i will share some experience afterall. (yah, yah, i said bye bye but this is a great forum):
you are close, whether the turbo is water cooled or not really makes very little difference.
this about this (and i am NOT talking down to you, this is the way i chat with people over at Mud when we are reasonably discussing a topic):
the coolant line to and from the turbo is small, very small and the amount of coolant that actually flows through it is minimal. the effect this would have on the overall cooling system is negligeble.

your coolant removes heat from the block, the castings and shoves it throught the rad to cool. this takes time and is a slow process.
the coolant temp gauge will move up and down in corelation to the heat transfered from the block to the coolant. the coolant will not move up and down in the snap of the fingers.

the pyrometer sensor is mounted (or supposed to be mounted) as close to the turbo as possible, preferably within 3" of the downspout elbo or preturbo. exhaust gasses can heat up and cool at an alarming rate. since the probe is in very close proximity to these gases it can move from 900 to 1400 in a matter of seconds, i have seen them move as fast as your tachometer.

if you are working the engine climbing a hill, bucking a headwind, passing then the heat from the exhaust gasses can hit 1400F very very quickly but the heat from the block has not reacted yet to the coolant temp gauge has not even moved. on a decent hill you could be at 1400F for minutes before the coolant guage starts to move.
of course once you crest that hill then the block is still generating or shedding heat but the exhaust gasses are already cooling since your foot is out of the throttle and the amount of fuel you are shoving through the cylinders is minimized. so in this case the coolant gauge is now showing higher heat than the pyrometer and it might for minutes as the block cools back down to normal temp ranges.

now lets take this one step further. you are climbing a hill, the EGTs are skyrocketing so you pull your foot out of the throttle just a whee bit (it doesn't take much to change the EGTs) or dropping a gear has the same results (rpms go up, faster air flow and lower EGTs) but the engine is still working harder than normal so the block is shedding heat into the coolant. now your EGTs could be at 1000F but the coolant is working harder than normal and the coolant guage registers this and starts to rise. if the hill is long enough (think BC hills) or if the head wind is strong enough (think driving west through the flatlands) and you could be in the red coolant temp but the EGTS are still reading at a safe 1000F.
now you take the situation of this couple in the thread, driving west through the flat lands, overall it is a steady gentle uphill drive, couple that with a steady headwind and that little engine is working harder than you think pushing a 7 ft tall brick up the road.
"the previous day we did a non stop drive into the wind from winnipeg to calgary... and you know how they are, when you're against the wind you get almost half the gas mileage"
realisticly they could have been pushing easily into the 1200F or even higher the entire day. this kind of heat will cook the head and the oil being passed through the turbo. theoreticly they could have been on the verg of a blown engine when they shut down the night before. the engine cools and the next morning the head for home. at the first decent hill the poor engine says "that is it, i quit. you are a cruel master".

add to this mix that factory coolant gauges are a joke, install an aftermarket coolant gauge and compare the two as you drive down the road and you will find the aftermarket is much more sensitive than factory.

this theory is based on 30 years of actual hands on experience, not book reading, web browzing. if anyone cares enough to check out my experience head over to Mud and read some of my 13,000 TECH realated posts (over there chitchat does not add to your post count). this does not mean i do not make mistakes but what it does mean is i have a very good grasp on diesel engines and what works and what doesn't.

a PROPERLY located quality pyrometer is one of the best gauges to install in any diesel followed closely by an quality aftermarket coolant gauge.