2 core versus 3 core radiators

[Alitis007]

Due to a diesels nature (compression ignition) if the engine is not at the right temp the combustion is harder to achieve and you can end up with something called diesel knock.

Have you never heard a diesel start when it's dead cold?

While testing that piston slap seems to go away with oil pressure after start up. Because td42's are simple mechanical injected they don't compensate by adding more fuel with lower water temps to warm the motor up quicker. You can see how sensitive they are when you block the egr which is used to help atomise fuel with heat in that on the td you won't get a flat spot during warm up unlike a petrol motor

They sound awesome...... bit like me when I wake nowadays!!!

Never heard a diesel moan and windge before......

Uuummmm... yes and no.
I agree with the delta T across the thermo but not how it works

Thermo's aren't an open and shut device, they are dynamic.
That means they will begin to open at 'x' temp and be fully open at 'y' temp.
Traditional engine thermos are wax pellet versus spring but bi-metallic is slowly becoming in vogue

Using hypothetical numbers and ignoring bypass circuits for ease of explanation.
At 85 degress my hypothetical thermo begins to open and pass coolant with a much lower temp from the Radiator to flow thru the engine
The thermo will settle at a percentage open, lets say 10%, where the coolant takes on heat energy from the engine and circulates thru the Radiator and has a temp of say 90 degrees.

Once the engine load starts to get significantly higher the coolant exiting the engine rises to, say, 95 degrees the thermo will open a tad more.
Lets say it now finds equilibrium at 50% open and 95 degrees.
The thermo cannot start to close as the heat is holding it open against it's mechanical pressure trying to move it closed.

The only thing that will move the thermo either further open is a further increase in engine load and thus coolant temp or towards close is a drop in engine load and the thermo mechanical pressure overcomes the expansion and begins to close.

If the thermo gets fully open, lets say 105, there can be no increase in coolant flow and any more load will cause the engine to overheat.

It is precisely for the above reasons that virtually all vehicle manufacturers use non linear temp gauges without a numbered scale.
This is actually quite a good idea because the temp of coolant exiting a vehicle engine is never constant but if it is within the 'normal' range then who really cares.

As an example my CRD dash temp had no discernible movement from it's "happy spot" just under 1/2 of scale if the engine sensor was between 80 ish degrees and 100 degrees.
From 100 to 106 it would move towards the upper limit mark.

On the bench uts a bit different coz you will notice that a 82*c thermostat will start opening roughly at 65-70*c and fully open by 80-83*c. I'm going to go thru basic operation of the thermostat but as one side heats ups (usually the bottom) the spring softens and looses its tention To allow water to pass thru usually at a lower temp which will cool the spring and its tention close the thermostat till it equals all if the cooling system.

On my 4.5 the gauge will show NOT from 64*c-96*c and will creep up at a higher temp.

The zd has more electronics to run more efficiently alot like carby vs efi so it will be significantly affected by water temp coz of the coolant temp sensor adding and decreasing fuel with different temperatures