So, here's my thoughts on how timing affects heat in the engine.
When combustion takes place the heat released by the combustion goes towards the following areas;
1)Exhaust heat
2)Thermal heat released into the coolant and lube oil
3)Frictional losses
4)Useable work (i.e. the kinetic force implied upon the piston)
Believe it or not, only about 30% of the heat released by the fuel durring combustion is turned into useable work on an IDI engine (more like 40% for a DI engine) the rest goes to the 'big three' being exhaust loss, thermal load loss, and frictional loss.
So this is where timing plays a key role in making the engine perform better, or worse, or average. When the injection timing is advanced, meaning the fuel is injected into the combustion chamber farther before the piston reaches top-dead-center, more of the fuel's energy is converted into kinetic force because the fuel is combusting longer, and at a higher pressure. This is both good and bad, good because more energy is released that can do 'work' by forcing the piston back down, but bad because it creates a much higher stress on the connecting parts, crank, DMF flywheel (which I love so well
).
The farther retared the timing is, meaning the fuel is injected closer to the piston being at TDC, or even being injected after the piston has moved past TDC and is moving away from the head, the lower the cylinder pressure will be, therefore the combustion pressure will be lower. The amount of fuel injected could be the exact same amount as when the timing was advanced, but less of the heat (in the form of expanding gasses) is being converted into useable work (to push the piston down), and more of the heat is leaving the cylinder as thermal load into the coolant, or exhaust heat. Either way, higher exhaust temps = higher coolant temps since the coolant flows through the head and around the cylinder walls.
Here's where it gets interesting... of course if your timing is retarded, you will not be injecting the same amount of fuel as before (when it was advanced) because you will need MORE fuel since you are not combusting it as effeciently. More fuel = more heat. More heat with less work = more thermal load on the coolant.
Most everything else in the engine is static, frictional losses are the same throught the timing range. Lube oil flow, viscosity, all that is the same.
Hope this helps shed some light on the timing/heat issue...
