4AGE 16V engine overheat when at high speed

[jondee86]

Found a reasonable explanation...

Quote:Retarded will over heat it most quickly. The burn occurs over about 80
degrees of crank rotation, when started late, there isn't time for the the
flame temps to be reduced by work against the crank. This combined with
the reaction still occurring when the exhaust valve opens conspires to
dump really hot gases into the exhaust passages. This greatly increases
the valve temp and the amount of heat picked up by the cooling system
thru the structure of the head and exhaust port.

This statement didn't have any hard evidence but it does seem plausible.
With the correct timing more heat is extracted in the form of mechanical
work. This likely lowers the temperature of the gases in contact with the
cylinder walls before they hit the exhaust valves.

With retarded timing combustion is still taking place when the exhaust
valves open and high temperature gases contact the head, valves and
exhaust ports. This increases heat transfer to the cooling system.

So yeah... severely retarded ignition timing could push the engine
temperature up at constant load, and your engine will lack power. The
exhaust manifold and down pipe (or headers) will be really hot. Upside is
that your engine should be easy to start and idle nicely

Cheers.... jondee86