Quote:
Originally Posted by Christ
Contrary - due to lack of control, the fuel timing was set non-optimal from the beginning, so that at it's normal operating speed, it was being injected at TDC or as close to it as possible, to prevent this very occurrence.
That's part of the reason I keep saying that power wasn't the main point of the experiment, and was only measured as a metric of efficiency per air temp/fuel consumption.
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Hmmm.
Diesel engines normally run with an excess of air beyond that which is required for complete combustion of the fuel, particularly forced induction ones.
High cylinder wall temperatures help to keep fuel off them and available for burning. Many people think complete combustion is a given in diesels. This is not the case. This is why fuel lubricity additives improve efficiency as they lubricate the walls of the cylinder. This is also why diesel sump oil is generally contaminated with fuel.
High fuel temperatures improve atomization and increase flame speed. This yields more pressure in the early part of the power stroke where it does the most good.
Increasing the air temperature continually advances the point of auto-ignition. If the engine fuel injection timing was initially tuned for maximum torque output then there should have been some advance built in, so prior to TDC. If the engine was not tuned for maximum torque output initially then the experiment would be meaningless as there would be no maximal "fixed reference point."
Hotter and hotter air would make the flame front progress quicker and a point of inflection would quickly be passed wherein increasing force would be applied counterclockwise in a clockwise running engine (to the extent that it is not quickly reached then the engine was not tuned to its peak possible performance prior to this). More fuel would be required to equal past performance since a percentage of the fuel would be working against itself. The effect of increasing intake temperature would likely be asymptotic on the point of auto-ignition until (If?) a point was reached when there was insufficient compressed air to complete combustion of the fuel. I suspect long before that the engine would have expired or possibly the supercharger. An interesting dilemma but best observed behind rugged barriers.
I think this explanation covers the observed data.