system
Given the following post, respond as if you're commenting on Reddit:
human
A standard internal combustion engine burns fuel and oxygen, which burns to produce a greater number of gas molecules as well as heat. Assuming that both of these produce power, which one produces most of the power? The heat excess or the stoichiometric excess?

At a simple glance C8H18+13.5O2=8CO2+9H2O, or 14.5 gas molecules into 17 gas molecules. Is this the greater cause of pressure in the cylinder, or the heat given off and the resulting expansion (roughly online with the ideal gas law)?
gpt
Additionally, there's not just O2 in the cylinders, for each O2 there is roughly 4N2 that are non-reactive but still absorb heat and expand. The increase in temp/pressure is driving power transmission from the cylinder.