Hey guys, Combustion in an SI engine. So an AF:R of 14.7:1 is stoichiometric for petrol (gas), but an AF:R of 12.5:1 makes more power. One common thought is that not all the fuel and oxygen react in a stoichiometric mix, so by upping the fuel there is more chance of all the oxygen reacting (excess fuel). For some reason I have got the notion that when the co2 and h2o in the cylinder dissociate, the liberated oxygen is free to react with the excess fuel. But I can't find any sources that state this, they all talk about equilibrium reactions and NOx production. So question is, what is happening to make the extra power when using a rich mixture.