A lean mixture contains more air than that, more than can actually be used in combustion. The opposite of a lean ratio is a rich ratio, which has less than 14.7 parts air and thus too much fuel.

(This mixture is described by chemists as "stoichiometric.") If the mixture is rich, containing an excess of fuel, or lean, containing an excess of air, the temperature of the combustion process ...

But 14:1 is still "rich" by stoichiometric standards. If you lean out past 14.7:1, all the way to something like 17:1, your engine will run cooler again. It just won't run smoothly.

Ever had your mechanic say your car is running “rich” or “lean,” and you just nodded like you totally knew what they meant? You’re not alone. It sounds like something out of a cooking ...

A slightly rich mixture also ensures against top-end overheating, lean misfire, and detonation. On gasoline, in general an A/F ratio of about 12:1 produces the best power (see graph B).

Unfortunately, the opposite is also true—varying pockets of lean and rich mixtures within the cylinder when the spark plug fires will cost power and the combustion process will not be as smooth.

Today's rich-lean combustors for kerosene operation are highly specialised systems designed to provide low emissions and robust combustion. Changing the fuel from hydrocarbons to pure hydrogen ...

If the engine is running lean, there will be excess oxygen in the exhaust because there was not enough fuel present in the combustion chamber to completely burn it. In rich conditions, the ...