Understanding AFR: Stoichiometric AFR
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Stoichiometric AFR
01.30
| 00:00 | Every fuel has an ideal air fuel ratio where enough fuel molecules are provided to properly mix with all of the available oxygen molecules. |
| 00:09 | This provides theoretically ideal combustion where all of the air and fuel is consumed during the combustion process. |
| 00:18 | This ratio is known as the stoichiometric air fuel ratio and it is dependent on the chemical composition of the specific fuel. |
| 00:27 | For normal pump fuel, this ratio is 14.7:1 which means that for 14.7 kilograms of air, we need to supply 1 kilogram of fuel. |
| 00:38 | A table is included as a file below which gives you the stoichiometric ratio for a range of the more common fuels you are likely to see. |
| 00:47 | When we discuss air fuel ratio, we often use the terms rich and lean to describe how the engine is running. |
| 00:54 | A rich mixture is defined as one which has an excess of fuel, while a lean mixture is defined as one that has an excess of oxygen. |
| 01:04 | Rich and lean are both referenced to the stoichiometric AFR of the particular fuel. |
| 01:10 | For example if we are tuning on pump fuel, numbers higher than 14.7:1 are considered lean and numbers lower than 14.7:1 are considered rich. |
| 01:22 | Another term you may hear in tuning circles to describe a rich mixture is ‘fat’. |
