Air–Fuel Ratio (AFR) & Excess Air
AFR and excess-air factor λ from measured fuel and air flows. Diesel engines typically λ = 2.0–3.5 at full load.
Actual AFR
39.05 -
Excess-air factor λ
2.69 -
Formula, assumptions, and limits
λ > 1 means lean; λ < 1 rich. Diesel operates lean at all loads; spark-ignited gas engines can operate either stoichiometric with 3-way catalyst (Otto DF) or lean-burn without catalyst (LBSI).
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| Air mass flow | kg/h | charge-air meter | |
| Fuel mass flow | kg/h | fuel-flow meter | |
| Stoichiometric AFR for the fuel | - | combustion chemistry | |
| Excess-air factor | - | result |