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.

EngineCombustion

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This calculator requires JavaScript to compute its result. The formula, symbols, and regulatory sources are shown in the Formula section below.

Formula, assumptions, and limits

AFR = \frac{\dot m_\text{air}}{\dot m_\text{fuel}}, \quad \lambda = \frac{AFR}{AFR_\text{stoich}}

Symbol	Meaning	Unit
$\dot m_\text{air}$	Air mass flow	kg/h
$\dot m_\text{fuel}$	Fuel mass flow	kg/h
$AFR_\text{stoich}$	Stoichiometric AFR for the fuel
$λ$	Excess-air factor

Source: Heywood - Internal Combustion Engine Fundamentals

AFR and excess-air factor \u03bb from measured fuel and air flows.