Convert AFR and lambda using a visible stoichiometric assumption. This is a unit converter—not a tuning-target or engine-safety calculator.
| Example | Lambda | AFR |
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Air-fuel ratio (AFR) is the mass ratio of air to fuel in a combustion mixture. Lambda (λ) is a normalized version - it expresses AFR as a fraction of the stoichiometric ratio for that fuel, making it universal across fuel types. Lambda = 1.0 always means stoichiometry, regardless of whether you're burning gasoline, E85, or methanol.
A wideband system derives lambda from exhaust oxygen. If its display is set to a gasoline AFR scale, it may show lambda × 14.7 even when the engine burns an ethanol blend. That number is a gasoline-equivalent display, not the actual fuel-specific mass AFR. Reading lambda avoids ambiguity, but sensor and controller accuracy still depend on correct installation, calibration, temperature, exhaust pressure, and a leak-free sample.
A unit converter cannot choose idle, cruise, full-load, boosted, catalyst-protection, or maximum-output targets. Those depend on the actual fuel, engine, combustion system, load, temperatures, ignition, emissions hardware, sensor setup, and the responsible calibration strategy. Use the target table from the exact ECU calibration or calibrator—not a generic internet range.
Pure compounds can have defined stoichiometric ratios, but commercial gasoline, diesel, and E85 are variable mixtures. The preset values are common references for conversion examples, not laboratory values for every pump batch. Use the custom field when the actual fuel specification is known.
Imagine your wideband reads 0.80 lambda at full boost and you want to know the equivalent AFR. On gasoline (stoich 14.7):
Now suppose you switch the car to E85 but the gauge is still scaled for gasoline. At the same true lambda of 0.80 the gauge keeps displaying 11.76 "AFR," but the real mixture is:
The same lambda produces a different fuel-specific AFR. A gasoline-scaled display is not necessarily malfunctioning; it is applying a different reference. Label the scale clearly or use lambda.
The Bosch Motorsport LSU 4.9 data sheet documents wideband range and application limits. Haltech's target-lambda documentation shows that targets are calibration tables indexed by operating conditions rather than one universal number.
There is no universal value. Use the target specified and validated for the exact engine, fuel, hardware, operating condition, and calibration.
A wideband system derives lambda, while an AFR display applies a configured stoichiometric reference. Read lambda or confirm whether the display is gasoline-equivalent or fuel-specific.
AFR is air mass divided by fuel mass. Lambda is actual AFR divided by the actual fuel's stoichiometric AFR, so lambda 1 represents stoichiometry.
Preset values are approximate references. Commercial gasoline, E85, and diesel vary in composition; enter the actual fuel's specified stoichiometric ratio when precision matters.
No. It only converts units. Target selection must be validated for the exact engine, fuel, sensors, hardware, and operating conditions.
A suitable wideband system is needed to measure across rich and lean ranges, but correct controller configuration, placement, temperature, pressure, and leak-free sampling are also required. Lambda alone does not verify safety.
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