Lambda
Another way to measure air-fuel ratio, expressed as a ratio where 1.0 = perfect stoichiometric combustion. Below 1.0 = rich. Above 1.0 = lean.
Why it matters
Lambda is universal across fuel types (1.0 always means stoich), while AFR changes based on the fuel. Some platforms log in AFR, others in lambda ratio.
What to look for
At WOT, lambda target is typically 0.78-0.82 regardless of fuel type. If lambda actual is higher than lambda target (leaner), that is dangerous.
Related terms
The ratio of air to fuel in the combustion chamber. Lower number = richer (more fuel). Higher number = leaner (less fuel).
The ECU's real-time, moment-to-moment adjustment to fueling. Think of it as the ECU saying "right now I need to add a little more fuel" or "right now I need to pull back a little."
The ECU's permanent, learned correction to fueling. Unlike STFT which changes moment-to-moment, LTFT is the ECU saying "over time, I've learned I consistently need to add or remove this much fuel."
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