In diesel tuning, you target power. In gasoline tuning, you target AFR — and then you get power as a result of getting it right.
What lambda control actually does
The gasoline ECU runs a closed-loop control system around stoichiometry (lambda = 1.0). The upstream oxygen sensor measures exhaust composition and the ECU adjusts fueling to correct toward target.
Why AFR matters for calibration
When you change ignition timing or torque maps — the lambda control will compensate for many of your changes. This means small errors don’t immediately cause problems. But it also means you can be fooled into thinking your changes are working when the ECU is just masking them.
Where it gets complicated
Under load, most gasoline ECUs switch from stoichiometric to enrichment (lambda 0.85–0.95). This is the enrichment table, and it’s where a significant portion of power calibration happens.
If you don’t understand the transition from closed-loop lambda to open-loop enrichment — you’re working half-blind.
What to monitor
Short-term fuel trim, long-term fuel trim, lambda sensor raw values, and the enrichment switch flag.
This is the foundation of Gasoline Fundamental. The 4 data flow videos at the start exist for exactly this reason.