O2 / Lambda Sensor¶
Measures the mixture in the exhaust so the ECU can trim fuelling toward target. Narrowband reads near stoich; wideband reads the full range.
What it is¶
The oxygen sensor sits in the exhaust and reports the burned mixture as a lambda value. It's the feedback signal that closes the fuel loop — the ECU's only direct measurement of whether it actually hit the mixture it aimed for.
Two types:
- Narrowband — accurate only right around λ = 1.0 (stoich). It can tell rich from lean near stoich but can't quantify how rich or lean elsewhere.
- Wideband — reads accurately across the full range, from deep rich to lean. Essential for tuning WOT mixtures, which sit well away from stoich.
Why it matters¶
The O2 sensor is what makes closed-loop fuel trim possible. Without it, the ECU is flying blind on the open-loop tables. With a wideband, you can read and tune the rich full-load mixtures that a narrowband simply can't see.
How to tune it¶
Use the live lambda readout as your truth source: compare measured λ to the target for the current cell, and correct the VE table where they disagree. Trust wideband readings across the range; trust narrowband only near stoich.
Rule of thumb
Tune VE so that measured λ matches target with closed-loop disabled — then closed-loop only has to make tiny corrections.
In the game¶
The lambda gauge displays the measured mixture. It's your primary feedback for all fuel tuning.