Fuel¶
How Engone decides how much fuel to inject, and when.
Fuelling at a glance¶
The ECU meters fuel in a chain you can follow cell by cell:
- Estimate air mass. Using speed-density, the ECU combines the MAP sensor, the VE table, and air temperature to work out how much air actually entered the cylinder this cycle.
- Pick a target. It looks up the desired mixture from the lambda target table — leaner for cruise, richer for full load.
- Compute the pulse. Given the air mass, the target lambda, and the injector flow at the current fuel pressure, it calculates the injector pulse width.
- Add enrichment. Cold starts and fast transients need more fuel than the base calculation — the enrichment stack layers that on.
- Trim to target. When conditions allow, closed-loop fuel trim reads the exhaust O2/lambda sensor and nudges fuelling toward the target.
Petrol vs diesel¶
A petrol engine throttles air and aims for a specific air–fuel ratio (usually near stoichiometric, richer at full load), with the spark timing the burn. A diesel engine runs unthrottled — it always has plenty of air — and controls power purely by how much fuel it injects, limited by a smoke ceiling. See Diesel Fuelling.