Understanding ECU Fuel Maps

A fuel map is the heart of how an engine control unit decides how much fuel to inject. It is a table of numbers the ECU looks up thousands of times per second — and it is usually the first thing a tuner edits.

What the table represents

Most fuel maps are indexed by two axes:

• RPM across one axis (engine speed)
• Engine load across the other — throttle position, manifold pressure, or airflow

Each cell holds a value the ECU uses to work out injector opening time. Depending on the platform that value might be a target air/fuel ratio (AFR/lambda), a volumetric-efficiency figure, or a direct injector correction. Between cells the ECU interpolates, so a smooth map gives smooth fuelling.

Open loop vs closed loop

At light, steady throttle the ECU often runs closed loop, trimming fuel to hit a lambda target using the O2 sensor. Under hard acceleration it switches to open loop and follows the map directly. That open-loop region — high load, high RPM — is where map accuracy matters most for power and engine safety.

What editing changes

Raising a cell adds fuel (richer); lowering it removes fuel (leaner). Richer generally lowers combustion temperature and knock risk but can cost power past a point; too lean runs hot and is dangerous under load.

Small, deliberate changes beat big guesses. A cell or two at a time, verified before the next step.

In MotoEditor

Open any definition and the fuel tables appear as editable grids. Switch between Table, 2D and 3D views to see the shape of the map, and the compare-to-stock overlay and guardrails flag cells that stray far from the factory calibration. When you're done, export a standard BIN — flashing it to the ECU stays with your own tool.

Browse the definition library to find your bike.