ECU Remapping

Fuel/Air Table (AFR Map)

A Fuel/Air table (AFR map) defines how much fuel the ECU injects at each combination of RPM and throttle position. Every cell in the table represents a specific load point, and the value inside determines whether the engine runs richer or leaner at that moment.

Richer (lower AFR) provides cooler combustion, stability under high load and safer operation at high RPM. Leaner (higher AFR) increases efficiency but raises combustion temperature and sensitivity to detonation.

OEM maps are compromises shaped by emissions, noise regulations and production tolerances. This leaves areas where the engine runs unnecessarily lean for emissions, or overly rich for safety margins. A proper remap corrects these deviations, giving the engine the optimal mixture across the full RPM range.

Closed Loop vs Open Loop Operation

The ECU operates in two modes that determine how fueling is controlled:

Closed Loop uses the lambda sensor to maintain a stoichiometric AFR of 14.7:1 for emissions. Active during idle, cruising and low load. This results in a lean mixture, sometimes causing heat and slight hesitation.

Open Loop ignores the lambda sensor and follows the AFR table directly. Active during acceleration, high load and high RPM. This allows richer mixtures for power and cooling.

On the Daytona 675, the transition from closed loop to open loop happens around 7000 RPM and is intentionally restrictive due to emissions. This creates a noticeable step in throttle behaviour and fueling. A remap smooths this transition, giving cleaner fueling, better throttle response and more predictable rideability across the entire RPM range.

Keihin ECU in where the adjusted a/f table is re-programmed

A lean-running engine feels sharp but unstable: higher combustion temperatures, reduced midrange torque and increased risk of detonation under load. A rich-running engine feels dull, with slower throttle response and reduced top-end power.

The key to a proper remap is shaping the AFR curve to match the engine’s breathing characteristics:

• Low RPM: slightly richer for smoothness and stability • Mid RPM: mildly lean for efficiency and clean throttle transitions • High RPM: richer for cooling and maximum power • Full throttle: fixed AFR targets around 12.6–13.0 for safe, consistent performance

It depends entirely on how the engine runs and which modifications are installed. In most cases it’s cheaper and more effective to do two dyno runs: a baseline run, then a second run with the DK34 stacks installed. If the engine already gains power there, a remap isn’t strictly necessary. If you do choose to remap, a third run will confirm whether the adjustments actually improved the curve. A proper remap simply ensures consistent fueling across the full RPM range, a stable torque curve and predictable throttle behaviour — nothing dramatic, just the engine running the way it should, specific for your engine condition.