📄️ After Start Enrichment
After-start enrichment is important because an engine that has just fired up is still stabilizing and needs extra fuel for a short period before it can idle cleanly. Even if cranking enrichment got the engine to start, the intake ports, combustion chambers, and sensors are still cold, fuel isn’t atomizing well yet, and airflow is uneven. This creates a natural tendency for the mixture to go lean right after the engine catches. After-start enrichment temporarily adds extra fuel to prevent stumbling, stalling, or surging during these first few seconds. As the engine warms slightly and airflow smooths out, the enrichment tapers off, handing control back to the base fuel table. Without after-start enrichment, engines often start but won’t stay running or will run very roughly right after ignition.
📄️ Cranking Duration Fuel Multiplier
The cranking duration fuel multiplier is used to add extra fuel during the first few engine rotations. This helps to get the engine to catch more quickly. Increasing the multiplier from 1 to e.g. 2 for the first 1-2 rotations is a reasonable starting point.
📄️ Cranking Fuel Coolant Multiplier
The cranking fuel coolant multiplier is used to add fuel when the engine is cold and to take fuel away when the engine is warm. A cold engine cannot atomize the fuel as well as a warm engine as the intake will be at ambient temperature. As the engine reaches operating temperature and the intake heats up, the fuel is able to vaporize in the intake causing better mixing.
📄️ Cranking Fuel Settings
Injection Mode
📄️ Fuel priming pulse
The priming pulse essentially "primes" the intake before the car starts by spraying a pulse of fuel into it. This wets the intake walls which helps atomization by vaporizing the fuel from the turbulence caused when the intake valve is opened, sucking tbe pulse into the engine. For cars with long intake runners and injectors far from the valves, this is more important to tune so there is no delay in fuelling when cranking is initiated. For cars like Miatas with injectors spraying almost directly onto the back of the intake valves, this setting isn't strictly necessary to tune.