After-Start Enrichment¶
A decaying boost of fuel for about a minute after the engine catches, to cover wall-wetting before the intake warms.
What it is¶
The moment the engine starts running on its own, cranking enrichment ends — but the intake is still cold and wet. After-start enrichment bridges that gap: it adds a percentage of extra fuel that decays over roughly 60 seconds to zero.
Two things shape it:
- Initial amount — set by coolant temperature (ECT) at the moment of start; colder starts begin with more.
- Decay — time-based; the boost tapers smoothly as the seconds pass and the intake warms.
Why it matters¶
Right after start, a lot of commanded fuel still condenses on cold intake walls (wall-wetting) rather than reaching the cylinder. Without this layer the engine would lean out and stumble in the first several seconds of running — exactly when it's most fragile.
- Too little → the engine sags or nearly stalls just after catching.
- Too much → it runs over-rich and rough for the first minute, possibly fouling.
How to tune it¶
Tune by feel in the first minute after a cold start. If the engine catches cleanly then stumbles a few seconds later, raise the initial amount. If it catches and runs rich/rough before smoothing out, lower it.
Rule of thumb
Cranking gets it to fire; after-start keeps it alive until warmup enrichment takes over. Tune them in that order: catch first, then stabilize the first minute.
In the game¶
The after-start curve is on the Fuel page. Its live multiplier visibly decays toward 1.0× over the first minute — watch it alongside the coolant temperature.