Ignition¶
Spark timing in one screen: advance the spark to give the flame time to burn, but retard it to stay clear of knock.
Spark timing at a glance¶
Combustion takes time. The spark must fire before the piston reaches the top of its stroke so that peak cylinder pressure arrives just after — when the crank can best turn it into torque. How far before top dead center the spark fires is the ignition advance, measured in degrees BTDC (before top dead center).
Two forces pull in opposite directions:
- Advance gives the flame enough time to develop — more is needed as RPM rises, because there are fewer milliseconds per degree.
- Retard keeps the end-gas from auto-igniting into knock — needed under high load, heat, or low octane.
The timing table holds the chosen advance across RPM and load; the fundamentals explain why there's a single best value (MBT); knock and octane set the limit you mustn't cross.
Engone currently simulates spark-ignition (petrol) engines.
Where it lives in the game¶
Everything on this page lives on the IGNITION page. The spark table is on the left. The right
column is a scroll panel (IDLE CONTROL) with four cards: COLD IDLE TARGET, IDLE STRATEGY,
KNOCK DETECTION and REV LIMITER. See Cold Idle,
Idle Control and Rev Limiter for the idle
and limiter cards.