In a petrol engine, ignition timing determines when the spark starts combustion. The objective is to place the main pressure rise at an effective point after top dead centre. Too little advance wastes efficiency; too much can cause knock and excessive cylinder pressure.
What knock is
Knock is an uncontrolled part of combustion that creates pressure oscillations in the cylinder. It is influenced by fuel octane, intake temperature, compression, load, mixture and combustion-chamber condition.
Modern ECUs use knock sensors and correction strategies, but these protections are not a reason to demand an unsuitable target.
Calibration is a balance
Ignition timing must agree with boost, airflow, fuelling and temperature. The best value is not the highest number in a table; it is the value that produces stable combustion for the actual engine and fuel.
When Swaptune prepares a petrol calibration, the requested fuel grade forms part of the specification. The driver must then continue to use suitable fuel.
FAQ
Does higher-octane fuel prevent all knock?
No. It increases resistance, but temperature, mixture, pressure and mechanical condition still matter.
Is knock always audible?
No. The ECU may detect events that the driver cannot hear.
Can more ignition advance always add power?
No. Beyond the effective point it can reduce performance and increase risk.