Fuel Combustion and Ignition Timing

These flashcards cover key concepts related to fuel combustion, ignition timing, flame rates, and detonation in engines.

Normal Ignition

The process in which a compressed charge is ignited by a spark leading to rapid and steady combustion.

Flame Speed

The rate at which the flame spreads, typically 60-80 ft. per second during normal combustion.

Maximum Pressure

The highest pressure generated when combustion is complete, ideally occurring when the crank is 8° -10° after top dead centre (ATDC).

Variable Ignition Timing

The timing adjustment of the spark ignition based on piston position to ensure maximum pressure occurs at 8° -10° ATDC.

Ignition Retardation

Delaying the ignition timing to prevent maximum pressure from building before the piston reaches top dead centre (TDC).

Ignition Advancement

Adjusting the ignition timing earlier to ensure maximum pressure occurs at the right engine position as speed increases.

Flame Rate Variation

Changes in flame rate due to mixture richness or increased cylinder pressure, influencing combustion speed.

Anti-detonation Properties

The ability of a fuel/air mixture to withstand higher pressures before detonation occurs, leading to enhanced engine efficiency.

Compression Ratio

The ratio between the maximum and minimum volume of the combustion chamber, affecting the pressure of the fuel/air mixture.

Detonation

An uncontrolled, rapid combustion of fuel/air mixture that can cause engine knock and is limited by the compression ratio.