Besides engine speed, what other factors affect the optimal ignition angle?

[DiGenevieve]

Besides engine speed, there are three factors that affect the optimal ignition angle: 1. The higher the cylinder temperature and pressure, the faster the air-fuel mixture burns, requiring a smaller ignition advance angle. Factors influencing cylinder temperature and pressure include engine compression ratio, ambient temperature, cylinder temperature, and load. 2. The octane rating of gasoline, where a higher rating indicates better anti-knock performance, allowing for a larger ignition advance angle. 3. The air-fuel mixture ratio. Both overly rich and lean mixtures burn more slowly, necessitating an increased ignition advance angle. The air-fuel mixture ratio mainly depends on throttle opening and altitude. Note: Modern engines are equipped with knock sensors. When knocking is detected, the engine control unit reduces the ignition advance angle. Achieving relatively complex and precise adjustments is difficult with traditional mechanical ignition systems. Only electronic ignition systems can achieve the optimal ignition advance angle with high speed, precision, and stability.