What are the factors affecting the optimal ignition advance angle of an engine?

[McJuliette]

Factors affecting the optimal ignition advance angle of an engine: 1. The higher the cylinder temperature and pressure, the faster the combustion, and the smaller the ignition advance angle should be. 2. The octane number of gasoline, which is the gasoline grade, the higher the anti-knock ability, the larger the allowable ignition advance angle. 3. The mixture ratio of the fuel being too rich or too lean leads to slower combustion speed, requiring an increase in the ignition advance angle. The following is an introduction to the ignition advance angle: The normal range of the ignition advance angle is from 6° to 12°. The ignition advance angle refers to the angle through which the crankshaft rotates from the moment of ignition until the piston reaches the top dead center of compression. The ignition advance angle that enables the engine to achieve optimal power, economy, and emissions is called the optimal ignition advance angle.

[DeFinn]

Throughout my driving experience, I've found that the optimal ignition timing of an engine is influenced by multiple factors. At higher RPMs, the ignition needs to be advanced to keep up with the combustion speed; otherwise, power output lags. When the engine is under heavy load, such as carrying passengers or climbing hills, the ignition should also be advanced to help it bear the burden. Fuel type is crucial too—high-octane gasoline allows for more advance to prevent knocking, while lower grades require a more conservative approach. As temperatures rise and air becomes thinner, the ignition angle should be slightly reduced to avoid overly rapid combustion. At higher altitudes with lower atmospheric pressure, ignition timing should be delayed to ensure more complete combustion. Engines with higher compression ratios typically have their ignition timing set earlier for improved efficiency. Older cars may struggle to start if not adjusted properly, whereas modern ECUs adapt in real-time to keep the vehicle running smoothly and fuel-efficiently.

[Michael]

Previously, adjusting the ignition timing angle incorrectly made the car feel sluggish. Influencing factors include engine speed—when it increases, the timing angle needs to advance to keep up with acceleration; otherwise, stepping on the gas feels weak. Under increased load, such as when towing, advancing the ignition angle improves power response. Higher-quality, higher-octane fuel allows more ignition advance for stronger bursts of power, while lower-quality fuel requires less advance to prevent knocking. High air temperatures thin the intake air, requiring less advance, whereas cold air allows more. A higher compression ratio setting is better, but overdoing it wears out spark plugs and strains the battery. In short, a balanced adjustment ensures a smooth ride, better fuel efficiency, and reliable performance.

[BentleyRose]

Common ignition issues in car repairs often stem from incorrect ignition timing. When engine speed changes rapidly, dynamic adjustment is needed—advancing the angle at high RPM and retracting it at low RPM. Under heavy engine load, increasing the angle compensates; otherwise, power loss occurs, leading to poor uphill performance. Poor fuel quality (e.g., high water content) requires retarded timing to reduce knock risk. High air temperature calls for smaller timing angles as intake density affects combustion. At high altitudes with thin air, slightly adjust the angle. High compression ratio designs favor earlier ignition. ECU malfunctions may cause excessive knock—proper tuning boosts power, lowers fuel consumption, and enhances driving safety.