Is a Negative Ignition Timing Normal?

[McJordan]

Negative ignition timing is not normal. If it is negative, it indicates a malfunction. The optimal ignition angle is influenced by the following factors: 1. Cylinder temperature and pressure. The higher they are, the faster the combustion, requiring a smaller ignition advance angle. Factors affecting cylinder temperature and pressure include engine compression ratio, ambient temperature, cylinder temperature, and load. This is why cars perform differently in seasons with varying temperatures. 2. Gasoline octane rating. Higher octane gasoline has better anti-knock properties, allowing for a larger ignition advance angle. 3. Air-fuel mixture ratio. Both overly rich and lean mixtures burn slower, necessitating an increased ignition advance angle. This mainly depends on throttle opening and altitude. Some cars are also equipped with knock sensors that automatically reduce the ignition advance angle when knocking occurs.