What is the appropriate ignition timing angle?
2 Answers
6°--12°. Ignition advance angle: The crankshaft rotation angle from the ignition moment until the piston reaches the top dead center of compression. The ignition advance angle that enables the engine to achieve optimal power performance, fuel economy, and emissions is called the optimal ignition advance angle. Theoretically, the minimum ignition advance angle is 0 degrees, but to prevent igniting the air-fuel mixture during the power stroke (which would cause power loss), it is usually set above 5 degrees. This is also the angle required for starting speed. The maximum ignition advance angle should not be too large, generally not exceeding 60 degrees, otherwise vibration and temperature rise issues will become prominent, and efficiency will decrease. In reality, the rotational speed of the crankshaft structure is limited. 3. The most significant factors affecting the ignition advance are rotational speed and the combustion speed of the air-fuel mixture. As the speed increases, the time to rotate through the same angle shortens, requiring a larger advance angle to achieve the corresponding advance time. The combustion speed of the air-fuel mixture is related to the mixture's composition, engine structure, and other factors such as combustion chamber shape and compression ratio.
I've been repairing cars for most of my life, and I've found that an ignition timing advance of 10 to 15 degrees is generally most suitable, but it really depends on the engine's compression ratio and the specific vehicle model. At idle, 8-12 degrees BTDC is usually optimal—too early can cause knocking and engine damage, while too late results in power loss and increased fuel consumption. When adjusting, use a timing light to align with the flywheel marks, then gently rotate the distributor to calibrate step by step. Regular maintenance must include checking this, such as inspecting it every 20,000 kilometers—don't wait until the car shakes badly before addressing it. DIY adjustments are risky; if you hear knocking, stop immediately and seek a professional shop. Safe and worry-free driving relies on maintaining these small but critical details properly.
