The engine is what supplies the required power to all parts of a running vehicle. Even when the required amount of fuel and air is supplied to the engine, it is crucial that the air-fuel mixture be ignited at the right time to get the most power out of it. This is where the ignition timing gains importance. The ignition spark should be generated at a precise time so that the air-fuel mixture burns completely. This article explains the significance of ignition timing on the performance of the engine, and details what can go wrong in a vehicle with an incorrect ignition timing.
The ignition timing sets the right point at which the air-fuel mixture in the engine's combustion chamber is ignited. The timing is measured in degrees before or after the piston reaches the top dead center (TDC). If the ignition system is set to ignite the fuel exactly when the piston reaches the TDC, the ignition timing is said to be 0 degrees. If the ignition system is set to produce the spark before the piston reaches the TDC, the ignition timing is said to be advanced. To get the optimal power for various engine speeds, the ignition timing should be altered accordingly. Generally, the ignition timing is advanced to get the maximum power from the engine.
Typically, the spark is fired 10-30 degrees before the piston reaches the top dead center (TDC). The air-fuel mixture burns at the same rate, irrespective of the engine speed. The faster the engine runs, the more will be the ignition timing advance, to achieve maximum pressure at the same point in the engine cycle. Older vehicles required the ignition timing to be set manually. They used either vacuum advances or centrifugal advances to set the right advance timing. Whereas, modern automobiles have the Engine Control Unit (ECU) to dictate the advance needed at a given engine speed. In some vehicles, the ignition timing will be retarded. This is usually done where reducing the emissions takes priority over producing more power.
The right time to ignite the fuel is affected by various factors such as the engine displacement, octane rating of the fuel, engine compression ratio, condition of the spark plugs and intake pressure of the engine. Typically, the ignition timing is adjusted when any changes or upgrades are made to the engine.
Effects of Wrong Ignition Timing
Improper ignition timing can cause several engine problems such as knocking or pinging, hard starting, overheating, increased fuel consumption and reduced power output.
Knocking or Pinging
This is one of the common symptoms in an engine. Knocking occurs when the ignition timing is set before the ideal advance timing. In these cases, the spark plugs produces the spark when the engine is still in its compression phase, resulting in improper burning of the air-fuel mixture. To prevent engine knocking, modern cars use knock sensors. To find a detailed description of knock sensors, click here.
This can be either due to a advanced or delayed ignition. In both cases, the engine will not produce the optimal power, causing the vehicle to experience difficulty while starting.
Overheating is one of the symptoms that the air-fuel mixture was ignited way before the power stroke. This causes the engine to generate more heat than usual.
All in all, a wrong ignition timing will bring down the engine power and efficiency. The air-fuel mixture that is fired anytime other than at the ideal time will result in improper combustion. This will also cause the fuel economy to decrease.