How does timing error affect engine performance and emissions?

• A. Increases power and reduces emissions
• B. No effect on performance
• C. Reduces power, increases fuel consumption, raises exhaust temperatures, and increases emissions or knocking
• D. Only affects idle performance

Answer: (C)

Timing controls when the air–fuel mixture ignites in relation to the piston position, so the energy from combustion is delivered to produce work at the right moment. When timing is off, combustion isn’t aligned with piston movement, so less of the fuel’s energy is converted into useful power. That means you get a drop in engine power, and to achieve the same output the engine ends up burning more fuel, increasing fuel consumption. Mis-timed combustion also changes how heat is released, often sending more heat into the exhaust, so exhaust temperatures rise. Because the combustion isn’t occurring in the optimal way, emissions tend to go up, and if the mixture ignites too early the engine can experience knocking. Proper timing is what keeps power, efficiency, and emissions in balance.