Gasoline powers your car by mixing with air, igniting, and creating controlled explosions that push the pistons down. This linear motion is converted into the rotational force that turns your wheels. It's a precise process involving the engine, fuel system, and exhaust system working in harmony.
The journey begins at the fuel tank. An electric fuel pump sends gasoline through fuel lines to the engine bay. The fuel first passes through a fuel filter to trap any contaminants that could damage sensitive engine components.
Next, the fuel reaches the engine. In most modern cars, it’s injected directly into the intake manifold or the combustion chamber itself by fuel injectors. The engine control unit (ECU), the car's main computer, precisely times the injectors to spray a fine mist of fuel. Simultaneously, air is drawn in through the air filter. The ideal ratio for combustion is about 14.7 parts air to 1 part fuel, known as the stoichiometric ratio.
This air-fuel mixture then enters the combustion chamber, located inside the cylinder. The piston moves up, compressing the mixture. At the peak of compression, the spark plug generates a spark, igniting the mixture. The resulting rapid expansion of gases forces the piston down in what’s called the power stroke. This up-and-down motion of the piston is linear, but it’s converted into rotational motion by the crankshaft, much like riding a bicycle.
Finally, after combustion, the piston moves up again, pushing the leftover gases—the exhaust—out through the exhaust valve. These gases travel through the exhaust manifold, into the catalytic converter (which reduces harmful emissions), and out the tailpipe.
The following table outlines key metrics of a typical combustion event in a modern engine:
| Combustion Parameter | Typical Value / Specification | Notes |
|---|
| Air-Fuel Ratio (Stoichiometric) | 14.7:1 | The ideal mass ratio for complete combustion. |
| Compression Ratio | 10:1 to 14:1 | Higher ratios generally improve efficiency. |
| Peak Combustion Temperature | ~2,500 °C (4,500 °F) | Extremely high temperatures require cooling systems. |
| Spark Plug Voltage | 20,000 to 40,000 Volts | Necessary to create a strong spark across the gap. |
| Cylinder Pressure at Ignition | 150-250 PSI | Pressure varies based on engine load and design. |
| Ignition Timing (at idle) | 5-15 degrees Before Top Dead Center (BTDC) | The ECU constantly adjusts this for optimal performance. |
