October 8, 2024

Juan Valenciana

12th Grade

St. Francis Preparatory School

Beneath the hood of a car is a symphony of controlled explosions that propels the vehicle forward. Automotive engines were first introduced in 1807 when Francois Isaac de Rivaz developed an engine powered by hydrogen and oxygen rather than typical steam engines. Although the design was originally limited in success, it provided evidence that a gaseous-powered car could produce mechanical work. 

To activate the engine, a starter motor is utilized. When you turn the key or press the ignition button in your car, an electric current is sent to the starter motor, which rotates the crankshaft of the engine. This initial rotation gets the pistons moving up and down in their cylinders. The crankshaft also has counterweights for smooth revolutions against the pistons. 

Automotive engines rely on internal combustion, a process that burns fuel to create energy. Most modern engines achieve this by undergoing a ‘four-stroke cycle’: intake, compression, power, and exhaust. 

When a piston reaches the ends of its range, it is called a stroke. During the intake step, the piston descends, sucking in air-fuel mixture into the cylinder from the intake port with both intake valves open. In the next step, the valves close and the piston travels up, compressing the air-fuel mixture. Then in the power stroke, a spark plug delivers an electrical spark that ignites the air-fuel mixture and the resulting combustion forces the piston to the bottom of the cylinder. A connecting rod is attached from the piston to the crankshaft to effectively transfer the linear motion into rotational motion. In the final exhaust step, the piston travels back up, pushing the remaining mixture out through the exhaust port. Cars have up to 12 cylinders, but the pistons do not fire simultaneously. In cars that have a greater number of cylinders, the cylinders may be grouped for even power delivery or simply to fit all the cylinders in the car. 

Cams welded onto camshafts, push the spring-loaded valves attached on top of the cylinder open. Cam gears and a timing belt/chain connect everything back to the spinning crankshaft. This rotation of the crankshaft is what is measured as the RPM. The cylinders and crankshaft are located in the engine block, while other parts such as valves and cams are located in the cylinder head. On one side of the crankshaft is a flywheel to connect to the transmission. 

There are a lot of other systems that support the engine. For example, the air intake system enters through an air filter and then mixes with the fuel before being sucked into individual cylinders through intake ports. Another example is the car's electrical system. The ECM (Engine Control Module) is a mini computer that directs many functions within a car such as spark and valve timing, and air-fuel ratio. The alternator is a part that converts the engine's mechanical energy to charge the battery or run other systems that require electricity. 

The engine is fundamental for the motion, performance, and simple functionality of a car. Current work on engines focuses on the mechanical processes within a car such as combustion without spark plugs. Engines should be studied to limit their environmental impact and improve their performance and sustainability.