What is the working principle of a car engine?

[AdelynLee]

The working principle of a car engine is divided into four processes: intake stroke, compression stroke, power stroke, and exhaust stroke. Therefore, piston engines are also called four-stroke engines. Intake stroke: The piston moves from the top dead center to the bottom dead center under the drive of the crankshaft. At this time, the intake valve opens, the exhaust valve closes, and the crankshaft rotates 180 degrees. During the piston movement, the cylinder volume gradually increases, the gas pressure inside the cylinder gradually decreases from pr to pa, and a certain vacuum is formed in the cylinder. The mixture of air and gasoline is sucked into the cylinder through the intake valve and further mixed in the cylinder to form a combustible mixture. Compression stroke: During the compression stroke, both the intake and exhaust valves are closed. The piston moves from the bottom dead center to the top dead center, and the crankshaft rotates 180 degrees. As the piston moves upward, the working volume gradually decreases, and the pressure and temperature of the mixture in the cylinder continuously rise due to compression. At the end of compression, the pressure pc can reach 800～2000 kPa, and the temperature can reach 600～750 K. On the indicator diagram, the compression stroke is represented by the curve a～c.

[LaLondon]

As a guy who loves tinkering with engines, the principle of car engine operation is quite fascinating. When you turn the key, the battery supplies power to the starter motor, which rotates the engine's crankshaft. The crankshaft drives the pistons to move up and down in the cylinders. First comes the intake stroke: the piston moves downward, drawing a mixture of air and gasoline into the cylinder. Then comes the compression stroke: the piston moves upward, compressing the mixture into a high-pressure, high-temperature state. Next, during ignition, the spark plug emits a spark, triggering a small explosion that generates tremendous force to push the piston downward. Finally, the exhaust stroke: the piston moves upward again to expel the exhaust gases. This cycle repeats continuously, transferring power to the transmission, which then turns the wheels. The internal combustion engine principle dates back to the 19th century, and most cars today rely on it to run. When driving regularly, it's important to maintain the spark plugs and air filter promptly to ensure smooth engine operation.

[Doreen]

This concept was also covered in physics class, where car engines operate based on the working principle of internal combustion engines. Simply put, turning the key activates the circuit to send electricity to the starter motor, which then pulls the engine flywheel to rotate. Subsequently, the engine cylinders begin working: the piston descends to draw in a mixture of air and gasoline, during the compression stroke the piston rises to compress the mixture, increasing temperature and pressure, the spark plug ignites the mixture instantaneously, causing an explosion that drives the piston downward, generating mechanical energy that rotates the crankshaft. This force is transmitted through the drivetrain to the wheels, propelling the car. Throughout this process, the chemical energy of the fuel is converted into kinetic energy and heat, with engine efficiency determining fuel consumption performance. Repair shops often remind us to check for aging spark plugs to prevent ignition failure. Additionally, it's important to monitor battery health during startup, as insufficient charge can make starting difficult.

[MacMichael]

Having driven for decades, starting a car is a basic task. Turn the key, the battery activates the starter, and the engine cranks to life. The pistons in the cylinders move to draw in the air-fuel mixture, compress it, ignite it, and generate power to propel the car forward. The key lies in the proper spark plug function and correct fuel-air ratio. Usually, I turn off the air conditioning before parking to reduce the load on the next start. The engine operates through the cyclic motion of those pistons, and maintenance is straightforward: change the engine oil every few thousand kilometers to prevent carbon buildup and seizing. If the engine runs rough upon starting, it might be an issue with the ignition coil or battery—get it fixed early to ensure safety.

[RafaelRose]

Explaining how a car moves to a child is like describing magic. Turning the key, the engine compartment sucks in air and fuel, compresses it tightly, a spark flashes to ignite the explosion pushing the piston into motion, transferring power to the wheels to move the car. Starting requires a charged battery and a starter motor. If it starts slowly on cold days, don't panic—let it warm up a bit as the oil temperature rises. Remember to maintain the engine filter regularly to protect internal operations and keep things running smoothly.

[DeCameron]

Automotive technology is advancing rapidly, with the core principle of operation being the four-stroke internal combustion cycle. During startup, the key signal activates the ECU computer control system, enabling precise ignition: the starter motor rotates the crankshaft, the piston draws in and compresses the air-fuel mixture, the spark plug ignites the mixture under high pressure to drive the piston, and the exhaust valve expels the waste gases. Modern vehicle models are equipped with sensors to monitor the air-fuel ratio in real time, improving efficiency and reducing pollution. The future may shift towards electrification, but the current mainstream still relies on this mechanical structure for power transmission. During startup, it is essential to ensure sufficient engine oil to lubricate internal components.