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How do Car Engines Work?

Aurora, IL
car, stroke, cylinder, fuel, engine, exhaust, combustion, piston, turbocharger, v8, intake
This vintage V12 engine was made by Lamborghini in 1966 and was used in the Miura, one of the company's first cars.

Cars are used daily by billions of people around the world and are the main source of transportation for people in the United States and many other countries. Nowadays, many manufacturers are introducing battery-powered cars, with Tesla at the forefront of the technology. However, cars using the internal combustion engine are still the most common type on the road today. The internal combustion engine was a breakthrough when it was first created and continues to be an engineering marvel today. The internal combustion engine is made up of multiple moving parts, each of which is integral to the success of the vehicle. Learning more about the engine can help us better understand the vehicles we use everyday.

Car engines use the process of combustion to extract heat energy from fuel such as gasoline or diesel. This heat energy is then converted to mechanical work (or torque) which then moves the wheels of the car. Combustion occurs inside a cylinder with a piston inside it. Most gasoline engines on the road today are four-stroke engines, meaning that four different processes happen in one cycle. The first stroke is known as the intake stroke. Combustion requires three main components: heat, fuel, and air. The air intake and filter, located behind the car’s grille, intake air for the first stroke. During the second step, the compression stroke, the fuel and air are then mixed and compressed by the piston. After that, during the third step or the power stroke, the spark is released, creating combustion. This combustion results in expanding gases which move a piston down the cylinder during the exhaust stroke, the fourth and final stroke. The excess gas is released through the exhaust pipes and the piston goes back up the cylinder to restart the process all over again.

car, stroke, cylinder, fuel, engine, exhaust, combustion, piston, turbocharger, v8, intake
This handy diagram visually depicts the four strokes of an engine.

The four stroke process is all contained within one cylinder–most cars have 4 or 6 cylinders, but the number can range from 3 to 16 cylinders! Having more cylinders allows the car’s engine to be more balanced and deliver power more smoothly, although having 12 or 16 cylinders may not have much of a benefit compared to having 8. Engines are differentiated by their cylinder count as well as their cylinders’ displacement; for example, a BMW M5, a luxury sports sedan, would have an engine labeled as a 4.4 liter twin-turbo V8. 4.4 liters corresponds to the engine’s displacement, and the V8 corresponds to the number of cylinders and their arrangement inside the vehicle. Additionally, some engines have turbochargers or superchargers, which are extra add-ons which help the engine take in more air, which in turn corresponds to more fuel being burned. The BMW example above has two turbochargers, hence the name “twin-turbo”. However, some turbocharged engines experience “turbo lag”, which is the period of delay between stepping on the accelerator and the moving of the vehicle caused by the turbochargers intaking all of that air.

Overall, cars are very fascinating machines and have a huge future ahead of them, even if that is not with internal combustion engines. The cars of tomorrow will have new technologies, possibly even more complicated than today’s engines, but all of them will follow the same basic principles of engineering that cars nowadays follow. These principles will take vehicles, and thus humanity, to new heights.

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