For most people, a car is a thing they fill with gas that moves them from point A to point B. But have you ever stopped and thought, How does it actually do that? What makes it move?
Unless you have already adopted an electric car as your daily driver, the magic of how comes down to the internal combustion engine—that thing making noise under the hood. But how does an engine work, exactly?
Specifically, a car engine is a heat engine in that it converts energy from the heat of burning gasoline into mechanical work, or torque. That torque is applied to the wheels to make the car move.
And unless you are driving an ancient two-stroke Saab (which sounds like an old chainsaw and belches oily smoke out its exhaust), your engine works on the same basic principles whether you’re wheeling a Ford or a Ferrari.
What is a Car Engine?
The engine is the heart of your car. It is a complex machine built to convert heat from burning gas into the force that turns the road wheels.
The chain of reactions which achieve that objective is set in motion by a spark, which ignites a mixture of petrol vapor and compressed air inside a momentarily sealed cylinder and causes it to burn rapidly.
That is why the machine is called an internal combustion engine. As the mixture burns it expands, providing power to drive the car.
To withstand its heavy workload, the engine must be a robust structure. It consists of two basic parts: the lower, heavier section is the cylinder block, a casing for the engine’s main moving parts; the detachable upper cover is the cylinder head.
The cylinder head contains valve-controlled passages through which the air and fuel mixture enters the cylinders, and others through which the gases produced by their combustion are expelled.
The block houses the crankshaft, which converts the reciprocating motion of the pistons into rotary motion at the crankshaft.
Often the block also houses the camshaft, which operates mechanisms that open and close the valves in the cylinder head. Sometimes the camshaft is in the head or mounted above it.
How Does An Engine Work In a Car?
Combustion, also known as burning, is the basic chemical process of releasing energy from a fuel and air mixture.
In an internal combustion engine (ICE), the ignition and combustion of the fuel occurs within the engine itself. The engine then partially converts the energy from the combustion to work. The engine consists of a fixed cylinder and a moving piston.
The expanding combustion gases push the piston, which in turn rotates the crankshaft. Ultimately, through a system of gears in the powertrain, this motion drives the vehicle’s wheels.
There are two kinds of internal combustion engines currently in production: the spark ignition gasoline engine and the compression ignition diesel engine.
Most of these are four-stroke cycle engines, meaning four piston strokes are needed to complete a cycle. The cycle includes four distinct processes: intake, compression, combustion and power stroke, and exhaust.
Spark-ignition gasoline and compression-ignition diesel engines differ in how they supply and ignite the fuel. In a spark ignition engine, the fuel is mixed with air and then inducted into the cylinder during the intake process.
After the piston compresses the fuel-air mixture, the spark ignites it, causing combustion. The expansion of the combustion gases pushes the piston during the power stroke.
In a diesel engine, only air is inducted into the engine and then compressed. Diesel engines then spray the fuel into the hot compressed air at a suitable, measured rate, causing it to ignite.
The Four Strokes of a Four-Stroke Engine
The engine creates power by following a four-stroke cycle, which consists of the intake stroke, compression stroke, power stroke, and exhaust stroke.
1. Intake Stroke.
The intake stroke starts at the “Top Dead Center” (TDC), where the piston is at the top of the cylinder. As the piston moves down the cylinder, it creates a vacuum, and the intake valve opens, allowing air to be sucked into the cylinder.
In carburetted engines and port and throttle body injected motors, the fuel comes in with the air. In direct-injected motors, the fuel is squirted directly into the cylinder.
2. Compression Stroke.
The compression stroke begins when the piston reaches the “Bottom Dead Center” (BDC). The intake and exhaust valves are both closed, and the fuel and air mixture is compressed by the piston into the combustion chamber.
The compression ratio is the volume of the cylinder plus the combustion chamber compared to the volume of just the combustion chamber. This ratio can be anywhere from 8:1 to 12:1 or more in some race engines.
Compressing the mixture greatly increases the amount of power produced by combustion, but the compression itself produces heat, which can cause detonation or pre-ignition.
3. Power Stroke.
The power stroke is where the engine produces power. The spark plug fires, igniting the mixture, as the piston is at the top of the stroke. The resultant explosion moves the piston rapidly back down the cylinder, turning the crankshaft, and making the car go.
In a diesel engine, there is no spark, the mixture just spontaneously ignites at the right moment due to the heat of compression. In a single-cylinder engine, at idle, you can practically hear each individual explosion.
4. Exhaust Stroke.
The exhaust stroke begins when the piston moves back up the cylinder due to the momentum produced during the power stroke and the weight of the flywheel (in a single-cylinder motor), or due to the firing of other cylinders.
The exhaust valve opens, and instead of compressing the burned gases, they are pushed out into the exhaust port.
As the piston gets close to TDC again, the exhaust valve starts to close, and the intake starts to open, for a small period called “overlap” where the escaping exhaust creates suction that helps pull air in via the intake valve opening.
The cycle then starts again, with the piston moving down on another intake stroke.
Parts of a Car Engine
The different parts that make up your car’s engine consist of: the engine block (cylinder block), the combustion chamber, the cylinder head, pistons, the crankshaft, the camshaft, the timing chain, the valve train, valves, the rocker’s arms, pushrods/lifters, fuel injectors, and spark plugs.
The engine block (cylinder block)
The engine block is the core of your engine. It is usually made of aluminum alloy and on rare occasions iron. It is also called a cylinder block because of the cylinder tubes that help make it up.
The cylinder block is the home for the pistons (where they move up and down). Often cars have more than one cylinder (usually four, six, or eight). The more cylinders that the engine has the more powerful it is.
The combustion chamber
The combustion chamber is where the energy is transformed in the combustion process. This is the area of the engine in which the fuel, air, electricity, and pressure have an explosive reaction that causes the pistons to move up and down.
The movement of the pistons gives the car the power to move.
The cylinder head
The cylinder head sits above the engine’s cylinders creating a space at the top of the chamber for combustion. It is also the home for various other parts such as intake and outtake valves, the spark plugs, and the fuel injectors.
The pistons
As explained before, when the energy is created the pistons then move up in down to give the vehicle power to move.
They look similar to cans and are connected to the crankshaft. Pistons also consist of compression rings and oil rings which help to seal the combustion chamber and prevent oil from leaking into that area.
The crankshaft
The crankshaft is the part of the engine that rounds out the up and down motion of the pistons. It is connected to rubber belts which are connected to the camshaft allowing for power to be delivered to various parts of the car.
The camshaft is connected to the drive train which is the part that transfers power to the wheels.
The camshaft
The camshaft works with the crankshaft, connected by a timing chain, allowing the intake and outtake valves to open and close according to a specific timeline.
The timing chain
The camshaft and crankshaft, as mentioned above, are connected by a timing chain. These parts work together to make sure certain actions take place at certain times, which is vital for the functioning of the engine.
The valvetrain
The valvetrain is the part of the engine that controls the movement of the valves. It is made up of the valves, as well as the pushrods and lifters, and rocker arms. It is connected to the cylinder head.
The valves
The valves in an engine are the intake valves and the outtake valves. Intake valves work to transfer the air and fuel levels into the combustion chamber.
The outtake valves work to move the exhaust that is created from the combustion out of the chamber.
The rocker’s arms
The rocker arms work with the cams (from the camshaft) to press down on the valve system and let the needed air into the chamber or the exhaust out.
The pushrods/lifters
In engines (overhead valve engines) in which the camshaft lobes don’t touch the rocker arms, the pushrods/lifters are used in place in the valve system.
The fuel injectors
For the combustion process to occur, fuel is necessary. The fuel injectors work to move fuel into the cylinders.
There are three different fuel injection systems: direct fuel injection, ported fuel injection, and throttle body fuel injection.
The spark plugs
There is a spark plugs that resides above each of the cylinders. During the combustion process, the spark plugs spark which ignites the compressed fuel and air and therefore causing the “explosive” process that pushes the piston down.
Types of Engines’ Layouts
While most vehicles use internal combustion engines, the setup of these engines can vary. The cylinder layouts can vary, depending on the amount of power a manufacturer wants the car to have or to ensure the engine will fit the space that’s allotted.
The most common cylinder layouts include:
Straight: Cylinders in a straight engine layout are arranged in a line parallel to the car from front to back. This allows more cylinders to fit, making this layout popular for powerful sedan models.
Inline: Inline engines feature cylinders that are arranged side-by-side and upright. This is a popular configuration since it allows for a smaller, compact engine.
V: When viewed from the front, the cylinders in a V-engine are arranged in a V-shape. They feature the cylinders arranged at a 60-degree angle. These engines allow a lot of cylinders to fit and are often found in high-performance models.
Flat: Also referred to as a boxer engine, the cylinders lie horizontally. This engine type is uncommon and is most often found in Porsche vehicles. They do offer the benefit of a low center of gravity within the engine bay.
Cylinder Configurations
The number of cylinders a vehicle has helps determine the amount of power an engine can produce. Items like turbochargers allow for extra compression in the combustion chamber, meaning engine power can be increased without adding more cylinders.
The smallest engine configuration is a twin-cylinder, but these don’t offer much power or capacity. However, they are sometimes found on smaller eco-friendly engines.
Three-cylinder engines typically are arranged in a straight-engine layout and can sometimes be found on smaller vehicles or hatchbacks. This compact design provides good fuel economy, and cars can still have a decent amount of power with the addition of a turbocharger.
The most common engine configuration is the four-cylinder, which is found on a variety of vehicles from small to midrange. A four-cylinder engine is set up in an inline design and offers a good amount of engine output.
The number of cylinders in an engine can continue to increase, like six-cylinder engines that are found in high-end performance and sports cars.
FAQs.
What is the engine of a car?
An engine is a machine that burns fuel and converts it into mechanical power. Most modern vehicles use internal combustion engines (ICE), which ignite fuel and use the reaction to move mechanical parts.
What are the parts of the car engine?
The different parts that make up your car’s engine consist of: the engine block (cylinder block), combustion chamber, cylinder head, pistons, crankshaft, camshaft, timing chain, valve train, valves, rocker’s arms, pushrods/lifters, fuel injectors, and spark plugs.
How does a car engine work step by step?
The intake function involves drawing a mixture of air and fuel into the combustion chamber. The compression function compresses the mixture. The power function involves igniting the mixture and harnessing the power of that reaction. The exhaust function expels the burned gases from the engine.
How does a car actually work?
A gasoline car typically uses a spark-ignited internal combustion engine, rather than the compression-ignited systems used in diesel vehicles. In a spark-ignited system, the fuel is injected into the combustion chamber and combined with air. The air/fuel mixture is ignited by a spark from the spark plug.
What starts a car engine?
The starter is a tiny but powerful electric motor that spins a small starter gear. When you turn the key, power is sent to the starter which engages its starter gear with the engine. The starter then “cranks,” creating that unmistakable sound of a car engine starting up.