Car Engine Parts Guide & Resources
An internal combustion engine powers your car (unless you drive a pure electric vehicle). You know that much, but are you familiar with the engine’s internal components and how they work?
If you’re like most drivers, the answer is probably no. But not to worry—we have the information and resources you need to get up to speed.
How Does a Car Engine Work?
Your car’s engine is a complex assembly that uses energy from the combustion of air and fuel to create mechanical motion. When the vehicle is running, the engine pulls in air through the intake system. That air is mixed with fuel supplied by the fuel injectors.
The air-fuel mixture is then compressed and ignited inside of the engine to create a series of small explosions that cause the engine to continually rotate. The rotational force from the engine is then transferred through the drivetrain to the drive wheels to get the vehicle moving.
Four-Stroke Engine Operation
Inside the engine, there is a crankshaft and one or more camshafts. The crankshaft is attached to the connecting rod and piston assemblies, which move up and down inside the engine’s cylinders. At the same time, the intake and exhaust valves are operated by the camshaft(s).
When a piston assembly travels from the top to the bottom of the cylinder or vice versa, that’s referred to as a stroke. Automobile internal combustion engine operation involves a four-stroke cycle of events that repeat in each cylinder.
In a gasoline-powered engine, the four different stroke events take place as follows:
- Intake stroke: During the intake stroke, the camshaft opens the intake valve(s) as the piston moves downward, allowing the air-fuel mixture to be drawn into the cylinder.
- Compression stroke: When the compression stroke begins, the intake and exhaust valves close as the piston moves upward, compressing the air-fuel mixture.
- Power stroke: As the piston reaches the top of its travel, the spark plug ignites the air-fuel mixture, causing an explosion that forces the piston downward. The linear movement of the piston causes the crankshaft to turn, creating the rotational force needed to propel your vehicle down the road.
- Exhaust stroke: During the exhaust stroke, the camshaft opens the exhaust valve(s) as the piston moves upward, allowing spent exhaust gases to be forced from the engine into the vehicle’s exhaust system.
Obviously, the crankshaft and camshaft(s) must be kept in sync (“in time”) so that the pistons are at the correct point of travel when the valves open and close. Depending on the engine design, either a timing belt or timing chain performs this task by connecting the crankshaft to the camshaft(s).
Parts of a Car Engine (with Pictures)
An internal combustion engine is a complex assembly made up of many different parts. Nearly all engines have these key components:
The engine block is a cast iron or aluminum casting that houses the cylinders, piston assemblies, crankshaft, and (in some cases) the camshaft. Basically, the block acts as a frame or foundation for the rest of the engine components.
Piston and Connecting Rod Assemblies
There is one piston and connecting rod assembly for each of the engine’s cylinders. The piston assemblies move up and down during the four-stroke engine cycle. As a result, the crankshaft, which is connected to the piston assemblies, is forced to turn.
Each piston has two compression rings and one oil control ring, each of which forms a seal between the piston and the cylinder wall. The compression rings prevent combustion pressure from sneaking past the pistons. Meanwhile, the oil control ring prevents oil from getting on top of the piston and being burned in the combustion chamber.
The camshaft is a rotating assembly that opens and closes the engine’s valves. Some engines have an overhead camshaft (OHC) design that houses the camshaft in the cylinder head. Others have an overhead valve (OHV) setup with the camshaft in the engine block.
Also, some engines have two camshafts—one for the intake valves and one for the exhaust valves—in each cylinder head. Such a layout is referred to as a dual overhead camshaft (DOHC) configuration.
Like the camshaft, the crankshaft is a rotating assembly inside the engine. The crankshaft is connected to the pistons and connecting rods.
During the combustion process, the pistons move up and down in the cylinders, forcing the crankshaft to rotate. In this way, the crankshaft converts the linear motion of the pistons into the rotational force that causes the vehicle to move under its own power.
All engines have one or more cylinder heads. Engines with a ‘V’ or flat configuration have two cylinder heads, whereas engines with an inline or straight configuration have one.
The cylinder head seals the tops of the cylinders inside the engine block. Also, the head contains the valves, which allow the air-fuel mixture to enter the engine and exhaust gases to exit. In some cases, the cylinder head also houses the camshaft(s).
Timing Belt or Timing Chain
All engines have either a timing belt or timing chain that connects the camshaft(s) to the crankshaft to ensure the rotating assemblies are in sync. A timing belt is made of rubber, whereas a timing chain is composed of metal links connected together.
There are two types of engine valves: intake and exhaust. The intake valves allow air (and fuel in the case of port injection) into the engine, whereas the exhaust valves allow exhaust gases to exit.
Depending on the engine’s design, there are usually two to four valves per cylinder. The valves are located in the cylinder head.
In an OHV engine, the camshaft operates a lifter, which, in turn, moves a pushrod that opens the valve with a rocker arm. An OHC engine will have a different setup in which the camshaft may open the valve via a bucket tappet, camshaft follower, or some other means. Each valve has a spring that keeps it closed against its seat until the camshaft forces it open.
The intake manifold contains passages that distribute air to the engine’s individual cylinders. You’ll find the manifold mounted to the cylinder head(s).
An exhaust manifold is used to route spent exhaust gases away from the engine’s cylinder head and toward the exhaust pipe. Engines with a ‘V’ or flat configuration have two exhaust manifolds, whereas engines with an inline or straight design have just one.
There is a valve cover (also known as a rocker cover or camshaft cover) located on top of each of the engine’s cylinder heads. The valve cover’s purpose is to protect the valves and related components while also preventing oil from escaping the cylinder head.
Flywheel or Flexplate
The flywheel is attached to the rear of the crankshaft. When the vehicle is running, the flywheel stores inertial energy created during engine firing pulses to help the crankshaft maintain a constant speed.
Vehicles equipped with an automatic transmission have a device called a flexplate that’s similar to a flywheel. However, flexplates are thinner than flywheels because automatic transmissions have a type of fluid coupling device, called a torque converter, that helps dampen engine firing pulses.
The flywheels (or flexplate) also has a toothed outer ring gear that can make contact with the starter motor’s pinion gear. When the ignition key is turned to the “start” position, the starter motor rotates the flywheel to get the engine turning and the vehicle running.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.