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The Mechanics of a Modern Car Engine Explained

A car engine is a complex machine that transforms heat from burning gasoline into the force to turn your wheels. To do this it pulls air (along with fuel) in, squeezes it, combusts it and then pushes the exhaust out.

Inside the cylinders, pistons move up and down in a metal box called a combustion chamber. They are connected to a crankshaft that turns their back-and-forth motion into circular movement at engine speed.


A car engine is a complex machine built to convert heat from burning gasoline into the force that drives your wheels. The engine accomplishes this task by converting fuel into energy via thousands of tiny controlled explosions that occur every minute inside the car’s cylinders. These explosions push pistons within the cylinders, turning a crankshaft connected to a transmission, which sends torque to your vehicle’s wheels. Whether you’re an automotive enthusiast or just curious, understanding how your car’s engine works can make for an interesting conversation piece – even for something such as to how Vail Valley businesses adapt to pandemic aftermath.

The basic engine mechanism consists of between four and twelve cylinders arranged in a flat or V-shaped configuration. The cylinders are housed in an engine block that contains all the essential bottom end components. It’s typically made of cast iron or aluminum and has many holes designed to keep the cylinders contained and to allow water and oil to flow through it for cooling and lubrication. The cylinders are separated from each other by a cylinder head, which contains the spark plugs and valves.

There are different ways to arrange the cylinders in an engine and each has its own benefits and drawbacks. The most common arrangement is a straight-four layout that can be found in nearly all cars. This design offers good fuel economy, but does not produce as much power as other options. Car manufacturers are constantly experimenting with ways to improve an engine’s performance, including increasing its displacement. More cylinders allow each one to burn more gas per engine revolution, which increases the amount of power that it can generate.

A cylinder’s piston is short cylindrical parts that seal one end of the cylinder from the high-pressure air and combustion products, while sliding continuously up and down inside the cylinder during operation. A camshaft, positioned either in the block or in the cylinder head, operates mechanisms that open and close the valves at the correct time during each cylinder’s stroke.

As each piston moves down the cylinder, it creates a vacuum that draws in air and fuel mixture from outside the engine. The combination is ignited by a spark plug and burns to create expanding gases that propel the piston back up. The spark plug then fires off another spark to initiate the next cycle, and a fresh supply of fuel is fed into the cylinder.

The Crankshaft

The pistons move up and down in the cylinders, creating linear motion, and this motion is converted to rotation by the crankshaft. This movement powers the car’s transmission, which in turn propels the wheels.

At one end of the crankshaft are a pair of rod-bearing journals – these are offset from the main journal and connected to the connecting rods. A feed of pressurised oil is forced into the space between these bearings to keep them separate and prevent metal-to-metal contact.

When the piston moves downwards during the intake stroke it uncovers a duct that runs from the crankcase to the cylinder and is filled with fuel mix. This mixture is then ignited by spark plugs at the top of the compression stroke. As the piston moves upwards the flame burns off the remaining fuel and gases, and are expelled as exhaust during the exhaust stroke.

A crankshaft has a pair of counterweights attached to its ends, these are used to balance the forces created by the piston and connecting rod moving up and down. This ensures smooth operation and allows the engine to run at higher RPM’s.

The front of the crankshaft is attached to a flywheel and on its rear end is a pulley. The flywheel is designed to be extremely heavy, and this helps to create a large amount of rotating energy in the engine. This energy is used to power accessories such as the alternator, air conditioning compressor and power steering pump.

The cylinder block is a solid piece of cast iron or aluminium that sits on top of the cylinder heads and houses the crankshaft, connecting rods and a number of other essential components. It also contains the cylinders and has a detachable upper section called the cylinder head that contains valve-controlled passages through which air, fuel and combustion products enter and leave the cylinders. It also has a number of other important functions including, in some cars, a camshaft which operates mechanisms that let the air and fuel into and out of the cylinders at the right time to achieve proper combustion.

The Cylinder Head

The cylinder head seals off the top of the cylinders and houses the valves, fuel injectors and spark plugs that ignite the air-fuel mixture and propel the pistons up and down. It also contains the intake and exhaust passages that feed air and fuel into the engine, as well as the ducts needed for circulation of coolant and combustion gases. The cylinder head is subject to very high temperatures and pressures and must be robust enough to withstand these conditions without cracking or breaking.

Modern engines are much more sophisticated than their older counterparts, but they still operate on the same basic principles. While today’s car engines have more advanced parts and systems, they still require regular maintenance and care to perform properly. A failure of the cylinder head can severely compromise the operation of the entire engine and vehicle as a whole.

Cylinder heads are generally made of cast iron or aluminum alloys. They are designed for use in an environment that imposes extreme mechanical loads, high thermal stress, and chemical corrosion. Cast iron is the most common material due to its high strength and good resistance to corrosion. Aluminum is lighter, has better thermal conductivity, and is easier to work with than cast iron.

There are different kinds of cylinder heads, each designed to suit a specific kind of engine. The earliest heads were known as flatheads and had their valves on the sides of the head. Flatheads are now rare, as they have a number of flaws in their design, including the fact that the valves open and close at the wrong times, which causes poor combustion and inefficient operation.

The cylinder heads on modern cars are usually shaped more like bowls to allow for better gas flow. The shaped head can help to increase engine efficiency and power, as well as reducing its emissions.

The cylinder head houses the fuel injection system, the spark plugs and the camshaft. The cylinder head is also the location of the ducts that carry coolant, combustion gases and lubricating oil. Because they are fixed in place and sealed with a head gasket, cylinder heads don’t experience the same wear and tear as other moving engine parts.

The Valve Train

The internal-combustion engine in your car uses a series of controlled explosions to turn the fuel you put in it into mechanical work that drives the wheels and gets you to the grocery store. Whether you’re driving an ancient two-stroke Saab that sounds like a chain saw and belches oily smoke, or a high-tech V-8 Ferrari that does the same job with more power, the basic mechanics are the same. Fuel, air and spark create the explosions that propel the pistons within the cylinders, turning a crankshaft connected to a transmission which turns the wheels. It’s a simple formula, but it takes a lot of energy to power your car.

Every modern car engine relies on a set of mechanisms to open and close the intake and exhaust valves at the correct time, so the engine can produce the explosions and power it needs in an efficient and effective manner. The entire system of parts that performs this vital function is called the valve train.

There are basically three basic types of valve train systems, based on the way in which the engine’s cylinder head opens and closes its intake and exhaust valves. The most common systems are the Over Head Valve (OHV), Single Over Head Cam (SOHC) and Dual Over Head Cam (DOHC).

During the combustion stroke, as the piston moves down through the cylinder, it exposes the intake valve to the crankcase. At this point, the fuel mix in the crankcase is under pressure, and as the piston moves down it compresses it until it reaches what is known as top dead center or BDC. At this point, the spark plugs ignite the air and fuel mixture to produce a controlled explosion that burns the fuel to create electricity and heat.

As the piston moves down through the cylinder on its power stroke, it uncovers the exhaust valve, and as it approaches BDC, the residual combustion pressure begins to blow the exhausted gases out of the cylinder. As the exhaust valve opens, it also allows the intake valve to begin its opening cycle.