How a Car Engine Works

Types of Car Engines

The automobile was first introduced in 1672. It was steam-powered. Since then, the modern vehicle has gone through many upgrades, bringing us to the types of engines used today.

• Internal combustion engine (ICE) – This has been the most popular engine type over the past century. Fuel and air mix and ignite within the cylinder to create high-pressure gas that pushes on the piston to generate mechanical power.
• Diesel – This is another form of ICE, but instead of using spark plugs to ignite the mixture, it utilizes compression.
• Hybrid – This powertrain combines an electric motor with an internal combustion engine.
• Electric – An electric motor provides all the motivation to power the vehicle.

How Does an Internal Combustion Engine Work?

Unless your vehicle runs only on electric power, it will have an internal combustion engine. While the size and layout may differ, the general operation remains the same.

Inside the engine, a mixture of fuel and air ignites. This combusts the fuel, and the released energy is converted into torque, otherwise referred to as mechanical energy.

The ICE has fixed cylinders with moving pistons. Mechanical energy pushes the pistons, causing the crankshaft to rotate. The gears are then pushed into motion to make the wheels move.

The combustion stroke is the most important process in the engine. It’s what keeps the engine running. The majority of ICEs have a four-stroke combustion cycle.

1. Intake – The air-fuel mixture is brought through the intake valves and sent to the cylinders.
2. Compression – The intake and exhaust valves are both closed during this stroke. The pistons move up, and the air-fuel mixture becomes compressed toward the plugs.
3. Combustion – The plugs ignite the mixture with a small explosion. This force pushes the pistons down.
4. Exhaust – During the exhaust stroke, the exhaust valve opens, and the gasses that were created by combustion are expelled while the piston travels back up the cylinder.

Most modern diesel engines are also four-stroke, but the combustion occurs differently. Instead of spark plugs igniting the mixture, high compression ignites the fuel and air.

Internal Combustion Engine Configurations

V-Style Engines

The Chevrolet LS7 is a comparatively compact V-8 engine that produces well over 500 horsepower.

V-type motors have a durable design and exceptional engine displacement. They are usually installed in larger vehicles, such as SUVs and trucks, but they also have a place in performance vehicles. However, these are more expensive to manufacture and maintain.

• V-6 – three cylinders on each side
• V-8 – four cylinders on each side
• V-12 – six cylinders on each side

Inline Engines

An inline four-cylinder Ecoboost 2.0-liter turbocharged engine.

Inline engines contain all of the cylinders in one straight row in line with the crankshaft. In these engines, there is one cylinder head instead of the two found in V-engines. The Ford Model T relied on an inline design, and the basic configuration is still used. Because these engines are compact and lightweight, they help to improve fuel efficiency.

They are also easier to fix. However, three- and four-cylinder inline engines don’t tend to produce a lot of power. A straight six can produce a lot more power, but it’s not as common as the smaller variants.

Flat Engines

The flat engine, sometimes known as a boxer engine, is very similar to the V-style. The only difference is that the cylinders are installed at a 180-degree angle from one another. The flat engine is well-balanced and offers a lower center of gravity. However, they are larger engines, so they take up more room.

A Subaru flat four-cylinder engine.

Radial Engines

The radial engine isn’t found in a lot of vehicles these days, but it is still commonly used in propeller-driven aircraft. It contains a single crankshaft at the center of the pistons that moves in a star pattern instead of up and down.

Rotary Engines

The rotary engine uses a rotor—typically shaped like a rounded triangle—within an epitrochoidially-shaped housing, spinning around a central crankshaft. These engines are compact and incredibly powerful for their size, but tend to be inefficient and finicky to maintain.

These engines are basic and durable. However, not all mechanics know how to work on them.

Rotary engines are assembled like sandwiches. This is an exploded view of a two-rotor engine.

How Does a Hybrid Engine Work?

Hybrid engines use a battery to augment power from the ICE. The primary goal is fuel economy, but hybrids can also combine their two power sources for enhanced performance.

A typical internal combustion engine supplies fuel from the gas tank to power the engine. In a hybrid, the onboard computer determines how much power should be supplied from gasoline, with the rest coming from the battery.

There are two main configurations with a hybrid.

• Series – The electric motor is responsible for supplying most of the energy to the wheels. Power comes directly from the batteries or from a generator run by the gasoline engine. When the battery is fully charged, battery energy is used first. When it’s depleted, the vehicle switches to power from the generator.
• Parallel – Power comes from the electric motor or gas engine, or a combination of both. The onboard computer determines which is best for the driving conditions. It may use the electric motor to pull away from a stop but rely on the gas engine to merge into freeway traffic.

The Toyota Prius is known as a parallel-series hybrid. This configuration allows the gas engine and electric motor to drive the wheels at the same time. The Prius uses a planetary gear set connecting the generator, electric motor, and gas engine.

Most hybrid vehicles recharge through regenerative braking. When you take your foot off the accelerator, regenerative braking reclaims the mechanical energy created when stopping the car and converts it to electrical energy that charges the battery. Plug-in hybrids, as the name suggests, use regeneration but are also plugged in to recharge.

Does an Electric Car Have an Engine or a Motor?

An electric car, or battery electric vehicle (BEV), does not have an internal combustion engine. BEVs are powered by one or more electric motors and a rechargeable battery. The electric car motor is made from two basic parts.

• Stator – Stationary part made from a core, conducting wire, and frame that is needed to create a magnetic field.
• Rotor – Cylindrical part made from a core, conducting rods, and end rings.

Electric car motors on the production line. (Source: Chevrolet)

The battery connects to the motor. When electrical energy is transferred to the stator from the battery, the coils in the stator begin acting as magnets. These coils create a rotating magnetic field that pulls the conducting rods on the rotor. The spinning rotor creates mechanical energy that is transferred to the wheels.

Electric cars don’t use an alternator. They must be plugged in to receive a charge and store energy to be used for propulsion. However, they have a major advantage over ICE vehicles. They don’t need gasoline or diesel fuel to run, and EVs do not emit pollution via a tailpipe.