THE DISCOVERY OF THE INTERNAL COMBUSTION ENGINE: HOW THERMODYNAMICS, PRESSURE, AND THE LAWS OF HEAT CREATED THE MACHINE THAT POWERS THE WORLD

 

Every modern car—every roar, every acceleration, every highway moment—is built on a discovery born not from automotive engineering, but from pure thermodynamics. Long before pistons, crankshafts, spark plugs, or fuel injectors existed, scientists were trying to understand the invisible nature of heat, pressure, and work.

The internal combustion engine is not merely a mechanical device. It is the physical embodiment of several fundamental laws:

• Boyle’s Law

• The First Law of Thermodynamics

• Gas expansion principles

• Heat-to-work conversion

• Chemical energy release

To master the auto world, you must understand how these laws shaped the engine’s invention, evolution, and dominance.

THE ROOT: HEAT AS A SOURCE OF POWER (1600s–1700s)

Before engines existed, heat was seen as a force that caused things to expand but not something that could perform useful work. The revolution began when Otto von Guericke, Robert Boyle, and Edme Mariotte uncovered the relationship between pressure and volume:

When gas volume decreases, pressure increases. When volume increases, pressure decreases.

This became the first pillar of combustion theory.

Later, the First Law of Thermodynamics established that energy cannot be created or destroyed—only transformed. This meant:

• Fuel contains chemical potential energy.

• Burning it releases heat.

• Heat expands gases.

• Expanding gases perform work.

This logic chain is the foundation of the internal combustion engine.

THE FIRST CRUDE ENGINES: HEAT MAKES POWER (1700s)

Early machines were not internal combustion; they were external combustion steam engines, but they established crucial principles.

James Watt improved the steam engine dramatically, proving:

• expanding vapor can move pistons

• piston motion can rotate shafts

• rotating shafts can perform mechanical work

This system birthed the industrial revolution.

Yet steam engines were massive, slow, and unsuitable for small vehicles. The world needed a machine that burned fuel inside the cylinder—small, light, and efficient.

THE FIRST INTERNAL COMBUSTION ATTEMPTS (1820s–1860s)

This era saw inventors attempting the first real combustion cycles:

1. Robert Street (1794) created a liquid-fuel engine using turpentine vapor ignited by a burner.

2. Samuel Brown (1823) built a gas vacuum engine.

3. Étienne Lenoir (1860) created the first commercially successful internal combustion engine, powered by coal gas.

Lenoir’s engine was inefficient but revolutionary. It introduced:

• an actual piston driven by combustion

• the ancestor of the modern two-stroke cycle

• the idea of igniting fuel inside a cylinder

Its main flaw? It had no compression stroke.

Combustion without compression is weak. This discovery set the stage for the next leap.

THE INVENTION THAT CHANGED EVERYTHING: NIKOLAUS OTTO AND THE FOUR-STROKE ENGINE

In 1876, Nikolaus Otto invented the most important cycle in automotive history: the Otto Cycle, also known as the four-stroke cycle.

The sequence:

1. Intake — piston moves down, pulling in air-fuel mixture

2. Compression — piston moves up, compressing mixture to raise density and energy potential

3. Power — spark ignites mixture; expanding gases force piston down

4. Exhaust — piston moves up, expelling burnt gases

This cycle transformed efficiency because compressed fuel burns harder and delivers more power.

Otto’s breakthrough established the scientific blueprint behind every gasoline engine on Earth.

GOTTLIEB DAIMLER, KARL BENZ, AND THE FIRST TRUE CAR ENGINES (1880s–1890s)

Once the four-stroke cycle existed, two pioneers turned theory into drivable machines:

Gottlieb Daimler

• Miniaturized the engine

• Increased RPM dramatically

• Made compact, high-speed piston engines

• Created carburetion systems for controlled air–fuel mixing

Karl Benz

• Designed the first practical automobile

• Integrated the engine into a chassis

• Created functional ignition systems

• Innovated spark timing and drivetrains

The Benz Patent-Motorwagen became the world’s first true automobile because it combined:

• a four-stroke engine

• a working vehicle frame

• controlled steering

• operational brakes

• a fuel system

• ignition and timing mechanisms

Everything modern cars use today originates from this merging of machine and chassis.

THE EXPLOSION OF COMBUSTION TECHNOLOGY (1900–1930)

Once automakers understood the four-stroke cycle, the next 30 years brought foundational innovations:

• carburetors (precise air–fuel mixing)

• magneto ignition (self-powered spark)

• water cooling (thermal stability)

• oil lubrication pumps (higher RPM stability)

• multi-cylinder engines (smoother power delivery)

• crankshaft balancing (reduced vibration)

By the 1920s, engines were producing reliable power, and combustion engineering became a scientific discipline of its own.

THE SCIENCE OF COMBUSTION: WHAT ACTUALLY HAPPENS INSIDE THE CYLINDER

A gasoline engine transforms chemical energy into motion through the following steps:

1. Fuel evaporates into air.

2. The mixture is compressed.

3. A spark initiates rapid oxidation.

4. Temperature rises above 2,000°C.

5. Gas expands violently.

6. Expanding gas exerts downward force on the piston.

7. The piston’s linear motion rotates the crankshaft.

8. The crankshaft powers the wheels.

Everything depends on pressure increase caused by heat expansion. This is pure thermodynamics:

High temperature → high pressure → mechanical work.

If pressure is lost, efficiency collapses.

DIESEL ENGINES: THE NEXT REVOLUTION (1893–1930s)

Rudolf Diesel invented a new creature: an engine that ignites fuel not with a spark, but through compression ignition.

Diesel cycle principles:

• Air is compressed alone

• Compression heats air to ~500°C

• Fuel is injected

• Fuel self-ignites

The advantages:

• higher compression ratios

• greater thermodynamic efficiency

• extreme torque

• better fuel economy

Diesel became the backbone of:

• trucks

• buses

• heavy machinery

• ships

• generators

• later: turbocharged performance sedans

Diesel engines are the undisputed kings of low-end torque.

TURBOCHARGING: USING WASTE ENERGY TO CREATE MORE POWER

In the 1960s–1980s, engineers discovered that exhaust gas contains unused energy. Turbochargers redirect this energy to:

• spin a turbine

• compress intake air

• increase engine oxygen density

• allow more fuel combustion

• create more power without increasing engine size

This principle unlocked:

• small engines with big power

• massive torque curves

• fuel efficiency improvements

• the modern performance era

Turbocharging revived combustion engines when emissions regulations nearly killed them.

THE MODERN COMBUSTION ENGINE: ELECTRONIC PRECISION (1990–2020)

The final evolution of combustion arrived through electronics:

• fuel injection replaced carburetors

• engine control units replaced mechanical timing

• knock sensors controlled detonation

• variable valve timing improved torque and efficiency

• direct injection increased combustion precision

• turbocharged downsizing became universal

This era maximized thermodynamic optimization.

THE ENDURANCE OF THE COMBUSTION ENGINE

Even as EVs rise, the internal combustion engine remains the most widespread mechanical power system in world history. Its survival comes from:

• energy density of liquid fuels

• mechanical simplicity

• durability

• adaptability

• global infrastructure

• thermodynamic efficiency improvements

A technology that began with basic heat experiments evolved into a planetary-scale engineering marvel.

CONCLUSION

The internal combustion engine was not invented—it was discovered through physics.
Heat expansion. Pressure laws. Energy transformation. Chemical reactions.
Then refined through mechanical engineering, metallurgy, electronics, and human ingenuity.

It is a machine that exists because of the fundamental laws of the universe.