Internal combustion engine: how fuel energy becomes movement

It is impossible to imagine a modern car without a reliable source of energy that drives it. Internal combustion engine (ICE) is just such a unit, designed to convert the chemical energy contained in the fuel directly into mechanical work. This process powers millions of vehicles around the world, providing mobility and comfort.

The principle of operation is based on the combustion of a combustible mixture inside a closed cylinder volume. When ignited, a colossal amount of heat is released, the gases expand and push the piston, causing the crankshaft to rotate. It is this sequence that converts the potential energy of gasoline or diesel into torque at the wheels.

Understanding exactly how internal combustion engine does its job, allows the driver to feel the car better, operate it more efficiently and notice signs of malfunctions in time. Let us consider in detail the device, work cycles and key systems that ensure stable operation of the power unit.

Basic operating principle and duty cycle

The fundamental task of any reciprocating internal combustion engine is to create a reciprocating motion of the piston, which is then transformed into rotational motion of the shaft. This process occurs in several cycles, making up a full operating cycle. Most modern passenger cars use a four-stroke cycle, which was developed back in the 19th century.

The first beat is intake. The piston moves down, creating a vacuum, and a fresh portion of the air-fuel mixture (in gasoline engines) or clean air (in diesel engines) is sucked into the cylinder through the open intake valve. The pressure inside the cylinder becomes below atmospheric.

Then comes the beat compression. Both valves close, sealing the combustion chamber. The piston rises up, compressing the mixture, which leads to a sharp increase in temperature and pressure. At the end of this stroke, sparking occurs (in gasoline internal combustion engines) or self-ignition from compression (in diesel engines).

• 🔥 Working stroke - the only stroke when energy is generated: the burnt gases expand and push the piston down.
• 💨 Issue - the piston rises again, pushing the exhaust gases through the open exhaust valve into the exhaust system.
• ⚙️ Inertia — three auxiliary strokes are performed using the energy accumulated by the flywheel during the power stroke.

⚠️ Attention: Violation of the valve timing (for example, when the timing belt breaks) leads to the fact that the pistons hit the open valves, causing major engine failure.

The fourth stroke completes the cycle, clearing the cylinder for a new portion of the mixture. This entire process is repeated thousands of times per minute. For example, at 3000 rpm of the crankshaft, each piston completes a full cycle 25 times per second. Such high speed requires perfect synchronization of all mechanisms.

The efficiency of energy conversion depends on the compression ratio. The more you compress the mixture before igniting, the more energy can be obtained. However, there is a limit determined by the detonation resistance of the fuel and the strength of the engine materials.

Crank mechanism (CSM)

The mechanical heart of the engine is crank mechanism. It is he who is responsible for converting the linear motion of the shaft into rotation of the crankshaft. The design of the flywheel is subject to enormous thermal and mechanical loads, and therefore requires high manufacturing precision.

The main elements are the cylinder block, pistons with rings, connecting rods and the crankshaft. The cylinder block serves as a frame in which all other parts are located. Pistons move inside the cylinders, on which compression and oil scraper rings are installed. The former ensure the tightness of the combustion chamber, preventing gases from breaking into the crankcase, and the latter regulate the amount of oil on the cylinder walls.

Connecting rods connect the pistons to the crankshaft. The crankshaft has a complex shape with cranks, which allows you to compensate for the displacement of the axis of rotation when the piston moves up and down. A heavy flywheel, which smoothes out jerks during engine operation and helps overcome dead spots during startup.

KShM element	Material of manufacture	Main function
Cylinder block	Cast iron or aluminum alloy	Load-bearing base, housing for cylinders
Piston	Aluminum alloy	Perception of gas pressure, transmission of force
Crankshaft	Forged or cast steel	Motion conversion, torque transmission
Earbuds	Bimetal (steel + anti-friction layer)	Reduced friction in plain bearings

Why are pistons made of aluminum and not steel?

Aluminum has less weight, which reduces inertial loads at high speeds. In addition, it better removes heat from the piston crown, preventing it from burning out. Steel pistons are rare, mainly in heavy diesel engines where strength rather than weight is important.

Lubrication of the rubbing pairs of the crankshaft is carried out under pressure. Oil is supplied through special channels in the block to the main and connecting rod journals of the shaft, creating an oil wedge. The absence of this layer leads to instant metal scuffing and engine destruction. Therefore, checking the oil level is a critically important procedure for the owner.

Gas distribution mechanism (GRM)

In order for an engine to breathe, it needs a precise mechanism to open and close the valves. Gas distribution mechanism (GRM) synchronizes the operation of the valves with the movement of the pistons. A phasing error of even a few degrees can result in loss of power or unstable operation.

Modern engines most often use an overhead camshaft design (OHC or DOHC). The shaft is driven by the crankshaft via a toothed belt or metal chain. There are cams on the shaft, which, when rotated, press on the pushers or directly on the valves, opening them.

The most important modern technology is the variable valve timing system (for example, VTEC, Vanos, VVT-i). It allows you to change the valve lift time depending on engine speed. At low speeds this improves traction and efficiency, and at high speeds it provides maximum power due to better ventilation of the cylinders.

• 🔧 Valves — are made of heat-resistant alloys, since the exhaust valves operate at temperatures up to 900°C.
• 🌡️ Thermoregulation — the gap between the valve and the seat must be strictly defined to compensate for thermal expansion.
• ⛓️ Timing drive — the chain is more durable, but noisier; The belt is quieter, but requires strict routine replacement.

⚠️ Attention: When the timing belt breaks on engines with the so-called “plug-in” design, the pistons meet the valves, which leads to costly repairs to the cylinder head.

The condition of the timing belt should be checked regularly. Chain stretching or belt tooth wear lead to phase shifts. The engine begins to “trouble”, fuel consumption increases and errors appear in the control system. Ignoring these symptoms can lead to the belt jumping onto a tooth and causing an emergency stop of the engine.

Power and ignition systems

For efficient combustion of fuel, it is necessary not only to supply it to the cylinder, but also to properly prepare the mixture. Power system is responsible for the dosage of fuel and its mixing with air. In modern cars, electronic injection reigns, where the amount of gasoline supplied is calculated by the control unit (ECU) based on the readings of many sensors.

The high pressure fuel pump (or electric in-tank pump) supplies fuel to the injectors. The injectors spray gasoline with fine dust, which ensures fast and complete combustion. In diesel engines, the Common Rail system allows fuel to be supplied under enormous pressure, which improves environmental friendliness and traction.

The ignition system is necessary to ignite the mixture in gasoline engines. The main element here is ignition coil, converting the low voltage of the on-board network into a high-voltage pulse. The spark plugs create a spark in the combustion chamber. The gap between the spark plug electrodes must be strictly determined by the manufacturer.

Ignition timing is a critical parameter. The mixture should burn exactly at the moment when the piston is at top dead center. If the ignition is too early, detonation occurs, destroying the pistons. If it’s later, the power drops and the temperature of the exhaust gases rises.

Diagnosis of the power system often begins with checking the pressure in the fuel rail and the condition of the injectors. Clogged injectors disrupt the spray pattern, which leads to excessive fuel consumption and loss of acceleration dynamics. Cleaning or replacing these items is standard maintenance procedure.

Cooling and lubrication system

The internal combustion engine converts only about 30-40% of the fuel energy into mechanical work. The rest is released as heat. If this heat is not removed, the engine will overheat and seize. Cooling system maintains optimal thermal conditions. The liquid pump (pump) circulates antifreeze through the cooling jacket of the block and head, as well as through the radiator.

The thermostat is a key element of this system. It closes off a large circulation circle while the engine is cold, allowing it to warm up faster. When operating temperature is reached, the thermostat valve opens, allowing fluid to flow through the radiator, where it is cooled by counter-flow air and a fan.

The lubrication system performs equally important functions: reduces friction, removes heat from rubbing parts, removes wear products and protects against corrosion. Oil pump creates the pressure necessary to lift the oil to the most distant points of the engine. The filter traps metal shavings and dirt.

• 💧 Antifreeze - not only cools, but also does not freeze at low temperatures, protecting the block from rupture.
• 🛢️ Motor oil - must comply with manufacturer’s tolerances and SAE viscosity.
• 🌡️ Temperature — operation below 80°C or above 105°C is harmful to the life of the motor.

It is important to monitor the condition of the pipes and radiator. Cracks in the pipes can lead to a sudden leak of antifreeze and overheating on the road. And contamination of the radiator with fluff and dirt from the outside reduces its efficiency, forcing the fan to work constantly.

⚠️ Attention: Never open the expansion tank cap on a hot engine! The pressure in the system can reach several atmospheres, and the release of boiling water will cause severe burns.

Efficiency and environmental friendliness of modern internal combustion engines

Every year, the requirements for environmentally friendly cars are growing. Engineers have to find a balance between power, fuel consumption and exhaust cleanliness. Catalyst in the exhaust system it burns harmful gases, turning them into safe compounds of nitrogen and carbon dioxide.

Turbocharging has become standard even for small engines. Using exhaust energy to spin a turbine allows more air to be forced into the cylinders, increasing power without increasing engine displacement. This phenomenon is called downsizing.

However, internal combustion engines have a limit to their efficiency. The theoretical Carnot cycle shows that most of the energy still goes into heat. Therefore, the industry is moving towards hybridization, where the electric motor compensates for the traction failures of the internal combustion engine at low speeds and allows the engine to operate in the most efficient range.

However, The internal combustion engine remains the most energy-intensive and autonomous source of energy for transport, capable of operating in any climatic conditions without complex infrastructure, unlike electric cars. Its evolution continues, becoming cleaner and smarter.

Frequently asked questions (FAQ)

Why does the engine stall at idle?

Tribbing (running on three cylinders instead of four) is most often caused by a misfire. The reasons may be a faulty spark plug, a broken ignition coil, air leaks in the intake manifold, or a malfunctioning injector. Computer diagnostics are required to determine a specific cylinder.

How often should you change your engine oil?

The replacement interval depends on operating conditions. If you only drive on the highway, you can adhere to the regulations (usually 10-15 thousand km). In city mode with traffic jams, it is better to reduce the interval to 7-8 thousand km, since engine hours in traffic jams accumulate faster than mileage.

What is engine knock?

This is the explosive combustion of the fuel mixture, accompanied by a characteristic metallic knock. Occurs when using low octane fuel, engine overheating or incorrect ignition timing. Prolonged detonation destroys pistons and ring partitions.

Is it possible to mix antifreeze of different colors?

Strongly not recommended. Different colors often (but not always) mean different additive chemistry. When mixed, a sediment may form that clogs the radiator, or a chemical reaction may begin that destroys the seals. It is better to add distilled water in an emergency than incompatible antifreeze.