Components of an Automobile Engine

Camshaft

In four-stroke engines, the camshaft is responsible for the timely operation of the valves, helping to perform different processes during the engine cycle. It is driven by the engine crankshaft. It operates by converting rotational motion into linear motion to control intake and exhaust valves. It can be located within the engine block or cylinder head. Each camshaft includes lobes that make contact with valve lifters, pushing them to open or close valves. The number of lobes corresponds to the engine’s valve count, ensuring precise operations. Camshafts can be made of hardened steel or cast iron, chosen based on engine requirements.

Crankshaft

The crankshaft transforms the reciprocating movement of the piston into rotational motion. It works according to the upward and downward movement of the piston. The crankshaft is located inside the engine block. It has many crankpins and cranks. The engine connecting rod is connected to the crankshafts through these crankpins and cranks. A 2-stroke engine completes a power cycle after one revolution of the crankshaft, while a 4-stroke engine completes a power cycle after completing two revolutions of the crankshaft.

Harmonic Balancer

It is a device that absorbs and dampens the vibrations produced by the crankshaft, connecting the crankshaft to the engine’s frame. This helps reduce wear and tear on the engine’s components, as well as reduce noise levels and smooth out engine operation. The harmonic balancer also helps keep the timing belt or chain in sync, as it controls the crankshaft’s speed of rotation. The crankshaft does not ride directly on the cast iron block crankshaft supports, but rides on special bearing material. The connecting rods also have bearings inserted between the crankshaft and the connecting rods. The bearing material is a soft alloy of metals that provides a replaceable wear surface and prevents galling between two similar metals. Each bearing is split into halves to allow assembly of the engine. The crankshaft is drilled with oil passages that allow the engine to feed oil to each of the crankshaft bearings and connection rod bearings and up into the connecting rod itself.

Cylinder Valves

The inlet and outlet valves install on the cylinder head, and cams are installed on these valves. The cylinder head blocks the nozzle, which permits the fuel suction or discharge and needs reciprocating movement. In a 4-stroke engine, the intake valve opens to allow the air-fuel mixture into the combustion chamber, while the exhaust valve opens to release burnt gases. These valves are precision-engineered to withstand high temperatures and pressures, typically made from steel alloys, and their timing is critical for efficient engine performance.

Piston

The piston is a cylindrical component that moves up and down within the engine’s cylinder, driven by the pressure of combusting fuel. In a 4-stroke engine, it facilitates the intake, compression, power, and exhaust strokes, converting chemical energy into mechanical energy. Pistons are typically made of aluminum alloys for their lightweight strength and heat resistance. They are fitted with piston rings that seal the combustion chamber, regulate oil, and transfer heat to the cylinder walls. In motorcycles, pistons may be smaller and lighter to suit higher RPMs, while in 2-stroke engines, they often feature ports in the cylinder wall for intake and exhaust, eliminating the need for separate valves. The piston’s crown design can vary, influencing combustion efficiency and power output, making it a critical component in engine performance.

Connecting Rod

The connecting rod links the piston to the crankshaft, transferring the piston’s linear motion into the crankshaft’s rotational motion. It endures significant stress from combustion forces and must be both strong and lightweight, typically forged from steel or aluminum. One end, the small end, attaches to the piston via a wrist pin, while the big end connects to the crankshaft’s crankpin, often with a split bearing for assembly. In high-performance automotive and motorcycle engines, connecting rods are designed for durability under extreme conditions, with some 2-stroke engines using needle bearings at the small end for reduced friction. Proper lubrication through oil passages from the crankshaft is essential to prevent wear and overheating of this vital linkage.

Cylinder Head

The cylinder head sits atop the engine block, sealing the top of the cylinders to form the combustion chamber. It houses the valves, spark plugs (in gasoline engines), and often the camshaft in overhead cam designs. Made from cast iron or aluminum, it must resist high temperatures and pressures while facilitating efficient airflow for combustion. In 4-stroke engines, it plays a key role in directing intake and exhaust gases via ports and valve operation. Motorcycle cylinder heads are often air-cooled with fins, while automotive heads may use liquid cooling. In 2-stroke engines, the head is simpler, lacking valves, as the piston controls gas flow. The head’s design, including combustion chamber shape, significantly affects engine power and efficiency.

Engine Block

The engine block, or cylinder block, is the foundation of the engine, housing the cylinders, crankshaft, and often the camshaft. Typically cast from iron or aluminum, it provides structural support and alignment for moving parts. In a 4-stroke engine, the block contains coolant passages and oil galleries to manage heat and lubrication, critical for durability and performance. In motorcycles, engine blocks are more compact, often integrating the transmission, while 2-stroke blocks include ports for air-fuel intake and exhaust. The block’s cylinder walls, sometimes fitted with liners, endure the piston’s motion, making material choice and machining precision essential for longevity.

Timing Belt/Chain

The timing belt or chain synchronizes the crankshaft and camshaft, ensuring valves open and close at precise intervals relative to piston movement. In a 4-stroke engine, this coordination is vital for the four phases of the cycle. Timing belts, made of reinforced rubber, are quieter but require periodic replacement, while chains, made of metal, are more durable but noisier. Motorcycle engines often use chains for their compact durability, while 2-stroke engines typically lack this component, relying on piston port timing. Misalignment or failure of the belt/chain can lead to catastrophic engine damage, underscoring its importance in multi-cylinder automotive designs.

Oil Pump

The oil pump circulates lubricating oil throughout the engine, reducing friction and wear on moving parts like the crankshaft, camshaft, and bearings. Driven by the crankshaft or camshaft, it draws oil from the sump and delivers it under pressure via passages in the engine block. In a 4-stroke engine, this ensures consistent lubrication during all operating conditions, enhancing component lifespan. In motorcycles, oil pumps are compact yet efficient, often integrated into the engine’s lower end, while 2-stroke engines may mix oil with fuel, reducing the need for a separate pump. Proper oil pressure is critical, with sensors often monitoring performance to prevent engine failure.

Flywheel

The flywheel is a heavy, rotating disc attached to the crankshaft, storing kinetic energy to smooth out the engine’s power delivery. In a 4-stroke engine, it helps maintain momentum between power strokes, reducing vibration and aiding in starting the engine. Typically made of steel or cast iron, it also serves as a mounting point for the clutch in manual transmissions. Motorcycle flywheels are lighter to match higher RPMs, while in 2-stroke engines, they play a similar smoothing role but with a single power stroke per revolution. The flywheel’s mass and balance are key to stable operation across engine types.