Engine Fundamentals and Operation

The stroke in the engine cycle where the air-fuel mixture is squeezed, increasing its combustibility, before ignition.

The stroke where the ignited air-fuel mixture burns, producing the force that drives the piston downwards, powering the engine.

The stroke removing burnt gasses from the cylinder, making it ready for a new cycle.

The engine's lower section, typically consisting of the block, crankshaft, connecting rods, and pistons.

The main body of the engine, containing the cylinders where pistons move up and down.

Large, round holes in the engine block that house the pistons.

The top surface of the engine block, where the cylinder head attaches.

Passages within the engine block that allow coolant to circulate, cooling the cylinders.

The space between the connecting rod bearing and crankshaft journal, allowing oil to enter and prevent metal-to-metal contact.

The part of the connecting rod that fits into the crankshaft journal.

A removable insert that sits between the connecting rod and crankshaft, allowing oil to lubricate the moving parts.

The amount of space between the sides of the piston and the cylinder wall, allowing for lubrication and expansion.

The part of the piston that sits at the top and is exposed to combustion heat and pressure.

Slots machined into the piston that hold the piston rings.

Metal pins that connect the piston to the connecting rod, allowing the piston to swing.

Rings that sit inside the piston ring grooves, sealing the gap between the piston and cylinder, preventing combustion gases from escaping and oil from entering the combustion chamber.

The part of the engine that converts the up-and-down motion of the pistons into a rotating motion.

These are precisely machined surfaces on the crankshaft that fit into the engine block's main bearings.

These are also machined surfaces on the crankshaft, but they are offset from the main journals. Connecting rods attach to them.

These are added to the crankshaft to balance out the weight of the connecting rods, pistons, rings, and the offset of the rod journals, preventing vibration.

A large metal disk mounted on the rear of the crankshaft. It connects the engine to the transmission and helps smooth out engine operation.

A part that connects the piston to the crankshaft, transferring piston movement and combustion pressure to the crankshaft rod journals.

The top end of the connecting rod, which fits around the piston pin, containing a one-piece bushing.

The center section of the connecting rod, shaped like an 'I', providing high strength-to-weight ratio and preventing bending, twisting, and breaking.

Includes cylinder heads, valves, the camshaft and other components. Regulates the flow of air, fuel and exhaust in and out of the engine cylinders.

Fastens to the cylinder block and houses the combustion chambers.

Small pockets within the cylinder head where combustion occurs.

Openings in the cylinder head that allow the flow of air/fuel into the combustion chamber.

Openings in the cylinder head that allow the flow of exhaust gases out of the engine.

Holes in the cylinder head that guide the valves for smooth movement.

Circular surfaces where valves seal when closed, preventing leakage.

A component that receives burnt gases from the cylinders during the exhaust stroke and directs them into the rest of the exhaust system. It can be made of cast iron, aluminum or stainless steel.

Covers the top of the cylinder head to prevent oil spray from escaping the engine.

The front end of the engine contains several components. It includes the mechanism that drives the camshaft, the front cover, an oil seal, and the crankshaft damper.

A critical component that ensures the camshaft rotates at half the speed of the crankshaft. It can be implemented by a belt and sprockets, gears, or a chain and sprockets. It's often referred to as the timing belt, gears, or chain.

Mounted on the crankshaft snout, this heavy wheel is designed to reduce vibrations and prevent potential damage to the crankshaft. It helps reduce the harmonic vibrations in the engine.

Precision-machined and polished surfaces that support the cam bearings, enabling the camshaft to rotate. Oil separates the cam journals and bearings.

A component that rides on the cam lobes and transfers motion to the valve train. Located either in the engine block or cylinder head, it's pushed up by the cam lobe to open the valve and pushed down by the valve spring to maintain contact with the cam.

Metal tubes that transfer motion from the lifters to the rocker arms. They are only needed when the camshaft is located in the engine block, not when it's in the cylinder head.

Components that pivot on top of the cylinder head, transferring motion to the valves. They open and close valves through a rocking motion.

Parts that open and close the ports in the cylinder head, controlling the flow of air or fuel mixture into the combustion chamber and exhaust gases out. Modern engines often have two intake and two exhaust valves per cylinder.

A spring that keeps the valves closed in the cylinder head. It ensures the valves are shut when they shouldn't be open.

A component that connects to the cylinder head. It carries fuel injectors or a carburetor and contains runners that guide the fuel mixture to each cylinder.

Larger than the exhaust valve, it controls the flow of air (diesel) or fuel mixture (gasoline) into the combustion chamber. It's located in the intake port.

Smaller than the intake valve, it controls the flow of exhaust gases out of the cylinder. It's located in the exhaust port.