Engine Operating Principles FOUR STROKE PRINCIPLES OTTO CYCLE

Engine Operating Principles

FOUR STROKE PRINCIPLES (OTTO CYCLE) 1. INDUCTION – piston moves down the cylinder, inlet valve open depression draws in petrol and air. 2. COMPRESSION– piston moves up the cylinder compressing the air fuel mixture, just before TDC spark at the spark plug ignites the charge. 3. POWER – Expansion of the gases pushes the piston down the cylinder. 4. EXHAUST – exhaust valve opens the rising piston forces the burnt gases out the cylinder.

What is the firing order of the cylinders?

Four Stroke Diesel Operation Induction – Piston moves down the cylinder, inlet valve opens and air only drawn in. Compression – Piston rises air heats up air temperature rises dramatically. Power - Diesel fuel injected into the hot air stream. There is a slight delay then the diesel fuel ignites creating pressure on the piston forcing the piston down the cylinder. Exhaust – Piston rises exhaust valve opens and exhaust gases are pushed out the exhaust port to atmosphere.

Two Stroke Cycle (Petrol) There is always a stroke ocuring above and below the piston at the same time. Induction/Power Stroke – Piston at TDC, pressure drop below piston draws in air and fuel. At the same time above the piston a spark ignites the air fuel mixture creating the power stroke. Compression/Exhaust Stroke – Piston moves down the cylinder compressing air/fuel to the top of the cylinder. As the air is pushed through the transfer port to the top of the chamber it pushes the old exhaust gases out through the exhaust port.

Cylinder Head 6 Cylinder Engine Burnt out Valve Seat

Piston Damage Incorrect ignition timing Cam belt failure