96 Petrol engines are popular because they are smooth, light, and can run at high speeds. They are also quieter than diesel engines. However, they usually use more fuel than diesel engines and can cause more pollution. Nikolaus August Otto (1832-1891) was the German engineer who developed the compressed charge internal combustion engine fueled with petroleum gas, which led to the modern internal combustion engine. smoothly: fluidamente stroke: colpo THE PETROL ENGINE A petrol engine is an internal combustion engine designed to run on petrol fuel. It operates by burning a mixture of petrol and air inside its cylinders to produce mechanical power. This type of engine is widely used in cars, motorcycles, trucks, and various machines because it gives good power and runs smoothly . The petrol engine is characterised by a spark ignition, which is the process of using a spark generated by a sparkplug to start the burning of fuel inside the engine. The four-stroke combustion cycle The four-stroke combustion cycle (also called the Otto cycle ) is the process most petrol engines use to turn fuel into power. It is the basis of almost all car engines today because it balances efficiency, power, and durability. It has four steps (or strokes ) that take place inside each cylinder every time the engine runs. The four strokes are: 1. the intake stroke: the piston moves down and the intake valve opens so a mixture of air and petrol can enter the cylinder; 2. the compression stroke: the piston moves up again and compresses the mixture to make it hotter and ready to burn. The intake valve is closed; 3. the power stroke: a sparkplug makes a small spark that ignites the compressed mixture. The burning gases expand quickly and push the piston down. This is the stroke that produces power. The intake valve is closed; 4. the exhaust stroke: the piston moves up one more time, and the exhaust valve opens to let the burnt gases leave the cylinder through the exhaust system. At the end of each cycle, a new one starts over very rapidly, many times per second, which keeps the engine running. Internal Combustion Engine Cycle Intake valve open Valves closed Combustion chamber Compressed air+fuel mixture Air+fuel Valves closed Exhaust valve open Spark Exhaust gases Ignited air+fuel mixture Piston Crankshaft Connecting rod Intake 226 MECHANICS Compression Power Exhaust