How do modern gasoline and diesel engines work?
Spark-ignition (gasoline) engines utilise the four-stroke cycle. During the induction stroke a small amount of fuel and air are drawn into the cylinder. The gasoline-air mixture is then compressed into a small volume and then ignited by an electrical spark from the spark plug. The explosion causes the gases to expand (power stroke) forcing the piston and turning the crankshaft. The burned gases are then expelled from the cylinder (exhaust stroke) via the exhaust valve. Whereas older designs used a carburettor to mix the fuel and air before combustion, newer engines employ electronically controlled fuel injectors to provide the correct amount of gasoline. In order to comply with EU legislation, three-way catalysts are fitted most new gasoline vehicles. These use precious metals (within the exhaust pipe) to catalytically reduce the amount of carbon monoxide, nitrogen oxides and unburned hydrocarbons from the exhaust. As the metals are poisoned by lead and sulphur, the introduction of cat
