A spark-ignition engine (also known as Otto engine, after the name of its inventor) is a combustion engine that–in contrast to a Diesel engine–utilizes internal combustion triggered by means of spark plugs. This type of engine, which originally derived its name from its inventor Nikolaus August Otto, is also popularly known as a “petrol engine”. It is classified in two-stroke power engines and four-stroke engines.
The functioning of a four-stroke spark-ignition engine
Otto further developed the two-stroke gas engine, which was patented in 1860 by Lenoir. The principle behind the four-stroke spark-engine designed by Otto is based on the burning of a fuel-air mix. First of all, the inlet valve of the engine is opened and a piston draws up the mix from the carburettor into the cylinder, with the mix ending up into the combustion chamber by means of fuel injection. Next, the gas mix is compressed while the valves remain shut. The spark plugs ignite the gas, which burns immediately–the piston gets pushed downwards, which allows it to operate via the movement of the rotating crankshaft (power stroke cycle). In the course of the fourth stroke, the outlet valve is opened and the combustion gases escape out of the cylinder. Subsequently, the whole process is repeated.
The functioning of a two-stroke spark-ignition engine
The two-stroke spark-ignition engine functions in a similar fashion to the 4-stroke spark-ignition engine. Yet, while in the 4-stroke spark-ignition engine the intake stroke and the outlet stroke occur separately, the two-stroke engine has no valves. The drawing up of the gas mix and the power stroke cycle are combined, and the compression stroke and the gas emission are also integrated together through a vent. As a result, the two-stroke spark-engine presents reduced friction as well as an inferior weight and a smaller volume, factors that allow it to run on lower fuel consumption. It is employed in the leisure sector for mopeds and for model aircrafts, as well as for working devices (lawnmowers and power chain-saws).
Well over 90% of all vehicles in the UAE have petrol engines. As a matter of fact, almost all passenger consumer cars are driving with petrol, while commercial trucks still prefer Diesel. Generally, in comparison to motor vehicles powered by a Diesel engine, cars that are driven by a spark-ignition engine possess, on average, a lower acquisition value.