The petrol engine's task is to convert the chemical energy contained in the fuel very efficiently and with the lowest possible emissions intomechanical energy. It should combinevibration-low and quietly - atleast for the lower revs - favorable Torque with high Performance at higher revs.
It was state-of-the-art that the fuel, in the form of a fine spray, was added to the air intake before reaching the cylinder block. (External mixture formation)Whereby, in almost all working conditions, a mixing proportion of Lambda = 1 is exactly adhered to. New developments almost exclusively dispose of direct injection, which also work with a fixed mixingproportion (homogeneous operation). Sporadically, systems already make use of a stratified charge operation, having a normal to fat mixture at the spark plug and avery lean mixture in the remainingcombustion chamber. In the petrol engine, it is important that, after the compression cycle, the combustion is initiated by an electric ignition system.
Compared with the diesel engine, the petrol engine should run more smoothly and be capable of considerably higher revs as well as a more immediate reaction to acceleratormovements. Besides the higherfuel consumption the petrol engine is more prone to cold start wear and tear. The fuel condenses on the cold cylinder walls, washing down the engine oil. In addition to this the oil is diluted which reduces thelubrication quality. The cold start (-20°C) wear and tear is said to correspond to approx. 200 km of highway driving at mid-range speed.The exhaust fumes are, due to fact that there are no soot particles, ecologically more superior than the fumes emitted from the diesel engine. For many years now, the catalytic converter with Lambda control,reduces the remaining exhaust pollution.
While formerly the compression for the diesel engine ranged between 18 and 24: 1 and for the petrol-driven car it is was not more than 11 to 12: 1, the geometrical compression ratios now clearly decrease forthe charged diesel engines, below this former border. Vice versa, the variable compression is hot for the petrol engine, testing with compression ratios far outreaching the diesel engine for cold engines withoutengine knocking. At the moment there remains just one clear distinction: the electric ignition system.
The petrol engine, unlike the diesel engine is also called an "Otto Motor" (internal combustion engine). However, Nicolaus August Otto did in fact invent the four-stroke engine, not the petrol engine. This engineran on illuminating gas. The diesel engine also has a compression stroke. For this he is actually even more important. Giving this principle his name was a way to honour one of the greatest pioneers of enginetechnology.
The biggest petrol engine to be produced in series is the V12 built by Pierce-Arrow (US) in 1912 with a 13.5 litre cubic capacity. The biggest single cubic capacity is the 1930 Bugatti Royale with a capacity ofjust 1.6 litres (125 * 130 mm). In the racing car area, (around 1905) collective cubic capacities of more than 18 litres and single cubic capacities of 3.5 litres (150 * 200 mm) can be found.