In this case, moreover, that the combustion is not at the moment, when necessary, so also it is accompanied by an extremely sharp increase in pressure in the cylinder, which leads to a knock, overheating and high toxicity of the exhaust. Whether it diesel, which raise the degree of compression only improves the reliability of ignition of fuel injection: it will be hotter than the air in the cylinder – the faster it will evaporate and the sooner will the combustion process. Although, of course, the limits of excellence, there are here. Only due to they are required to clean the exhaust gases, but the mechanical strength of parts and gear motor. But apart from the degree of compression is the second least important factor – is low resistance of the intake system of a diesel engine.
After all, unlike a gasoline engine, he did not want to "block the oxygen-throttle – power control in a diesel engine with a simple dosing injected Fuel: need for greater efficiency – serve more fuel. And as far as excessive amount of air in the cylinder – it the tenth most important to him enough to oxidize. With a gasoline engine is such a trick will not work: if the air there are too many, that is, the concentration of gasoline vapor in it will be very low, then the mixture from the spark just is not flash. Because of this, and you have to put the intake valve that regulates air flow and, indirectly, fuel quantity. Therefore, for small loads, for example, in the crush tubes, gasoline cars to expend energy on intake of air through the almost half-open throttle, creating a huge depression in the intake manifold. "Breath" as diesel is always free! Its impact on the overall cost estimate is easy. We compare the numbers of diesel and petrol engines the same size. For example, bmw 320d and 320i.
In the urban cycle, when engine load is small, economical diesel almost doubled: 6.8 l/100km vs. 11.3 l/100km! Surprising, because on his side and a high degree of compression, and low losses in the intake system. But in a country mode, the speed when load on the engine a little more, the throttle is opened more, and the gasoline engine is easier to breathe, the diesel is only one trump card – the compression level. As a result, melts and its advantage in fuel consumption: only 4.7l/100km against 5,9 l/100km. Details –