Engine knock cause (Dieselpartsworld) 2016-01-19
Engine knock cause:
1, the so-called oil label 90, 93, 97 is actually the gasoline octane value, namely practical gasoline antiknock and standard gasoline antiknock of ratio. So the uprising of gasoline itself is a major factor in the blast;
2, from the engine theory, the greater the compression ratio (four stroke gasoline engine has four jobs: intake, compression, work, exhaust, the piston in the cylinder for reciprocating motion. After the completion of the intake stroke, the piston is located in the lower part of the cylinder, which is called the lower dead point.
When the compression is finished, the piston is in the upper part of the cylinder, which is called the top dead point.
When the piston in the lower dead point volume of the cylinder and the piston at TDC cylinder volume ratio is defined as the compression ratio) can get more higher engine power, so the new engine power is more and more big, compression ratio is also growing, such as 307 1.6 compression ratio of 10.5, not
By domestic set-up was 10.8). Theory on power can be continuously improve, but in fact a very difficult to solve the dilemma, it is knock, the oil quality can not increase, at least by cost constraints, so the compression ratio and power and not
Infinitely improved. Fortunately, not necessarily produce high compression ratio of detonation, detonation can be adjusted by third.
3, modify and reduce the ignition advance angle (that is, the timing of the ignition delay), the popular saying that the earlier the ignition time, the higher the efficiency of the engine. But high efficiency, natural knock on the powerful. (according to the basic theory of the four stroke, after the end of the compression stroke ignition.
In fact, mixed gas from the beginning of combustion to complete combustion needs a certain amount of time, so if at the end of the compression stroke ignition, wait until the mixture for complete combustion piston has not in the stopping point of the, that is, then will be a part of the energy is wasted.
In order to pursue higher energy efficiency ratio, we can design such a ideal scheme, when the piston at the end of the compression stroke stroke at the beginning of that a moment, just is mixed gas burning the full at the moment. In this way, we need to arrive at the piston in the compression stroke
Before the end of the beginning of the ignition, the ignition time we call the ignition advance. The purpose of ignition advance is to obtain a higher output power of the engine. But the ignition advance also brings a problem, that is knock.
Reduce the ignition advance angle, delayed ignition can solve the knock problem. In addition to the factory has set a big rule, the ignition advance angle can also be adjusted by the electronic throttle, then how to draw the conclusion of how to adjust it? It is known by the knock sensor that once
A deflagration phenomenon, can automatically delay time of ignition in a certain range, reduce or eliminate knocking phenomenon. Knock sensors generally have 1, 2, 4, 6 and so on, of which 1 sensors located in the cylinder wall between the second and third cylinders, 2
The column is about the column, while the 4 is a cylinder.
Knock is not an individual phenomenon, a lot of cars have, the difference is that some cars are more common, and some cars are more individual, and some cars are only occasionally, and some cars often appear.