1 Engine knock
a non-knocking, the engine normal operating conditions, since the engine cylinders refers to abnormal ignition caused by the sudden shock non long-lasting, the user can clear feel abnormal engine noise and vibration, and weaken the engine output, increased temperature, increased fuel consumption, resulting in some degree of damage to the engine.
is characterized by knocking without intervention spark plug, ignition or gas mixture can still be self-combustion, forms roughly divided into two types: surface ignition and deflagration. However, it is worth mentioning that the premature ignition phenomenon, although not really knock, but very often, premature ignition will as the reason, cause surface ignition and deflagration.
cause knocking
1, the ignition advance angle is too
In order to move the piston after the end of the compression top dead point, the power stroke can be entered gained momentum immediately, usually in the piston reaches top dead point before ignition advance (because of the need for some time from ignition to complete combustion). The too early ignition causes the piston during the compression stroke is still the majority of oil and gas has been burned, unburned oil and gas at this time will be under great pressure to spontaneous combustion, causing detonation.
2, excessive engine soot
in the combustion chamber of the engine over carbon, in addition to make the compression ratio increase (high pressure generated), will produce high temperature hot spots on the surface of carbon, the engine knock.
3, the engine temperature is too high
in a hot environment such that the engine intake air temperature is too high, or the engine coolant circulation failure, will cause the high-temperature engine knocking.
4, incorrect air-fuel ratio
is too lean fuel-air mixture ratio, the combustion temperature will increase, combustion will cause the engine temperature is increased the temperature is raised, of course, easy to knock.
5, low fuel octane number
octane fuel is an anti-knock index, octaneThe higher the value, the stronger the knock resistance. Engine compression ratio, the higher combustion chamber pressure, if a low knock resistance of the fuel, knocking is likely to occur.
A method to avoid knocking
Generally, newer models are equipped with a knock sensor. The knock sensor can sense the engine knock is generated, and the ECU to reduce knock by modifying the ignition advance angle. However, this adjustment range is limited and can only be adjusted within a reasonable working range of the engine. When the engine is in an abnormal condition, retarding the ignition advance angle blindly, only weakens power, increased fuel consumption, the fuel will result in incomplete combustion of the engine temperature increases, catalytic converter damage. If you want to completely eliminate knock, you should also do more work.
1, conforming engine compression fuel ratio;
2, to avoid “lugging” with: grade low speed mode is likely to cause the engine load increases, thus increasing spark advance angle, and because in higher gear speed is not obvious, it is easy to produce detonation;
3, elimination of carbon: avoid prolonged idle and low speed, high speed appropriate to run a race, there is no chance, change can be improved when the rotational speed of the gear, automatic transmission can be linked with periodic S;
4, to avoid high temperature: periodically check the coolant level, regular inspection and replacement of the oil, to avoid prolonged intense driving, constantly monitoring the temperature Great traffic; [ 123]
always concerned about driving the car, if the vehicle is in a period of time, lack of motivation, fuel consumption increases, and could feel the vibration caused by knocking may not be, but very likely have a tendency to knock, shall go medical examination.