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Professional manufacturer of car mirror to interpret the reason for engine knock

Author : Date : 7/24/2013 3:07:56 AM

Professional manufacturer of car mirror to interpret the reason for engine knock

Engine knock is not complicated, just clear the reasons will be able to prescribe the right medicine knock solve the problem.

    What is a knock

    Gasoline engine, when the mixed gas (mixture of air and fuel sufficiently) into the combustion chamber during the intake stroke, the piston in the compression stroke put the compression, the high-pressure mixed gas spark ignited, the combustion pressure generated is converted into engine running power. Although the combustion engine can be used to describe a simple few words, but just the combustion engine research, I do not know how many have been created Bo, master's thesis, even many academics, engineers are working on a lifetime of learning burning, so to really understand the engine is takes a lot of effort.

   "Right high compression ratio setting, are prone to detonation, so to avoid the use of high octane fuel knock"

    Because of the combustion engine is very complex, so the need for extremely accurate design and control, just a little control failures or abnormal, it will cause abnormal combustion, and the "knock" is a abnormal combustion. Simply put, is an abnormal combustion knock caused by abnormal combustion chamber pressure.

Detonation causes

    When it comes to knock reasons, we have to understand two things.

    First, the combustion gas mixture in the combustion chamber, the flame from the ignition point to the "wave" way to spread around, so the complete combustion of oil and gas from the ignition to the need for a short period of time.

    Second, although the need to rely on oil and gas spark ignition, but too high temperature, high pressure environment also cause spontaneous combustion of oil and gas.

    Generally knock because the combustion chamber gas ignition, the flame has not yet fully spread unburned hydrocarbon that is remote because of high temperature or pressure while the ignition, the flame burning flame with the regular impact generated tremendous pressure, making the engine produces abnormal percussion.

The main cause detonation have the following reasons:

First, the ignition angle is too early:

    In order to make the compression top dead point of the piston after the power stroke can be entered to gain momentum immediately, usually the piston reaches the top dead point of the ignition advance (for complete combustion from the ignition to take some time). And too early ignition causes compression stroke when the piston is still, most of the oil and gas has been burned, unburned gas will be at this time under great pressure to spontaneous combustion, causing detonation.

Second, excessive engine carbon deposits:

    Excessive carbon deposits in the combustion chamber of the engine, in addition to make the compression ratio increases (to generate high pressure), but also in high-temperature hot coke surface, so that the engine knock.

Third, the engine temperature is too high:

    Environment makes the engine inlet temperature too hot too high, or poor engine cooling water will cause engine temperature and detonation.

Fourth, the air-fuel ratio is incorrect:

    Too lean fuel-air mixture ratio, will make the combustion temperature is raised, and the combustion temperature will result in increased engine temperature increase, of course, easy to detonation.

Five, fuel octane is too low:

    Octane fuel anti-knock index is, the higher the octane number, the stronger the anti-knock. Compression ratio of the engine, the combustion chamber pressure is high, if the use of low fuel anti-knock, is prone to detonation.

How to know the impact of detonation and detonation

    Knock English is Knocking, tapping means, so knock knocking sound when the engine will produce. Slight knocking sound quite discontinuous crisp, somewhat similar to the sound of tapping the triangle. And severe and continuous knocking, the engine will be "Lili Mile" sound, then the engine will obviously did not force.

    Now many depots in order to squeeze out the maximum performance engine and reduce fuel consumption, speed zone will usually be used to set the comparison ignition advance angle, so some engine 2000-3000 rpm between load is large, it is inevitable there will be a slight explosion shock, however slight knock on the engine will not have much impact, the owners do not have to worry too much. However, if the problem arising because the engine knock, such as severe adverse carbon or heat, etc., this is usually very severe knock, if it is in a continuous high speed and high loads and severe knock occurs, in a minute, light the spark plug and piston melting loss, severe and even cylinder and engine wear body will explode.

Knock sensor

    The most rapid and effective inhibition of detonation method is to delay the ignition advance angle, reducing combustion pressure. So knock sensor actuation principle is the engine knock is detected when the ignition advance angle will be postponed to no detonation ignition timing until the engine does not knock, and then slowly turn the ignition advance Reply . Knock sensor is the acceleration sensor to measure the acceleration of the engine changes, it is vibration. Engineers in the adjustment will knock knock sensor vibration mode when written ECU, once knock sensor detects the vibration mode, ECU is determined engine knock, then delayed ignition advance angle. At present, more advanced knock sensor can even determine which one cylinder knock, and for the individual cylinder ignition timing delay.

Yangzhou Pengying Mirror Co.,Ltd

Professional manufacturer of car mirror to interpret the reason for engine knock