1. Definitions
is the carbon during operation of the engine, the fuel and the unsaturated olefin gum produced at a high temperature state of the coke-like substance.
sparks during discharge, when the gap between the electrode and the workpiece is reduced to a certain distance, 0n time applied to the electrode and the workpiece medium (spark oil) breakdown, the discharge channel is formed, there is produced a spark start discharge.
instant discharge in concentration a lot of heat, the temperature may be up to ten thousand degrees Celsius, so that the workpiece surface is melted, vaporized explosively and splashing processing liquid, rapidly solidified into a slag discharge, with the flowing fluid go.
At this time will be left on the surface of the workpiece a small pit, then enters the discharge off time period, stop a short discharge between electrode and the workpiece recovery insulated.
However, when the metal particles between the electrode and the workpiece is not completely away working fluid, it can not be completely eliminated ionized. 0n time when the next short circuit will be formed when, at this time would make instantaneous high temperature surface of the workpiece to form a bump, the formation of coke.
carbon deposits in the EDM should try to avoid what happened, especially in precision tooling can be fatal impact.
2 cause carbon deposition
When the engine power from the engine the piston moves downward, the mixed gas of gasoline and air sucked into the cylinder, and then the upward movement of the piston oil compressed into a highly combustible gas, and finally spark plug ignition detonated, the piston is pushed this powerful explosive force, and thus the engine to generate power. It is clear from the general schematic view of the engine in the two right: the power source → the mixture gas into the combustion chamber must pass through the intake valve; gasoline small portion will be attached to the intake valve, the engine temperature met , gasoline can not be burned completely hydrocarbons, paraffin, colloidal carbon glue will be fired was the case if the contamination of the nozzle has poor ejection gasoline atomization state, uniform mixing of air and gasoline It will increase the amount of condensation in the intake valve gasoline. Worse carbon glueThere are characteristics to absorb gasoline, the coke layer which will absorb gasoline, gasoline is absorbed and then fired into a thicker line glue carbon soot, carbon thicker resorbable more gasoline vicious cycle to feed valve due to excessive carbon deposits that can not be closed, the engine is not working so far.
The carbon combustion is prompted by a gasoline component in the gum can not be completely detonated with hydrocarbons after the explosion, fine carbon particles that were not produced with the exhaust gases in the combustion chamber and deposited, the black particles as should emissions to the atmosphere, or accumulated in the muffler tube. If the combustion chamber causes serious coke combustion temperature, resulting in a spark plug while the ignition, the gas mixture in the combustion chamber is also self-detonated, the two share points to make exploding cylinder pressure suddenly rise, harm the surrounding parts inside the engine and cause similar percussion sounds cylinder, which is knock (knocking). The combustion chamber deposits observed conditions may be that spark plug firing end.
3, type coke
valves, combustion chamber deposits
determined by the EFI engine control characteristics, when each working cylinder is first injection re-ignition, the moment when we turned off the engine ignition is switched off immediately, but the duty cycle of the ejected gas can not be recycled, can only be attached to the intake valve and combustion chamber walls, gasoline is likely to be volatile, but gasoline but stayed waxes and gums, waxes and long run gasoline piled thick varnish, after repeated heating to form a hardened coke. If more impurities poor engine burning oil, or raise the quality of gasoline, then the valve is even more serious coke formation and faster. Due to the structure of sponge-like carbon, coke is formed when the valve after each injection of fuel into the cylinder will be a part of the adsorbed, so that the true concentration of the mixture into the cylinder becomes lean, resulting in poor operation of the engine starting difficulties, idle speed stability, speed up bad, acute fuel temper, excessive exhaust, fuel consumption increases and other anomalies. If we can cause severe valve closed lax, failing to make a cylinder and cylinder pressure does not work completely, even blocking valve so that it does not return. At this time, the valve and the piston motion is generated interference, ultimately damage the engine. Intake pipe carbon
Since the entire work of the various engine pistons are not synchronized, when the engine is off, the intake valve can not be completely shut down some cylinders, some of the continuous evaporation of unburned fuel oxidation, would be especially in the intake pipe section rear valves have some softer carbon black. The coke make on the one hand the intake pipe wall is roughened, the intake air swirl is generated in the rough places, affect the quality of the intake air and the effect of the mixed gas.
On the other hand, these carbon deposits can block the idle channel idling control apparatus jamming or beyond its adjustment range, to cause such a low idle, idle shaking speed of various accessory devices are malfunctioning, skimming off car exhaust excessive, charges oil phenomenon.
If you are experiencing slow speed while driving, emergency refueling tempered, difficult phenomenon cold start, your car’s valve is likely to have a coke. It found that low idle speed and idle car shaking, when the throttle card, change batteries without idling, your car’s intake manifold coke has been very serious. With the above phenomenon should go to a professional repair shop in time to check the car.
In vehicle maintenance for the intake pipe carbon diagnosis is very simple, as long as the throttle is removed can clearly see the extent of carbon deposition. But for the diagnosis of valve coke has always been a problem, in general, there are three diagnostic methods in professional repair shop.
coke diagnostic method
in vehicle maintenance for the intake pipe carbon diagnosis is very simple, as long as the throttle is removed can clearly see the extent of carbon deposition. But for the diagnosis of valve coke has always been a problem, in general, there are three diagnostic methods in professional repair shop.
Disintegration Method
The engine is open, check for carbon deposition. This is very intuitive, but time-consuming, and no matter what part each disassembly time there will be more or less affect its performance and shorten its life.
Endoscopy
Remove the spark plug or fuel injector, the valve endoscope to observe the extent of carbon deposition. This method is very convenient, but the cost of the endoscope is no trivial matter, and its usefulness in the maintenance is not very wide, so not all service companies are equipped with the device.
4, prevention and removal of carbon deposition
In the past, when all kinds of detergents are not yet available, the only way to remove carbon deposits are decomposed engine, but in the past most vehicles still configured for injection the amount of bold aesthetic of the carburetor, as long as coke is not serious to prejudice Valve operation, the affected engine soot is not obvious, it is designed to remove carbon deposits and decomposition engine situation is not much. With increasingly stringent emission standards States automobile, carburetor fuel injection quantity is gradually being replaced by the more accurate injection fuel supply system. Fuel injection control system for a more precise fuel injection quantity of oil and gas is carbon absorption will seriously affect the dynamic performance of the engine, fuel injection systems and even not work. So clear the steam inlet of the combustion chamber door and coke for jet engines, oil is part of the maintenance program.
filling high quality gasoline.
gasoline wax and impurities such as gum is the main component of carbon formation, so that a high cleanliness tendency to form coke on gasoline weaker. Unfortunately, there is a lower quality of gasoline compared with developed countries, it can only be crude. If we want high-quality high-grade does not mean, that No. 97 oil is not necessarily less than the number of impurity 93, octane numbers represent oil, it does not represent the quality and cleanliness.
Some owners In order to ensure the cleanliness of gasoline, gasoline will be used in the practice of adding gasoline detergent. This effectively prevents the formation of carbon layer on the metal surface of the junction, and can be gradually activated gradually removing the original soot particles, thereby protecting the engine from damage. But adding gasoline detergent must be careful, if added shoddy products will get the opposite effect. Do not idle for a long time traveling.
long idle time, the time to reach a normal temperature of the engine also becomes long, the evaporated fuel is injected to the back of the valve after the slow speed, coke also arises. At the same time often idle speed, air flow into the engine also small, so scouring effect of carbon deposition becomes too weak, it will promote the deposition of coke. Multi-speed running, the vehicle to maximize my hand shift speed
purpose is to run a high-speed airflow to scour the inlet to prevent carbon deposition. Further, also increasing the speed shift multi-speed running has the same purpose, the rotation speed of the original transducer 2000Converted into block 2500, not only can effectively prevent coke generation, may also improve the power of the vehicle, but also to avoid knocking caused the shift speed is too low, to protect the engine. Note that the timing is off the car.
For automobiles equipped with a turbocharger after high speed running or climbing off the vehicle do not immediately, after 10 minutes idling operation off the car, because the car is equipped with a turbocharger which is formed coke speed several times faster than the average naturally aspirated car.
because of the traffic of the city, the factors affecting the rhythm of people’s lives as well as our fuel market conditions, the above method of avoiding carbon deposition there may not be easy to achieve. It is recommended that car owners when to do something every 20,000 40,000 kilometers under conditions of routine maintenance are met to avoid demolition of the intake system clean, it is to use special methods and special equipment intake of the vehicle engine is not under the premise of disintegration channel, a valve, an oil passage is formed so easy to clear the site of carbon soot operation. This can effectively reduce the impact of carbon deposition on engine performance, the car’s “heart” in the best condition.