Automotive knowledge classroom: What is a coke!

Coke: spark machine EDM normal one performance.

0n time applied to the electrode and the workpiece on the medium (spark oil) breakdown spark machine during the discharge process, when the gap between the electrode and the workpiece is reduced to a certain distance, forming the discharge channel, and also produced a spark discharge starts.

Transient concentrate a large amount of heat energy in the discharge channel, the instantaneous temperature can be as high as 10,000 degrees Celsius, high temperature makes the workpiece surface melting, vaporization. And explosive splash to the processing solution, quickly solidified into a discharge slag, the working fluid is flowing away.

Then leaving a tiny pits on the surface of the workpiece, then discharge into offf time period, discharge stop short recovery insulated state between the electrode and the workpiece.

However, when the metal fine particles is not between the electrode and workpiece by the machining liquid is completely away, i.e. can not be completely eliminated ionization. Will line the moment a 0n time to short-circuit, instantaneous high temperature will be making the surface of the workpiece to form a bump, and the formation of coke.

Coke should try to avoid what happened in the EDM, particularly in precision mold to life. Coke cause engine power from the engine piston moves down, the mixture of gasoline and air is sucked into the cylinder, and then moving up the piston then these oil and gas is compressed into a highly combustible gas, the last spark plug ignition detonated piston this powerful explosive power to promote, and the engine thus produce power. You can clearly see from the diagram in the right two general engine → gas mixture: the source of power, must go through the intake valve into the combustion chamber; small portion of gasoline will be attached to the intake valve, encountered engine high temperature, gasoline can not burn completely hydrocarbons, paraffin, glial will be firing rubber carbon, if the injectors have the contamination, the poor state of spray atomization of gasoline, gasoline mixed with air is not uniform, will increase the amount of condensation in the steam inlet door petrol. Worse is the rubber carbon to absorb gasoline characteristics, so this layer of coke will absorb gasoline, gasoline is absorbed and then be fired gum the carbon line into thicker coke the more thick coke reuptake more gasoline, so a vicious cycle into the valve too much coke, so that can not be closed, so that the engine does not work so far.

The combustion chamber of the coke is due to glial unable to fully detonate hydrocarbons in the gasoline component after the explosion, the tiny carbon particles do not have the time to with the exhaust gas discharge and accumulate in the combustion chamber, these black particles should With emissions in the atmosphere, or accumulate in the muffler pipe. Combustion chamber coke serious combustion chamber temperature will rise, causing the spark plug ignition, combustion chamber mixture self-detonated two shares deflagration point of the cylinder pressure suddenly increased harm engine internal peripheral parts, and caused similar tap the sound of the cylinder, which is knock (Knocking). The status of combustion chamber deposits can observe the spark plug firing end learned. The removal of coke in the past, the kinds of cleaners are not yet available to remove carbon deposits only way is to decompose the engine, but in the past most vehicles still configure
bold aesthetic for the fuel injection quantity
Carburetor, as long as the coke is not serious enough to prejudice the operation of the valve engines affected by carbon deposition is not obvious, so the situation is not parsing engine designed to remove coke. With increasingly stringent vehicle emission standards in countries, carburetor and fuel injection volume precision injection supply system replaced. The fuel injection system is more precise control of the fuel injection quantity, oil and gas absorption by carbon deposits will seriously affect the power of the engine performance, and even let the fuel injection system does not work. So clear the intake valve and combustion chamber carbon deposits for the jet fuel supply engine is part of the maintenance project.

Coke type of valve and combustion chamber deposits by the decision of the control characteristics of the EFI engine cylinder each work is the first fuel injection re-ignition, when we put out the moment of the engine ignition is cut off immediately, but the duty cycle of the sprayed gasoline can not be recycled, and can only be attached to the intake valve and combustion chamber walls, gasoline is likely to be volatile, but the wax and varnish gasoline has stayed in the long run gasoline, wax and glial material piled thick repeatedly heated to harden to form carbon deposits. Poor quality of gasoline if the engine is burning oil, or filling a lot of impurities, valve carbon deposits more serious form and faster. Sponge-like structure of coke, a time when the valve after the formation of coke fuel sprayed into the cylinder will be part of adsorption, the real concentration of the mixture into the cylinders thinning, resulting in poor engine work appears difficult to start, idle speed is not steady, poor acceleration, emergency refueling temper, excessive exhaust, fuel consumption increased anomalies. If serious cause the valve closed lax, a cylinder to cylinder pressure and completely does not work, even sticking valve not return. The valve and piston movement interference will produce, and ultimately damage the engine.

Intake pipe coke As each piston of the engine work is not synchronized, when the engine off, some of the intake valve of the cylinder can not be completely closed, some of the unburned fuel continuous evaporation of oxidation, especially in the intake pipe is the throttle generated behind some relatively soft black coke. One hand, such coke can cause the intake pipe wall roughening, the intake vortex will be generated in these rough areas, affecting the quality of the feed gas effect and the gas mixture.

On the other hand, these carbon deposits will clog the idle channel so that the idle speed control device catching or exceeds its adjustment range, so will

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