In engine fuel system, the core of electronic control lies in the electronic control of fuel rate quantity, that is in fact,
electronic control of the excessive air coefficient?.Because intake air amount of gasoline engine is determined through
throttle control by the driver, the fuel rate quantity can be determined through determination of?.
Fuel supply system is composed of the following parts: fuel tank, fuel pump, fuel filter, pressure regulator, fuel injector,
gasoline vapor absorption device etc.
ECU controls fuel feed according to actual engine working condition. Fuel goes through filter to pressure regulator, which
will then keep the fuel pressure within injector constant. Electronic fuel pump immersed in fuel tank continuously supplies
fuel into fuel pipe, and redundant fuel flows through fuel return pipe back into fuel tank.
Engines based on closed-loop control shall use unleaded gasoline.
1. System makeup (See Fig. 208)
2. Fuel pump
II. Structural Characteristics of Piston, Piston Pins and Piston Rings
9. Convenient to cut off fuel supply
Measurement of fuel quantity does not depend on vacuum degree within venturi, so it is still possible to cut off fuel supply
even if the engine is running during intake stroke. This provides convenience for cutting off fuel supply in the event of
overspeed and employing the engine to brake down a long slope.
10. Reduced temperature inside cylinder
Because fuel enters directly into cylinder or arrives at inlet (in this case injection time will overlap the inlet open time), some
fuel will absorb heat and be vaporized, resulting in reduced temperature within cylinder. This can not only increase volume
efficiency thereby enhancing torque and power, but also decrease tendency toward knocking. The latter enables it feasible
to increase ignition advance angle or raise compression ratio by from 0.5 to 1.5 when keeping fuel octane number constant,
thus lowering fuel consumption, or lower requirment for octane number and boiling range for the used fuel when keeping
compression ratio unchanged.
11. Accurate measurement of fuel rate
Carburetor shall carry out quantitative control of fuel rate in addition to various processing functions including atomization,
vaporization, diffusion, and mixing. Its control accuracy is difficult to guarantee. In gasoline injection system, fuel pump and
injector carry out fuel delivery while ECU dynamically controls fuel rate quantity, thus enabling higher control accuracy. For
example, determination of fuel rate quantity in gasoline injection system can take into consideration instant coolant
temperature, inlet temperature and pressure, etc., which cannot be realized by carburetor.
12. Reduced fuel consumption and extended work life
Multiport injection system can realize instant control of mixture according to particular driving conditions and circum-
stances.
At the same power level, reduced fuel consumption means lighter heat load, which is helpful for extending work life of such
parts as valve, valve seat ring , cylinder head, and piston.
13. Large speed range for stable running
Gasoline injection engine can work stably within the entire speed range with full load imposed on it, where the ratio of the
highest speed to the lowest speed can reach 10:1 to 12:1. This is because gasoline injection system can accurately control
the air-fuel ratio at any speed, while carburetor is incapable of doing so.
14. Shortened engine height
Elimination of carburetor enables lowered air filter, which will shorten the total engine height so as to make it more conve-
nient to arrange the engine in car.
Compared to carburetor, gasoline injection system has the following defects: complicated, costly, difficult to service, and
demanding higher fuel cleanliness and control of gel content in fuel. No or bad control of gel content in fuel will easily lead
to clog of the injector, causing carbon deposit to occur on the back of intake valve. Especially for domestic gasoline based
on the catalyzed cracking process where there is always more than 3% alkene content, some cleanser shall be used.
However, excessive cleanser may lead to deposits occurring within the combustion chamber.
95
Содержание JL481Q
Страница 1: ......
Страница 9: ...5 Fig 3 Components Assembly Drawing of MR479Q MR479QA Engine ...
Страница 10: ...6 Fig 4 MR479Q MR479QA Engine and Its Power System ...
Страница 11: ...7 Fig 5 Assembly Drawing of Engine and Its Auxiliaries MR479Q MR479QA ...
Страница 12: ...8 Fig 6 Electronic Control Fuel Injection System in Engine MR479Q MR479QA ...
Страница 13: ...9 Fig 7 Front view of Engine JL481Q MR481QA ...
Страница 14: ...10 Fig 8 Sectional elevation of Engine JL481Q MR481QA ...
Страница 15: ...11 Fig 9 Electronic Control Fuel Injection System in Engine JL481Q MR481QA ...
Страница 21: ...17 Fig 13 Exterior Feature of JL481Q Engine Power Me N m Torque Pe Kw ge g kwh Fuel Consumption Ratio ...