JAC S2. Engine. Service Instruction - page 1
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Engine Mechanical System
Engine Mechanical System 14
Engine Mechanical System
I. Summary
(I) structure overview
break-down table
Cylinder cover
1. Exhaust valve
2. Intake valve
3. Intake Valve Seat
4. Intake Valve Seat
5. Intake Valve pipe
6. Exhaust valve pipe
7. Intake valve oil seal
8. Intake valve spring shim
9. Intake valve spring
10. Intake valve spring seat
11. Valve lock clamp
12. Mechanic tappet
13. Exhaust valve spring seat
14. Exhaust valve spring
15. Exhaust valve spring shim
16. Exhaust valve oil seal
17. Cylinder cover
(II) System theory
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Engine Mechanical System
Engine Mechanical System 15
Working principle of reciprocating piston engine
- Intake stroke:Piston moves from TDC to BDC under the drive of CrankshaftAt this time,
exhaust valve closes, intake valve opensWhen piston is moving, volume of cylinder is increasing,
which creates kind of vacuum inside of cylinder.ECM controls oil injector and spray oil into intake
pipe, now intake valve opens,
the mixture of air and oil is sucked into the cylinder through intake valve, and creates mixed
air which can burn inside of cylinder.
- Compression stroke: After the intake stroke, crankshaft will continuouslly take piston to
move from BDC to TDC.Now, intake valve and exhaust valve are all closed, along with movement
of piston, the volume of cylinder is decreasing. Because air can be compressed, and temperature
will rise after compression.
- Power stroke: When the compression stroke is finished, ECM controls the initial coil circle
of ignition coil to disconnect, and creates high-voltage power at secondary polar, the high-voltage
power is quickly conducted to piston on top of cylinder cover, finally high voltage breakthrough
the interval of spark plug, and ignite the mixed air inside the cylinder. The flame will spread to
the whole combustor quickly, and unleash much heat. Volume of the burning gas will expand
dramatically, pressure and temperature will rise samutanuously, the expansion power act on
surface of piston, push piston move from TDC to BDC, transform the piston from reciprocating
movement to rotational motion through connecting rod. At the same time, intake and exhaust
valves are still closed.
- exhaust stroke
：when exhaust stroke starts, intake valve is still closed, the crankshaft takes
piston to move from BDC to TDC through connecting rod, now, expanded burning gas, under the
push power of self pressure and piston, is exhausted out of cylinder through exhaust valve. When
piston arrives to TDC, the exhaust stroke finishes, exhaust valve closes. But in reality, intake valve
opens before TDC and closes after the BDC.
Purpose of this kind of design is for sufficient intake and to decrese the power consumption
during intake period. During exhaust period, exhaust valve opens before the BDC, and closes
after the TDC. The purpose is to decrese the mixed gas inside cylinder and decrease the power
consumption during intake period, at the same time, because intake and exhaust valve has certain
overlapped angle, which means within certain crankshaft angle intake and exhaust valve open
samutanuously, and because already burnt gas has been exhausted through exhaust valve, creating
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Engine Mechanical System
Engine Mechanical System 16
inertia, which can take mixed gas in, which is beneficial to air intaking to some extent. However,
it is not always good to have bigger overlapped angle, requirements for overlapped angle under
different conditions are different. Therefore, this engine adopts VVT technology, whose purpose
is to satisfy the need to open angel of intake valve under different conditions, and this function is
realized through OCV.
OCV system working principle
VVT is the abbreviation of Variable Valve Timing. All the objects with mass have inertia
，
including the air which is intaken into the engine cylinder
，air still has the trend of getting in after
the air intake stroke. Now, if the valve closure time postpones , cylinder can intake more air,
which can improve the volume efficiency.
The result is: the more time postponed when valve closes, the higher performance is under
high rpm situation; Otherwise, if the valve closes in advance, performance under low rpm is
much stable, torque is much bigger.
(III)technical parameters、maintenance parameters
Technical specifications
type
HFC4GB2.3D
Engine type
In-line 4 cylinder
、double overhead camshafts、16 valves、 VVT
Whole car carry type
Horizonontally
Cylinder number
4
Cylinder diameter(mm)
75
troke(mm)
84.8
displacement (L)
1.499
Compression ratio
10:1
cylinder liner type
Dry ( aluminium cover)
ignition order
1-3-4-2
Rated power(kW)
83
Rated rotation speed(r/min)
6000
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