SsangYong Actyon Sports II. Manual — part 28
04-8
3. INPUT/OUTPUT OF INTAKE SYSTEM
For more information, refer to Chapter " Engine Control".
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4. OPERATING PROCESS
Work Flow
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1) Types of swirl
Swirl: One cylinder has two intake air ports, one is set horizontally and
the other one is set vertically. Swirl is the horizontal air flows in cylinder
due to the horizontal intake air ports.
Tumble: Tumble is the vertical air flows in cylinder due to the vertical
intake air port
Squish: Squish is the air flows due to the piston head. Normally, this is
appears at the final process of compression. In CRDi engine, the
piston head creates the bowl type squish.
2) Swirl control
In DI type diesel engine, the liquefied fuel is injected into the cylinder directly. If the fuel is evenly
distributed in short period, the combustion efficiency could be improved. To get this, there should be
good air flow in cylinder. In general, there are two intake ports, swirl port and tangential port, in each
cylinder. The swirl port generates the horizontal flow and the tangential port generates the longitudinal
flow. In low/mid load range, the tabgential port is closed to increase the horizontal flow. Fast flow
decreases the PM during combustion and increases the EGR ratio by better combustion efficiency.
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Load
Engine speed
Swirl valve Amount of
swirl
Remarks
Low speed,
Low load
below 3,000 rpm
Closed
Heavy
Increased EGR ratio, better air-fuel
mixture (reduce exhaust gas)
High speed,
High load
over 3,000 rpm
Open
Light
Increase charge efficiency, higher
engine power
The variable swirl valve actuator operates when
turning the ignition switch ON/OFF position to
open/close the swirl valve. In this period, the soot
will be removed and the learning for swirl valve
position is performed.
Swirl: This is the twisted (radial) air flow along the cylinder wall during the intake stroke. This
stabilizes the combustion even in lean air-fuel mixture condition.
Swirl valve
3) Features
Swirl and air intake efficiency
To generate the swirl, the intake port should be serpentine design. This makes the resistance in air
flow. The resistance in air flow in engine high speed decreases the intake efficiency. Eventually, the
engine power is also decreased, Thus, the swirl operation is deactivated in high speed range to
increase the intake efficiency.
Relationship between swirl and EGR
To reduce Nox, it is essential to increase EGR ratio. However, if EGR ratio is too high, the PM also
could be very higher. And, the exhaust gas should be evenly mixed with newly aspired air. Otherwise,
PM and CO are dramatically increased in highly concentrated exhaust gas range and EGR ratio
could not be increased beyond a certain limit. If the swirl valve operates in this moment, the limit of
EGR ratio will be higher.
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4) Relationship between swirl and fuel injection pressure
The injector for DI engine uses the multi hole design. For this vehicle, there are 8 holes in injector. If the
swirl is too strong, the injection angles might be overlapped and may cause the increased PM and
insufficient engine power. Also, if the injection pressure is too high during strong swirl, the injection
angles might be overlapped. Therefore, the system may decreases the fuel injection pressure when the
swirl is too strong.
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