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Twinport system
The Twinport system, already in use in the Z 16 XEP DOHC-I
petrol engine now also features on the two new members of the 2nd
generation DOHC-0 petrol engine series, the Z 10 XEP and Z 14 XEP,
albeit in modified form.
Advantages of Twinport
- Greater movement of the charge
- Combustion stabilisation
- Increase in exhaust gas recirculation rate
- Reduction in throttle losses
- Reduction in fuel consumption
Special features
- When the Twinport system is activated (part load), combustion
is stabilised because of the increased movement of the charge.
Thanks to more efficient combustion, both throttle and wall heat
losses can be overcompensated for by the high EGR rates, resulting
in a reduction in fuel consumption.
- Advanced injection of the fuel onto the closed inlet valve
- Stratification of the charge with a richer mixture at the point
of ignition at the spark plug.
Inlet manifold with Twinport system
The structure of the inlet manifold is in principle the same for
both the Z 10 XEP and Z 14 XEP engines. They only differ in length,
which is tailored to the respective engine version (3-cylinder or
4-cylinder).
A vacuum unit actuates the Twinport system; the unit uses a
shared actuation rod to close and open the flaps in the inlet
ports.
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1
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Inlet manifold - Z 14 XEP
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3
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Reverse-transfer lever
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2
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Vacuum unit
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4
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Actuation rod
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Control valves - Twinport system
At idle when the vehicle speed signal = 0, the control flaps of
the Twinport system are closed and the system is active.
As soon as the vehicle drives away, and a driving speed signal
is thus present, the control valves are opened or closed, depending
on the operating point (load, engine speed).
The engine control unit gives a command to the vacuum unit which
in turn closes or opens the control flaps via the actuation
rod.
• Service:
So as not to diagnose the Twinport system incorrectly when checking
it, the following should be taken into account:
- At idle and when the driving speed signal = 0, is when the
vehicle is stationary, the control flaps must be closed, the
actuation rod is withdrawn and there is a vacuum at the vacuum unit
diaphragm.
- When the vehicle is being started, the control flaps are opened
and after a short while (a few seconds) the control flaps are
closed when the vehicle is at idle and the driving speed signal =
0.
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- Control flaps opened
- Control flaps closed
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| 1. |
Reverse-transfer lever |
| 2. |
Connection for engine wiring harness |
| 3. |
Vacuum hose |
| 4. |
Vacuum tank (engine control unit removed) |
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The following diagram shows the Twinport system in both
activated and deactivated states.
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- Twinport system inactive with opened control flap
- Twinport system active with closed control flap
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Twinport sensor
The Twinport sensor incorporated into the inlet manifold records
whether the Twinport flaps are open or closed and sends this
message to the engine control unit.
There, the signal of the Twinport sensor is compared with the
specified setpoint position.
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| 1. |
Inlet manifold |
| 2. |
Twinport sensor |
| 3. |
Test connection - fuel pressure |
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• Service:
The control flaps cannot be exchanged or replaced.
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