Audi 4.2-litre V8 FSI, Service Training

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Air circulation system
Air intake
The intake path of the Q7 is double-chambered and
discharges into a variable inlet manifold made of
gravity die cast aluminium. A Bosch throttle valve
module with a diameter of 82 mm is located
upstream of the variable inlet manifold.
The variable inlet manifold is of the two-stage type.
In the lower RPM range, the long intake manifold
path is activated in order to increase torque. In the
upper RPM range, the short intake manifold path is
activated. This positionproduces an increase in
engine power output. Intake manifold path change-over is map-control-
led. The adjustment is made by the variable inlet
manifold motor V183. No feedback is given on the
position of the variable inlet manifold.
If the intake manifold shutoff is not functioning,
exhaust gasquality is not impaired. In this case, the
driver will notice a loss of power.
Intake system in the Audi Q7
Intake manifold flaps
As with the variable inlet manifold, the intake mani-
fold flaps in both engine variants are controlled
according to a characteristic map. In both engines
the intake manifold flaps are activated in the lower
engine load and RPM ranges.
They are brought into abutment with the port baffles
in the cylinder head and thereby seal the lower part
of the intake port. The aspirated air mass now flows
through the upper section of the intake port and
induces a tumbling charging motion inside the
cylinder.
When not activated, the intake manifold flaps are
open and sender and maximises the cross-sectional
area of the port. All flaps in a cylinder bank are
attached to a common shaft. In the basic engine in the Q7 the intake manifold
flaps are activated via an electrical actuator.
For each cylinder bank, the position of the intake
manifold flaps is monitored by a Hall sensor.
In the high-revving engine, the intake manifold flaps
are activated by a single vacuum actuator per
cylinder bank. In this case, too, the flap position is
indicated by means of Hall sensors.
Hot-film air mass meter (HFM5)
Throttle valve module
Intake manifold flaps
Hot-film air mass meter (HFM5)
Variable inlet manifold