Audi 4.2-litre V8 FSI Service Training page 40

Engine management
Engine management in the new V8 FSI is by two
versions of the Bosch MED 9.1.1.
A single control unit is used in the Q7 engine.
There are two control units for the RS4 engine.
A master-slave concept is required here due to the
requisite processing power at engine speeds up to
8250 RPM.
Further differences between the Q7 and RS4
engines in respect of engine management are as
follows:
Engine speed sender G28
An inductive sender is used in the Q7 engine.
A Hall sensor is used in the RS4 engine with master-
slave concept.
The signal from the Hall sender, can unlike the
signal from the inductive sender, be split with the
result that it can be utilised by both engine control
units.
Applying the signal directly to both engine control
units ensures that the control units are absolutely in
sync.
Throttle valve module
The Bosch throttle valve module used in the Q7 is
the largest in the range with a diameter of 82 mm.
The Pierburg system was selected because the air
intake system in the RS4 has a diameter of 90 mm.
However, both systems work in exactly the same
way.
Spark plugs
In contrast to the Q7, spark plugs with a higher heat
rating (colder plugs)* are used because the RS4
engine is subjected to higher thermal stresses.
* applies to NGK spark plugs
Injectors
Due to the higher fuel demand and the shorter time
window available for injection at very high engine
speeds, the RS4 engine is fitted with larger injectors
than the Q7 engine.
Diagnosis
The RS4 engine is diagnosed via the K-wire.
The Q7 is diagnosed via the powertrain CAN bus.
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The processor operates at a clock frequency of
56 MHz. The internal memory has a storage capacity
of 512 Kbytes. Each of the two external memories
has a storage capacity of two Mbytes.
The connection to the vehicle network is made
by means of a CAN data bus.
In the case of the master-slave concept, data is
additionally exchanged across a private bus.
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