Audi 4.2-litre V8 FSI Service Training
Audi 4.2-litre V8 FSI engine
Self-Study Programme 377
Service Training
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Special features of the current Audi vee engine family are the 90-degree included angle between the
cylinder banks and the spacing of 90 mm between the cylinders.
The first member of the family was the 3.2-litre V6 FSI engine. The 4.2-litre V8 FSI engine is also a member
of this family.
It is available in two versions - a comfort-oriented basic version (used for the first time in the Audi Q7) and
a sporty high-revving version for the new RS4. A V10 engine with 5.2 litres of displacement will also be
available.
Like the RS4 engine, the V8 in the Q7 has FSI direct injection, which – following five victories in the
Audi R8 Le Mans racing car – is now being introduced in a production eight-cylinder model.
The V8 was retuned for use in the Audi Q7. A fuller torque curve up to nominal speed and spontaneous
response – these are the characteristics of this new engine.
The engine excels not only with its dominant power output and high maximum torque. The resultant
driving performance is excellent, even in the face of tough competition.
RS4 high-revving engine
Table of contents
Engine mechanicals
Oil circulation system
Cooling system
Air circulation system
Cranktrain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Crankcase ventilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Chain drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Drive, ancillary units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Cylinder head . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Oil pump and oil filter module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Oil pan Audi RS4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Oil circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Cooling system in Audi Q7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Cooling system in Audi RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Air intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Intake manifold flaps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Vacuum hoses in the Audi RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Vacuum hoses in the Audi Q7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Engine management
System overview, Audi Q7 (Bosch MED 9.1.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
System overview, Audi RS4 (Bosch MED 9.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
CAN data bus interfaces (powertrain CAN data bus) in the Audi Q7. . . . . . . . .42
CAN data bus interfaces (powertrain CAN data bus) in the Audi RS4 . . . . . . .43
Start mode of the Audi RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Sport mode of the Audi RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
The self-study programme teaches the basics of the design and function of new models,
new automotive components or new technologies.
The self-study programme is not a Repair Manual!
All values given are intended as a guideline only and refer
to the software version valid at the time of publication of the SSP.
For maintenance and repair work, always refer to the current technical literature.
NoteReference
Exhaust system
Exhaust system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Exhaust flap control in the Audi RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Secondary air system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Fuel system in the Audi Q7/RS4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Fuel system
6
The 4.2-litre V8 FSI engine is supplied in the new
Audi Q7, Audi A6, Audi A8 and in the RS4.
Note
The technical descriptions of this engine refer
mainly to the V8 basic engine in the Audi Q7
and the high-revving engine in the Audi RS4.
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Introduction
The following main objectives were set for
the development of the Q7 engine:
– High specific engine power:
257 kW/350 bhp out of 4.2 litres (15 bhp more
than MPI engines)
– High torque: 440 Nm out of 4.2 litres
– Reduction of fuel consumption by approx. 5 %
(~360 g/kWh at 2000 rpm and 2 bar)
– Short and compact design
– Modular engine concept based on V6 FSI engine
for V8 and V10 FSI (synergy)
– High idling quality
– High standard of comfort with regard to
acoustics and running quality
– Low engine weight
– Off-road capability of Audi Q7 engine
Q7 engine
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Technical features
– Petrol direct injection
– Homogeneous-charge mode
– Roller cam followers with hydraulic backlash
compensation
– Flywheel-side chain drives for camshafts and
ancillary units
– Variable camshaft adjustment for intake and
exhaust camshafts
– Two-stage magnesium variable inlet manifold
with integrated tumble flap (not fitted in RS4)
– Drive-by-wire throttle control
– for compliance with exhaust emission standards
EU IV/LEV II
The main technical differences between the base
engine and the high-revving engine lie in the
following modules:
– Cranktrain
– Timing gear
– Cylinder head
– Oil supply
– Engine cooling
– Intake path
– Exhaust system
– Engine management
For an exact description of the differences, please
refer to the relevant section.
RS4 engine
8
160
200
240
280
320
80
kW
Nm
460
300
380
420
20000
5000
7000 9000
Introduction
Torque/power curve
Max. torque in Nm
V8 FSI basic engine in Q7
V8 FSI high-revving engine in RS4
Max. power output in kW
V8 FSI basic engine in Q7
V8 FSI high-revving engine in RS4
Engine speed in RPM
Specifications
Q7 RS4
Engine code BAR BNS
Type of engine V8 90° vee angle 4V FSI
Displacement in cm
3
4163
Max. power output in kW (bhp) 257 (350) at 6800 rpm 309 (420) at 7800 rpm
Max. torque in Nm 440 at ~3500 rpm 430 at 5500 rpm
Number of valves per cylinder 4
Bore in mm 84.5
Stroke in mm 92.8
Compression ratio ~12.5/-0.4 : 1
Firing order 1–5–4–8–6–3–7–2
Engine weight in kg approx. 198* approx. 212**
Engine management Bosch MED 9.1.1 Bosch 2x MED 9.1
Fuel grade 98 / 95 RON
Exhaust emission standard EU IV/LEV II
* with automatic transmission
** manual gearbox including clutch and dual-mass flywheel
9
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*Aluminium alloys are classed as hypoeutectic or
hypereutectic, depending on their silicon content.
"Alusil" has a hypereutectic silicon content of 16 to
18 % so that primary silicon is precicipated on
solidification of the molten metal.
A multistage honing process is applied. The silicon
grains in the cylinderbores in the form of microscopically small, very hard particles are stripped to
give the necessary wear resistance of the cylinder
surfaces for the piston and piston rings.
– Cylinder spacing: 90 mm
– Cylinder bank offset: 18.5 mm
– Overall engine length: 464 mm
– Cylinder block height: 228 mm
Engine mechanicals
Cranktrain
Cylinder block
The cylinder crankcase has a closed-deck design.
The closed-deck design is stronger than the opendeck design.
In an open-deck cylinder block, the water jacket for
cooling the cylinders is open at the top.
The cylinder crankcase is made of a low-pressure
gravity diecast aluminium-silicon alloy, is
hypereutectic* and has a silicon content of 17 %
(AlSi17Cu4Mg).
The cylinder crankcase underwent special heat
treatment in order to increase its strength.
The cylinder liners are mechanically stripped.
The cylinder crankcase of the high-revving engine
was machined to higher specifications due to the
higher stresses in this component. To minimise
warping of the cylinder manifolds, the crankcase is
honed under stress. For this purpose, a honing
template is attached to the crankcase before the
honing process in order to simulate the warping of
the bolted cylinder manifold.
The cylinder crankcase lower section (bedplate
bearing cross-member) is made of aluminium with
press-fitted iron main bearing covers made of grade
50 nodular cast iron. It is centred using centring
pins, sealed with liquid sealant and bolted to the
cylinder crankcase.
The main bearing is symmetrically to the centre of
the main bearing attached by four bolts.
The bedplate type design provides high stability.
The bedplate has the same stabilising effect as a
ladder frame.
Cylinder crankcase bottom section
Press-fitted main bearing
Cylinder crankcase
10
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Engine mechanicals
Crankshaft
The crankshaft runs on five bearings and is made of
high-alloy tempering steel (42CrMoS4). It is 90°
cranked and has no conrod journal offset.
The vibration damper is a vulcanised single-mass
damper with unbalance.
– Main bearing: Ø 65 mm
– Main bearing width: 18.5 mm
– Big-end bearing: Ø 54 mm
– Big-end bearing width: 15.25 mm
Modifications to high-revving engine
At the very high engine speeds, axial vibration
occurs due to the unbalance in the single-mass
damper. This can cause the crankshaft to break.
To avoid this vibration, a dual-mass damper without
unbalance is employed in the high-revving engine.
To compensate for unwanted engine vibration,
heavy metal inserts are integrated in the first and
eighth crank webs by way of unbalance.
Heavy metal inserts
Cranktrain in the RS4
11
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Piston
For strength reasons forged pistons with a slightly
higher weight than conventional pistons is used.
Both engines have the same piston geometry.
– Piston weight
without rings: approx. 290 g
– Piston pin: Ø 20 mm x Ø 11.5 mm x 40 mm
Con-rod
Cracked con-rods made of 36MnVS4 are used in the
basic engine while the conventionally split con-rods
in the RS4 engine are made of 34CrNiMo8 for
strength.
In addition, the geometry of the con-rods was
reduced for the high-revving engine and the tolerances were reduced.
– Bearing journals: Ø 54 mm
– Bearing bushings: 1.4 mm thick,
15.25 mm wide
– Length of bushing: Ø 20 mm rolled
– Con-rod length: 154 mm
Cracking
During the cracking process, the con-rod is split at a
predetermined breaking point using a special tool.
The resultant unique breaking surface ensures the
high joining precision of the two mating parts.
Breaking surface
Predetermined
breaking point
12
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Note
Modifications after start of production
In both engines, the separated oil flows
into the crankcase through the cover in the
inner vee adjacent the crankcase breather
(no longer through the chain housing).
In the Q7 engine the crankcase is vented
through a single chamber, i.e. via bank 2
only. Better antiicing protection is achieved
in this way.
After the blow-by gas has passed through the fine
oil separator, the gas flows into the intake manifold
downstream of the throttle valve.
This inlet point is integrated in the coolant circulation system and heated. This prevents the crankcase
breather from freezing up.
Engine mechanicals
Crankcase ventilation
The crankcase is ventilated through both cylinder
heads.
The valve hoods incorporate a large settling space.
This space acts as a gravity-type oil separator.
A fine oil separator is connected to the valve hoods
by means of plastic hoses.
A control piston, a bypass valve, a two-stage
pressure limiting valve and an oil drain valve are
integrated in the oil separator housing.
Pressure limiting valve
Heater
Bypass valve
Fine oil separator
Crankcase breather system
Non-return valve
(crankcase breather)
Breather pipe
Breather pipe
13
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Function of fine oil separator
Blow-by gas volume is dependent on engine load
and RPM. The fine oil ("oil spray") is separated by
means of a cyclone separator. Cyclone separators
only have a high separation efficiency over a small
volumetric range. For this reason, one, two or three
cyclones of the fine oil separator operate in parallel
depending on the gas flow rate.
The cyclones are released by the control piston.
The displacement of the control piston against its
spring force is dependent on the gas flow rate.
Piston ring flutter at very high engine RPM and low
engine load can result in a very high gas flow rate.
The crankcase internal pressure is set by the twostage pressure control valve.
The bypass valve together with the control piston
ensures that the cyclones operate at the optimum
operating point (if the volumetric flow rate is too
high or too low, this will impair the functioning of
the cyclones).
When the bypass valve opens, a fraction of the
blow-by gas flows to the engine untreated, but the
remainder is optimally treated by the cyclones.
The separated oil is collected in an oil reservoir
beneath the cyclones. The oil cannot drain out of
the reservoir until the oil drain valve is opened.
The oil drain valve is closed as long as the pressure
in the crankcase, i.e. below the valves, is higher
than in the oil separator. The valve opens automatically due to gravity only at very low engine RPM
or when the engine is at a standstill, because the
pressure conditions above and below the valve are
in equilibrium.
The crankcase ventilation system also includes the
crankcase breather. Air is extracted downstream of
the air filter and flows through a non-return valve
into the crankcase from above.
The non-return valve is located at the end of the
vent line and is bolted between the two cylinder
banks in the engine block.
A damping chamber is located below the non-return
valve in the engine block. This prevents non-return
valve flutter and eliminates noise.
A restrictor bore connects this chamber to the
inner chamber of the crankcase. It has the task of
supplying only a defined volume of fresh air to the
crankcase.
Control piston
Oil reservoir
Oil drain valve
Triple cyclones
14
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Engine mechanicals
Chain drive
The timing gear concept is identical in all Audi veeengine series.
The chain drive runs on two planes.
Plane 1
Basic drive A:
drives idler gears to camshafts from crankshaft
Plane 2
Top drive B and C: drives camshafts from idler gears
Chain drive D: drives ancillary units drive module
from crankshaft
Correct chain tension is ensured by spring hydraulic
tensioners. The chain drive is maintenance-free and
designed for lifetime service.
The two engine types differ in terms of the type of
chains used and the reduction ratios in drives A, B
and C. The load on the roller chains was reduced in
the basic engine version by selecting a higher
number of teeth.
Illustration shows the Q7 engine
Q7
The camshafts in the basic engine are driven
by 3/8“ simplex roller chains.
Due to their acoustic advantages, the chains were
developed to meet the high comfort requirements.
In this case the idler gears have 40 and 24 teeth.
The camshaft sprockets have 30 teeth.
High-revving engine
3/8“ simplex sleeve-type chains are used here.
Their advantage is their reduced wear and higher
stress resistance at high engine speeds.
In this case the idler gears have 38 and 19 teeth.
The camshaft sprockets have 25 teeth.
Chain drive B
Chain drive C
Chain drive D
Chain drive A
15
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Ancillary units drive
The oil pump, water pump, power steering pump
and the compressor are driven by chain drive D.
The chain is driven directly by the crankshaft,
deflected by an idler gear and drives the chain
sprocket seated on the gear module.
Chain drive D
Power steering pump
Coolant pump
Gear module
Air conditioner compressor
Oil pump
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