module

Engine Temperature Sensor
G407
Map Controlled Engine Cooling
Thermostat
F265
Radiator supply (hot)

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View of transmission side
Coolant supply line turbocharger

Coolant return line turbocharger

Coolant line for
transverse pipe

Coolant line for
transmission
cooling

Heating supply line

Heating return line

After-Run Coolant Pump
V51
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After-Run Coolant Pump V51
V51 is activated when greater cooling is required for the turbochargers at high engine loads. In addition, the pump operates
for a defined period after the engine is switched off. This helps prevent heat-soak in the turbochargers. The electric radiator
fan runs as well. To activate V51, the thermal management system performs calculations using the engine speed, engine
torque, ambient temperature and coolant temperature.
›
›

The after-run time lasts between 10 and 45 minutes (depending on the operating status of the engine).
Delivery rate ~ 132.0 gal (500 L) per hour.
63

Coolant distribution module
The primary component of the thermal management
system is installed on the front of the engine. In the
coolant distributor housing, the flow of coolant is directed
to the radiator, ancillaries and engine. The vacuum-controlled coolant pump and the map-controlled engine
cooling system thermostat are located here as well. The
coolant pump is driven by the intermediate shaft via a
sprocket.

When the coolant pump opens the passage for the coolant,
it flows through the entire engine, that is, through the
cylinder heads as well. In other words, “split cooling” is not
used on this engine. The flow to the cylinder block and
cylinder head is distributed at a ratio of 20:80. For this
reason, only one temperature sensor (G407) is installed for
the entire engine; it is installed at an optimal location on
the cylinder head of bank 2.

Map Controlled Engine
Cooling Thermostat
F265

Coolant from radiator
(cold)

Coolant to radiator
(hot)

Oil Pressure Sensor
G10

To belt-driven
starter-alternator

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Map Controlled Engine
Cooling Thermostat
F265

Coolant return (hot)
from ancillaries directly
to coolant pump

Coolant return (hot)
to radiator via thermostat
and coolant pump

Coolant supply (cold)
from radiator

Coolant pump/vacuum
regulating assembly

Coolant supply (cold)
from radiator
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64

Map Controlled Engine Cooling Thermostat F265
The coolant temperature calculated in the characteristic
map can be regulated between 201.2 °F - 222.8 °F
(94 °C - 106 °C) as required. If the temperature is above
201.2 °F (94 °C), the ECM actuates the map-controlled
engine cooling system thermostat via a PWM signal.
To protect the engine, the coolant temperature is lowered
(F265 is not actuated) in the following situations:
›
›
›
›
›

Driving mode Sport.
Vehicle speed greater than 124.2 mph (200 km/h).
Engine torque 438.8 lb ft (595 Nm).
Engine temperature greater than 246.2 °F (110 °C).
System DTCs.

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Map Controlled Engine
Cooling Thermostat
F265

Coolant distribution
module

Gasket
676_022

Coolant pump/vacuum
regulating assembly

Reference

For more information about the map-controlled engine cooling thermostat please refer to eSelf-Study Program
920173, The Audi 3.0L V6 TFSI EA839 Engine.
65

Regulating strategy of the mechanical coolant pump
The on-demand mechanical coolant pump is activated
when the following conditions are met:
›
›
›
›

›

Coolant temperature between -14 °F - 176 °F (10 °C - 80 °C).
Ambient temperature greater than 50 °F (10 °C).
Engine torque greater than 368.7 lb ft (500 Nm) with all
cylinders activated.
Engine torque greater than 110.6 lb ft (150 Nm) with half of
cylinders activated, depending on the coolant temperature and
engine speed.
Time since engine start greater than 600 seconds (10 minutes).

If a signal is sent indicating the need to heat the passenger
compartment during the engine warm-up phase, the
impeller of the mechanical coolant pump is covered by the
sleeve and Coolant Recirculation Pump V50 is switched on.
In this way, pump V50 pumps coolant from the cylinder
head into the heat exchanger.

Conditions prohibiting activation:
›
›

Coolant temperature greater than 176 °F (80 °C).
Engine speed greater than 3250 rpm.

Mechanical Coolant
Pump Switch Valve
N649
Sleeve

Cover plate

Pump gear
Drive gear

Vacuum regulating unit

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66

Transmission coolant circuit

High Temperature Circuit
Coolant Pump V467

3
2
1

Transmission Fluid
Cooling Valve
N509

ATF heat exchanger

ATF return line
ATF supply line

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ATF return line

ATF supply line

N509

3
V467

ATF heat exchanger

1

N488

2

Supply flow
1. From radiator outlet
2. Warm coolant from engine

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The transmission coolant circuit can operate in three
different system states:
Standing coolant

Return
3. To distribution pipe (hot), engine
N488
N509
V467

Transmission Coolant Valve
Transmission Fluid Cooling Valve
High Temperature Circuit Coolant Pump

›
›
›

N509 supplied with current (valve closed).
V488 not supplied with current (valve closed).
V467 not running.

ATF heating
›
›
›

N509 supplied with current (valve closed).
N488 supplied with current (valve open).
V467 running.

ATF cooling
›
›
›

N509 not supplied with current (valve open).
N488 not supplied with current (valve closed).
V467 running.

67

Transmission Fluid Cooling Valve N509 and Transmission Coolant Valve N488
These map-controlled solenoid valves control the inflow of
warm coolant from the engine to the ATF cooler/cold
coolant from the main radiator to the ATF cooler. Both
valves are supplied with 12 Volt current. To activate them,
the corresponding control module switches them to
ground.
Valve N509 is activated by Transmission Control Module
J217, which closes it. Activation is initiated by the thermal
management system of the ECM. The valve is open when it
is not supplied with current.
N488 is activated by the Engine Control Module J623. The
valve is closed when it is not supplied with current.

High Temperature Circuit Coolant Pump V467
This pump is identical in form to pumps V50 and V51. It is
responsible for pumping the coolant through the
transmission coolant circuit.

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Note

Valves N488 and N509 look similar and are easily mistaken for one another; however, the part numbers are different.

68

Air supply
Overview of air ducts
Different versions of the air supply system are used
depending on the vehicle type and engine power output.
The system shown here is for the 2020 Audi A8L. The air
pipe connected to the air cleaner distributes intake air to
both turbochargers.

Air pipe

Connection for crankcase breather

Charge Air Pressure
Actuator 2
V546
Manifold Absolute Pressure
Sensor 2
G429

Throttle Valve Control Module
GX3

Throttle Valve Control Module 2
GX4

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69

Intake side
An inlet guide element is installed in the air pipe at the
point where the air pipe connects to the turbocharger. This
calms the flow of air before it enters the turbocharger. In
addition, the air flow is given a slight “swirl” in the direction of the fan blades, which improves the acoustics of the
air intake.

From air cleaner

Inlet guide element

Pressure side
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The air compressed in the turbochargers is channeled to
the charge air coolers via pulsation dampers as an acoustic
measure against air noise. The connecting pipe joins both
outlets of the turbochargers with one another. This
dampens out-of-phase pressure oscillations and helps
prevent compressor surge.

From air cleaner
From charcoal canister

Pulsation
damper

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Connecting
pipe

676_142

Pulsation damper
Pulsation
damper
70

Intake manifolds
The intake manifolds are bolted to the cylinder heads. A
throttle valve module is installed upstream of each intake
manifold. EA825 engines do not require intake manifold
flaps.

Both intake manifolds have connections for the activated
charcoal canister and crankcase breather. Fuel vapors/
blow-by gases enter the intake manifold when there is
vacuum pressure inside it. The third connection is for the
brake servo (note: the connection on the intake manifold
for bank 1 is non-functional).

Manifold Absolute
Pressure Sensor
G71
Intake manifold,
bank 1
Manifold Absolute Pressure
Sensor 2
G429

Throttle Valve
Control Module
GX3

Intake manifold,
bank 2
Throttle Valve Control Module 2
GX4

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The intake manifold pressure sensors measure the intake
manifold pressure and the temperature of the intake air.
The ECM uses the signals from the sensor downstream of
the throttle valves to measure the air mass (volumetric
efficiency measurement).

The signals from the sensors upstream of the throttle
valves are used by the ECM to calculate and set the desired
charge pressure. The signals are transmitted to the ECM by
SENT protocol.

Manifold Absolute Pressure
Sensor 2
G429

Connection for brake servo to
intake manifold, bank 1 (blind)

Charcoal canister connection

Crankcase Ventilation Thermal
Resistor 2
N483

Throttle Valve Control Module 2
GX4
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71

Throttle Valve Control Modules GX3 and GX4
A throttle valve module is installed upstream of each intake
manifold. Non-contact throttle valve position sensors (Hall
sensors) are used to determine the position of the throttle
valves. They operate on the principle of redundancy,
meaning that the feedback regarding the position of the
throttle valve is delivered by two sensors working independently of and opposed to one another.

A DC motor with a two-stage gear assembly acts as an
actuator for the throttle valve. This keeps the throttle valve
positioned between the two mechanical limit stops. The
position of the throttle valve is calculated based on the
position of the accelerator pedal and the required engine
torque.

DC motor power
supply

Electrical
connection

DC motor

Sensor unit

Throttle valve

Two stage gear
assembly

Note

There are no master list terms for the throttle valve position sensors.
72

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Turbocharging
Twin scroll exhaust manifold
The exhaust manifolds have a twin scroll design. With this separation, two cylinders create one stream of exhaust which is
kept separate in its own channel inside the turbocharger until it reaches the turbine. Keeping the channels separate helps
prevent the individual cylinders from affecting one other adversely during gas exchange.
Background:
The firing order on each cylinder bank creates a 180° firing interval for some cylinders. The exhaust compression waves
(created when the valves open) from these cylinders would affect one another if they were able to interact via the exhaust
manifold. This, in turn, directly affects the gas exchange, because the volume of fresh air would be reduced. The twin scroll
design keeps the gases from those cylinders separate which correspond unfavorably with one another. This provides a
significant torque advantage in the low engine RPM range.

Exhaust manifolds located in the inner V of the engine.

Twin scroll exhaust manifold

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73

Twin scroll turbochargers
The gas flow paths are very short because the turbochargers are located centrally in the inner V of the engine. As a result,
turbocharger response is very direct. The turbines rotate in opposite directions: The turbine on bank 1 rotates counter-clockwise; the one on bank 2 rotates clockwise. This design makes the best use of the space available.

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Oil return line
Coolant supply line

Vacuum unit for charge pressure
regulating valve
676_139

74

Twin scroll turbochargers continued

Twin scroll turbocharger
Turbine (intake side)

Turbine (exhaust side)

Charge pressure
regulating valve

Twin scroll exhaust manifold

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75

Turbocharger mounting
The turbochargers are secured to the exhaust manifolds
with screw-type clips (V-band clamps). A gasket (made of
mica-based material) seals off the connection between the
two components.

The hot side of the turbocharger and the exhaust manifold
are surrounded by insulating covers. This protects the
adjacent components in the inner V and helps conserve a
larger percentage of the exhaust energy.

Screw-type clip (V-band clamp)

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Insulating cover for
exhaust manifold

Screw-type clip (V-band clamp)

Seal

Locating pin for V-band
clamp (assembly aid)

Integral insulation (temperature can be lowered
by up to 752 °F (400 °C)