vw 3 2 and 3 6 liter fsi engine pdf
The Variable Intake Manifold
The variable intake manifold design increases low
rpm torque and high rpm power by taking advantage
of the self-charging or “ram effect” that exists at
some engine speeds.
By “tuning” the intake manifold air duct length,
engineers can produce this ram effect for a given rpm
A manifold that has two different lengths of air
ducts can produce the ram effect over a broader rpm
The 3.2 and 3.6-liter V6 engines use two lengths of
air ducts but not in the same way as the dual path
manifolds used on other engines.
Instead of using high velocity air flow in a long
narrow manifold duct to ram more air into an engine
at low rpm and then opening a short, large diameter
duct for high rpm, the 3.2 and 3.6-liter V6 engines
take advantage of the pressure wave created by
the pressure differential that exists between the
combustion chamber and the intake manifold.
All air enters the intake manifold plenum and torque
port, then is drawn down the long intake ducts to
Performance Port Valve Actuation
Intake manifold change-over is engine speed
dependent. The Motronic Engine Control Module
J220 activates the Intake Manifold Change-Over
Valve N156, which supplies vacuum to the vacuum
solenoid that operates the performance port valve.
Principles of Variable Resonance
Intake Manifold Operation
After combustion has taken place in a cylinder,
there is a pressure differential between the cylinder
combustion chamber and the intake manifold. When
the intake valves open, an intake wave forms in the
This low pressure wave moves from
the intake valve ports toward the torque port at the
speed of sound.
The Air Mass Meter with
Reverse Flow Recognition
To guarantee optimal mixture composition and
lower fuel consumption, the engine management
system needs to know exactly how much air the
engine intakes. The air mass meter supplies this
The opening and closing actions of the valves cause
the air mass inside the intake manifold to flow in
The hot-film air mass meter with reverse
flow recognition detects reverse flow of the air mass
and makes allowance for this in the signal it sends
to the engine control unit.
Thus, the air mass is
metered very accurately.
The electronic circuit and the sensor element of the
air mass meter are accommodated in a compact
Located at the lower end of the housing is a
metering duct into which the sensor element
The metering duct extracts a partial flow
from the air stream inside the intake manifold and
guides this partial flow past the sensor element. The
sensor element measures the intake and reverse air
mass flows in the partial air flow.
The resulting signal
for the air mass measurement is processed in the
electronic circuit and sent to the engine control unit.
Two temperature sensors (T1 and T2) and a heating
element are mounted on the sensor.
The sensors and heating element are attached to a
Glass is used because of its poor
This prevents heat which the
heating element radiates from reaching the sensors
through the glass membrane. This can result in
The heating element warms up the air above the
The two sensors register the same
air temperature, since the heat radiates uniformly
without air flow and the sensors are equidistant from
the heating element.
Induced Air Mass Recognition
In the intake cycle, an air stream is ducted from T1
to T2 via the sensor element.
The air cools sensor
T1 down and warms up when it passes over the
heating element, with the result that sensor T2 does
not cool down as much as T1.
The temperature of T1 is then lower than that of T2.
This temperature difference sends a signal to the
electronic circuit that air induction has occurred.
Reverse Air Mass Flow
If the air flows over the sensor element in the
opposite direction, T2 will be cooled down more
than T1. From this, the electric circuit recognizes
reverse flow of the air mass.
It subtracts the reverse
air mass flow from the intake air mass and signals
the result to the engine control unit.
The engine control unit then obtains an electrical
signal: it indicates the actual induced air mass and
is able to meter the injected fuel quantity more
The V-angle of the cylinder block is 10.6°.
By changing the V-angle from 15° to 10.6°, it was
possible to provide the necessary cylinder wall
thickness without changing the dimensions of the
By reducing the V-angle, the cylinder longitudinal
axis moves outward relative to the bottom of the
The distance between the cylinder longitudinal axis
and the crankshaft center axis is the Offset.
The Offset is increased from 12.5 mm to 22 mm
compared with the manifold injection engine.
The pistons are recessed and are made of aluminum
In order to improve their break-in properties,
they have a graphite coating.
The pistons are different for the cylinder bank 1 and
the cylinder bank 2.
They differ in the arrangement
of the valve pockets and the combustion chamber
The location and design of the piston recess
generates a swirling motion of the injected fuel and
mixes it with the intake air
The Connecting Rods
The connecting rods are not cast but milled.
The connecting rod eye is of a trapezoidal design.
The connecting rod bearings are molybdenum coated.
This provides good running-in properties and high
During the exhaust stroke, the intake and the exhaust
valves are both open simultaneously.
As a result
of the high intake manifold vacuum, some of the
combustion gases are drawn out of the combustion
chamber back into the intake manifold and swirled
into the combustion chamber with the next induction
stroke for the next combustion cycle.
Benefits of the internal exhaust gas recirculation:
Improved fuel consumption due to reduced gas
Partial load range expanded with exhaust gas
Exhaust gas recirculation possible even with a cold
It prevents hydrocarbon-enriched vapors (blow-by
gases) from escaping from the crankcase into the
Crankcase ventilation consists of vent
passages in the cylinder block and cylinder head, the
cyclone oil separator and the crankcase ventilation
The blow-by gases in the crankcase are drawn out by
intake manifold vacuum through:
the vent ports in the cylinder block,
the vent ports in the cylinder head,
the cyclone oil separator and
the crankcase ventilation heater
The blow-by gases are then rerouted into the intake
Crankcase Ventilation Heating
The heating element is installed in the flexible tube
from the cyclone oil separator to the intake manifold,
and prevents icing of the blow-by gases when the
intake air is extremely cold.