PORSCHE 911 GT2 2008 5.G Information Manual

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The 911 GT2 |Drive
Lightweight design.
The six-cylinder twin-turbo boxer
engine is a compact unit offering
excellent cylinder charging and
torque-curve characteristics
as well as first-rate balance with
minimal vibration. The flat-six
design allows a low centre of
gravity with resulting advantages
for traction and driving dynamics.
The alloy crankcase consists of
two main sections, each contain-
ing one bank of cylinders. Thecrankshaft runs in eight main
bearings and is driven by forged
connecting rods. For optimum
strength and durability, we’ve used
forged aluminium pistons running
in Nikasil-coated aluminium liners
and cooled via individual oil-spray
jets. The results: lower frictional
resistance and a lengthy service
life – even when subjected to
heavy use.
The cylinder heads are made
from an extremely heat-resistantlightweight alloy. Each cylinder
bank has two overhead camshafts
driving a set of four valves (two
inlet and two exhaust) on each
individual cylinder. The valves are
arranged in a ‘V’ formation and
have a highly efficient dual-spring
closing action enabling higher
engine speeds. Performance is
enhanced with the aid of both
Variable Turbine Geometry (VTG,
see page 28) and VarioCam Plus
(variable valve timing and lift on
the inlet side). The benefits are
not only greater power and
torque, but also better fuel
econ-
omy and lower emissions.
Dry-sump lubrication.
This racing technology uses a
separate oil reservoir to ensure
consistent oil pressures through-
out the engine, even during pro-
longed periods of lateral and longi-
tudinal loads. After passing
through the engine, every drop of oil is returned directly to the
external reservoir. The flow is dri-
ven by two scavenge pumps in
each cylinder head and a further
two pumps in the crankcase. Gas
is removed from the returning
oil via a defoaming device in the
reservoir. The oil is returned
to the lubrication points in the
engine by means of a dedicated
oil-feed pump. With a further
scavenge pump in each of the
twin turbocharger units, the
911 GT2 has a total of nineseparate pumps driving the lubri-
cation system. The oil level can be
checked from inside the car via
the standard on-board computer.
The 911 GT2 is factory-filled with
Mobil 1 high-performance fully
synthetic oil. The exceptional
properties of this premium-quality
lubricant ensure reliable starting
even in the coldest conditions. It
also reduces wear and contributes
to the long-term durability of the
engine.

· 26 ·· 27 ·
The 911 GT2 |Drive
VarioCam Plus
Engine cooling.
The engine of the 911 GT2 features
cross-flow water cooling with fully
integrated coolant management.
This technology ensures a consis-
tent flow of coolant to each of
the engine’s cylinders. Waste
heat from the oil is transferred to
the coolant via two oil/water heat
exchangers. The coolant is routed
through twin radiator modules
ahead of the front wheels and a
centrally placed unit in the nose.
VarioCam Plus.
VarioCam Plus is a variable valve
timing system on the inlet side
which also features two-stage valve
lift. The benefits it provides include
greater power and torque at all
engine speeds, as well as excellent
running characteristics, better fuel
economy and fewer emissions.
Essentially, VarioCam Plus makes
two engines out of one. The first is
geared for normal road driving, thesecond for high-performance use.
The system switches seamlessly
between the two as the driver
inputs change. All operations
are controlled by the engine
management system. The results:
emphatic acceleration and
smoother running.
The two-stage lift mechanism
on each inlet valve consists of an
electro-hydraulically switchable
tappet. Each of the 12 tappets con-
sists of two concentric parts – anouter ring and a central shaft –
which can be locked together by
means of a pin. The system can
then vary the valve lift by using
two large profile cams on the outer
ring or a smaller cam lobe on the
central shaft. The timing of each
valve is steplessly controlled by
means of an electro-hydraulic
rotary vane adjuster at the head
of the corresponding camshaft.
To improve responsiveness during
warm-up in cold weather, VarioCam
Plus will select the higher valve
lift setting and retard valve timing.
At medium revs and low engine
loads, the lower valve lift setting
is activated and timing advanced in
order to reduce fuel consumption
and emissions. The economy of
the engine is particularly enhanced
at lower engine speeds. For maxi-
mum power and torque, the higher
lift setting is selected and the tim-
ing of the valves is advanced.This results in copious torque
and exceptional fuel economy,
particularly in comparison with
much larger engines offering
similar power output.

· 29 · · 28 ·
The 911 GT2 |Drive
turbine has a lower mass, it
responds more quickly to increas-
ing pressure, spinning up easily
to its optimum speed. The key
disadvantage of using a smaller
turbo is that the back-pressure
generated at higher engine speeds
causes a significant reduction
in performance. Resistance is
caused by the smaller cross-
sectional area through which
the exhaust is required to flow.
On a conventional turbocharger,
the exhaust flow drives a turbine
that is connected to a compressor
on the intake side. By compressing
the incoming air, the amount
of oxygen in a given volume is
increased. Since compression also causes an increase in
temperature, the air must be
cooled in a device known as an
‘intercooler’. With more oxygen
present in each cylinder charge,
more fuel can be burnt, yielding
greater energy. Since higherexhaust pressures generate
greater loads on the intake side,
the intake pressure must be
carefully controlled in order to
protect the engine. This ‘boost
pressure’ is limited using ‘waste-
gate’ valves that bypass excess
pressure around the turbine.
Another important factor in
the system is the size of the
turbocharger. Since a smaller Porsche has a long and celebrated
tradition of using turbocharged
power on both road and track.
On the 911 GT2, we’ve
enhanced
this technology with Variable Turbine
Geometry (VTG).Larger turbo units, which create
lower back-pressure at higher rpm,
take considerably longer to spin
up under power due to the large
cross-sectional area and relative
inertia of the heavier turbine.
Generally, this type of turbo will
only be effective in the medium
rpm range. This phenomenon,
known as ‘turbo lag’, means there
is virtually no turbocharging
effect at lower engine speeds.
Turbocharger with Variable Turbine Geometry (VTG)
Breathe easy – when holding your breath.
Variable Turbine Geometry (VTG).

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The 911 GT2 |Drive
1. Turbine casing
2. Movable guide vanes
3. Turbine wheel
4. Electric motor for guide
vane adjustment
5. Guide vane adjuster
6. Compressor casing
7. Compressor wheel
8. Recirculation valve
9. Oil inlet
10. Coolant inlet
Guide vanes open Guide vanes closed
Guide vanes open Guide vanes closedTurbocharger guide vane adjuster
To overcome this problem, the
twin water-cooled turbochargers
on the 911 GT2 feature Variable
Turbine Geometry (VTG). With
this technology, the gas-flow
from the engine is channelled
onto the turbines via electronically
adjustable guide vanes. By chang-
ing the vane angle, the system
can replicate the geometry in all
types of turbo, large or small,
and thus achieve the optimum
gas-flow characteristics. The guide
vanes are controlled by the engine
management system. The result
is a high turbine speed – and
therefore higher boost pressure –
even at low engine rpm. With
more air available, the combustion
is increased, yielding greater
power and torque.
Special features on the 911 GT2
include flow-optimised turbines
and larger compressors which
generate a higher boost pressure.
Maximum torque is
achieved at
low rpm and sustained across
much of the engine speed
range.With 680 Nm available between
2,200 and 4,500 rpm, the
resulting acceleration is nothing
less than phenomenal.
When the boost pressure reaches
its maximum value, the guide
vanes are opened further. By
varying the vane angle, it is
possible to generate the required
boost pressure at all engine
speeds. As a result, there is no
need for excess pres
sure valveson the intake side as found
on
conventional turbocharged
engines.
This delivers impressive
engine efficiency and lower
fuel consumption.

· 33 · · 32 ·The 911 GT2 |
Drive
Unfortunately, compression not
only increases air volume, it also
increases air temperature and this
has a negative effect on ignition.
Our new expansion manifold simply
turns that principle around. The
internal geometry is radically
different from that on a resonance
intake system. Key modifications
include a longer distributor pipe,
with a smaller diameter, and
shorter intake pipes.Expansion intake manifold.
More power than a 911 Turbo -–
from the same engine? Not easy.
But feasible, which is why it
required yet another spectacular
innovation from Porsche.
The 911 GT2 has an innovative
expansion intake system with a
unique working principle which
overturns the methods previously
used. Our ‘expansion’ intake
mani-
fold is a radical new
developmentthat is the polar opposite of
the resonance principle used
on conventional turbocharged
engines.
A resonance manifold increases
engine output by forcing add-
itional air into the combustion
chambers. To do this, the mani-
fold is designed in such a way
that the air – which vibrates
due to the action of the valves –
is in a compression phase as it
passes through the inlet ports.As a result, the air is in the
expansion phase as it enters the
combustion chambers. Since
expansion always cools, the
air/fuel temperature is lower and
ignition is significantly improved –
thereby increasing performance.
Of course, the amount of air
that enters the engine under
expansion is less than it would
be under compression. To
compensate for this, we’ve simply
increased the boost pressurefrom the turbochargers by
approximately 0.2 bar. The result-
ing increase in temperature –
again through compression – is
immediately offset by the uprated
intercoolers.
Instead of hot compressed
air entering the combustion
chambers, we now have cooler
air generating more power and
torque. As a consequence,
there is a major improvement in
engine efficiency and thereforelower fuel consumption even under
heavy loads and at high rpm.
A simple solution, but then that’s
often the way when you take
a new approach to old ideas.
Expansion intake manifold

· 34 ·· 35 ·
The 911 GT2 |Drive
Exhaust system.
The rear silencer and tailpipes
of the 911 GT2 are made from
ultra-lightweight titanium to re-
duce the weight on the rear axle,
and improve driving dynamics.
The exhaust leaves the engine
through high-performance
manifolds into separate tracts
for each of the two banks of
cylinders. Twin three-way catalytic
converters clean the two streams
before they converge in the main
silencer unit. The twin
titaniumtailpipes are fully integrated
within
the rear apron moulding. Large-
diameter tubes reduce back-
pressure
on the engine,thereby
increasing performance. The
catalytic
converters are close
to the engine,
enabling faster
warm-up and therefore improving
efficiency. When starting from
cold, the process is assisted by a
secondary air injection system.
A system of ‘Lambda’ or oxygen
sensors in each of the exhausts
provides continuous monitoring of engine efficiency. Data supplied
by one pair of sensors enables
the engine management system
to perform separate adjustment
of the air/fuel mix for each bank
of cylinders. A further pair of sen-
sors*, one on each tract, is used
to monitor the efficiency of the
respective catalytic converter. This
facility enables much more accu-
rate control of potentially harmful
emissions.
The exhaust system on the
911 GT2 produces a warm,
deep and bass-rich sound –
even when the engine is idling.
Fuel system.
Fuel is supplied to each of the six
cylinders using a sequential fuel
injection system. The timing of
each injection and the volume
supplied to each bank of cylinders
are controlled by the engine
management system. Adjustmentsare based on a range of variables,
including throttle position, engine
speed, boost pressure, coolant
temperature and exhaust gas com-
position. The results are optimised
combustion and fuel consumption.
A hot-film air mass sensor moni-
tors the volume and density of the
incoming air to ensure the best
possible air/fuel mix, regardless
of weather and altitude.
Ignition system.
The 911 GT2 features static
high-voltage ignition technology.
Separate coils on each of the
plugs with platinum electrodes
ensure perfect ignition every
time. The role of distributor is
performed by the engine manage-
ment system, which controls the
individual spark plugs directly,
for optimum performance and
minimum fuel consumption.
* Not in markets with leaded fuel.Exhaust system

· 37 · · 36 ·
The 911 GT2 |Drive
benefits, such as optimum econ-
omy, emissions and performance
in all driving scenarios.
One of the most important tasks
performed by the engine manage-
ment system is cylinder-specific
knock control. By preventing pre-
ignition at high engine speeds
and loads, this function can avert
costly damage to the pistons and
cylinders. Since temperatures
tend to vary across the engine,
each cylinder is monitoredseparately. If a risk is detected,
the individual ignition timing is
adjusted.
The on-board diagnostics system,
designed to European standard,
quickly detects any faults in the
exhaust and fuel system and
displays them during driving
via the car’s instruments. The
benefits include active prevention
of harmful emissions as well
as consistent rates of fuel con-
sumption.Input data Used to regulate /control
Digital engine electronics
(ME7.8.1 control unit)
Engine load
Pressure upstream from throttle
Throttle-valve angle
Engine speed (from crankshaft)
Inlet camshaft phase angle
Throttle-pedal position
Oxygen sensor signals
Knock sensor signals
Ignition
Fuel injection
Throttle valve
Heating elements in oxygen sensors
Fuel pump
Fuel-tank venting
CAN interface to transmissionMoment interface to Porsche
Stability Management (PSM)
VarioCam Plus
– camshaft phase angle
– valve lift control
Electronic controller for
Variable Turbine Geometry (VTG)
Recirculation valve
Secondary air injection
Engine-bay fan
Starter
On-board diagnostics
Air-conditioning compressor
Interface to instrument cluster
Radiator fans (front control unit via CAN)
Vehicle speed
Air-conditioning settings
Engine immobiliser status
Clutch pedal switch
Ambient air pressure
Temperatures
– coolant
– air upstream from throttle
– engine oil
– air in engine compartment
– ambient air
Exhaust-gas temperature
Engine management system.
The Motronic ME7.8.1 engine
management system facilitates
optimum performance at all
times. This high-precision ECU
controls all engine-related func-
tions and assemblies (see
dia-
gram), such as Variable Turbine
Geometry, VarioCam Plus and
the electronic throttle, one of the
key prerequisites for the standard
Porsche Stability Management
(PSM). This produces various

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The 911 GT2 |Drive
The six-speed manual gearbox in
the 911 GT2 is specifically
designed for the high engine
performance. The individual ratios
are carefully matched to the spe-
cific characteristics of the engine.The gear-lever throw is short and
precise, enabling fast and
accurate gearshifts.
A typical feature of the 911 GT2
is the Launch Assistant – for maximum acceleration from a
standing start. The clutch and
accelerator are depressed when
the vehicle is stationary.
When a
boost pressure of approximately
0.9 bar is displayed in the instru-ment
cluster, release the clutchas
quickly as possible and maximum
a
cceleration automatically ensues.
Normally on a turbocharged vehicle
with manual gearbox, the boost
pressure under acceleration from
a standing start is relatively low.
The turbo effect is delayed as
the engine gathers speed and
the boost pressure starts to build.On the 911 GT2, this initial delay
is reduced. While the car is still
stationary, the fuel injection is
modified to help the engine reach
maximum output earlier. The boost
pressure is significantly increased
and the engine readied for a faster
start.
A specially designed traction
control system adapts the acceler-
ation procedure automatically
in the ECU to ensure optimum
traction. The clutch remains
engaged. This reduces load and
prevents high clutch wear. The
power is transmitted directly to
the road via the rear axle.
The gearbox is combined with
a cable linkage and dual-mass fly-
wheel offering added comfort and
precision. The close ratio spread
enables powerful acceleration
within the optimum engine power
band.
Steel baulk rings on gears two to
five ensure a precise gearshift
action even under extreme loads.Cooling is provided by an add-
itional oil-to-water heat exchanger
and spray lubrication. Both of
these features are essential for
durability in endurance racing
conditions.
Other standard features include
a limited-slip differential with
asymmetrical lock factor. Offering
better traction and handling
when exiting a corner, it applies a
higher proportion of drive torque
to the loaded outer rear wheel.
The term ‘asymmetrical’ means
that one lock factor is applied
when cornering under power
(28 %), and another when braking
for a corner (40 %).
Maximum response to minimum effort.
Transmission.

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The 911 GT2 |Drive
1. Bi-Xenon headlights
2. Radiator module (left)
3. Radiator module (centre)
4. Radiator module (right)
5. Coolant pipe9. Intercoolers
10. Pressure pipe
11. Throttle valve
(electronically actuated)
12. Expansion intake manifold 6. Coolant expansion tank
7. Air filter
8. Exhaust-gas turbocharger
with Variable Turbine
Geometry (VTG)17. Generator
18. PASM damper
19. PCCB brake
20. Tandem brake booster
21. 6-speed manual gearbox
22. Sport bucket seat
13. Main silencer (titanium)
14. Tailpipe (titanium)
15. Oil filter
16. Engine oil reservoir
(dry-sump lubrication)

Chassis
An extraordinary car with
everyday capability.