Variable Turbine Geometry
(V TG).
The 911 Turbo and 911 Turbo S
models are straightforward, almost
mat ter-of-fact, when it comes
to handling power. V TG has con -
tributed enormously to this.
The variable turbine geometry of
the t win water-cooled exhaust gas
turbochargers goes a long way
to resolving the conflict of aims of
normal turbochargers. With this
technology, the gas flow from the
engine is channelled onto the
turbines via electronically adjust -
able guide vanes. By changing
the vane angle, the system can
replicate the geometry in all
t ypes 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.
Maximum torque is reached at
lower rpm and is retained across
a wider rev range. Both engine
variants deliver a torque of just
650 Nm from as low as 1,950 rpm.
In the case of the 911 Turbo
models, this torque is available
up to 5,000 rpm. The increased
maximum torque of 700 Nm in
the 911 Turbo S models is avail -
able bet ween 2,100 rpm and
4,250 rpm.
When the boost pressure reaches
its maximum value, the guide
vanes are opened further. By var -
ying the vane angle, it is possible
to achieve the required boost pressure over the entire engine
speed range. As a result, there is
no need for excess-pressure
valves as found on conventional
turbocharged engines.
In the 911 Turbo models, engine
performance can be further
enhanced by selecting the SPORT
but ton on the optional Sport
Chrono Package Turbo. Under
full acceleration, the maximum boost pressure in the lower and
medium speed ranges is tempo
-
rarily increased by approximately
0.2 bar. As a result, engine torque
is temporarily boosted by 50 Nm
to a maximum of 700 Nm. The
911 Turbo S models, by contrast,
are configured to operate with a
higher boost pressure level, which
means that their maximum torque of 700 Nm is available for an
unlimited period.
These values are sure to impress.
Yet, combined with the fuel
economy achieved despite the
high power output, they are
even more impressive. Because
power alone is not enough.
Guide vanes closed
Guide vanes open
Performance | Engine
Variable Turbine Geometry (VTG)
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