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Kolbenschmidt Pierburg in the new Allroader from the German car manufacturer
Engine block and intake
manifold for Audi Q7
Ingolstadt/Düsseldorf. The booming
market for Sport Utility Vehicles (SUVs)
demands a high seat position, good
overview, sturdy appearance and representative
dimensions, all of which
the Audi Allroad Quattro can only fulfill
to a limited degree although it still offers
a good mix between on and off
road capabilities. Audi has now decided
to venture onto the highly competitive
SUV market with a new model. Series-production
of the Audi Q7 that is
based on a study of the Pikes Peak
Quattro will probably be launched in
early 2006. It will initially be available
in two engine variants: a diesel V6-TDI
engine and the 4.2 liter V8 FSI gasoline
direct injection engine.
The engine block for the V8 drive
with bedplate concept will be supplied
by KS Aluminium Technologie AG
(ATAG). The engine block of the V8 engine
will be cast from a hypereutectic
aluminum-silicon alloy known under
its tradename ALUSIL®, a material offering
numerous advantages. The
monolithic, linerless concept allows
an extremely compact design with
minimal bridge width of only 5.5 mm
between the cylinders, allowing low
weight and high integration. This concept
is also distinguished by the optimum
thermal conduction properties
which permit high specific engine performance
characteristics. The non-armored
cylinder bore surfaces are extremely
resistant to seizure, and the
pistons and piston rings run on hard
silicon crystals.
The low pressure die-cast engine
block guarantees a uniform deposit of
silicon crystals in the cylinder bore surface
combined with minimal porosity.
Besides the controlled, low-turbulence
mold filling process, the directional solidification
is also noteworthy. The
casting process allows the introduction
of sand cores, so that structurally stiff
engine blocks are manufactured in a
closed deck design as for the V8 engine.
Another advantage derived from
the low pressure die-casting process is
the unlimited heat treatment of the
casting, permitting not only greater
hardness and higher strength, but also
volume stabilization.
The mechanical “uncovering” of silicon
grains is just one of the outstanding
features of the V8 FSI engine bock. The
process employed by Audi is very similar
to the ATAG-patented Siplamec honing
method. This process consists of three
phases: pre-honing, basic honing and
finish-honing, the third step being determining.
The desired surface structure
is obtained by using elastic honing
stones, which – due to the resilience of
the cutting grains – remove more Al-matrix
than Si-grain at the hard cutting
grains. The Si-grains protrude slightly
from the Al-matrix contrary to chemical
process with rounded edges. This reduces
the risk of splinters and also decreases
piston ring wear susceptibility.
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Yet not just the technology as such
but also the time needed to develop
the engine block for the new Audi Allroad
V8 engine has set new standards.
The simultaneous engineering process
adopted by Audi, ATAG and the tool
manufacturer made it possible to reduce
the development time very considerably,
backed by the benefits of virtual
product development.
A further technical highlight of the
Audi Q7 is the new 2-length magnesium
intake manifold from Pierburg
GmbH. The longitudinal actuating
flaps and tumble plates of this intake
manifold are driven by the EAM-b electrical
adjusters developed by Pierburg.
Vacuum-pressure actuators are therefore
not needed so that the intake
manifold can switch independent of
the vacuum supply. To achieve optimum
torque values over a larger speed
range, the intake manifold installed in
Kolbenschmidt supplies the engine block, Pierburg the advanced 2-length intake manifold: the new Audi Q7 Allroader.
the Audi Q7 has two lengths – irrespective
of the engine speed: a short
intake length assures good performance
in the upper speed range and a
longer intake distance permits optimum
torque behavior at medium
speeds.
One general difficulty encountered in
connection with optimum intake manifold
functions is the internal sealing of
the unit. To achieve high torques, Pierburg
has given the manifold maximum
internal sealing properties. This has
been done in three different ways: firstly,
the longitudinal actuating flaps attached
by hot-riveting are sealed with
elastomerics, secondly the welded
tumble plates are pressed-in thus ensuring
good tightness and thirdly, the
channel-shaped magnesium parts are
package-bolted.
Photos (2): Audi