| In the 406, and before that, the 405,
Peugeot had representatives in the upper medium segment that were good,
solid competitors. While neither model was outstanding in any particular
area, they sold well in their home country while also achieving useful
sales throughout the rest of Europe. Now, though, Peugeot has turned up
the stake and hopes that the 407, which replaces the 406, will have a
wider appeal and become more aspirational. The “open mouth”
styling will be a feature that will be as much loved as it will be loathed.
There is nothing new about the engines as the 407 shares the same powertrain
as the Citroen C5, so there are four petrol engines ranging from the 1.8
to the 3.0 litre V6, and two HDi diesel engines – the 1.6 and 2.0
litres. However, a 2.7 litre HDi is on its way.
Unique to the V6 petrol engine, though, is the Aisin AW 6-speed automatic
gearbox that has a torque capacity which extends to 450 Nm (332 lb ft).
Although that of the V6 is “just” 295 Nm (218 lb ft), the
transmission has been designed to accommodate future engines.
Due to its internal construction – using the gear ratio combination
of two epicyclic gear trains, one single, the other double controlled
by five friction clutches managed by a control unit – the gearbox
is both compact and at 93 kg, only 3 kg heavier than the 4-speed transmission
found in the V6 406.
Inspired by racing
Inspired by a design first seen on a 405 Super Tourism racing saloon in
1995, the 407 sports a double wishbone drop link front suspension that
allows the separation of vertical suspension travel and deflection. With
this new design, the wheels turn about an axis formed by two ball joints
located between the hub carrier and a hub carrier support. Vertical movement
is managed by three flexible joints situated between the hub carrier support
and the two wishbones. This design ensures a small hub carrier angle with
relatively little wheel axis offset (caster) and preserves optimum body
control characteristics. The result is very positive directional control
under all circumstances and almost the total elimination of steering adjustments
to give a very precise feel when cornering.
The front axle incorporates a 23.5 to 25 mm diameter anti-roll bar. Mounted
on two bearings rigidly attached to the sub-frame cross-member, each of
its ends is connected to the hub carrier support by means of a link with
two ball joints. This construction greatly enhances the efficiency of
the anti-roll bar by ensuring accurate and fast mechanical transmission
of the slightest movement of the body during cornering.
The multi-arm rear suspension is supported by an aluminium cross-member.
It consists of two cast-iron sections connected by a profiled tube, to
which they are welded. The assembled cross-member weighs 14 kg and is
joined to the structure by means of four flexible mountings with inbuilt
radial stiffness and axial flexibility. This extremely rigid cross-member
provides the interface with each suspension unit. Each one has an upper
wishbone, manufactured from Cobapress aluminium, two lower transverse
arms, one longitudinal arm, a hub carrier, also manufactured from Cobapress
aluminium, a spring and damper assembly, inclined rearwards and connected
between the cross-member and the hub carrier, and a solid anti-roll bar
– 19 and 19.8 mm diameter – that connects the suspension units.
The anti-roll bar is maintained by two bearings rigidly attached to the
rear floor and connected to each hub carrier by means of a link with two
ball joints.
The upper wishbone operates vertically and has two traditional flexible
joints rigidly attached to the cross-member. The third, connected to the
hub carrier, is special since it has a high radial stiffness corresponding
to the wheel axis and axial flexibility to absorb peak longitudinal forces
“gently”. The upper surface of the wishbone makes contact
with a bump stop located on the structure.
In its lower section, the suspension unit has two transverse arms manufactured
from pressed steel that connect the hub carrier to the cross-member. The
rear arm contributes to the lateral integrity of the hub carrier and absorbs
dynamic vertical stresses. The adjustable front arm, or track control
arm, absorbs transverse stresses and at the same time controls tracking.
Its static adjustment is finalised during assembly of the suspension on
the cross-member.
Still in the lower section, each suspension unit has a third, forward-facing
arm. This provides the link between the hub carrier and the underframe
and absorbs longitudinal forces. Manufactured from Cobapress aluminium,
it filters impacts and helps to control axle geometry and movement as
it exhibits radial flexibility and axial rigidity.
Upholding the Peugeot tradition and following the example of its predecessors,
the 407 is equipped with dampers developed in-house at the front and rear.
There is a light-alloy sub-frame formed by two distinct sections under
the engine compartment. The front section consisting of welded aluminium
sections is rigidly attached to the rear cross-member. Weighing less than
6 kg, it essentially performs three passive safety functions: support
of an impact beam to “contact” the legs of pedestrians; repairability,
thanks to a pre-deformed absorption zone; and, in the event of high-speed
impact, absorption of energy through a programmed deformation.
The rear section, consisting of a cast aluminium cross-member, is dedicated
to the suspension and is very strong, being joined to the structure by
means of vibration absorbing mountings. It weighs only 15 kg – 8
kg less than any welded-steel equivalent. This section is located so as
to absorb braking forces transmitted by the front movement of the wishbone.
While the 407 uses platform three from the middle and upper segments of
the PSA Peugeot Citroën range, it has been significantly modified.
For example, the body has a torsional rigidity of 0.77 mrad which has
never before attained on a Peugeot saloon while special attention has
been given to the front structure to improve passive safety. Here, a new
lower structure absorbs impacts and adds its benefits to the “classic”
top structure made up of the chassis legs. Two thirds of the energy is
absorbed via the top section and one third via the bottom one. This bottom
structure consists of a long sub-frame, made up of a standard sub-frame
with the addition of extensions, a front cross-member, energy absorbers
and a pedestrian beam covered by impact absorbing foam.
With the exception of the pedestrian beam, all parts of the long sub-frame
are manufactured from aluminium. This front structure represents a new
strategy of impact absorption. By creating better distribution of forces
it combines the attractive features of a car rigid enough to offer protection
in the event of a high-speed front impact, while at the same time supple
enough to offer protection to pedestrians and ensure compatibility in
collisions with lighter vehicles.
An engine mount/restraint device anchors the engine to the sub-frame,
and completes the protection against high-speed front impact by limiting
the intrusion of the engine into the passenger compartment.
Pedestrian protection is ensured by the structural suppleness of the front
of the car and by means of shock absorbing foam padding fitted to the
lower part of the pedestrian beam – the final element of the bottom
structure, and to the top of the bumper bar. Finally, the bonnet limits
the effects of this type of impact even further, since its rigidity, and
its distance from the mechanical components it houses have been optimised
to reduce head injuries.
The 407 has been given a 5-star front and side impact rating by EuroNcap
(94 and 89 per cent respectively) and a 4-star rating for child protection
(80per cent). However, it rated just 2 stars (42 per cent) for pedestrian
safety, attracting the comment that while there was limited protection
available for where a child head’s might strike, none was evident
for an adult.
Much work has been devoted to optimising the aerodynamic qualities of
the 407, which has a drag coefficient or Cd of 0.29 versus 0.32 for the
406. These results were obtained thanks largely to the overall fluidity
of style, with specific enhancements – lower front panel and tailgate
– and significant underbody shielding, and the seamless styling
of the front of the vehicle.
In the 407 Peugeot has a model that has moved the upper medium segment
on in terms of looks and road presence. Now it is just a question of how
ready the public is in accepting it.
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