- Weight of body shell reduced by 22kg
- Greater crash resistance from use of high-tensile
steel
- Survival cell significantly strengthened
The chassis for the second generation of the Mazda2 is based on
a newly-developed architecture that underscores the company's long
years of experience engineering small vehicles. In contrast to the
Mazda2 introduced in 2002 which prioritised practicality, for new
Mazda2 interior space became a shared priority along with
delivering a more contemporary design and the same Zoom-Zoom
driving fun as the other members of the modern Mazda family.
With a new state-of-the-art chassis as a foundation, Mazda
engineers sought to provide outstanding handling for a car of this
class, combined with high stability even on highways and a
harmonious ride quality. The low weight and high rigidity of the
body shell played an important role in optimising handling and
comfort. For handling, Mazda focused on manoeuvrability and agility
on city streets, on steering that is spontaneous and linear, on
achieving high grip on curving country roads and well-tempered
reactions during fast lane-changing on the motorway.
An ingenious plan to reduce vehicle weight by as much as 100kg -
about 60kg in Australian specification - compared to the former
model was seen as the most efficient way to lower fuel consumption
and C02 emissions. At a very early stage in development, a special
team began looking for the best diet plan using advanced computer
aided design or CAD technologies. After that, the engineers tested
the ideas in drivable prototypes - initially in the previous Mazda2
- and examined the effects they had on the dynamic qualities of the
car.
Their efforts were successful; once again, as it had done with the
MX-5 roadster, Mazda was able to resist the spiral of ever
increasing weight. As a result, the new Mazda2 weighs jut a few
kilograms over a tonne. But Mazda2's trend-bucking character is
also evident by its length, which is now 41mm shorter, at
3885mm.
Use of Ultra High-Tensile Steel Has Several Positive
Effects
Thanks to the optimised structure of its body shell and an
increased use of new kinds of steel, the new Mazda2 is not only
significantly lighter, but also improved when it comes to safety,
body shell rigidity and NVH performance - all attributes that
normally add weight to a car.
Through smaller dimensions alone, the weight of the body shell
would have been cut by only 4kg to 233kg. Measures taken to
increase rigidity and crash resistance would have quickly raised it
again to 244kg.
Thanks to the altered body structure and new materials, the team
under the leadership of Program Manager Shigeo Mizuno was able to
decrease weight to 215kg - 22kg less than the old Mazda2 body
shell.
Up to 20 Per cent Stiffer for Torsional
Rigidity
The use of high and ultra high-tensile steel contributed first
and foremost to a reduction in body shell weight. For example, the
B-pillars are made of 980 MPa-grade steel sheet (MPa = measurement
of tensile strength). They act as central support columns and
extend in the form of a 'roll-over bar' into the roof. Despite
stronger joint reinforcements in the area of the door openings and
the tailgate, the use of high-tensile steel with reduced thickness
resulted in a weight saving of 6kg. At the same time, torsional
rigidity was increased. By employing additional spot welds and
adding new weld-bonded joints in the tailgate opening of the new
Mazda2, it is 20 per cent stiffer than the square-edged hatch
opening of the outgoing model.
Mazda weight specialists were able to save an impressive 13kg
using weight optimising measures in the suspension. These included
making the rear trailing arms shorter and the front lower arms
lighter. This reduction in unsprung weight promotes better handling
and ride comfort, as well as enhanced fuel economy. But Mazda
engineers did not stop there. They also eliminated the underfloor
catalyst. For the intake system, Mazda engineers modified the
intake duct design to the top of the radiator shroud. This new
intake system eliminated the resonator and a baffle, which also
saved valuable weight, as did fitting a smaller radiator and fan
for the cooling system.
Shortened Wiring Harness Saved 2.86kg
Taking inspiration from the MX-5 gram strategy, the Mazda2
calorie-cutting team even found ways to reduce weight in the
vehicle electrical system: a shorter wiring harness saved a total
of 2.86kg. What sounds like sorcery is in fact the result of an
insightful placement of large units and power-supply parts. The
bonnet also contributed to a weight saving of exactly 0.69kg, with
a smaller striker assembly and slightly thinner hinges. Even the
audio speakers mounted in the doors were engineered to be
lightweight: by changing the magnets from a ferrite type to
neodymium, and making the frame and protective cover a single-piece
plastic moulding, a total weight saving of 0.98kg was achieved.
Acclaimed Suspension Concept Modified and
Retuned
The front MacPherson strut suspension and the torsion-beam rear
suspension also profited from the use of high-tensile steel in
certain areas of the body shell to increase local stiffness and
ensure optimal suspension geometry. The suspension system uses the
same basic concept as that of the previous model, but the
components have been modified in many details and retuned to match
the much more agile attributes of the new Mazda2. For example,
Mazda made the suspension mounts at the axles 15 per cent stiffer
compared to the outgoing model. In the front suspension, new bushes
on the A-arms reduce road surface influences on the toe angle,
which has a positive effect on ride comfort and improves handling
stability and the integrity of steering feel.
The trailing arm bushes of the rear suspension are now less
sensitive to side forces. The rear monotube dampers have the same
diameter as before, but because of the lower vehicle weight they
now are as effective as larger-diameter dampers.
Electric Power Assist Steering Supports Driving
Fun
Mazda2's electric power assist steering system is appealing for
its very linear and direct response and supports the Mazda goal of
oneness between driver and car - the philosophy of Jinba Ittai so
completely embodied by the Mazda MX-5.
This new steering system provides very high levels of power
assistance when the vehicle is being driven at very low speed,
which is especially handy when manoeuvring in tight spots and
parking. With only 2.7 turns lock-to-lock, the steering system is
very direct. Together with a small turning circle of only 9.8
metres, this makes the Mazda2 an ideal urban vehicle.
The brake system of the Mazda2 includes ABS, EBD, as well as EBA
and ventilated front disc brakes. In order to improve pedal feel,
the pedal ratio was lowered from 3.79 to 2.85, which means less
play in the pedal stroke and a more defined response. At the same
time, Mazda reduced the diameter of the master cylinder from 23.8mm
to 20.6mm and optimised brake booster characteristics.
By improving the brake piston seal structure, the drag that results
from friction between the pads and the discs of the front brakes
was significantly reduced.
For the first time on a Mazda in this market segment, DSC and
TCS are available on all models.
Testing in Europe
Engineers from the Mazda's European development centre in
Oberursel near Frankfurt, Germany gave the new Mazda2's chassis a
specifically European assessment on the meandering roads of
Germany's mountain region. Alexander Fritsche, Team Leader
Chassis/Suspension in Oberursel, says, "Our testing areas feature
all conceivable kinds of curves and surfaces - ideal for us testers
and the Autobahns there are ideal too, with relatively little
traffic."
Together with suppliers, Mazda engineers conducted extensive
tests that not only identified the most harmonious damper settings,
but also the ideal characteristics for the electric power assist
steering.
"This system is speed dependent - a lot of assistance when
manoeuvring at parking speeds and driving around town, less when
driving fast," Fritsche says. "For this reason it was important for
us to always have sufficient road feedback in the city and to tune
the steering to be both sporty and comfortable as speed
increases."
Mazda not only made a quantum leap when it comes to steering
feel and response compared to the outgoing model, but also for
driving comfort and NVH.
"We wanted to get away from the typically slightly harsh,
B-segment feel and to significantly increase the sense of ride
comfort," says Fritsche in outlining the goal of his team. New
pancake-type bushes are introduced for the lower arms of the front
suspension, which are better at isolating the steering from
exterior influences. The trailing arm bushes of the rear suspension
are also better at smoothing out bumps and the geometry is designed
to reduce roll and dive.
"Europe usually represents the biggest challenge for Mazda's
development engineers when it comes to driving comfort. I'm
confident that the new Mazda2 is impressive proof of just how
consistently those challenges have been met," concludes
Fritsche.
Three-way Load Path Keeps Body Deformation Away From
Occupants
Mazda2's passive safety package is based on a body shell
developed using the highly capable Mazda Advanced Impact
Distribution and Absorption System (MAIDAS), which is able to
disperse impact energy through the body shell along exactly defined
load paths. In order to better absorb the energy from a frontal
crash, the front side chassis members are straighter and have a
larger cross-section. An ultra-high strength structure in the front
bumper and a straight main underbody load path provide effective
occupant protection.
During an offset crash, a three-way load path deflects impact
energy away from the feet and lower legs of the front occupants.
And the brake pedal is designed to collapse down and away from the
driver's feet.
Two Impact Beams in the Front Doors Provide Side
Protection
During a side impact, B-pillars made of 980 MPa-grade steel,
specially strengthened side sills and floor pan cross members
provide effective occupant protection. In the front doors there are
two side impact beams, which help protect occupants from injury,
while a single beam in each rear door limits intrusion. Additional
protection from injury is provided by shock-absorbing pads in the
door trims, pillars and roof side rails. In case of a rear impact,
the back seat passengers and the fuel tank (located below the cabin
floor and directly in front of the rear axle) are given increased
protection by a large rear bumper beam and new side members, which
are also straighter than the old model and are made of 590 MPa
grade steel.
This crash-resistant survival cell of the Mazda2 is enhanced by
two front airbags and seatbelts with pretensioners and
load-limiters, anti-whiplash front seats and a breakaway brake
pedal that reduces the chance of lower leg injury in a heavy
impact.
Side (front) airbags and curtain (front and rear) airbags, for
helping protect all occupants sitting in the outer seats, are
standard on Genki models and optional on Neo and Maxx.
Pedestrian safety is also optimised by the special design of the
bonnet, fenders and windscreen wipers.
Ultra High-tensile Steel
The use of ultra high-tensile steel materials provides a
solution to the seemingly contradictory goal of providing low
weight and high crash resistance. By using higher tensile steel,
the thickness of the steel sheeting can be reduced, while still
retaining the desired body shell strength and structural
characteristics.
This saves weight and costs, while simultaneously increasing
safety levels for the occupants. For the body shell of the Mazda2,
high-tensile and ultra high-tensile steels with strengths of 440,
590, 780 and 980 MPa (mega-Pascal) are used. Varying degrees of
strength are obtained through specific chemical and baking
processes. Especially strong kinds of steel are used for the A- and
B-pillars and the front door sills. Together wit h an increased
number of spot welds - especially in the door openings and the side
walls of the boot - this gives the Mazda2 a survival cell that
truly deserves the name.
Environmentally Friendly Production Methods
Besides making the interior surfaces nice to touch and providing
the best ergonomics, the creators of the new Mazda2 also were keen
to make sure the cabin does not release unhealthy substances into
the air.
The design team's special focus concerned volatile organic
substances (VOCs). An example of their efforts to cut VOCs was the
reduction of toluene. For the first time, Mazda used a new
substance for waterproof sealing the joints between interior
panels, which gives off only one tenth of the emissions previously
emitted by conventional sealers. By adopting this new substance,
the total concentration of toluene has been reduced by around 60
per cent compared to the outgoing model. And not only that, the
amount of xylene, formaldehyde, acetoaldehyde and polyvinyl
chloride has been significantly lowered.
Lead, cadmium, mercury and chromium were banned completely from
the Mazda2.
Mazda2's environmentally friendly character is also evident by
its high recyclability. The new Japanese sub-compact meets the ISO
22628 norm and is more than 95 per cent recyclable. The bumpers,
for instance, are made of a material that can be recycled into foot
rests and splash shields, or can be recycled into new car
bumpers.
For more information contact:
Alastair Doak
(03) 8540 1961
0418 626 329
adoak@mazda.com.au
Lydia Richards
(03) 8540 1962
0439 347 658
lrichards@mazda.com.au
Or visit:
www.mazda.com.au