| A performance CX-7 will give Mazda foothold
in the European SUV market and make it some money, says Tristan
Honeywill
Mazda introduced the CX-7 compact SUV in the US last spring. It is now
using the model to enter Europe’s growing SUV market. Here, it has
been one of the fastest growing segments: roughly half of all SUVs sold
today are compacts. In 2001, the segment accounted for around 280,000
units. In 2006, it was 560,000.
 Mazda
expects this sort of growth to continue until 2010 at least, so launching
the CX-7 here seems like a safe way of increasing its sales from the 301,000
it achieved last year. But the Japanese OEM aims to sell just 7,000 a
year and one in four will go to Russia.
The Russian market will develop quickly in the next five years and Mazda
is preparing the ground for sales of higher volume models. In the meantime,
demand for four-wheel drive models there is strong and those that can
afford them are prepared to pay.
 The
CX-7 will make money for Mazda. Programme manager Masashi Ohtsuka, helped
by engineers at Mazda’s European R&D Centre in Oberursel, Germany
worked hard to produce a low-volume variant that will get the OEM the
best possible return on investment. Mazda builds the car at its Ujina
plant in Hiroshima, which also manufactures the Mazda3 and Mazda5.
In North America, the CX-7 sells as a comfortable Cross Utility Vehicle,
but the European version is surprisingly fun to drive: it’s quick
and handles well. Work to change the car into a performance model for
Europe was confined to a few key areas, says Ohtsuka, but Mazda also did
a lot of detailed benchmarking.
“The target was to make it lighter in all areas,” says Ohtsuka.
“BMW and Audi are very good at increasing the body rigidity; we
achieved the same rigidity but with a lighter body.” The vehicle’s
kerb weight is 1,770kg.
Ohtsuka tried to the same thing as on the MX-5 – the CX-7’s
projection areas compare with the rest of the SUV, but the height makes
its hard to achieve sportscar characteristics.
The vehicle’s front bumper and floor areas received the most attention
from aerodynamicists in order to achieve a drag coefficient of 0.34Cd,
necessary for stable European motorway driving. Figures of between 0.35Cd
and 0.40Cd are typical on SUVs.
“The front bumper has a lip spoiler to improve stability at speed,”
says Ohtsuka. Front and rear flow deflectors in front of each tyre, an
undercover for the engine bay and add-on parts for the side sill also
helped.
NVH countermeasures changed too. The base vehicle uses a seaming welt
around the door openings, one-way valves at the bottom of the doors and
a double layer seal around them. A firmer ride on the European version
gave noise new paths by which to enter the cabin.
“We also introduced foam structures to absorb road noise from the
rear suspension and special low road-noise tyres,” says Ohtsuka.
During initial chassis development of the European version, CAE methods
identified areas of the body most likely to flex or deform under harsher
driving conditions. By reinforcing only these weight and costs were kept
to a minimum, says Ohtsuka.
Mazda strengthened the rear lamp apertures, the roof rail inner pressings
where they meet the C-pillars, the tailgate aperture and the suspension
mounting points. The OEM presses from thicker steel to improve torsional
and flexural rigidity.
To improve handling for Europe, engineers optimised the rear bushes and
the multilink suspension. The pull bars linking the rear suspension to
the body have a different layout and the rear coil springs and dampers
are separate with the springs placed under the floor to reduce the friction
produced by the dampers on uneven roads. The result is a layout similar
to that of the Mazda3 MPS with better lateral toe change and camber control
than the base CX-7.
The European version has only one engine – with the turbocharged
2.3-litre direct injection gasoline engine used in the MPS performance
versions of the Mazda6 and Mazda3. It produces 191kW (260hp) at 5,500rpm
and 380Nm of torque at 3,000rpm.
And it comes with a six-speed manual gearbox only. This is the three-shaft
unit used in the Mazda6 MPS, but with a noticeably shorter first gear.
The CX-7 has an automatic in the US but this is unlikely to come to Europe.
Homologation is expensive and would not be worthwhile unless volumes were
substantially greater than Mazda predicts.
© Automotive Engineer, 2007 |
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