Munich. As the new BMW 3 Series Sedan prepares for
its world premiere, it can already look back over a lifetime of hard
work. The new generation of the sports sedan is entering the final
phase of an extensive programme of testing that every new BMW model
must go through as part of its pre-production development. Here, the
full range of stresses and strains a car will encounter over many
years of everyday driving are reproduced in concentrated form. From
extended periods driving flat out to endless stop-start traffic,
sub-zero temperatures to searing heat, twisty country roads and
high-speed autobahns to pothole-infested tracks, ice and snow to
gravel and desert sand – the prototypes sent through the test
programme for the new BMW 3 Series Sedan have experienced everything
their production equivalents will come across in everyday life. Only
they have done so at a much higher level of intensity and with
seasoned developed engineers on board to record in detail the
pre-production model’s every response to the various weather and road
conditions and countless other influencing factors. In short, the
testers ensure there are no circumstances – however unusual – which
might compromise driving pleasure in the final production car.
Welcome to Death Valley, in the US state of Nevada. Here, it is not
only the automatic climate control system of the new BMW 3 Series
Sedan that can expect a taxing work-out. The multi-day heat tests see
the cars fried repeatedly in the sun for several hours, then cooled
and thoroughly checked over. Everything has to work, there can be no
squeaks or creaks – even when the temperature tops 50 degrees Celsius
in the shade outside the car and 60 degrees inside, and the interior
is then cooled again as quickly as possible.
Heat, dust, hill climbs and electromagnetism – ideal
conditions for informative testing.
The heat certainly
gives the electronics something to think about, but that’s not the
whole story: the electromagnetic rays emitted by the hydroelectric
plant at the Hoover Dam represent the ultimate test of strength for
the functional reliability of the electronic systems on board the new
3 Series. This is why all the car’s functions – from the digital
instrument cluster to the tyre pressure indicator – are tested
extensively in the shadows of the huge forest of electricity pylons on
the banks of Lake Mead. At the same time, another development team is
putting engines, transmissions and brakes through their paces. They
are even given police protection for their runs up and down the
4,000-metre-high Mount Whitney. While law enforcement secures the test
route at the top and bottom of the climb, the testers hustle the
prototypes time and again up the snaking roads and back down –
accelerating hard and braking suddenly to a standstill with crushing
frequency. The bone-dry desert roads of Death Valley and beyond also
provide an ideal place to find out how effective the cars’ flaps,
doors, bonnets and lids are at keeping out dust. In their test drives
around the gambling hot-spot of Las Vegas, the engineers leave nothing
to chance.
There could be few greater contrasts with the hot-weather testing in
the USA than what goes on at the BMW Group’s winter testing centre not
far from the Arctic Circle. Arjeplog in Sweden offers the perfect
conditions for a testing programme that eclipses anything day-to-day
driving in central Europe, North America or Asia can throw at a car.
However, Arjeplog doesn’t only give the prototypes the chance to
demonstrate their imperviousness to extreme cold – it also provides
the stage for the new model’s chassis controls systems to show off
their full range of abilities. The closed-off expanses of ice offered
by Lake Kakel and the “Mellanström-Runde”, one of the most popular
test routes around Arjeplog, couldn’t be better suited for fine-tuning
the DSC stability system and its myriad functions. Indeed, on this
glassy surface you don’t need to drive quickly to provoke the control
systems into action and therefore analyse their responses. All of
which allows the link-up between DSC and the xDrive all-wheel-drive
system and the interplay with the new BMW 3 Series Sedan’s M Sport
differential to be refined down to the last detail under constant conditions.
Here again, cutting-edge technology helps to identify and
consistently eliminate weak points. If an inconsistency crops up
during testing, the engineer presses a button on the small testing
screen next to the transmission’s selector lever to log it for
subsequent analysis. For the problem to be solved, the relevant
situation has to be reproduced exactly. The vehicle data is stored on
a large hard drive in the car’s boot, pored over every day and reworked.
Dressed to test – in tailored camouflage
suits.
In the north of Sweden, as in the west of the
USA, the test drives carried out by the BMW development teams rarely
go unnoticed. Which means that, to prevent curious onlookers from
clocking too many details of the new BMW 3 Series Sedan’s design,
every prototype is carefully clad in a disguise before it heads out
onto public roads. In the basement of BMW’s Research and Innovation
Centre (FIZ) in Munich, pre-production vehicles are kitted out with a
made-to-measure and confusingly patterned cloak of camouflage.
Applying the black-and-white wrap requires an expert hand and takes a
whole working day to complete. Then comes the plastic cladding, which
distorts the lines and surfaces of the car. The light units, sections
of the window surfaces and, of course, the brand badges also get a
layer of sticky camouflage. The interior needs to be hidden from sight
as well. To this end, the cockpit is “curtained off” with black
matting, which the test engineers partially remove at the start of
testing and then painstakingly replace at every pause in proceedings –
so that no prying eyes can spot or even get a photograph of the
displays and controls.
From a computer model via a test bench to the road.
Long before the first test runs on public roads, the development
process sees each new model taken into the company’s own testing
facilities. In the initial phase of the programme, computer
simulations help to set important areas of the car off on the right
path. Here, the testing programme – which is still purely digital at
this stage – involves simulating more than 12,000 driving manoeuvres
(from lane changes to cornering and roundabout driving to dynamic
acceleration and braking) using a computer-generated vehicle model,
with the sole aim of determining and optimising its dynamic
properties. On the basis of the knowledge gained here, development
mules are made consisting of just a body and chassis. On the
kinematics compliance test bench they are fixed into a test assembly
and sent on virtual test drives. A variety of road conditions can be
faithfully reproduced on this test rig, from cobblestones to the
Nürburgring’s Nordschleife circuit, so the rigidity of the body
structure or the susceptibility to vibrations of axle constructions
can be properly inspected. This intensive development work is
essential in enabling the first full prototypes to already display the
target driving characteristics. However, they still have to prove they
can do it on the road. In normal traffic, on BMW proving grounds and
on the race track they undergo a detailed tuning process, which gives
the eventual production cars their inimitable driving pleasure.
Wind tunnel for detailed touches, crash tests for controlled
deformation.
Optimisation of aerodynamics and passive
safety also takes place largely behind closed doors. At the BMW
Group’s Aerodynamic Test Centre in Munich, full-size vehicle models,
prototypes and production vehicles are tested using precise
reproduction of real-life airflow conditions on the road. At the
centre’s wind tunnel, the new BMW 3 Series Sedan has been given the
detailed touches required to bring its drag coefficient down to 0.23.
The key factors here are not only how the car manipulates the airflow,
the ideal channelling of air around the underbody and the optimisation
of the spoiler lip at the rear of the body, but also details such as
combinations of wheels and tyres. The introduction of the WLTP fuel
consumption testing procedure has meant all the wheel variants
available for a particular model have to be put through an extensive
aerodynamics test. Every variant is checked to establish how the wheel
design and tyre size impact on the aerodynamic characteristics of the
new BMW 3 Series Sedan and therefore its fuel consumption and emissions.
Differences in the stipulations for occupant protection applicable in
different continents mean that several pre-production examples of a
new model have to be deformed in a controlled process as part of crash
testing at BMW’s Safety Centre. As a result, the new BMW 3 Series
Sedan not only provides driving pleasure to customers around the
globe, it also meets the full set of safety requirements to score top
marks in all the relevant crash tests worldwide.
Driving pleasure made in Aschheim, at Miramas and on the Nürburgring.
The proving grounds at Aschheim, a few miles north-east of the
development centre in Munich, provides the venue for undisturbed
dynamic testing. It was here, at an early stage of the development
process, where the first steps were taken in imbuing the new BMW 3
Series Sedan with its impressive dynamic potential. The testing
programmes at the BMW Group’s test facility in Miramas, southern
France are even more extensive. Used by BMW for the development and
testing of new models for over 30 years, Miramas has a long asphalt
oval, a motorway “ring” for high-speed testing, slalom, twisty and
spherical tracks, plus several handling courses and circuits with
surfaces of every kind. Detailed analysis and optimisation of the new
BMW 3 Series Sedan’s acceleration, steering and braking responses was
also carried out here.
The acid test for a vehicle’s driving dynamics remains the
Nürburgring’s Nordschleife circuit. Precise tuning of all powertrain
and chassis systems is carried out at the legendary venue in Germany’s
Eifel mountains. Here, too, every lap of testing with the new BMW 3
Series Sedan carries far more weight than the number of miles notched
up might suggest. After all, if a car gets the thumbs up from the BMW
test engineers at the Nordschleife, you can be confident it will
provide driving pleasure in everyday conditions throughout its lifetime.