The
new Mercedes-Benz SL coupe/roadster, which makes its public debut at a press launch
in Hamburg today and goes on sale across Europe inthe autumn and in the U.S. next
spring, features the motor industry’s first electronic brake system.
The brake pedal on the first version to be revealed, the SL500, works with
a computer that tells four fast-acting valves exactly how hard to apply the
brakes on each wheel.
A backup hydraulic master cylinder comes into play only if there’s a serious
problem or electrical failure.
In a split-second, the system can change brake pressure on each wheel over
uneven surfaces and can increase brake pressure on just the outside wheels when
braking in turns, taking advantage of the higher loading during cornering.
Mercedes-Benz says that the ABS anti-lock and ESP stability control work more
efficiently since they are more deeply integrated with the brakes, instead of
functioning as parallel systems.
An electric hydraulic pump and a high-pressure reservoir (accumulator) provide
‘always-on’ full brake pressure at each wheel.
The computer-operated modulator valves control how much pressure actually operates
the brakes at each wheel. In this new system, the conventional, bulky vacuum
brake booster is now obsolete.
If the driver switches his foot quickly from accelerator to brake pedal, the
electronic brake system recognises the early signs of an emergency situation
and reacts automatically.
With the help of the high-pressure reservoir, the system raises the pressure
in the brake connectors and instantaneously moves the pads onto the brake discs,
which can then spring into action with full force as soon as the brake pedal
is pressed.
At highway speeds, this pre-loading of the braking system reduces stopping
distance by about three percent.
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| The SL500 features the motor industry’s first electronic brake system |
In addition, the system automatically senses when the road is wet and imperceptibly
applies the brakes just enough to keep the discs dry, so that brake operation
remains fast and consistent in the rain.
The new braking system stars in an all-new SL range which is only the fifth
generation of a line which began in 1954 with the legendary ‘gullwing’
300SL.
Other technological features include ABC active suspension and ESP stability
control.
The new SL also features an SLK-style retractable hardtop that combines the
benefits of both a convertible and coupe in one car.
However, the new SL500’s retractable hardtop can be fully opened or closed
in just 16 seconds compared with 25 seconds for the SLK’s lid.
The SL roof is also a completely new design which operates in a different manner.
As the power roof retracts, the rear window glass also rotates so that its curvature
nestles inside the stowed roof panel, providing a much larger cargo area of
6.8 cubic feet.
With the top up, the boot holds 9.7 cubic feet – over 1.8 cu. ft. more than
its predecessor.
A hydraulic pump and 11 computer-controlled hydraulic cylinders power the system.
As in the SLK, the new SL’s top is controlled by a centre console switch.
When the top is stowed, pressing a red button located inside the trunk raises
the folded roof about 20 degrees, making cargo access easier.
The 500SL’s five-litre V8 engine produces 302 horsepower, accelerating the
new model from 0 to 60 mph in approximately six seconds.
Twin sparkplug, three valves-per-cylinder technology also means the new car
qualifies as an Ultra Low Emission Vehicle in the U.S.
The new SL features a light weight body with the bonnet, doors, boot lid and
roof all made of aluminum. The bonnet alone is 33 pounds lighter than a comparable
steel hood.
Over 30 percent of the body structure is made of high-strength steel, so that
the body is 20 percent stiffer than the previous model’s with the top down and
the drag coefficient is 0.29 – over nine percent lower than before.
The latest SL, which will be launched early in 2002 as a 2003 model in the
U.S., features new head/thorax side airbags in the doors as well as two-stage
front airbags that deploy with partial force in less severe collisions and with
full force in more serious impacts.
The airbags are designed to work in concert with the three-point seatbelts,
which are equipped with tensioners that remove belt slack in a collision as
well as belt force limiters that help prevent seatbelts injuries in severe impacts.
Following on from the pioneering automatic roll bar for the previous SL, the
new car model has a similar bar which pops up in 0.3 of a second when its electronic
control senses an impending rollover.
As before, the shoulder belt is anchored directly into the seat back, ensuring
good seatbelt geometry regardless of seat position and providing an extra measure
of protection in the event of a rollover.
To view related research reports, please follow the links The Germany World
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