Mercedes-Benz Roadsters

The Mercedes-Benz SLK-Class models available from April 2008 incorporate around 650 newly developed parts, including new-look front and rear sections.

The two-seater SLK 350 features a fast-running V6 sports engine developing 224 kW/305 hp and an optionally available direct-steer system. All of the engines in the line-up are now far more economical on fuel and, therefore, emit even less CO2, despite a substantial increase in output in many cases.

The SLK features a vario-roof that transforms the car from a roadster into a weatherproof coupé in a matter of seconds. The new interior includes a three-spoke sports steering wheel with multifunction buttons and an instrument cluster with captivating dial surrounds.

Eye-catching features include the new-look front bumper with a modified air-dam arrangement and a more pronounced arrow shape, plus the area around the Mercedes star has been restyled. In addition, the designers have modified the rear end by introducing a diffuser-style lower section that makes the Roadster appear more powerful when viewed from behind - an effect enhanced by the trapezoidal exhaust tailpipes and the AMG-inspired darkened tail lights. The now larger exterior mirrors feature LED indicators with a pronounced arrow shape, while the range of light-alloy wheels is also almost entirely new.

Standard features integrated in every radio with the new NTG 2.5 audio and telematics generation include a hands-free system with Bluetooth technology and a new media interface in the glove compartment, allowing the full integration of mobile audio devices such as an iPod. An optional extra is the Linguatronic voice-operated control system. Passengers can also enjoy a unique listening experience, regardless of whether the vario-roof is open or closed, thanks to the optionally available harman kardon Logic7 sound system.

The sporty credentials of the 2008 SLK generation are further enhanced by three modified engines that consume less fuel and, therefore, emit less CO2. The four-cylinder engine in the SLK 200 Kompressor and the six-cylinder sports engine in the SLK 350 both offer substantially more power and torque. Only the SLK 55 AMG retains its familiar 5.5-litre eight-cylinder engine, developing 265 kW/360 hp and a peak torque of 510 Nm.

The Mercedes-Benz engineers paid special attention to the fast-running V6 sports engine that makes its debut in the new-generation SLK, totally altering the six-cylinder unit's character by making sweeping changes to the mechanical setup. Although the displacement remains the same at 3498 cc, the engine now develops 224 kW/305 hp at 6500 rpm - some 24 kW (33 hp) more than its predecessor. The peak torque has also been boosted, by 10 Nm, and now stands at 360 Nm when the engine is running at 4900 rpm. This result was achieved by raising the engine speed limit to 6800 rpm; it can even be increased to 7200 rpm for a brief period - oil temperature and other engine parameters permitting. Other changes introduced include a higher compression ratio, a new intake manifold and an extensively modified valve train.

The new engine includes a sporty sound design when decelerating. In combination with the 7G-TRONIC automatic transmission, the engine management system also blips the throttle automatically during downshifts. This throttle-blipping function reduces load alteration effects.

Despite the higher output and high-calibre performance, the SLK 350 consumes considerably less fuel. With the six-speed manual transmission on board, combined fuel consumption is 29.7 mpg; if the 7G-TRONIC automatic transmission is fitted, the sports engine returns a combined fuel consumption of 30.7 mpg. Lower fuel consumption means that CO2 emissions are also reduced - by 23 g/km to 219 g/km in the automatic version and by 28 g/km to 227 g/km in the manual version.

The output of the four-cylinder supercharged engine has been boosted by 15 kW/21 hp (to 135 kW/184 hp), while its torque has been increased from 240 to 250 Nm. Combined fuel consumption has been reduced to 36.7 mpg whilst CO2 emissions have been reduced by 27 g/km to 182 g/km.

The SLK 280 has also been further improved with respect to fuel economy and, therefore, CO2 emissions. Fuel consumption has been cut to 30.4 mpg (if an automatic transmission is fitted, the figure is 31.0 mpg), while CO2 emissions have been reduced by 11 g to 220 g/km (if an automatic transmission is fitted, the figure is 6 g lower at 216 g/km).

Standard equipment for the three new SLK models includes a precise six-speed manual gearshift, while the SLK 55 AMG still comes with the 7G-TRONIC Sport seven-speed automatic transmission fitted as standard. Optional extras available include a five-speed automatic transmission for the SLK 200 and the 7G-TRONIC seven-speed automatic transmission or, alternatively, the 7G-TRONIC Sport with shift paddles on the steering wheel for the six-cylinder SLK 280 and SLK 350 models.

A newly developed direct steering system with variable steering assistance, available as an optional extra (standard for the SLK 55 AMG), operates by purely mechanical means, meaning that there is no need for elaborate actuators and complex sensors. Based on the previously installed speed-sensitive power steering system, at its heart is a new rack with slick gearing, which ensures that the steering gear ratio changes in tune with the steering angle. The ratio is indirect when the steering is in or around the central position so as to ensure excellent straight-line stability and, therefore, a high degree of assuredness when travelling at high speed. At a steering angle of just 5 degrees, the ratio starts to increase extremely rapidly and the steering feels much more direct. As a result, the number of steering wheel revolutions from lock to lock is reduced by around 25 percent if the new direct steering is fitted. This means that, even in city traffic, relatively little steering wheel movement is required to correct the car's path, offering steering comfort when parking. Fast sequences of bends on rural roads can be negotiated with relatively small steering movements.

On a technical level, the SLK 55 AMG remains almost unchanged. The only differences are a few visual enhancements. The front end of the AMG model now features a new apron with a black-painted cross strut and side air outlets as well as darkened headlamps.

Familiar features that remain include a vario-roof that transforms the roadster into a coupé in 22 seconds, head/thorax sidebags, adaptive front airbags and two-stage belt-force limiters. Plus the roadster also comes with the option of the unique AIRSCARF neck-level heating system, which allows open-top driving all year round, even in winter.

Since their first appearance in 1997, over 40,000 SLK-Class roadsters have been sold in the UK. Pricing for the new-generation SLK will be confirmed early in 2008.

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