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Mercedes-Benz SLK250 UK-Version

Combining arresting design, superb four-season versatility, sophisticated direct-injection petrol and diesel engine technology and advanced driver assistance systems, the sleek and athletic new Mercedes-Benz SLK-Class once again establishes Mercedes-Benz at the forefront of UK's exclusive roadster sector.

Available with a UK-specific 12-strong model line-up the new generation Mercedes-Benz SLK-Class is priced from £29,985 for the SLK 200 BlueEFFICIENCY to £54,695 for the range-topping SLK 55 AMG.

Buyers will have the choice of three petrol engines and - for the first time - a refined and punchy turbo diesel powerplant, which all deliver a class-leading combination of refinement, economy and performance. An integrated ECO start/stop system is fitted to four- and six-cylinder SLK models fitted with either six-speed manual or 7G-Tronic Plus seven-speed automatic transmissions, helping achieve up to 56.5 mpg and 132 g/km CO2 on the combined cycle.

As well as the options of the innovative Airscarf neck-level heating system (£395) and Airguide wind deflector for a warm and buffet-free cabin (£285), drivers can also specify the panoramic vario-roof with Magic Sky Control which, at the touch of a button can alter the transparency of the glass roof from clear to dark (£1,995).

The new third-generation Mercedes-Benz SLK-Class, model number R172, arrives in the UK armed with superb new styling, a trio of sophisticated and engaging engines, ground-breaking safety and convenience technologies and an abundance of style and panache to once again make it the default choice for the discerning alfresco-loving driver.

Featuring bold new styling that forms a striking visual like with the SLS AMG, the two-seater SLK retains its compact dimensions (length 4,134 mm; width 1,810 mm excluding wing mirrors; 2,430 mm wheelbase; 1,301 mm height; front track 1,559 mm; rear track 1,565 mm). The SLK's growth - it's now 31 mm longer and 33 mm wider and 5 mm higher than its predecessor - has resulted in a significantly more spacious and accommodating cabin, while roof-up luggage space is now a generous 335 litres (225 litres with roof stowed).

The SLK shares the chassis architecture of outgoing model, but extensively revised and updated to deliver a sharper driver focus and higher levels of dynamism and agility. The kinematics for both the McPherson strut front and multi-link rear suspension have been recalibrated for enhanced roadholding, while new forged aluminium hub carriers further reduce unsprung masses.

Similarly, the rack and pinion steering is now quicker at just 2.6 between locks rather than the 2.8 turns of the outgoing model. Its chassis and bodywork also benefit from extensive use of lightweight alloys - the bonnet and wings are made of aluminium, and the rear bulkhead is made of strong and lightweight carbonfibre, for example - to keep kerbweight down to a low 1,435 kg.

Meticulous attention was paid to the SLK's aerodynamics resulting in a drop in drag-co-efficient from a Cd figure of 0.32 for the previous model to 0.30 for the new generation, despite the more striking, steeper nose and larger frontal area. The result is a cabin that's quieter and more refined, irrespective of the roof's position.

Since the Mercedes-Benz SLK-Class made its international debut in 1996, its ingenious two-piece folding metal vario-roof has taken centre stage, and this new generation SLK model is no different. As well as featuring a lightweight magnesium frame and a new electronic mechanism that converts the two seater from roof-up coupe to open-topped roadster in just 20 seconds - two seconds quicker than before - the roof is now optionally available with the Magic Sky Control which, at the touch of a button can alter the transparency of the glass roof from clear to dark. In conjunction with the optional Airscarf neck-level heating system and Airguide wind deflectors, the new generation SLK is the perfect four-season sportscar.

UK buyers will have the choice of 12 models, powered by punchy performance-oriented four-, six- and eight-cylinder engines that all feature lightweight all-alloy construction, high-pressure direct fuel injection and fully integrated ECO start/stop systems on four- and six-cylinder SLK models, to deliver outstanding economy and responsiveness.

The petrol engine range starts with the SLK 200 BlueEFFICIENCY. This is powered by an advanced four-cylinder engine that features the very latest in down-sizing technology including all-alloy construction, turbo-charging, high-pressure direct petrol injection and logic-controlled engine warm-up. The 1,796 cc unit develops 184 hp at a relaxed 5,250 rpm and a generous 250 Nm of torque between 1,800 - 4,600 rpm. The engine is fitted with a wrist-flick six-speed manual transmission (the 7G-Tronic Plus 7-speed automatic is a £1,520 option) and it powers the SLK 200 BlueEFFICIENCY to 62 mph in 7.3 seconds and onto a 149 mph top speed while returning 41.5 mpg and CO2 158 g/km on the combined cycle (7.0 seconds, 147 mph, 43.5 mpg and 151 g/km for the automatic model).

The SLK 250 BlueEFFICIENCY benefits from a more powerful version of the same turbocharged 1,796 cc engine, which serves up 204 hp at 5,500 rpm and 310 Nm of torque between 2,000 rpm - 4,300 rpm. Mated to the six-speed manual transmission, the SLK 250 BlueEFFICIENCY sprints to 62mph in 6.5 seconds before topping out at 152 mph. Combined economy and emission figures are 40.9 mpg and 169 g/km (7G-Tronic Plus 7-speed automatic - 6.6 seconds, 151 mph, 42.8 mpg and 153 g/km).

Beneath the SLK 350 BlueEFFICIENCY's fluted bonnet sits Mercedes-Benz' naturally-aspirated 3,498 cc V6 engine. Fitted with advanced direct injection technology, the all-alloy engine is mated to the 7G-Tronic Plus 7-speed automatic transmission as standard, and it will rocket the roadster to 62 mph in just 5.6 seconds and onto an electronically limited 155 mpg top speed. Despite this muscular performance, the SLK 350 BlueEFFICIENCY post some exceptional combined economy and CO2 figures - 39.8 mpg and just 167 g/km.

This latest generation SLK will also be available with a turbo-diesel engine - the first time Mercedes-Benz has offered its iconic roadster with a compression-ignition powertrain. This advanced biturbo 2,143 cc four-cylinder unit continues the rollout of two-stage turbocharging across the Mercedes-Benz range, providing improvements in start-up performance and peak output. In the SLK 250 CDi BlueEFFICIENCY, this lightweight engine develops 204 hp at 4,200 rpm and an impressive 500 Nm of torque at 1,600 - 1,800 rpm.

Driving the rear wheels through the standard-fit 7G-Tronic Plus 7-speed automatic transmission, the twin-turbo diesel will power the SLK to 62 mph in just 6.7 seconds and onto a 151 mph top speed. Economy and emission figures are equally impressive - the SLK 250 CDi BlueEFFICIENCY returns 56.5 mpg and 132 g/m CO2 figures on the combined cycle.

The dynamic AMG Sport model line will also be available across the range. Standard on the top SLK 350 BlueEFFICIENCY AMG Sport model and available as a £4,000 set-up on the other SLK models, the AMG Sport adds wheelarch-filling 18 inch AMG alloy wheels, headlamps with dark surrounds, muscular AMG bodystyling, cross-drilled front brake discs, lowered Sports suspension, leather-upholstered sports seats, red seatbelts and an eye-catching instrument cluster with chequered flag design, among others.

The innovation of the vSLK-Class' vario-roof is matched by its ground-breaking safety and driver-assistance technologies. On the safety front, the Attention Assist driver drowsiness monitor and the Pre-Safe® anticipatory safety systems are joined by the Adaptive Brake System with hold function, four adaptive airbags, Active Bonnet to mitigate pedestrian injury and full roll-over protection, while the Distronic Plus, including BAS Plus and Pre-Safe® Brake can be specified as an option (£1,495).

Driver assistance and in-car entertainment features include COMAND Online system with Media Interface. This incorporates radio, seven-inch colour display, hard disk drive (HDD) navigation with three-dimensional map display and TMC (Traffic Message Channel), Speed Limit Assist and Linguatronic voice control in centre console. Also includes SD card slot, 10 GB music register and MP3 compatibility. Media Interface allows connection and control of portable media devices (e.g. MP3 player, USB storage media) via ports in the glovebox. Cables included for aux-in, USB or iPod® connectivity.

Interior

The SLK's growth - it's now 31 mm longer and 33 mm wider and 5 mm higher than its predecessor - has resulted in a significantly more spacious and accommodating cabin, while roof-up luggage space is now a generous 335 litres (225 litres with roof stowed).

As always, the SLK comes equipped with an extensive array of standard convenience and infotainment features, including automatic dual-zone climate control, LED daytime running lights, pre-wiring for Becker® Map Pilot navigation system, a fully integrated ECO start/stop system on four- and six-cylinder models, and the Audio 20 sound system, which incorporates a 5.8-inch colour display, integrated six-disc MP3-compatible CD drive, eight speakers, Bluetooth® interface for hands-free telephony, telephone keypad, central controller dial and USB DAB digital radio tuner.

The SLK is available with a wide range of optional equipment including Dynamic Handling Package (£1,205), Intelligent Light System (£895), COMAND Online system with Media Interface (£1,995) and harman/kardon® Logic 7® with Dolby Digital 5.1 (£645).

With its round chromed air vents and deeply cowled circular instruments, the SLK's cabin architecture strikes a visual ink with that of the SLS AMG, and this driver-focussed design is enhanced by the leather-wrapped three-spoke Sports steering wheel, low-slung SLK-specific seats and rubber-studded chromed pedals.

Attention Assist, Adaptive Brake, PRE-SAFE®, Neck-Pro active head restraints and Active Bonnet are all fitted as standard, backed up by six airbags and the latest generation of anti-lock braking, traction, stability and skid reduction systems.

Exterior

The optional £1,995 MAGIC SKY CONTROL Roof uses electro-reactive particles sandwiched between the Panoramic roof's polycarbonate sections, allowing the driver to switch from clear to opaque at the touch of a button. It's available with the options of the innovative Airscarf neck-level heating system (£395) and Airguide wind deflector for a warm and buffet-free cabin (£285).

The SLK's advanced two-piece vario-roof now features a new lightweight magnesium frame and uprated electronic mechanism that converts the two seater from roof-up coupe to open-topped roadster in just 20 seconds.

Available with a UK-specific 12-strong model line-up the new generation Mercedes-Benz SLK-Class is priced from £29,985 for the SLK 200 BlueEFFICIENCY to £54,965 for the range-topping SLK 55 AMG.

The SLK range is powered a trio of punchy performance-oriented four-,six-and eight-cylinder petrol and diesel engines. The petrol range includes the SLK 200 BlueEFFICIENCY, SLK 250 BlueEFFICIENCY, the SLK 350 BlueEFFICIENCY and the SLK 55 AMG. In a first for the vSLK-Class, there's now a diesel-powered variant, the SLK 250 CDI BlueEFFICIENCY. All four- and six-cylinder SLK variants are fitted with a fully-integrated ECO start/stop system to deliver up to 56.5 mpg and 132 g/km CO2 on the combined cycle.

A dynamic AMG Sport model line will also be available across the range. Standard on the top SLK 350 BlueEFFICIENCY AMG Sport model, it's available as a £4,000 set-up on the SLK 200 BlueEFFICIENCY and SLK 250 BlueEFFICIENCY ranges.

Meticulous attention was paid to the SLK's aerodynamics resulting in a drop in drag-co-efficient from a Cd figure of 0.32 for the previous model to 0.30 for the new generation, despite the more striking, steeper nose and larger frontal area. The result is a cabin that's quieter and more refined, irrespective of the roof's position.

The new-generation SLK delivers a sharper driver focus and higher levels of dynamism and agility from its recalibrated McPherson strut front and multi-link rear suspension, lightweight forged aluminium hub carriers, quicker the rack and pinion steering and extensive use of lightweight alloys and composites that keep kerb weight down to a low 1,435 kg.

Design

The new generations SLK's rakish and low-slung proportions instantly personify the dynamic athleticism of its inspiration, the 1955 190 SL. Like the iconic 190 SL, this new SLK features a boldly styled upright grille with large centrally located star emblem that also strikes a direct design link with the SLS AMG supercar and the award-winning CLS four-door coupé.

With a length of 4,134 millimetres (up 31 millimetres over predecessor), a width of 1,810 millimetres (up 33 millimetres) and 1,301 millimetres high (up 5 millimetres), the new generation SLK is wider and longer than its forebear, and this growth has resulted in an even roomier and more accommodating cabin that offers even greater leg, hip and shoulder room. Despite this larger cabin, luggage capacity has increased from 300 to 335 litres roof up, and from 208 to 225 litres roof stowed.

Other design highlights include the piercing headlamps that flank the floating grille, the powerful LED daylight driving lights, functional air outlet grilles with a chromed fin located behind the front wheel arches, integrated rear spoiler lip, LED tail lights and twin trapezoidal exhaust outlets.

The more generously proportioned cabin of the new generation SLK strikes the perfect balance between cossetting luxury and engaging dynamism. The round chromed air vents and deeply cowled circular instruments strike a visual ink with the cabin of the SLS AMG, and this driver-focussed design is enhanced by the leather-wrapped three-spoke Sports steering wheel, broad centre console, low-slung SLK-specific seats, dash-mounted analogue clock (£195 option) and rubber-studded chromed pedals.

SLK drivers seeking a higher level of individuality will be pleased to hear that in addition to the standard 11 exterior colours, eight upholstery fabrics and three trim materials, there are an extensive range of designo trim and paint options available.

SLK 200 BlueEFFICIENCY and SLK 250 BlueEFFICIENCY

Both four-cylinder SLK 200 BlueEFFICIENCY and SLK 250 BlueEFFICIENCY models are powered by new variants of Mercedes-Benz acclaimed M 271 EVO family of downsized lightweight engines. Key to their exceptional economy and performance is their combination of advanced turbocharging and sophisticated direct injection system.

The 1,796 cc engines are made almost entirely of aluminium: the crankcase is made of cast aluminium, while a special high-strength aluminium alloy is used for the cylinder head. Two forged overhead camshafts with variable adjustment are used to control the 16 valves. A vane-type adjuster with integrated control valve allows fast and smooth adjustment of the timing, ensuring that it is always at the optimum setting.

This setup has two advantages: firstly, the variable camshaft adjustment enables a high torque yield even at low revs; secondly, this technology allows high specific outputs. The valves are controlled by means of cam followers and feature maintenance-free, hydraulic valve clearance compensation.

The new direct-injection petrol model features an electronically controlled thermostat to ensure that circulation of the coolant is stopped when the engine is cold. This allows the engine oil to heat up quickly and, therefore, minimises in-engine friction and improves fuel consumption.

The turbocharger module is joined to the exhaust manifold on the engine's exhaust side and features a wastegate valve and a deceleration air function for controlling pressure characteristics. There are many benefits from using a turbocharger rather than a supercharger, which is driven by the engine. By not requiring engine power to operate, a turbo is more efficient. It also takes up far less space, weighs around 4 kg less and offers better noise and vibration characteristics than a supercharger.

Mercedes-Benz has a long tradition in the field of direct petrol injection. As early as the mid-1950s, the company unveiled the technology in the legendary 300 SL Coupe 'Gullwing'. This classic sports car was the first series-produced automobile to feature a four-stroke engine with direct injection - a sensational development that significantly boosted the six-cylinder's output.

In the direct-injection system of the new generation Mercedes-Benz SLK-Class Roadster, the air and fuel are not mixed until they reach the combustion chambers. With the help of an injector, the fuel is injected into the cylinders at an angle of 30 degrees and, depending on the engine operating characteristics, at a pressure of up to 140 bar.

Here the fuel droplets and the air particles form a mixture, which is guided to the spark plugs via specially shaped recesses in the pistons. By way of comparison, the fuel pressure in a four-cylinder engine incorporating conventional injection technology is approximately 3.8 bar.

To ensure optimum swirl in the mixture, thus making combustion fast and as complete as possible, the engines have intake ports with specially calculated flow characteristics. An adjustable swirl flap is also used to produce high turbulence in certain operating ranges and thus improve the combustion process.

The high-pressure fuel pump is driven by the intake camshaft, while a quantity control valve integrated in the pump module ensures on-demand metering of the fuel supply. A pressure regulator with its own sensor, monitored by the engine control unit, controls the pressure in the fuel line (rail), which is directly connected to the multi-hole solenoid injectors. The new four-cylinder direct-injection engines meet the EU5 emission standard.

The new engines are exceptionally refined thanks to the newly-developed Lanchester balancer: two forged shafts supported in three bearings, which are arranged below the crank mechanism and counter-rotate at twice the crankshaft speed.

The exhaust system in the new-generation SLK has been painstakingly tuned to deliver an emotionally-charged soundtrack in keeping with the car's dynamism. A new sound generator, housed immediately in front of the throttle flap, enriches the engine note buy combining it with elements of the induction acoustics. This emotive sound is then piped into the cabin to create the perfect soundscape, whether driving with the roof open or closed.

The SLK 200 BlueEFFICIENCY also features an SLK first - an electrically-actuated adjustable radiator shutter. This enables the airflow through the engine's cooling system and engine compartment to be continuously and variably controlled. A circular, louvred shutter located parallel to the radiator fan improves the aerodynamics and in turn lowers fuel consumption. The engine also reaches its optimal operating temperature more rapidly, cabin heating speed is improved and engine noise is further suppressed.

SLK 350 BlueEFFICIENCY AMG Sport

The SLK 350 BlueEFFICIENCY AMG Sport is equipped with one of the world's most advanced naturally-aspirated V6 engines and features ground-breaking spray-guided direct injection. In 2006, Mercedes-Benz was the first car manufacturer to introduce spray-guided direct petrol injection into series production. Thanks to higher thermodynamic efficiency, this technology allows better use of the fuel and, therefore, lowers fuel consumption and exhaust gas emissions.

The key benefit of the V6 engine is delivered in stratified-charge mode, when the powerplant operates with a high degree of excess air and, therefore, extremely fuel-efficiently. This advantageous 'lean-burn operation' is now also possible when the direct-injection unit is running in higher engine speed and load ranges because the combustion chambers are supplied with fuel several times in succession within a fraction of a second in every combustion cycle, thus improving mixture formation, combustion and consumption.

Fast and precise piezo injectors are key components of the second-generation direct petrol injection system. They open their nozzle points outwards, forming a gap that is mere micrometres in size, shaping the jet of fuel and ensuring its even, hollow-cone-shaped dispersion.

Thanks to their ability to switch within microseconds, the piezo injectors also allow multiple injections for exceptionally efficient lean-burn operation, thus playing a crucial role in achieving the engine's exemplary consumption figures. A high-pressure pump with downstream distributor and pressure valve supplies the fuel and ensures on-demand flow control. With a level of up to 200 bar, the system's fuel pressure is several times higher than that in a conventional port injection system.

The combustion process with several injections in succession per combustion cycle also enhances the refinement and emission characteristics of the V6. Untreated emissions (hydrocarbons) are reduced by more than half in the warm-up phase, while specifically targeted injection and combustion control allows higher temperatures in the exhaust manifold, ensuring faster heating of the catalytic converters.

Emissions are controlled by two close-coupled three-way catalytic converters with linear lambda control, which are activated immediately after a cold start. Mercedes-Benz reduces nitrogen-oxide emissions by means of two-pipe electrically controlled exhaust gas recirculation, which directs up to 40 per cent of the exhaust gases back into the cylinders, depending on the engine's operation, and by means of two NOx storage catalytic converters on the underbody. During lean-burn operation, these catalytic converters absorb the nitrogen oxides and re-release them in short regeneration phases so that they react chemically to form harmless nitrogen.

Four valves per cylinder, variable intake and exhaust camshaft adjustment, a two-stage intake manifold, a balancer shaft and intelligent thermal management are further highlights of the V6 engine with direct injection. The crankcase and cylinder head are made of aluminium; the cylinders are equipped with liners that have a low-friction aluminium-silicon coating.

 

SLK 250 CDI BlueEFFICIENCY

The SLK 250 CDI BlueEFFICIENCY model features Mercedes-Benz' newly developed 2,143cc twin-turbo diesel engine, a highly compact motor that follows Mercedes-Benz' strategy to use smaller displacement turbocharged engines.

This engine also continues the rollout of two-stage turbocharging across the Mercedes-Benz range, providing improvements in start-up performance and peak output. Results also include a reduction in weight, reduced internal friction and a more economical fuel-consumption map.

The compact module for the new two-stage turbocharger consists of a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger, connected in series. The HP turbine is located directly at the exhaust manifold and initially allows exhaust gas to flow through it; it then rotates at up to 215,000 rpm.

Its housing features an integral bypass duct, which can be opened or closed by means of a charge-pressure control flap triggered by a vacuum cell. If the flap is closed, the whole exhaust stream flows through the HP turbine, allowing optimum charge pressure to be built up at low engine revs.

As the engine speed increases, the charge-pressure control flap opens and a portion of the exhaust stream then flows through the bypass duct to relieve the HP section. Downstream, the two exhaust gas streams join up again, and any remaining exhaust gas energy drives the HP turbine at a maximum speed of up to 185,000 rpm.

To protect against overloading, the LP turbine is also equipped with a bypass, which is opened or closed by means of a wastegate. Once the engine reaches medium revs, the HP turbine's charge-pressure control flap is opened so wide that the HP turbine ceases to perform any appreciable work. This allows the full exhaust gas energy to be directed with low losses into the LP turbine. The two compressors are similarly connected in series to create a genuine two-stage turbocharging process.

The key benefit of this sophisticated, on-demand control of the combustion air supply by means of two turbochargers is the improved cylinder charging and, consequently, high torque even at low revs. Other benefits include better fuel economy, a lack of turbo lag, a good torque curve across the entire engine speed range, spontaneous throttle response and noticeably improved performance.

As a logical addition to the turbocharger system, Mercedes-Benz installs a large intercooler, which reduces the temperature of the compressed and heated air by around 140 degrees Celsius so that a larger volume of air can enter the combustion chambers.

This trio of diesel engines features Mercedes-Benz' fourth-generation common-rail direct injection, which sees a 400-bar increase in the maximum rail pressure, to an extremely high 2000 bar for incredibly controlled and precise measurement of fuel during the injection phase.

Newly developed piezo injectors are key components in this latest CDI generation. They use their piezoceramic properties to change their crystal structure - and therefore their thickness - in a matter of nanoseconds when electrical voltage is applied. The injectors are equipped with a stack of thin piezoceramic layers (called the 'piezo stack') to enable them to achieve a sufficient overall lift from the very small lift per layer.

In contrast to the systems commonly used to date, this lift activates the nozzle needle directly so that the fuel injection can be adjusted more precisely in line with the current load and engine-speed situation - for example by means of precise multiple injections, which have a favourable effect on emissions, fuel consumption and combustion noise. And the engine is far quieter when idling than its predecessor.

The newly developed EGR valve works like a rotary disc valve and ensures precise control of the fresh air and recirculated exhaust gas. To optimise the quantity of exhaust gas recirculated and thereby achieve high recirculation rates, the exhaust gases are cooled down as required in a highly efficient heat exchanger with a large cross-sectional area.

Together with the HFM (hot-film air-mass) sensor module integrated in the fresh-air ducting, which provides the engine control unit with precise information about the current fresh-air mass, this setup brings about a significant reduction in nitrogen oxide emissions.

Another feature of the new diesel is the rear-mounted camshaft drive, which allows statutory pedestrian protection requirements to be met when the engine is installed longitudinally.

The valve timing mechanism is another new development and reduces friction at the 16 intake and exhaust valves, which are controlled by one overhead intake camshaft and one overhead exhaust camshaft acting via cam followers featuring hydraulic valve clearance compensation. The camshaft, Lanchester balancer and the ancillary assemblies are driven by a combination of gearwheels and just a short drive chain.

A switchable water pump helps to quickly heat up the combustion chambers as well as improving fuel consumption and untreated emissions. The pistons are cooled by an oil pump with a central control valve for all four piston-cooling sprayer units with large oil-spray nozzles. The generous dimensions ensure optimum piston cooling, even at full load, and make for a long service life.

BlueEFFICIENCY

All models in the SLK line-up benefit from a full suite of BlueEFFICIENCY economy-boosting measures. Together they play a vital role in the SLK achieving its class-leading consumption and emission figures - new-generation engines are up to an incredible 25 per cent more economical than those they replace.

Transmissions

Whether fitted with manual or automatic transmissions, all the direct-injection engines in the Mercedes-Benz SLK-Class line-up are fitted with ECO start/stop technology as standard. This intelligent system seamlessly stops the engine when it's not needed and then silently and swiftly restarts the moment it's called into action.

For the ECO auto/stop to operate, a number of other criteria must be met. Firstly, the car must be stationary, the transmission must be set in Drive or Neutral in automatic models, or the brakes must be applied, the transmission left in neutral and the clutch released in manual models. There must be no movement in the steering wheel, the driver's foot must be on the brake pedal or the HOLD function must be active, the doors and bonnet must closed of course, the driver's seat belt must be fastened, and specific speeds must have been exceeded.

In manual versions, the direct-injection petrol engine is switched off as soon as the driver applies the brakes, shifts the manual transmission to neutral and releases the clutch. The engine is restarted as soon as the driver depresses the clutch.

In the new 7G-TRONIC Plus transmission, the ECO start/stop function - active only in C mode - deactivates the engine as soon as the vehicle is motionless and the driver depresses the brake pedal. The engine restarts automatically when the driver removes his foot from the brake pedal, or depresses the accelerator pedal.

The ECO start/stop system employs a new crankshaft sensor that constantly monitors the angle of the crankshaft and the position of the individual cylinders. When restarting the engine, the sensor determines which cylinder is in the optimal position for initial ignition for smooth and instantaneous start-up.

Thanks to direct-start technology, the Mercedes-Benz-developed system operates spontaneously and with little noise - fuel is injected directly and ignited during the piston's compression stroke, allowing the engine to be started with only very little assistance from the starter. Advanced software management ensures the ECO start/stop system only operates when the engine and cabin have both reached the correct temperature, and the driver can also independently switch the system off.

To handle the requirements of the ECO start/stop system, the starter motor has undergone thorough modification. It's now engineered to cope with eight times as many starting procedures as before to ensure that even in continuous urban driving involving frequent auto-starting, it will last the car's lifetime. A second battery supports the on-board electrical system.

The ECO start/stop system also functions according to a strict set of safety parameters. The engine will automatically restart if a vehicle-related precondition for the auto-stop function - such as the conditions pertaining to air conditioning, the on-board electrical system, the brake system, the chassis and other vehicle-related influences - is no longer met.

Likewise, if the driver releases his seat belt or opens the driver's door, the engine will restart to prompt the driver to actively switch off the engine using the ignition key, and thus ensure the ECO start/stop system is safely deactivated when the vehicle is parked.

Six Speed Manual Transmission

Available on the SLK 200 BlueEFFICIENCY as standard, Mercedes-Benz' tried-and-tested six-speed manual transmission has been adapted to suit the high torque figures of its turbo-charged four-cylinder petrol engine. With recalibrated gearing, a dual-mass flywheel and a larger clutch it's now easily capable of transmitting peak torque of up to 500 Nm. Particular attention has been focused on the transmission's linkage, resulting in a shift quality that is light, short and direct.

New 7G-TRONIC PLUS Transmission

The new 7G-TRONIC PLUS transmission (standard on the SLK 250 BlueEFFICIENCY, SLK 250 CDI BlueEFFICIENCY and SLK 350 BlueEFFICIENCY models, and available on the SLK 200 BlueEFFICIENCY as a £1,520 option) features a new torsional vibration damper, which significantly reduces the degree of low-load slip in the torque converter's lockup clutch. This results in reduced engine speeds in ECO mode for heightened economy in urban driving conditions.

As well as a new hydraulic circuit and a recalibrated torque converter, the 7G-TRONIC PLUS is also fitted with a centrifugal pendulum for exceptional drivetrain refinement, particularly at lower engine speeds. In addition, the gearbox is fitted with a separate automatic transmission fluid pump, which ensures the drivetrain always responds promptly to initial throttle responses when the fixed-displacement oil pump is deactivated during the engine shut down phase of the ECO start/stop system. The transmission also operates with a new lower-viscosity automatic transmission fluid, which has a longer 77,000 mile life but the same exceptional cooling performance.

Vario-Roof

Since the Mercedes-Benz SLK-Class made its international debut in 1996, its ingenious two-piece folding metal vario-roof has taken centre stage, and this new generation SLK model features a heavily revised version of this innovative piece of engineering. Using a new lightweight magnesium frame for the two roof panels not only cuts weight by six kilogrammes per panel but has a marked impact on the SLK's athleticism by lowering the two-seater's centre of gravity.

The one-touch powered mechanism has been engineered to be significantly quicker - it now converts the SLK from coupe to roadster in just 20 seconds, two seconds quicker than before. This fast-operating electro-hydraulic set-up is also more compact, benefiting the SLK's roof-down luggage capacity. Boot capacity with the roof raised is 335 litres (compared to 300 litres in the outgoing model) while when the roof is open, this drops to 225 litres (including 51 litres of luggage box capacity under the boot's reversible floor) a full 17 litres up on the outgoing model and a huge 80 litres over the original SLK.

UK-bound SLK models are available with the choice of three version of the vario-roof - the standard all-metal roof, a Panoramic version (£410 option) that features a transparent polycarbonate insert in the central roof section. This fixed-transparency roof creates an open-top feeling even with the roof closed.

In an exciting new development, the Panoramic vario-roof is also available with the MAGIC SKY CONTROL Roof, that allows the transparency of the central roof section to be switched from clear to dark at the touch of a button, allowing driver and passenger to choose between maximum light or effective protection from glare.

The MAGIC SKY CONTROL Roof uses electro-reactive particles sandwiched between the Panoramic roof's polycarbonate sections. When subjected to an electrical voltage, particles in the structure position themselves in a manner that enables light to pass through the glass. If the voltage is turned off, the particles instantly position themselves in a random manner, blocking out and leaving the roof dark. The system's control unit and converter are integrated into the front section of the roof, and the MAGIC SKY CONTROL Roof switch is handily located in the overhead control console.

This technology not only cuts out sunshine, but ultraviolet and infrared light are also effectively blocked in transparent mode. The roof's insulatory properties help to keep the temperature on interior parts such as armrests cooler by up to 10 degrees Celsius compared with conventional tinted glass, which in return results in lower CO2 and greater economy as less load is placed on the car's climate control.

The SLK engineers tested the MAGIC SKY CONTROL Roof in one of the most inhospitable parts of the world - Death Valley. Employing a star pyranometer, which measures the intensity of exposure to sunlight, the engineers measured the cabin's temperature. With the roof down, the sun's thermal load reached between 1000 to 1100 W per square metre. Erecting the Panoramic transparent glass roof, this figure dropped to 200 W, which activating the dark setting of the MAGIC SKY CONTROL Roof resulting in a reading of just 60 W - a twentieth of the original roof-down reading.

AIRSCARF®

Taking a leaf out of the SL and E-Class Cabriolet's books, the new generation SLK is available with an upgraded version of the optional innovative AIRSCARF® neck-level heating system (£395). On chilly days, this patented system functions like an invisible scarf, wrapping the driver and front passenger's head and neck area with warm air.

Fully integrated into the backrests of the front seats, AIRSCARF® delivers warm air through outlets in the head restraints. As well as its compact size, AIRSCARF® also delivers warm air quickly and constantly. The heating element in the backrest uses sophisticated PTC (Positive Temperature Coefficient) technology to energise ceramic particles so they heat up in seconds and then emit continuous heat. The system protects itself against overheating by monitoring its own surface temperature and reducing the power consumption automatically when required, without affecting air temperature.

AIRSCARF® can be instantly activated at speeds of up to 75 mph. It's sophisticated control unit instantly and automatically calculates the ideal distribution of warm air depending on the vehicle speed, interior and exterior temperatures, and whether the soft-top is retracted or not. Above 75mph the system operates on a constant setting.

For greater control, both driver and front passenger can set the air temperature and speed to one of three levels, all at the push of a button on the centre console. When developing the AIRSCARF® systems, Mercedes-Benz engineers used a thermo camera and special shirts embedded with fourteen temperature sensors located around the neck and chest area to fine tune the flow of air and its temperature.

And from a safety point of view, the warm air outlet in the head restraint is slightly recessed for heightened user comfort, and it only clips into place so that in the event of an impact, the outlet can disengage to not pose an injury risk for occupants.

Airguide

The optional Airguide (£285) set-up employs a pair of pivoting Plexiglas panels fixed to the reverse of the roll-over bars. These transparent panels can be quickly and safely be adjusted by both driver and passenger to vary the degree of airflow through the cabin - a world first. And because the panels are permanently fixed to the headrests, there's no need for any time-consuming installation or removal.

Chassis

The SLK is underpinned by the bodyshell that saw service in the outgoing model, but with a raft of revisions and enhancements to boost rigidity and cut weight. In the new SLK, the bonnet and front wings are now made of lightweight aluminium, as are the dashboard cross members, while the rear bulkhead is now made of ultra-strong carbonfibre-reinforced plastic composite. Combined, these have resulted in a weight reduction of some 13 kilogrammes. Magnesium has also been used for the frame that supports the two lightweight roof panels, cutting a further six kilogrammes from the weight of the roof.

The doors of the new SLK are of an all-new design and feature heavy reinforcement along the beltline and at the doors' lower edges using high-strength steel for optimal side-impact protection. The A-pillars feature the same exceptionally robust construction as before - they use oval tubes of hot-formed ultra-high-strength steel that are welded in to the pillar, with the pillars themselves connected to the side members using a hugely robust nodular connection system.

Another new feature of the chassis are the prescribed cutting points on the front side members which cause them to deform ahead of these points, significantly reducing the repair costs of minor front collisions.

As always, the aerodynamicists at Mercedes-Benz paid careful attention the way the SLK slices through the air. Despite a more upright nose and a frontal area some three per cent larger than before (up from 1.93 to 1.98 square metres), the drag co-efficient of the new generation SLK has been cut from 0.32 to 0.30, effectively reducing CO2 emissions by up to 2 grammes per kilometre.

Meticulous modifications to the A-pillar cladding - it took the engineers a year to develop a composite cover for the A-pillar that ensures an exceptionally clean flow of air around the pillar as well as ensure rain water is cleanly channelled away to keep exterior mirrors and side windows clean in all conditions - as well as a demand-controlled radiator shutter, aerodynamic tyres and newly designed wing mirrors also contribute to the SLK's excellent aerodynamics.

Steering

The new SLK is fitted with a constant ratio rack-and-pinion steering system, as before, but this time with just 2.6 turns between lock, as opposed to the 2.8 of the preceding model.

This quick and more direct layout can be enhanced by the new Direct-Steer system (a £215 stand-alone option or part of the £1205 Dynamic Handling Pack), which is fitted with variable hydraulic assistance that reduces assistance as vehicle speeds increase, but now also adds a variable steering ratio that changes according to the steering angle.

The ratio is indirect when steering straight ahead for exceptional straight-line stability at all speeds. The ratio of the Direct-Steer system then increases rapidly once a five degree steering angle is reached, becoming extremely direct from a steering angle of just 100 degrees. This results in the driver having to make only relatively small steering movements when manoeuvring the car both in urban environments - such as a multi-story car park - or when pouring the car through a series of tight corners on an engaging country road.

This is achieved by purely mechanical means, using a steering rack with different profiled teeth. In the middle section, these are wave-shaped and have varying flank profiles, while the teeth on either side of this central section are spaced at varying distances apart.

By adopting a mechanical base for this system, Mercedes engineers have been able to dispense with the complex actuators and sensor systems, to create a low-weight set-up with a low susceptibility to faults. And the system's predictable responses mean the driver does not need to adapt to the way the SLK steers.

 

Brakes

The new SLK is fitted with the same proven all-disc dual-circuit hydraulic braking system as its predecessor, with all models in the line-up equipped with single-piston floating calliper brakes all-round, and backed up by the latest-generation ABS anti-lock brakes, BAS brake assist and Adaptive Brake systems, as well as a Brake Pad Wear indicator.

In the range-starting SLK 200 BlueEFFICIENCY the calliper housings are of aluminium, while the more powerful engine variants use housings of composite aluminium at the front and aluminium at the rear. In addition, the brake covers at the front axle were further optimised in the wind tunnel for even more efficient cooling of the brakes and wheel bearings, and to protect the brake discs from the affects of road spray and debris.

Specifying the Dynamic Handling Pack (optional £1205) also includes the advanced Torque Vectoring Brake system. This uses meticulously metered out one-sided braking by the ESP® Electronic Stability Programme on the inside rear wheel when cornering. If ESP® detects a tendency to understeer, within a fraction of a second, the actuation of the Torque Vectoring Brake system generates a defined turning or yawing moment around the vehicle's vertical axis, turning the SLK into the corner without loss of control or dynamism.

Torque Vectoring Brake can be implemented without an increase in vehicle weight and therefore no disadvantages in terms of fuel consumption - a key advantage over more complex mechanical components such as an active steering rear axle, additional multi-disc clutches or an active differential.

The new SLK also arrives on the market with a new electrically operated parking brake. Located beneath the rotary light switch on the right-hand side of the dashboard, the simple button frees up further space in the cabin. In models witted with the 7G-Tronic Plus automatic transmission, the brake is automatically once the engine is running, Drive or Reverse is selected, the driver's seatbelt is fastened and the throttle is operated.

Suspension

The new SLK arrives is available with the choice of three suspension settings - conventional steel suspension, a lowered Sports suspension with uprated springs and dampers for enhanced body control, and the Dynamic Handling Package, which adds continuously variable damping.

The standard set-up features Mercedes-Benz' trusted MacPherson strut layout up front and a sophisticated multi-link setup at the rear, with both ends fitted with coil springs and anti-roll bars. The suspension has been enhanced by the introduction of forged aluminium hub carriers at the rear, which further reduce unsprung mass for enhanced dynamism.

The optional sports suspension (£205 option, standard on AMG Sport models) has a stiffer damper setup, shorter suspension springs and thicker anti-roll bars. The suspension is also lowered by 10 millimetres.

The Dynamic Handling package (optional £1205, and also includes Direct Steering and Torque Vectoring Brake) introduces continuously adjustable damping and a 10 millimetre drop in ride height. With a reaction time of just 10 milliseconds, this electronic system automatically and continuously ensures that the dampers are always set to suit the driving situation. The driver has the choice of 'Sport' and 'Comfort' suspension settings, with 'Comfort' reverting to the car's standard ride qualities, while Sport delivers a far more responsive experience.

The SLK 55 AMG

The new SLK 55 AMG, priced at £54,965, is the most powerful SLK model to date and is powered by a new 5.5-litre naturally aspirated AMG V8. Developing 421 hp at 6,800 rpm and 540Nm of torque at 4,500 rpm, this direct-injection engine is the world's most fuel-efficient petrol-fuelled V8.

It drives the SLK's rear wheels through a responsive seven-speed AMG SPEEDSHIFT 7G-TRONIC PLUS automatic transmission, complete with three shift modes. The dynamic results speak for themselves - the compact two-seater accelerates to 62 mph in just 4.6 seconds and onto an effortless 155 mph electronically limited top speed.

The SLK 55 AMG - the third generation of SLK AMG models - combines performance with exceptional combined economy and CO2 emission figures of 33.6mpg and 195g/km. The results - a full 30 per cent improvement over the outgoing model - have been achieved by the introduction of AMG's Cylinder Management System.

Similar to the system deployed on Formula 1 engines, this sophisticated programme shuts off two cylinders on each bank of the V8 when the car is running on light throttle loads. The SLK 55 AMG is also fitted with an ECO stop/start system as standard, ensuring no fuel is used and no emissions are generated when the roadster is stationary in traffic.

In keeping with its performance credentials, the SLK 55 AMG is fitted as standard with AMG sports suspension featuring the AMG high-performance braking system with Torque Vectoring Brake, AMG Direct-Steer system, as well as an advanced three-stage ESP®.

The result, is a four-season coupé-roadster that effortlessly combines the agility and high levels of lateral grip demanded by performance-oriented drivers with the long-distance ride comfort that is an intrinsic part of any Mercedes-Benz. And with its unique AMG bodywork and SLS AMG-inspired interior styling, the SLK 55 AMG delivers a powerful visual punch.

Options specific to the SLK 55 AMG are headed by the AMG Performance Package of revised suspension and brakes with a rear differential lock (£4,105) and the AMG Driver's Package, which raises the limited top speed and includes attendance at an AMG 'Power and Passion' driver event (£2,755).

Hand-assembled 5.5-litre naturally-aspirated AMG V8 The SLK 55 AMG is powered by a new, naturally-aspirated version of the AMG's award-winning AMG M157 5.5-litre V8 biturbo engine. While this hand-assembled 187 kg unit shares numerous characteristics with its turbo-charged variant - displacement, bore/stroke ratio, distance between cylinders, four-valve-per-cylinder design, ECO start/stop function and direct petrol injection technology are all common to both powerplants - the SLK 55 AMG's M152 engine is distinguished by its cylinder shut-off system, new intake air ducting, new cylinder heads, the modified valve drive, a modified oil supply system and an reinforced crankcase.

The new M152 engine's combination of direct fuel injection at an ultra-high 200 bar pressure, spray-guided combustion, piezo injectors, map-controlled cylinder shut-off, an all-aluminium crankcase, ultra-low friction cylinder linings, four-valve-per-cylinder design with continuous camshaft adjustment, a highly efficient 12.6:1 compression ratio, fully-integrated ECO start/stop function and generator management, and the ability to rev beyond 7000rpm instantly elevate it onto a new level of mechanical sophistication.

The M152 also features an innovative new sports exhausts system that employs twin integrated flaps in the exhaust silencer layout. At low loads and engine speeds below 2000 rpm the flaps remain closed, causing the exhaust gases to cover a longer distance and flow through an additional damping element for a subdued low-level soundtrack.

Under part acceleration, the flaps open at an angle of between 15 and 50 degrees so that some of the exhaust gases cover a shorter distance, bypassing the damping element to deliver a rich and engaging exhaust note. Under full acceleration both flaps open fully to deliver the V8 engine's full muscular soundtrack.

AMG Cylinder Management System - from the Formula 1 track to the open road The AMG Cylinder Management System significantly improves efficiency by shutting off cylinders two, three, five and eight and their intake and outlet valves under partial load to the considerable benefit of economy and emissions. This system follows the same principle of F1 cars, which employ a cylinder shut-off system when the driver has lower load demands during slow corners, when the Safety Car is deployed or during pit stops.

The cylinder shut-off operates between 800 rpm and 3600 rpm when the automatic transmission is in 'C' Controlled Efficiency mode. When running in four-cylinder mode, no less than 230 Nm of torque is always available - ample twist action for most driving situations. The moment the driver summons up more power the system instantly and imperceptibly reactivates the dormant cylinders. At an engine speed of 3600 rpm the activation process takes no more than 30 milliseconds, ensuring seamless driving dynamics.

The standard ECO start/stop function - also active in the transmission's 'C' Controlled Efficiency mode - also plays a key role in boosting economy and slashing emissions. Once the driver comes to a halt, the V8 engine is automatically switched off. The moment the brake pedal is released or the accelerator is depressed, the engine is immediately restarted and the car is able to move off quickly. An illuminated symbol in the main AMG menu shows when the system is running in economy-enhancing four-cylinder mode - 'ECO4' or in full eight-cylinder mode - 'ECO8'.

In the performance-oriented Sport and Manual modes, both the ECO start/stop and cylinder shut-off systems are automatically deactivated. A generator management system makes a further contribution to fuel economy - whenever the engine is on the overrun or when braking, kinetic energy that would otherwise be lost is used to charge the battery.

AMG SPEEDSHIFT PLUS 7G-TRONIC

The AMG SPEEDSHIFT PLUS 7G-TRONIC seven-speed automatic transmission has three transmission modes: Controlled Efficiency (C), Sport (S) and Manual (M), which can be selected by means of a button on the centre console. The gears can be changed using the AMG shift paddles on the steering wheel.

In 'C' mode, the SLK 55 AMG generally moves off in second gear and makes use of the high torque already available at low engine speeds to shift up to the highest viable gear as quickly as possible. The resulting dethrottling effect on the intake side lowers fuel consumption.

In modes 'M' and 'S' the engine and transmission are far more alert, working at revving higher and with much faster shift times. The automatic rev-matching throttle blip on downshifts is activated, as are the brief, precisely defined interruptions to the ignition and injection when shifting gear under full throttle. The highly visible upshift indicator - integrated into the AMG instrument cluster - informs the driver when a manual gearchange is advisable.

The transmission features an integrated double turbine torsional damper and is fitted with a centrifugal pendulum which adapts to engine speed and thereby helps to minimise vibrations in four-cylinder mode for enhanced driver comfort.

Driving Dynamics - Torque Vectoring Brakes, AMG Direct-Steer and AMG three-stage ESP®

The SLK 55 AMG rides on an AMG sports suspension - MacPherson strut layout up front and a sophisticated multi-link setup at the rear, with both ends fitted with coil springs and anti-roll bars. Compared to the standard Mercedes-Benz SLK-Class, the SLK 55 AMG features uprated springs and dampers, stiffer torque strut bearings on the front axle as well as more negative rear axle camber. AMG light-alloy wheels measuring 8 x 18 (front) and 9 x 18 (rear) with 235/40 R 18 and 255/35 R 18-sized wide-base tyres, are fitted as standard for exceptionally high levels of grip.

The SLK 55 AMG's high-performance brake system features ventilated and perforated 360mm diameter cast aluminium discs gripped by four-piston fixed calipers up front, with ventilated and perforated 330mm diameter cast aluminium discs at the rear, clasped by a single piston floating caliper. The parking brake is now electric for added convenience.

The SLK 55 AMG's dynamic repertoire is further enhanced by the addition of Torque Vectoring Brakes and AMG Direct-Steer system. In critical cornering conditions, the Torque Vectoring Brake system selectively and precisely brakes the wheels on the inside of the corner, tucking the car tightly into the bend for enhanced dynamism, even under full throttle conditions.

Fitted with a new power-assistance pump and recalibrated software, the AMG Direct-Steer system delivers enhanced responses and feedback while also reducing the amount of physical effort required when parking. The system also features, the AMG Direct-Steer system, which has a parameter function that matches assistance and responses according to the characteristics of the AMG sports suspension.

The AMG-exclusive three-stage ESP® gives three individual control strategies at the touch of a button: the ESP® button in the centre console allows the driver to choose between 'ESP ON', 'SPORT Handling Mode' and 'ESP OFF'.

AMG Styling - inside and out The arresting style of the Mercedes-Benz SLK-Class is dramatically enhanced by AMG's styling package. The bespoke front and rear apron, side skirts, V8 Biturbo badging on the flanks, 18 inch AMG lightweight alloy wheels, LED daytime running lights and clear glass headlamps with their darkened reflectors coalesce to deliver a powerful external visual punch.

This visual dynamism is carried through to the SLS AMG-inspired interior design, complete with AMG Performance steering wheel. The emphasis here is on high-quality workmanship, precision engineering and ergonomic excellence. The AMG instrument cluster features bespoke AMG dials as well as the AMG main menu. This has three display modes. 'Warm Up' shows the engine oil and coolant temperatures as well as the current status of the ECO start/stop function. 'Set Up' provides information on the current ESP® and transmission mode, while in 'RACE' mode is activated enabling the driver to record lap times when driving on a closed-off race track.

And like the other models in the SLK range, the SLK 55 AMG sports seats are available with an upgraded version of the optional innovative Airscarf neck-level heating system (£395). On chilly days, this patented system functions like an invisible scarf, wrapping the driver and front passenger's head and neck area with warm air.

The optional Airguide (£285) set-up employs a pair of pivoting Plexiglas panels fixed to the reverse of the roll-over bars. These transparent panels can be quickly and safely be adjusted by both driver and passenger to vary the degree of airflow through the cabin - a world first. And because the panels are permanently fixed to the headrests, there's no need for any time-consuming installation or removal.

Safety

Since its European launch in 1996, the SLK has set peerless safety standards in its sector - a legacy of Mercedes-Benz' unrivalled heritage of building open-topped performance cars that stretches back to the SSK of 1928. Key to this exceptionally high level of passive protection was its incredibly robust chassis structure - and this latest generation SLK is no different.

It's new side-impact structure stiff chassis, fully integrated roll-over hoops and carbon-fibre reinforced A-pillar, ensures the driver and passenger are offered the highest level of protection in the unfortunate event of an impact. This protection is enhanced by its ellipsoid front bulkhead that not only delivers optimal impact distribution from a frontal impact, but also prevents the engine and gearbox unit moving backwards into the car interior.

This strong chassis structure forms the ideal platform for the numerous electronic safety systems fitted to the SLK that together create a holistic safety umbrella. Employing the latest radar, camera and sensor technology to cover frequent accident caused by tailgating, fatigue and darkness, they effectively work alongside the driver as an 'intelligent' partner, with the ability to respond instinctively and react on their own accord to avoid accidents if possible or mitigate their severity if they are not.

Attention Assist

Fitted as standard, Attention Assist's highly sensitive sensors monitor the driver's behaviour and, based primarily on steering wheel movements, detect when the driver is becoming drowsy. The system, which made its debut in the E-Class in 2009 - monitors over 70 parameters, which are then assessed for drowsiness detection.

This continuous monitoring is crucial for detecting the floating transition from alertness to drowsiness and for giving the driver plenty of warning to take a break. According to Mercedes-Benz' own research, around a quarter of all serious road accidents are caused by drowsy drivers - making tiredness an even bigger cause of accidents than drink-driving.

During the first few minutes of every individual journey, Attention Assist generates a bespoke driver profile, which is then compared with the current flow of data in combination with prevailing driving conditions. In addition to vehicle speed, lateral acceleration and longitudinal acceleration, the system also detects use of the turn indicators and pedals as well as certain control inputs and external influences such as side winds or road unevenness.

Developed after studying and testing more than 670 drivers, Mercedes-Benz safety engineers determined that during the early stage of drowsiness - the crucial period before the driver momentarily falls asleep - drivers make numerous minor steering errors, which are then invariably quickly and abruptly corrected.

If the Attention Assist system detects the indications of drowsiness through its high-resolution steering angle sensors, it emits an audible warning signal and flashes up an unequivocal message on the display in the instrument cluster: ATTENTION ASSIST. Break! The system is active at speeds of between 50 and 110 mph.

ADAPTIVE BRAKE

The standard-fit ADAPTIVE BRAKE system creates even higher levels of safety and comfort. Incorporating the ABS anti-lock, ASR acceleration skid control and GMR active yaw control units, ADAPTIVE BRAKE prevents the vehicle from unintentionally rolling back when pulling away up a slope and keeps the SLK stationary without having to continuously apply the brakes.

The system also reacts instantly to driver inputs. Should the driver abruptly lift off the accelerator pedal - the first reaction in a potential emergency brake scenario - it primes the brake pads so that they come into light contact with the brake discs, so that should emergency braking be required the necessary braking pressure can be instantly achieved. And during wet weather it systematically applies brake contact to dry the brake discs for enhanced performance. The contact is so light that the driver will be unaware of the discs' actions.

PRE-SAFE®

This multi-award-winning anticipatory safety system is fitted as standard to the new generation SLK and is able to recognise an impending accident because it offers an intelligent synergy of active and passive safety features. It is networked to Brake Assist and the Electronic Stability Program whose sensors recognise potentially dangerous driving situations and then transmit this information to the electronic control units within milliseconds. This allows the seat belts and airbags to deploy with maximum effect in the event of a collision.

PRE-SAFE® can also be activated if the optionally available Distronic Plus (£1,495) radar-assisted cruise control's short- and long-range radars have detected an impending collision and a certain level of deceleration is exceeded when braking. Occupants are prepared for the collision by tensioning of the seat belts, automatic closing of the windows and repositioning of the optionally available, fully electrically adjustable seats (with the optional Memory Package at £1,030 ).

Neck-Pro active head restraints

The new-generation SLK is equipped with bespoke seat designs that incorporate Neck-Pro active head restraints. In the event of a rear impact, these innovate restraints rise 30 mm and move forward a full 40 mm to be in the optimal position to cradle the occupant's head and neck as quickly as possible to mitigate the forces travelling through the car.

Active Bonnet

The SLK's suite of standard safety features also extends to providing the best possible protection for pedestrians. Operating between 15 and 35 mph, the roadster's Active Bonnet enlarges the bonnet's deformation area to significantly reduce the risk of injury to pedestrians. This system, fitted as standard, incorporates three impact sensors in the front section as well as special bonnet hinges pretensioned and arrested by powerful springs.

On impact with a pedestrian or animal, the sensors send information to the electronic control unit, which, in turn, activates two solenoids in the hinges instantaneously. These solenoids release the arresters so that the rear section of the bonnet is pushed upwards by 85 millimetres using a spring. It all takes just a fraction of a second. As well as being extremely fast, the newly developed Active Bonnet technology has a further crucial benefit in that it is reversible. If the bonnet is released in another type of collision, for example, SLK customers can easily reset it in a matter of seconds, reactivating the system themselves, allowing them to continue driving.

Distronic Plus with BAS Plus and Pre-Safe® Brake

The new generation SLK can be specified with Distronic Plus that incorporates BAS Plus and Pre-Safe® Brake (£1,495 option). Available on models fitted with both the 7G-Tronic Plus 7-speed automatic transmission and either the Becker® Map Pilot or COMAND Online system, this advanced safety system uses long and medium-range radars to assist the driver during emergency braking. If the driver is distracted and fails to react even after receiving a visual and acoustic warning, the PRE-SAFE® Brake is able to activate the maximum braking pressure around 0.6 seconds before an accident.

At this point the accident is identified by the system as being unavoidable and primes the PRE-SAFE® anticipatory system - but the emergency braking action significantly mitigates the severity of the impact, reducing the severity of injuries to occupants.

Intelligent Light System

This sophisticated lighting package (£895 option) includes bi-Xenon headlights with LED daytime running lights, Adaptive High Beam Assist, cornering light function and powerful headlamp wash system.

The Intelligent Light System features five light functions - country mode, motorway mode, enhanced foglamps, active light function and cornering light function - which are designed specifically for typical driving situations or weather conditions.

Low beam is replaced by country mode, which illuminates the driver's side of the road more brightly and widely than before. In the dark, this enables the driver to appraise the situation more effectively and respond more rapidly when other road users cross their path.

At speeds above 55 mph, motorway mode is activated automatically, increasing the driver's range of vision by up to 60 per cent. This lighting function is activated in two stages: the Intelligent Light System first increases the output of the bi-xenon bulbs from 35 to 38 watts, thereby increasing the light intensity and providing noticeably better illumination of the road ahead and the side verges.

The second stage is triggered at 68 mph, when the beam of the bi-xenon module on the driver's side is elevated slightly. Motorway mode has a range of around 120 m, and the driver is able to see about 50 m further at the centre of this cone of light than is the case with conventional low-beam headlamps.

With enhanced fog lamps, driver orientation is improved when visibility is poor. The new lighting function is activated at speeds below 40 mph, as soon as the rear fog lamp is switched on. The variable headlamp technology incorporated in the Intelligent Light System makes it possible to pivot the bi-xenon headlamp on the driver's side outwards by eight degrees, while lowering the beam of light at the same time. This adjustment illuminates the inner half of the road more brightly and reduces the degree of glare from light reflected back by the fog.

The Intelligent Light System, also includes the active light and cornering light functions. These are switched on automatically: depending on the steering angle, yaw rate and vehicle speed, the active-light-function pivots the headlamps sideways by up to 15 degrees almost instantaneously, thereby greatly enhancing illumination of the road. On an extended bend with a radius of 190 metres, this system enables the driver to see 25 metres further than is possible with conventional low-beam headlamps. This function operates in both low-beam and high-beam mode.

The cornering light function improves safety at crossroads, at T-junctions and on tight bends. It is activated automatically when the driver turns the steering wheel at speeds below 40 mph. The headlamps then illuminate the area diagonally in front of the vehicle for a distance of around 30 metres, with a coverage angle of up to 65 degrees.

The Intelligent Light System is complemented by Adaptive Highbeam Assist, unique to Mercedes-Benz. This system constantly and automatically adjusts the range of the headlamps based on the distance of oncoming vehicles or moving vehicles in front of the car.

By selecting the optimum headlamp range so that the cone of light emitted by the headlamps ends before it reaches these vehicles, headlamp range can be increased from around 65 to up to 300 metres - without dazzling other motorists. The system operates at lightning speed, sending new data to the headlamps every 40 milliseconds. Advanced LED lights are also used on the daytime driving lights fitted to all Mercedes-Benz SLK-Class models, as well as for the indicator repeaters, tail lights and side lights.

Tests confirm that motorists who use Adaptive Highbeam Assist are safer on the road in the dark: dummies placed at the side of the road to simulate pedestrians were detected from a distance of around 260 m - around 150 m earlier than when conventional low beam was used - despite the presence of oncoming traffic.

The gradual transition through the stages, rather than the two stage 'low beam or high beam' system also relieves driver stress as there is no longer any need to flick the stalk on the steering wheel repeatedly, allowing the driver to concentrate on driving the car with the best possible levels of illumination possible.

Speed Limit Assist

Part of the COMAND Online system (£1,995 option), Speed Limit Assist uses invisible infrared light from two separate headlamps to recognise approaching speed limit signs and display the relevant speed limit in the instrument panel's central display, ensuring the driver is made aware of any changes to the prevailing speed limit.

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