February 15, 2008 Mercedes' high performance tuning subsidiary AMG has announced the April release of its sportiest-ever SL class Benz. The SL 63 AMG's 6.3-litre engine's now tuned for 525 horses and 660Nm, and even the most ham-footed driver can hit 100kmh in 4.6 seconds thanks to the AMG Race Start launch control package. Chilly temperatures don't have to put you off driving with the top down, as the AMG features a new "Airscarf" neck-level heating system, and the electronically adjustable suspension lets you strike the right balance between racetrack grip and touring comfort on the road. The transmission's a beauty - a four mode manual auto with superfast 100ms shifting and auto-double declutching on downshifts. And if this baby's not fast enough for you, there's always the SL 65 AMG biturbo V12.

AMG, which famously provides the safety cars for Formula One events and also builds the V12 engine for the Pagani Zonda supercar, has been Mercedes' official high-performance division since its acquisition in 1999. The latest Benz-on-steroids to be announced is the SL 63 AMG, which will go on sale beside its evil older sister, the SL 65 AMG, in April.

While the 525 horsepower/660Nm engine will doubtless raise eyebrows (it's the most powerful naturally aspirated motor in its class), the AMG 7-speed Speedshift multi-clutch transmission is probably the SL's biggest step forward in technology. The Speedshift's wet startup clutch elminates slip on the throttle, producing a very direct response from the wheels. From there, it's a matter of which drive mode you engage; Comfort, Sport, Sport Plus or a completely manual shift system that runs from F1-style paddles either side of the steering wheel. These modes modify not only the shifting speed (up to a very sprightly 100 millisecond shift time in Manual mode) but the engine mapping, throttle response and engine revs at which a shift will occur.

In Sport, Sport Plus and Manual modes, every automatic or paddled downshift is accompanied by precisely metered double-declutching, which matches engine revs to deliver the new gear extremely smoothly.

The SL 63 features AMG's Race Start function for total-traction max-power takeoffs. Once it's activated, you hold the brakes down with your left foot, confirm the race start fuction with a click of the upshift paddle, then floor the gas pedal and lift off the brakes. The Race Start system holds the motor at optimal launch revs and you're off in an instant, heading for 60mph in 4.6 seconds, or hooning all the way up to the electronically limited 155mph top speed as all gearchages are performed automatically and optimally.

The Active Body Control electronically adjustable suspension on the SL 63 AMG allows a wide range of suspension tuning options to cater for touring comfort, racetrack handling and anything in between. The wheels are sexy 19-inch jobs, and are fitted with AMG's high-performance composite brakes, which are well up to racetrack action and obscenely overqualified for road duties.

The convertible roof (also available in glass as an option) opens in 16 seconds, and once it's open gives you few reasons to close it - the radio volume self-adjusts to counteract wind noise, and the optional Airscarf system directs a nice warm stream of air right at your neck to keep you feeling toasty warm even when it's chilly outside.

Other AMG upgrades to the car include a stylish bodykit, nappa leather sports seats, plenty of carbon fibre bits and pieces, and an infotainment system that features DVD, CD, MP3, Bluetooth integration, Sat Nav, voice recognition, music library storage, SD card interface, a 6.5 inch screen... And a partridge in a pear tree.

If you feel the need to go bigger in the engine department, there's always the 4-year-old SL 65 AMG, with a biturbo 6.0 litre V12 that slams out 612 horsepower and 1000Nm of torque. While the older 65 does get a bodykit similar to the 63, it doesn't get the new transmission.

Pricing will be announced closer to the April launch, but will likely be up around USD$200,000.

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