The Mercedes-McLaren SLR 722 supercar - company car of the reigning back-to-back Formula One champ Fernando Alonso - just got a major upgrade. As if the 650hp (485kW) under the go pedal weren't enough to move the carbon-fiber and aluminum shell at breakneck speeds, McLaren put the silver supercar on a crash diet, according to the German speakers at Carpassion forums.

The new 722 GTR appears to be nearly identical to the 722 it's based on, but tipping the scales at just 2860lb (1300kg), the GTR is 660lb (300kg) lighter. What does this added lightness mean for performance? Well, very good things of course. Acceleration is enhanced, knocking 0.6s off the dash to 62mph (100km/h), trimming the time down to 3s flat. Top speed is unchanged at 210 mph (337km/h).

Weight was reduced by replacing as many alloy parts as possible with carbon fiber substitutes. Exactly which pieces were converted is unknown at this time.

Only 21 of these units will be built, ensuring exclusivity for the niche upgrade to an already exquisite supercar. Although, you could always send it to RENNTech and have them up the output of the 5.5L V8 to 722hp. Then it'd be really, really exclusive.

Originally released in 2003, the SLR was a disappointment to some buyers who were expecting a hardcore supercar like the McLaren F1 but ended up with a relatively heavy grand tourer fitted with an automatic transmission. In this sense, the SLR never gained the fame of its predecessor. While the automatic transmission remains, lopping 300kg off a car is a big deal so we're interested in finding out how well this one handles around a track.

[via Jalopnik]