Mercedes-Benz's AMG arm has declared the horsepower war over two years in a row, all the while continuing to turn out new and improved - and more powerful - cars. Renntech has taken its cues from the spirit, if not the letter, of AMG's announcements with its latest modification, boosting the SLR supercar's output to a massive 777hp (580kW).

Going a step beyond even its own previous SLR 722 package, the new Renntech 777 is the result of founder Hartmut Feyhl's relentless pursuit of more: more performance, more power, more impressive looks.

On the other hand, Feyhl also describes the car as having the much-needed less when it comes to weight. "This 777 concept is really an all-new car that makes use of the advanced carbon fiber chassis of the SLR McLaren. It can be described as a street-legal track car, or something closer to what the enthusiasts were hoping for from the SLR, originally - which is more a successor to the McLaren F1."

In addition to lightweight bodywork, the 777 also features an upgraded cooling system to help cope with the demands of the supercharged 5.5L engine under heavy track use. The company also fitted a special limited-slip differential, custom built for the application by OS Giken of Japan. The new diff offers 100% locking of the drive wheels, helping to keep the power down.

Sticky Nitto NT-05 street/performance tires keep things road-legal while providing high levels of grip, working with the redesigned suspension for ideal performance. This isn't likely to be the last such car from Renntech either.

"The first example is being built now, and will be ready this Spring. We intend to build a few different extreme vehicles like this for our 20th anniversary, with each one being strictly limited to 20 units. They are all very exciting projects, and we will be announcing them throughout the year, as they approach completion," said Feyhl.