This black SL might look just like any other Kleeman-tuned car, but when the driver stops the car and opens the door, it surprises onlookers by moving outward to clear the bodywork and then decisively upward. The Kleeman Xtreme uses an electro-hydraulic mechanism to move the striking doors, with the final act of pulling them completely shut carried out by factory Mercedes-Benz technology.
The body kit on the Xtreme is from Kleeman's SL tuning program, but the carbon-fiber spoiler lip is new. At the rear, the valance now has two diffusers to clean up the separating air and reduce lift at speed. The new TS-6 forged alloy wheel was designed not only to cool the brakes but also to help expedite airflow from under the car, reducing lift at speed. Kleeman also made the TS-6s with spokes that are left- and right-handed, which not only look better but also draw through cooling air on both sides of the car. To complete the tougher look, the suspension is lowered 15mm.
The Extreme prototype presented at Frankfurt 2003 was based on an SL500, but the limited edition of 20 customer cars will be built around SL55 AMGs. Since the factory motor was developed for forced aspiration from day one, it has all the right internal components-reinforced block, crank, rods and pistons and a lower compression ratio-to produce something quite spectacular.
Kleeman felt the IHI supercharger on the AMG motor was not as efficient as it could be, so it was replaced with one of Kleeman's own, essentially a larger version of the Swedish-made AutoRotor unit on the SL500. This twin-screw positive-displacement supercharger has very low internal friction and is said to produce less heat than rival units. The secret is cool air and low boost, so Kleeman approaches heat as the root of all problems. The innovative watercooled intercooler, from Laminova, another Swedish engineering firm, is so efficient that, at full power, it can dissipate nearly twice as much heat from the charge air as the comparable unit from AMG. Net horsepower gain is significantly higher and is achievable on significantly lower boost pressure-the Kleeman car uses just 0.75 bar of boost compared to 0.9 bar on the 500-bhp SL55 AMG.
Unfortunately, the supercharged AMG motor does not use an air mass sensor, so for ease of application Kleeman fits an air mass sensor to the AMG motor when it changes the supercharger for one of theirs. They also change the complete exhaust with new manifolds, downpipes, four 100-cell steel catalysts and bigger exhaust pipes.
The modified motor makes a spectacular 640 bhp at 5800 rpm on the dyno, with 616 lb-ft (835 Nm) of torque from 2000 to 6000 rpm-that is, more power at high revs on 0.5 bar boost than the factory car does at 0.9 bar. The 0 to 100-km/h time is just 4.4 sec. and would be even better if traction off the line were not such an issue. Top speed is electronically limited to 206 mph (330 km/h) to remain within the safe limits of the tires.
The Kleeman Xtreme show car was sold to an enthusiastic Japanese customer and after being returned to Denmark for finishing was soon on its way to Tokyo.