Vehicle: Mercedes-Benz F 400 Carving
Introduced in: 2001
Where: Tokyo Motor Show
Goals: Testing of novel dynamic handling systems
Powertrain: Four-stroke spark-ignition engine, six cylinders, 3.2 litres displacement, 160 kW (218 hp), rear-wheel drive, electrohydraulically controlled five-speed manual transmission
Active camber control
Electronic steering system (steer-by-wire)
Electronic brake system (brake-by-wire)
Production launch under the name Sensotronic Brake Control (SBC™) in the Mercedes-Benz SL (2001, R 230 series)
Brake discs made of carbon-fibre reinforced ceramic
Production launch in the Mercedes-Benz CL 55 AMG F1 (2000, C 215 series)
Active hydropneumatics with a new type of Active Body Control (ABC)
Aluminium space frame with CFRP body (carbon-fibre reinforced plastic)
Xenon headlights incorporating fibreglass technology
Additional headlights for cornering, which double as fog lamps
Production launch in the Mercedes-Benz E-Class (2002, W 211 series)
Turn signals with high-performance LEDs
42-volt onboard power supply
The company gathered extensive experience with the active adjustment of wheel camber using the F 300 Life Jet research car. The engineers therefore extended their research work to a four-wheeled vehicle and in 2001 presented the F 400 Carving. Its systems enhance especially handling safety, driving dynamics and motoring pleasure.
The most conspicuous feature of the F 400 Carving which gets its epithet from the sporty carvers on ski slopes: during cornering, the outer wheels tilt by as much as 20 degrees, which distinctly improves directional stability and roadholding and reduces the danger of skidding. Electronics have been combined with mechanics to achieve this. Sensors measure road speed, acceleration, steering lock and yaw of the car and send control signals to the hydraulic servo cylinders of the outer wheels, which are made to tilt at a precisely defined angle. Like the body, the tyres on the inside of the bend remain in their normal position.
Active camber adjustment for enhanced safety
In the F 400 Carving, owing to the active camber control the cornering forces are up to 30 per cent higher compared with today’s car chassis. The longitudinal forces are improved by up to 15 per cent. Due to the high lateral forces acting on the outer wheels, lateral acceleration is up to 28 per cent higher than for sports cars featuring conventional chassis technology. This technology not only affords more dynamic cornering and sporting agility but also improves handling safety, particularly in critical situations caused by taking bends too quickly or by sudden evasive manoeuvres.
If skidding threatens due to understeer or oversteer, with the help of efficient hydraulics the system briefly tilts one or more wheels to a precisely computed angle, thereby increasing cornering forces and stabilising the vehicle. For emergency braking, all four wheels can be cambered in a flash so that only the insides of the wheels with their friction-optimised tread compound have contact with the road. This shortens the stopping distance from 100 km/h (62 mph) by a good five metres. Another feature of the chassis technology: if aquaplaning threatens, the system can selectively change the tyre contact patch.
Special tyres for the research car
The success of the F 400 Carving is attributable to a major part to its tyres. The latter were developed specifically for this car and combine the advantages of car tyres with those of motorcycle tyres. On the inside, the tyre has a rounded tread for best cornering behaviour; this tread additionally features an especially high coefficient of friction. When the wheels are tilted, the transmitted forces are particularly high. The outer shoulder of the tyre features a proven car tread with good straight-line stability. The tyre is mounted on a special rim which has a diameter of 17 inches on the inside, the active cornering side, and 19 inches on the outside. This ensures that the research car, when going straight ahead, rolls only on the part of the tread which is not arched. In bends, the largest possible tyre contact patch is made available, thanks to the smaller inside diameter.
Drive-by-wire technology was a further development goal of the F 400 Carving. The F 400 Carving does not have mechanical joining elements like a steering column with its spindles and joints, or linkage between brake pedal and brake booster. Cables take their place, which transmit the driver’s steering and braking commands solely by electronic means. This makes additional safety features possible: in a hazardous situation, automatic intervention in steering control reduces the risk of skidding. The electronics compute and proportion brake pressure for each wheel as required in any given situation for highly reliable braking in bends.
Brake discs made of carbon-fibre reinforced ceramic
The brake discs are made of carbon-fibre reinforced ceramic, a high-tech material which resists extreme temperatures in the range of 1,400 to 1,600°C and permits optimal deceleration. In addition to the standard onboard power supply, the F 400 Carving is equipped with two 42-volt systems which mainly serve the electronic steering.
Suspension and lighting
The F 400 Carving features a new kind of Active Body Control (ABC) which is coupled with an active hydropneumatic system which influences both the springing and damping of the car. The result once more is enhanced handling safety, but also better ride comfort.
The headlight system is likewise a new development. Light source and headlight proper are separate – glass fibres transmit the bunched light of the xenon bulbs without loss to the outlets, where special lenses distribute it over the roadway. This is to the advantage, in particular, of the design of the sports car’s front end since the headlights take up only very little space. In bends, additional side headlights are switched on depending on the angle of the wheels; they also function as fog lamps. For the turn signals, high-performance light-emitting diodes are used whose light is distributed by prismatic rods.
Materials were also studied in the F 400 Carving. The body is made of carbon-fibre reinforced plastic (CFRP) and weighs a little over 100 kilograms. The space frame chassis is made of steel, aluminium and also CFRP. The F 400 Carving roadster brings back the gullwing doors – a distinctive characteristic of special sports cars from Mercedes-Benz.