Tech Briefs
Mercedes' V12 and V8 plans

Mercedes-Benz' new V12 engine.

DaimlerChrysler has revealed that it will be adding the CLK Cabriolet in V8 form for MY2000. The CLK 430 gets a 4.3-L V8 with an output of 205 kW (279 hp) and maximum torque of 400 N•m (295 lb•ft) between 3000 and 4400 rpm. Combined fuel consumption (NEDC) is 12.5 L/100 km (22.6 mpg Imp). Performance figures include a 0-100 km/h (62 mph) time of 7.4 seconds and a top speed of 250 km/h (156 mph). All CLK models have been updated for MY2000 with changes to some 800 components as well as chassis modifications. Standard equipment includes a five speed automatic transmission and ESP (electronic stability program). The high performance CLK 55 AMG Coupe with a 255 kW (347 hp) V8 engine is now in series production. The car's performance figures include a 0-100 km/h (62 mph) time of 5.4 seconds. Other changes to regular CLK variants include the body riding 25 mm (1 in) lower with stiffer suspension and larger brakes.

Mercedes also released details of its new 5.8-L V12 engine that will be offered for its CL Coupe flagship and for the S-class sedan. The V12 version of the CL Coupe, the CL 600, has a 0-100 km/h (62 mph) acceleration of 6.1 seconds, a 90-120 km/h (56-75 mph) time of 5.2 seconds, and a combined fuel consumption figure of 13.4 L/100 km (21.1 mpg Imp). The engine has dual ignition, automatic cylinder shut-off, and low-friction cylinder liners. Power output is 270 kW (367 hp) at 5500 rpm with 530 N•m (391 lb•ft) of torque at 4250 rpm. Mercedes reports that weight of the engine compared to the company's previous V12 has been reduced by some 22% to 222 kg (488 lb) which is slightly heavier than the company's 5.0-L V8. The crankcase is made of aluminum, with magnesium used for the intake manifold, while the exhaust manifold is made of laser-welded, high pressure formed sheet steel. Mercedes said that cylinder liners utilizing aluminum-silicon alloy, and connecting rods manufactured via a cracking process, also bring significant weight savings. The engine uses three-valve technology for improved fuel consumption and emissions as well as saving some weight.

Overall size has also been contained. The gap between cylinders is 90 mm (3.5 in) and the cylinder angle is 60o. Valves are operated via roller-type rocker arms for reduced friction. A microcomputer controlled adjustment mechanism adapts camshaft control times to the appropriate mapping. Mercedes says that dispensing with one outlet valve per cylinder helps reduce heat losses within the engine and speeds cold start warm-up. It also creates the space to introduce two spark plugs for each combustion chamber. What the company describes as "an innovative alternating current ignition system" controls the engine. To identify and cure misfiring, ion-flow sensing is used which contributes to catalytic converter protection. Like the company's 5.0-L V8, the V12 has cylinder shut-off using valve and fuel injection deactivation. A complete cylinder bank is shut off when only part torque is needed. When the driver squeezes the throttle again, the idle cylinders reactivate, with the engine-management system altering throttle valve position and adjusting ignition timing to smooth the torque increase. A valve in the mixing tube downstream of the catalytic converters closes immediately when shut-off is in operation, preventing exhaust system pressure waves. The V12 engine is allied to six catalytic converters (four firewall, two underfloor). Emissions are said to be "well within" the European Union's EU4 limits slated for 2005 introduction.