To achieve seemingly divergent goals of performance and efficiency, Mercedes employs a number of technologies to make the 3.5-liter V6 strong yet thrifty. For example, special flaps vary the length of air intake according to engine speed and load on the vehicle. At revolutions above 3,500 rpm, the flaps open to shorten the distance it takes the air to reach the combustion chambers and produce higher output for improved passing power. But at low engine speeds, the flaps remain closed, thereby increasing the distance air travels to the combustion chambers, in the process creating pressure waves that increase the torque potential for better off the line throttle response. Other attributes of the six-cylinder motor include lightweight aluminum crankcase and head construction, variable camshaft adjustment vapor recovery technology for cleaner emissions, and secondary air injection that is engineered with an “afterburning” process that reduces carbon monoxide and hydrocarbons while simultaneously helping to heat the catalytic converter more quickly for optimal performance.

With an impressive output of 302 horsepower and 339 lb.-ft. of torque, the 5.0-liter V8 is also tuned for Mercedes-quality performance, providing 90 percent of maximum twist at 2,000 rpm and peak torque between 2,700 and 4,750 rpm. In contrast, Cadillac’s SRX V8 develops 320 horsepower and 315 lb.-ft. of torque from a 4.6-liter engine.

The standard seven-speed automatic transmission is a major achievement in shifting, besting the current standard by one extra gear. That additional cog is not the only impressive innovation, however. Direct Shift, also found on the new M-Class, replaces the conventional shift lever on the console with a column-mounted lever that electronically determines the drive-by-wire transmission’s mode. If sporty manual control is desired, steering wheel buttons are available. With seven gears, the incremental steps are small but the total rev span is large, so Mercedes provides up to four-gear downshifts when more power is required. Score one here for Mercedes, as the SRX only offers a five-speed automatic.

Connected directly to the transmission, the permanent all-wheel-drive system splits torque 50:50 front to rear, and traction control is included in the 4ETS (Electronic Traction System). Four-wheel disc brakes with ABS are standard inside the 17-, 18- or optional 19-inch wheels. Ventilated front rotors are used on both models, while the R500 also gets them in back.

The fully independent suspension features double-wishbone front and four-link rear configurations. The optional Airmatic air suspension automatically lowers ride height by 20mm at speeds over 77 mph to improve handling and reduce drag by up to three percent providing a boost to fuel economy, and can raise the R-Class by 50mm for better ground clearance. In addition to maintaining a constant ride height regardless of payload, the Airmatic suspension functions in parallel with the Adaptive Damping system that automatically varies the shock response according to road conditions, vehicle load and driving technique.

Distronic Cruise Control, which can automatically maintain a proper driving distance between the R-Class and traffic ahead, will be available in 2007.