From Acura press: The engineers who designed the MDX tested a range of competitive SUVs to help quantify off-pavement use patterns, customer needs, and engineering targets for the new MDX. Nine off-road parks in California, Nevada, Kentucky, North Carolina, and Michigan were visited to study SUVs in their natural off-road habitat.
While a few competitors offer the extra ground clearance, driveline equipment, and chassis hardware necessary to support ambitious excursions off-roads, the engineers learned that few customers use these extreme capabilities regularly. Accommodating extreme off-road use would impose unreasonable compromises elsewhere in the vehicle, such as added weight, awkward entry and egress, poor fuel economy, and reduced dry-pavement performance.
The conclusion was that surpassing the class's most capable off-road machine was not in MDX's best interests. Instead, a more realistic goal was established. After observing casual off-roaders, MDX engineers concluded that a medium-duty off-road capability was most consistent with the philosophy embraced by the MDX. Medium-duty capability would readily support trips into the wilderness for camping or to launch a boat without providing the rigorous equipment needed to conquer the Rubicon Trail.
To define exactly what constitutes medium-duty off-road capability, the MDX engineering team selected 14 key performance criteria based on observations of casual off-road adventurers. They then constructed special test courses at their R&D facilities in North America to assure that MDX delivers all the intended capabilities with impeccable reliability and durability.
An advanced powertrain is essential to meet MDX's primary goals of outstanding performance, class-leading low emissions, and excellent fuel economy. To that end the MDX is powered by an advanced 3.5-liter SOHC VTEC engine that delivers 240 horsepower at 5300 rpm and 245 lb-ft of torque from 3000 to 5000 rpm. Acura's renowned Variable Valve Timing and Lift Electronic Control (VTEC') valvetrain, first used in the NSX supercar, adjusts the timing, duration, and lift of the intake valves according to engine speed. In conjunction with a two-stage intake manifold, VTEC yields high peak-rpm performance, muscular response at low- and medium-rpm, very low emissions, and best-in-class fuel efficiency.
MDX's new 5-speed automatic transaxle has several features engineered specifically for use in a mid-sized luxury SUV, including: extra-wide gear ratios to optimize both start-up acceleration and highway cruising comfort, a lock-up torque converter and a rigid alloy case design.
The MDX's innovative VTM-4' (Variable Torque Management' 4-Wheel Drive) all-wheel drive system provides extra traction during acceleration and slippery road conditions. Additional benefits are improved dry-road vehicle dynamics, medium-duty off-road capability, and a lock feature to aid extraction from severe "stuck" conditions. A compact transfer case is bolted directly to MDX's front-mounted transaxle. A two-piece propeller shaft delivers torque from the transfer case to a rear axle drive unit. Two computer-controlled, electromagnetic-actuated clutches engage as needed to provide torque to the rear wheels.