2007 Acura RDX

All right, so it's not really a new idea, but given recent fuel spikes, the desire for more carlike accoutrements, and aging competitors in the segment, the notion of building compact SUVs that no longer ride like lumbering buses has taken on new significance.

BMW took the lead in this exclusive segment several years ago with the addition of the X3 (which is just a hair's breadth smaller than the midsize X5). And now Acura, the X3 (and maybe the Infiniti FX35) square in its sights, is predicting strong growth in this segment, with sales more than quadrupling by 2011. Considering this, Acura has taken its first shot to bring down BMW with its all-new RDX.

Acura engineers had the critical measurable numbers from the X3 (compare length, width, height, track, and turning-diameter specifications, and the RDX is a ringer for the compact BMW). Their assignment from Japan? Beat the BMW, even if only slightly, in every possible category. Acura even gave us an X3 to run back-to-back comparison laps--more on that later.

The RDX rides on a new platform and fits underneath the current midsize MDX SUV in size and cost. Simple and athletic, the RDX's exterior design is meant to evoke its sportier personality. A fast-raking windshield and racing-stripe-style line running the length of the body, in addition to the wraparound rear glass and wind fin, make for an aerodynamic look--think Mazda3 wagon or Toyota RAV4. But any manufacturer that wants a piece of the luxury-vehicle pie had better match that look with a strong engine.

RDX buyers will get an all-new 2.3-liter turbocharged and intercooled I-4 engine that produces 240 horsepower at 6000 rpm and 260 pound-feet of torque at 4500 rpm. The latter, although typically not an important number in smaller SUV segments, is significant because the RDX makes more torque than any other vehicle in the current Acura or Honda lineups. Much of the credit is due to the fact that the turbocharger uses a unique "variable flow" approach to feeding the smaller turbo exhaust gases. A smaller turbo can ramp up faster, reducing lag at slower speeds. At higher speeds, a movable control valve can open to allow even more of the exhaust gases into the runners to spin the turbo even faster, allowing for strong pulling power at higher speeds and rpm. On the intake side, the RDX channels air (through the hood) into an air-to-air intercooler before mixing fuel and cooled air on its way to each cylinder. The large front fascia air inlet above the grille creates a ram effect to keep air constantly moving through the intercooler.

Off the line, RDX responsiveness is smooth and impressive. Where some turbocharged engines tend to kick into first gear abruptly after a short lag, the RDX uses its new five-speed transmission, with a specially designed torque converter, to slip and even out any hard hit while still offering a sturdy feel. The tranny has normal and sport settings as well as F1-style paddle shifters (right upshift, left downshift) on the back of the steering wheel that can be used in either mode. In Drive, the transmission comfortably selects among the five forward ratios, as expected. However, by pulling the lever into Sport, the transmission provides a more aggressive shift pattern, holding up- and downshifts several hundred rpm longer as well as eliminating overdrive. The SportShift paddle shifters can be actuated in both "D" and "S" modes, but will revert after a few seconds when in normal mode and hold the gear when in sport. The five-speed is quick to respond when enthusiastically run through the gears (paddles or stick), and the separation between normal and sport modes are two distinct personalities.