Road Test: 2007 Acura RDX & 2007 Mazda CX-7

Brothers from Different Mothers: Mazda and Acura Troll the Same Part of the Sea for Success

Mark Williams
Dec 27, 2006
Photographers: Brian Vance
It's official: The next big idea the auto industry's ready to exploit is compact SUVs that perform more like sport sedans. All right, so that's not such a new idea. But with recent fuel spikes and quite a few aging competitors in the segment, there may be an opportunity for someone new to take the lead. It may have been a small group at the time, but BMW earned the number-one spot several years ago in the compact premium-SUV segment with the addition of the X3, which was actually just a hair's breadth smaller than the midsize X5.
Photo 2/4   |   2007 Acura RDX front View
Now Acura takes aim.
On an entirely new platform, the 2007 RDX fits underneath the current mid-size MDX SUV in size and cost. And, when comparing specifications (length, width, height, track, turning diameter), the RDX is practically identical in every way with the X3. Acura even gave us an X3 at one point to run back-to-back comparison laps--but more on that later.
Acura's exterior design is simple and athletic, clearly meant to evoke its sportier personality. Generally speaking, the design looks like a low-slung new RAV4. The fast-raking windshield and racing-stripe style line running the length of the body, in addition to the wraparound rear glass and wind fin, add up to make the RDX appear quick. But it's more than just looks.
Photo 3/4   |   2007 Acura RDX engine View
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. This latter number, although typically not all that important in small-SUV segments, is significant because the RDX makes more torque than any other vehicle in the current Acura or Honda lineup. Much of the credit should go to the turbocharger, which uses a unique "variable flow" approach to feeding the smaller turbo exhaust gases through two separate runners--a short one to spin the turbo quickly to reduce turbo lag, and a longer one to flow more air for higher-rpm passing power. On the intake side, the RDX channels air through the hood into an air-to-air intercooler before mixing fuel and cold air on its way to each cylinder. The large front-fascia inlet above the grille creates a type of ram effect to keep air constantly moving through the intercooler.
Off the line, RDX responsiveness is impressive and surprisingly smooth. 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, smoothing out any hard hit while still offering a strong 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, which can be used in either mode. The five-speed is quick to respond when enthusiastically run through the gears (paddles or stick), making it obvious that normal and sport mode have distinct personalities.
Last but not least, the third player in the all-important dance among engine, transmission, and traction is Acura's first application of the SH-AWD (super handling all-wheel drive) system in an SUV. It uses a staggering series of sensors to anticipate where traction will be lost or where understeer might occur and distributes the existing traction (sometimes by braking, sometimes by accelerating) where it's needed--even before it's needed. This system can specifically accelerate a single rear wheel during hard cornering to mitigate front-wheel slide or plowing.
Photo 4/4   |   2007 Acura RDX interior View
We enjoyed pushing our test unit around tight and twisting highway roads and found the grip of the Michelin 235/55R18 high-performance all-season tires almost eerie. Where you expect to hear tire squeal, you get nothing but grip. The chassis is balanced when pushed, having little trouble transitioning from a hard left to a hard right turn. This is where the RDX walks all over the X3 (hats off to Acura engineers on this one). Likewise, braking feel is predictable and smooth, thanks to 11.7-inch discs in front and 12.0-inch discs in the rear. Although minor, our only complaint is with the speed-sensing software that controls the power rack-and-pinion steering response. Compared with the X3, the RDX is hesitant and noncommunicative, even with a 15.0:1 steering ratio, as if the extra grip of the SH-AWD and the high-performance tires were used to compensate for a softer, gentler steering feel, yet still provide sporty handling. We would've preferred a sportier response from all three.
Look for RDX models to make it into showrooms by July and August with base models starting just above $31,000--expect fully loaded models to approach $37,000. That could translate to $10,000 less than a similarly equipped X3. Maybe that's not a kill, but it's certainly a serious flesh wound.
2007 Acura RDX
General
Location of final assembly Marysville, Ohio
Body style 4-door SUV
EPA size class Compact utility
Drivetrain layout Front engine, AWD
Airbags Dual front, head
Powertrain
Engine type Turbocharged I-4, all aluminum
Bore x stroke, in 3.4 x 3.9
Displacement, ci/L 140.3
Compression ratio 8.8:1
Valve gear DOHC, iVTEC, 4 valves/cyl
Fuel induction Multipoint
SAE horsepower, hp @ rpm 240 @ 6000
SAE torque, lb-ft @ rpm 260 @ 4500
Transmission type 5-speed auto
1st 2.70:1
2nd 1.61:1
3rd 1.07:1
4th 0.77:1
5th 0.61:1
Reverse 1.89:1
Axle ratio 4.53:1
Final-drive ratio 2.76:1
Rpm @ 60 mph 1600
Recommended Fuel Premium Unleaded
Dimensions/Capacities
Wheelbase, in104.3
Length, in180.7
Width, in73.6
Height, in65.2
Track, f/r, in61.9/62.6
Headroom, f/r, in38.7/38.3
Legroom, f/r, in41.8/37.6
Shoulder room, f/r, in58.2/56.3
Hiproom, f/r, in54.4/53.0
Total interior volume, cu ft 101.4
Behind front row, cu ft 60.6
Behind 2nd row, cu ft 27.8
Ground clearance, in 6.3
Approach/departure angle, deg 28.0/22.0
Load lift height, in 26.0
Base curb weight, lb 3968
Payload capacity, lb 800
GVWR, lb 4800
GCWR, lb 5400
Towing capacity, lb 1500
Fuel capacity, gal 18.0
Chassis
Construction Unit-body
Suspension, f/r IFS, MacPherson strut, coilover/ IRS, multilink, coil spring
Steering type Power-assist rack and pinion
Ratio 15.0:1
Turns, lock to lock 2.76
Turning circle, ft 37.4
Brakes, f/r 11.7-in vented disc, dual piston/ 12.0-in disc, single piston
Wheels 18x7.5-in JJ cast alloy
Tires 235/55R18 Michelin
Load/speed rating 99V
EPA fuel economy, city/hwy 19/24 (est)
Price
Base price $31,000 (est)
Price as tested $36,000 (est)
2007 Mazda CX-7
By Frank Markus

Mazda's suggested test route for the all-new CX-7 crossover started with a long freeway slog, during which the MacPherson-strut front and multilink rear suspension smothered freeway chop with a suppleness that served to reinforce my doubts about the chassis's alleged athleticism. The chaperone riding shotgun fired up the nine-speaker Bose Centerpoint surround-sound system, and it sounded darned near good enough to warrant the $1585 package price, even without the moonroof.
Soon our route left the super-slab and headed for the hills, where I predicted I'd be disappointed by this "sports-car crossover." But the little sport/utility scooted around corners flatly with no tire squeal and with linear and communicative steering. Hmph. Even the four-wheel vented disc brakes delivered smooth, strong stops via a firm pedal.
Other things we like include the electronic all-wheel-drive system ($1700) shared with the praiseworthy Mazdaspeed6. A wet clutch on the rear (open) differential directs up to 50 percent of the torque to the rear axle on demand. Mazda's choice of a 2.3-liter, 244-horse four-cylinder turbo also will distinguish the CX-7 from competitors. Based on the Mazdaspeed6's 274-horsepower engine, the CX-7's turbo features a smaller inlet. This limits torque somewhat to protect Mazda's six-speed automatic.
The turbo four is well matched to its manually shiftable tranny. Closely spaced gears keep the turbo on the boil (99 percent of peak torque is available from 2000 to 5000 rpm). Firm shifts accentuate the CX-7's sporty flair, but some part-throttle downshifts felt abrupt, possibly because the turbo boost spools up a split second after the shift, resulting in an unwelcome jerk. We clocked a 0-to-60-mph time of 7.8 seconds, ahead of the similarly sized and equipped 8.1-second Nissan Murano and well ahead of the similarly priced but smaller 8.9-second Honda CR-V automatic. Only the Saturn Vue Redline (7.4 seconds) and likely the new RAV4 V-6 will outrun the CX-7 for similar money.
Rear-seat passengers have plenty of headroom, but to achieve it the rear seat cushion is lower than optimal, putting adult knees in the air and hampering visibility for kids who've just outgrown their booster seats. Cargo space also is slightly cropped, but 60/40 seatbacks fold flat at the flick of a lever to provide 70 inches of nearly flat floor. Flip the carpeted rear floor panel over to carry messy loads on a washable plastic surface. And whatever won't fit in back can be towed in a 2000-pound-capacity trailer.
CX-7s come in three flavors: Sport, Touring, and Grand Touring, distinguished only by standard equipment, not badges. Sport models start at $24,310, with six airbags and stability control. Another $1750 buys heated leather seats with power for the driver, and for $26,860 the Grand Touring gets HID headlamps, fogs, and fancier trim. The pricing lines up with the V-6 cute 'utes, while the size and spec rivals midline models like the Toyota Highlander.
Cool Under Pressure
By Frank Markus

How does Mazda wring 106 horsepower per liter from the CX-7's motor? The oil- and water-cooled turbo blows 15.6 psi through an air-to-air intercooler mounted on top of the engine, and then after it enters the cylinders it's cooled again when fuel is injected at between 430 and 1600 psi. At these pressures, the liquid evaporates immediately, and this phase change absorbs enough heat to permit a compression ratio of 9.5:1--quite high for a turbo. Raising the compression ratio boosts low- and midrange torque by 10 percent. The fuel is pressurized by a mechanical pump driven off the exhaust cam. Other high-performance features include forged crank and connecting rods and a baffled oil sump to prevent oil starvation while cornering at max-lat in the Corkscrew at Laguna Seca.

2007 Mazda CX-7
Body style 5-pass, 4-door SUV
Drivetrain layout Front engine, AWD
Engine type Turbocharged I-4, all aluminum
Displacement, ci/L 138/2.3
Valve gear DOHC, 4 valves/cyl
SAE horsepower, hp @ rpm 244 @ 5000
SAE torque, lb-ft @ rpm 258 @ 2500
Transmission 6-speed auto
Wheelbase, in 108.3
Length, in 184.0
Width, in 73.7
Height, in 64.8
Curb weight, lb 3869
Weight distribution, f/r, % 59/41
0-60 mph, sec 7.8
Quarter mile, sec @ mph 15.9 @ 85.8
Braking, 60-0 mph, ft 115
Speed through 600-foot slalom, mph 62.5
EPA fuel economy, city/hwy 18/24
Base price $24,310
Price as tested $32,565

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