2011 Infiniti M56S Full Test

We want to love this car, we honestly do. The 2011 Infiniti M56S has so much to offer. It has a direct-injected 420-horsepower V8, a four-mode seven-speed automatic transmission, active rear steering and a list of standard comfort and infotainment systems that rivals that of any luxury sedan from Germany. Nevertheless, we're not entirely smitten with the M56 — not just yet, anyway.

Based on Nissan's ubiquitous FM platform, the 2011 Infiniti M56 is an executive-size sedan very much in the same mold as the BMW 550i. This second-generation M has grown a bit in width and adopted new bodywork derived from the Infiniti Essence showcar. And with the new direct-injected 5.6-liter V8, there's nearly 100 hp more, so the rest of the car has been tuned up to meet this demanding standard.

As it is, the M56S is poised to contend with the heavy-hitting participants from Inside Line's last V8 Sport Sedan comparison: the BMW 550i, Jaguar XF Premium and Mercedes-Benz E550.

Tough crowd. Now where are the sticky bits?

Revolution, Evolution
The 2003 Infiniti G35 seemed to come out of the ether and it brimmed with fresh thinking, raw talent and optimism. Yet, as good as it was then, the G has evolved, built on its strengths, and finally when the second-generation 2007 Infiniti G35 Sport appeared, this car was able to nudge aside the mighty BMW 335i from the top spot in a comparison test of sport sedans.

The 2011 Infiniti M56S hopes to do much the same thing. We'd certainly say that this car has at last found its own sense of style, especially in the interior. Both Nissan and Infiniti have gained a great deal of ground in recent years with successively upscale interiors, and both the look and function of the M56 takes this trend to its inevitable pinnacle. Elsewhere around the car you find all kinds of innovative technology, and this blend of elegant styling with modern technology is an avenue Infiniti should continue to pursue for all its vehicles.

But the blend isn't quite right yet, as if the technology still needs a little evolution to match the sophistication and style of the car's identity.

Motoring
We learned from our first drive of a preproduction 2011 Infiniti M56 that the engineers were paying particular attention to throttle and transmission calibration. We'd say this test car is about 8/10ths of the way there in this regard. It's not an easy task, as even BMW seems to be struggling with the throttle mapping of its recent crop of turbocharged V8s.

We recorded this performance on the fifth of seven stops, so brake fade clearly is not an issue.

There are four modes that can be selected with a rotary dial on the center console: Snow, Economy, Normal and Sport. Yet in Normal and Sport (the two most important and most oft-used modes) throttle tip-in feels unnatural to us. From a stop, too much damping of the throttle action leads suddenly to an abrupt throttle opening and a noticeable surge in acceleration. Sensitivity to part-throttle inputs also made it difficult to maintain a slow, steady speed in bumper-to-bumper traffic.

At the test track, we had difficulty achieving a crisp launch. Wheelspin was virtually impossible, even with both stability and traction control disabled. How could that happen with a peak of 417 pound-feet of torque at 4,400 rpm, if not for the throttle calibration?

Too Many Gears?
The transmission also befuddled us. We're big fans of the matched-rev downshift, because it delivers quicker shifts without unsettling the balance of the chassis. In Normal or Sport mode, however, the M56's transmission seemed to hunt for gears unnecessarily, especially on the freeway while you're gently rolling into and out of the throttle to find a pace with traffic.

Also, when you change the transmission's shift mode into manual, the transmission doesn't default back into Drive if the manual shift action goes unused for a time. Some people like this, but we don't. You must use the right-hand paddle to upshift beyond 7th gear to get Drive again, or you have to snick the shift lever on the center console to manual mode and back.

These criticisms aside, the 2011 Infiniti M56's transmission and throttle worked very well in concert when we put the spurs to this sport sedan in the mountains. The M56 Sport holds gears intelligently, applies power predictably, upshifts smoothly and, generally speaking, kicks some alpine ass. This car also turns into corners with an especially crisp response that must be due in part to the rear-steering axle that's part of this car's comprehensive Sport package ($3,650), which includes a tauter suspension, upgraded brakes and 245/40R20 Bridgestone Potenza RE50A tires.

Yeah? How Did It Perform?
On the relatively smooth and grippy surface of our test track, the Infiniti M56 put said Sport package to good use. We clocked 5.2 seconds to 60 mph from a standstill (4.9 seconds with a 1-foot rollout like at a drag strip), while the car passed through the quarter-mile in 13.4 seconds at 106 mph. The only cars to exceed such performance carry the very expensive high-performance hardware of a dedicated specialty division, like Audi's R-line, BMW's M, Cadillac's V or Mercedes-Benz's AMG.

Around the skid pad, the M56 Sport clings to the pavement with 0.88g of lateral force. Through the slalom, the big sedan dances between the cones at an average speed of 66.8 mph — again at or near the top of the class. While you can't necessarily detect the rear-steer working, it does feel as if the rear of the car is helping to rotate it past each cone. Maybe that's how it's supposed to feel.

Meanwhile the R-spec brake pads (a dealer-installed option, so remember to ask for it) within the upgraded brakes from the Sport package (four-piston front calipers and two-piston rears) bring this 4,084-pound car to a halt from 60 mph in just 112 feet. And we recorded this performance on the fifth of seven stops, so brake fade clearly is not an issue (and we didn't even smell anything from the brake pads, either).

From all these performances, we'd safely predict that this 2011 Infiniti M56 Sport has the hardware and tuning to outperform any sport sedan with an as-tested price of $64,435. Incidentally, this price also includes a $2,000 Sport Touring package and the R-Spec high-friction brake pads ($370).

Back to Reality
We suspect the M56's throttle and transmission mapping will be addressed before long, so were it not for the roaring 20-inch tires and unyielding suspension, we'd consider this an excellent all-around sport sedan. Problem is, the world ain't so perfect out there.

We were utterly in awe of the ability of the M56 to transmit both aural and textural information about nearly every patch of pavement it covered. From grooved concrete and worn asphalt to tarmac and macadam, and over expansion joints or cupped pavement, the M56 issued different and distinct reports from the tires and suspension for each. We could hear the surfaces and we could feel the surfaces, and we also wished we could simply press a button to quell the sensations a bit.

In many ways, this clever, handsome and rapid 2011 Infiniti M56 is reminiscent of another highly regarded though similarly stiff-legged sport sedan, the 2010 Jaguar XF Premium with its rough-riding 20-inch wheels and tires. With a little fine-tuning, we're confident the 2011 M56 Sport will rise to the top of any sport sedan comparison of style, technology, speed and handling.

We once encountered a ribbon of freshly paved asphalt, and here the M56 Sport was as placid as a lake at 5 a.m. It made us realize that this Infiniti would deliver unwavering excellence if only a paving crew had been hired to work a day ahead of the M56S wherever it went.

The manufacturer provided Edmunds this vehicle for the purposes of evaluation.