2019 Infiniti QX50 First Drive Review | A high-tech engine flies under the radar
Thu, Feb 1 2018
Even as manufacturers rush headlong into electrification and autonomous driving, revolutionary internal-combustion engine technologies are still being developed. Consider the Mazda Skyactiv-X Spark Controlled Combustion Ignition process, for example. But Infiniti's VC-Turbo four-cylinder engine, which makes its debut in the 2019 QX50, is truly a work of engineering fortitude. The engine realizes the long-held ambition among engine manufacturers to create a way to alter the compression ratio on the fly, a boon to both power and fuel efficiency. It's a brilliant bit of science that's, unfortunately, still in search of the right car.
Don't get us wrong, the QX50 is perfectly competent — it's an exceedingly quiet and comfortable cruiser. However, it's no longer the driver-pleasing machine its predecessor was. That car, originally known as the EX35, was built atop Nissan's sporty FM platform, a front-midship, rear-wheel-drive layout putting the engine aft of the front axle line and giving the vehicle the athletic driving dynamics of a sport sedan. In fact, it was basically a G37 hatchback, and it was sold as the Skyline Crossover in Japan. A shortened FM chassis underpinned the 370Z, to put a finer point on it.
For those more concerned with comfort than corners, the 2019 QX50 might actually be a more useful. It rides atop an all-new front-wheel-drive chassis, which means it's able to add more space for both passengers and cargo. It trades a heap of the old QX50's sportiness for comfort and packaging efficiency. If that sounds good to you, perhaps the new QX50 is the right crossover. You might also want to skip this next bit about the wondrous VC-Turbo engine — suffice it to say it's efficient, quiet and powerful. But engine nerds? Read on.
At the heart of the 2019 QX50 is the world's first production variable compression engine, whose basic concept "was sketched 20 years ago," said Nissan's chief powertrain engineer, Shinichi Kiga. "It took us that long to get the math right." Ostensibly a turbocharged 2.0-liter four-cylinder, its party trick is the fact that the compression ratio can vary anywhere from 8:1 to 14:1, mechanically.
That essentially gives the VC-Turbo an infinitely variable combustion chamber size, which can be optimized for power or fuel economy. The engine can operate at low compression ratios ideal for a turbo-assisted burst of power, but switch without interruption to a high compression ratio for maximum efficiency without the threat of predetonation knocking. In a traditional engine with a fixed compression ratio, it's a compromise between the two.
The result is 268 horsepower at 5,600 rpm, which is lower than the outgoing 3.7-liter V6's 325 hp at 7,000 rpm, but peak power comes earlier. More to the point, the VC-Turbo generates 280 lb-ft of torque at a mere 1,600 rpm, besting the V6's 267 lb-ft at 5,200 rpm. That's a lot more usable grunt, even as it sips 35 percent less fuel (27 miles per gallon versus the V6's 20 mpg).
The key to the VC-Turbo is a novel piece of engineering called the multilink, which Kiga, an old-school motorhead, carried around with him during our entire interview session. Unassuming in both name and appearance, the metal rhombus links the conventional piston connecting rod to the crankshaft to a lower rod attached to an actuator arm. To vary the compression ratio, a harmonic drive rotates the arm, which in turn changes the angle of the multilink, which shortens or lengthens the distance the piston travels. It's pretty hard to visualize, so hopefully this video helps:
This content is hosted by a third party. To view it, please update your privacy preferences. Manage Settings.
At first glance, it appears that the variable compression system adds complexity and mass to the engine, but according to senior manager Chris Day, "It doesn't add as much weight as you would think." That's because the multilink eliminates the need for other parts, such as counterbalance shafts.
"The multilink reduces the angle of the connecting rod, which reduces side-to-side motion of the pistons," Day explained. "Because the piston motion is closer to vertical, you don't need the counterbalance shafts." An external "torque rod," a fancy name for an active motor mount, also helps the VC-Turbo maintain smoothness.
Automakers have been working on variable compression ratios since the early days of the internal-combustion engine. Saab, Volvo and Peugeot as well as Nissan experimented with mechanical versions. So why is it that Nissan was the first to bring it to market?
"Computer processors haven't been fast enough until recently," Day explained.
"The multilink needed very high manufacturing tolerances," Kiga added, pulling out a socket wrench to loosen the bolts holding together the two halves of his multilink. "These bolts are 30 percent stronger than those of regular connecting rods. Aerospace grade," he pointed out, holding them in his hand.
"The VC-Turbo is the first automotive application for such hardware." Then he held the multilink up as if it were moving down an assembly line. "We had to develop a new manufacturing technique, since they must be torqued onto the crankshaft simultaneously from opposite sides."
Nissan says it owns more than 300 patents surrounding the VC-Turbo, including a series of "ring" patents designed to prevent other companies from even getting close to duplicating the technology. The timing seems odd, however, especially considering that Infiniti made a big announcement at the Detroit Auto Show that it would electrify all its cars by 2021. The company insists that VC-Turbo is a bridge to that, and that there's a method to its madness, but it smells of a retcon.
When asked whether the variable compression technology could be applied to V-configuration engines that Nissan is so fond of, Kiga simply laughed. "It's too complex," he chuckled, "But any inline configuration is possible." Then he indicated that the VC-Turbo would still have a home, even under an electrified regime. "You could cut off a cylinder for use as part of a hybrid system," he suggested. Then he added slyly, "NISMO is also interested in the technology."
It almost seems a pity, then, that this amazing technology will go completely unnoticed by its earliest adopters. Sure, that's kind of the point, as Infiniti has made every effort to integrate the VC-Turbo seamlessly into the QX50. There's no hint of the compression ratio changing, just a torquey purr when you mash the accelerator. North of 4,500 rpm, it even mimics the croon of a high-performance four-banger, not unlike a well-tuned Honda mill from the 1990s. In fact, the only clue to something special under the hood is a digital meter in the instrument pod reducing two decades of development to a marketing-friendly Power-versus-Eco mode display.
Beyond the engine, the QX50 offers little of interest to the motoring aficionado. Its overboosted steer-by-wire system is painfully light. Give the wheel a hearty flick, and watch it spin as if you're competing for a dinette set on "The Price is Right's" Showcase Showdown. Even in Sport mode, it offers little in feedback, just a vague veer in the general direction you've indicated.
Matched with a softly sprung suspension, the driving experience is more of a wafting experience. In cornering, you can feel its mass shifting awkwardly as it exhibits an overall reluctance to hustle. Where the chassis shines is in its ability to absorb surface irregularities, cushioning occupants from even the slightest on-road protuberances. It's quieter than a cocoon too, a combo that's sure to put any little ones to sleep, if not the driver.
It's probably a good thing, then, that the QX50 is the first Infiniti to come with Nissan's ProPilot Assist suite of safety features and assisted driving functions — a finalist for our Tech of the Year award this year, incidentally. It includes forward emergency braking, beeps and haptics to warn you of lane departure, and backup collision intervention.
With the push of the ProPilot button, the QX50 can lock onto the vehicle in front, maintaining a set distance and keeping itself centered in the lane. It's like you're being pulled along by a tractor beam, and seems to work as long as there are lines in the road. However, the fact that you have to hover your palms on the wheel with a semi-loose grip — the system looks for slight torque readings as the steering wheel turns beneath your fingers and blares an alarm if you lift your hands completely — is more tiring than actually steering the car yourself. In stop-and-go traffic, though, the follow function lets you keep your feet off the pedals.
What the QX50 is, then, is exceedingly comfortable for passengers. Infiniti says it's the finest interior it has ever created, and we can't find reason to disagree. It's sumptuously appointed, with pliable leather surfaces and pleasant organic curves throughout. The optional 16-speaker Bose sound system offers a satisfying auditory experience, beautifully quilted seats cradle occupants pleasantly and seat cooling fans do their job very effectively. It's almost a ridiculous level of comfort, with surfaces comprised of cowhide, wood, brushed aluminum and at least two colors of suede.
Rear legroom increases to 38.7 inches, a jump of more than 3 inches from the previous QX50. The second row slides, too, so you can lounge back while enjoying the view out of a magnificent panoramic roof. Cargo capacity behind the second row expands from 18.6 cubic feet to 31.1 cubic feet (65.1 with the seats folded down). All this, despite the fact that the QX50 is 2 inches shorter overall than its predecessor.
It's so serene that the driver almost feels like an afterthought. It's surprisingly difficult to find a comfortable seating position, even though your humble author is the exact average male height of 5-foot-10. The steering wheel is hard. There's no Apple CarPlay or Android Auto integration, and the navigation map looks like a VGA version of "Sim City."
We're sure you're sick of hearing us harp on CVTs by now, so we'll just say that if Nissan insists on using them, the QX50's eight-step unit isn't completely terrible. What is terrible, though, is the gear selector, which springs back to its default position no matter whether you're in Drive, Reverse, Neutral or Park. That uncertainty creates an absolute requirement to double-check your mode before moving your feet off the pedals – frustrating at a minimum.
Exterior styling is of course subjective, but the QX50 is a very good-looking crossover. Its sculpted curves hide brilliantly what is essentially a two-box shape. Infiniti's trademark double-arch grille is distinctive and integrates cleanly into a well-sculpted hood and complex curves along its flanks. The overall look is cohesive rather than forced ( ahem, Lexus) or plain ( cough, Audi Q5).
A base QX50 Pure starts at $36,550, which includes dual-zone climate control, a power liftgate and forward emergency braking. The next level up, Luxe, adds the panoramic roof, fog lamps and roof rails, and rings in at $39,400. Our tester, the Essential, begins at $43,350 and includes navigation, remote start, leather seats and Infiniti's around-view monitor. At any level, AWD is an $1,800 option. If you check every box, it's possible to option out an Essential to more than $60,000 before the $995 destination charge.
The Infiniti QX50 bests rivals such as the Audi Q5, Lexus RX, BMW X3 and Mercedes-Benz GLC when it comes to cargo room, rear legroom and fuel economy. It beats all except the Lexus in power and torque. It has a lot going for it — excellent design both inside and out, comfortable ride and that newfangled engine — if you ignore our gripes about the drive. You probably should, too, because according to Infiniti's own market research, qualities such as handling rank pretty low on the list of priorities for luxury crossover buyers. In fact, one could argue that it's much better at its job as a midsize luxury crossover than its predecessor. It's a great car to be driven in, but not to drive.
Compare the 2019 Infiniti QX50 with its rivals using the Autoblog Compare Cars tool.
Infiniti has proven it can build a truly sporty crossover when it wants to. In another life, the VC-Turbo might even be the ideal engine for such a car. It probably goes too far to say that the engine is wasted on the QX50. After all, what better way to test its real-world mettle than with buyers looking purely for a lazy, hassle-free driving experience? Once the technology is proven, then perhaps the investment will pay off as it percolates to other Nissans. New Z, anyone?
Related Video:
Featured Gallery 2019 Infiniti QX50
View 20 Photos
- Infiniti
- First Drives
- Technology
- Emerging Technologies
- Crossover
- SUV
- Luxury
- infiniti qx50
Autoblog accepts vehicle loans from auto manufacturers with a tank of gas and sometimes insurance for the purpose of evaluation and editorial content. Like most of the auto news industry, we also sometimes accept travel, lodging and event access for vehicle drive and news coverage opportunities. Our opinions and criticism remain our own — we do not accept sponsored editorial.
By Ben Hsu
See also: How Lexus, Infiniti plan to win back luxury buyers from Germans, Tesla, Infiniti EV coming in 2021, Infiniti Q Inspiration Concept | 2018 NAIAS.