THE PROS & CONS
- WHAT’S BEST: Outstanding high-quality and comfy interior; stylish exterior; excellent performance with probably class-leading fuel consumption in a segment not generally known for such.
- WHAT’S WORST: Centre console touch screens; lack of Android Auto or Apple CarPlay capability; innovative engineering may scare some people off ...
- WHAT’S INTERESTING: ... but not me. The new engine is the most interesting technical innovation we’ve seen in decades.
MALIBU, Calif.-If there’s an automotive engineers’ heaven, Per Gillbrand is up there smiling.
The SAAB engineer who went aloft in November 2016 once said that eventually, all automotive engines would be two-litre turbos. He lived long enough to see that more-or-less come true.
And now another idea he championed has made it to production — a variable compression ratio engine.
It is a feature in the 2019 Infiniti QX50 SUV which goes on sale in June. Canadian pricing is expected to be announced Monday. Judging from U.S. pricing, which has been announced, I’m guessing it will start around $43,000.
Now, on the technical side: the compression ratio in an engine is the volume of the cylinder when the piston is at the lowest point of its travel, divided by the volume at its high point.
Gasoline engines generally run at ratios in the 8.0:1 to 12.0:1 range, with Formula One engines reaching the upper teens; the higher the number, the more power the engine can produce, and the more efficient it will be.
So, why doesn’t everyone use high compression ratios, as Mazda has done with their SKYACTIV engines? Good question.
One problem with high compression ratio engines is that the air-fuel mixture will ignite by itself due to the heat inside the cylinder, without waiting for a properly timed spark from the plug. This can cause engine-destroying detonation.
Nissan has figured out a way to make their new VC-T (Variable Compression-Turbo) engine work with, well, a variable compression ratio, using articulated connecting rods whose operation you’d have to see to believe. I’ve seen it, and I still don’t quite believe it …
Nissan’s solution operates the engine at a higher compression ratio at low loads to increase fuel efficiency, then when more power is needed, it reduces the compression ratio and cranks up the turbo. It can run a ratio anywhere from 8.0:1 to 14.0:1, depending on conditions.
Nissan claims it produces roughly the same performance as the 3.7-litre V6 in the previous-generation QX50, but much more efficiently. Actually, peak horsepower is down to 268 at 5,600 r.p.m. from 325 at 7,000 r.p.m. in the previous V6. But who ever drives at 7,000 r.p.m.?
The key is torque, which is what actually accelerates a car. It’s up from 267 to 280 pound-feet. Vastly more important, the torque peaks at 1,600 r.p.m. and stays at that level until 4,800 r.p.m., meaning the accelerative force is there when you most need it, such as starting from rest, or passing. The former engine’s torque peaked at a lofty 5,200 r.p.m.
Infiniti promises fuel consumption will be somewhere around 30 per cent better. Transport Canada consumption ratings are 10.0 city, 7.8 highway, which are certainly better than the 13.7/9.8 of the outgoing model, but just in the ballpark of current competitive models. My guess is that the real-world numbers will show a larger delta. Better performance, on less fuel? That, my friends, is progress.
So, why doesn’t everybody use this variable displacement trick? As noted above, many have tried. Some experiments date back almost a century. SAAB’s never saw production. A Mercedes-Benz engineer I spoke with recently said they were looking at this concept over a decade ago, but decided it was too complex to be worth the effort. Nissan says they have done all the durability testing on it.
Still, there are those who will worry about any new technology in the longer term. Fine; buy something else. Time alone will tell.
Meanwhile, it’s an interesting concept that makes the vehicle quick, but with far less impact on our environment, and who would contradict that objective?
The QX50 is all-new, running on a new platform that is exclusive to Infiniti. It’s a compact SUV/crossover, and it shines in a couple of areas.
First, it is handsome, outside and especially in. The interior looks and feels much more expensive than it is. It is beautifully finished, with high-quality materials seemingly well screwed together. This is where you spend all your time in a car, so why not optimize here? Seemingly more room inside than in most of its ilk, too. The rear seat seems particularly commodious for its class. One major concern, however, is the touchscreen dashboard. It’s a two-screen setup, but the two screens seem to have come from different decades. Others, notably Audi, do the two-screen thing much better. Also, the lack of Android Auto and Apple Car Play capability in the QX50 seems odd in a brand-new car.
Apparently, Nissan does not have a transmission that will fit in a transverse-engined car of this size other than its Continuously Variable (CVT) unit. I must say, I don’t have the big hate on for these things that most of my colleagues do. The point of any transmission is to keep the engine in its most efficient rev range as long as possible, and that’s what this one does. The car is quick, a stab of the loud pedal engages the turbo seamlessly, and acceleration is strong, with very little apparent turbo lag. Who’s got a problem with that? It has a nice gravelly sound when pressed, too, but is otherwise suitably subdued.
As before, QX50 will be offered in the U.S. with either front-wheel or full-time four wheel drive, but we will only get the latter back home.
Nissan’s power steering has also come in for its (largely fair, again I must say) share of criticism for its utter lack of feel. Now, perhaps shoppers in this category don’t care or wouldn’t notice such a thing. But I’ve also never heard anyone complain that a car’s steering felt too good. They have improved it in this car, and I doubt anyone attracted to this sort of vehicle will beef about it. Nor is anyone likely to complain about ride quality, which is fine.
I always applaud carmakers who are brave enough to try something new. In a market segment that is huge, growing, and, frankly, not generally full of innovation-oriented customers, this involves a fair amount of risk for Nissan. You might have thought they’d try this new engine technology out on a lower-volume sports car or some such.
But it is here, and it brings new levels of performance combined with low fuel consumption, an attribute for which this segment is often rightly criticized.
And even if you don’t care about the mechanicals, the interior is a lovely place to be.
The Infiniti QX50 is definitely worth a look.
2019 Infiniti QX50
BODY STYLE: 4 doors, 5 passengers, compact SUV.
DRIVE METHOD: Full-time four-wheel drive. Premium unleaded fuel.
PRICE: $43,000 (est.).
ENGINE: 2.0-inline, four-cylinder, double-overhead camshafts, 4 valves per cylinder, variable valve timing, variable displacement, turbocharged.
POWER/TORQUE, horsepower / lb-ft: 268 @ 5,600 r.p.m. / 280 @ 1,600-4,800 r.p.m.
FUEL CONSUMPTION, Transport Canada City/Highway, l/100 km: City: 10.0, highway 7.8
Follow Wheels.ca on