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Infiniti's new VC-T changes the rules of small turbocharged engines

The upcoming Infiniti QX50 crossover does not get our pulse racing, no matter how shapely the QX Sport Inspiration concept that previews it may be. No midsize SUV does, to be fair. But it has something special under the hood – the world's first production variable-compression-ratio engine. That means the QX50's 2.0-liter turbo four, which makes 268 horsepower and 288 pound-feet of torque, will have up to 27 percent better fuel economy. Here's how it works. The trend of moving to smaller, turbocharged engines carries with it one big falsehood. Under low load when the turbo isn't needed, these engines are less efficient than an equivalent engine without a turbo because of the low compression ratio the turbo requires. That is, if you never need the extra power, you're wasting fuel. Turbocharged (and supercharged) engines use a lower compression ratio to prevent detonation. When you force extra air in a cylinder and mix it with fuel, it's more likely to prematurely go boom. Lowering the compression ratio prevents this problem, but it's less efficient. Infiniti's VC-T promises the best of both worlds, with a compression ratio that ranges from 8.0:1 for high-power turbo needs to a 14.0:1 ratio for fuel-sipping efficiency. At its heart the VC-T engine is a simple idea, but it's complicated to explain. Consider yourself warned. The photo below from Infiniti serves as a good visual overview. For the truly nerdy, this patent application covers the mechanical concept. Instead of having the pistons connected to the crankshaft, Infiniti's engine has a pivot arm with a connection on each end. One end connects to the piston, the other connects to a second lower shaft, which is controlled by an actuator arm. At any given time the engine's pistons move up and down according to the lobes on the crankshaft. But the actuator arm can change the angle of the pivot arm up and down. That is, the pistons still move in the same motion with the same stroke, but phase the entire stroke up or down. Move the pivot up and there's less room at the top, which means a higher compression ratio. Move the pivot down and the compression ratio goes down, too. As an added bonus, the lower shaft eliminates the need for counter-rotating balance shafts. Infiniti says this system works constantly and can vary the compression ratio to any number between 8:1 and 14:1. It also uses electronic variable valve timing on the intake valves to switch into Atkinson-cycle combustion for greater efficiency.

Infiniti QX50 concept previews production model with variable compression engine

Infiniti revealed its QX50 concept ahead of its official debut at the Detroit Auto Show, and despite the concept title, it looks pretty much production-ready. The company calls the crossover "an evolution of the QX Sport Inspiration" concept, and that's certainly accurate. Side-by-side, the QX Sport, which we already figured was previewing a new QX50, and this concept look nearly identical. The primary changes are bumpers and side skirts that feature the obligatory aluminum trim to look like skid plates, and simple black plastic fender flares. The overall result is a crossover that is pleasant but not exactly exciting that bridges the gap between the small and swoopy QX30 and the large QX60. The plain wrapper hides plenty of impressive technology, though. Under the hood is Infiniti's fascinating variable-compression turbocharged engine. It's a 2.0-liter inline-four that can alter its compression ratio to anything between 8:1 and 14:1. The result is an engine that produces an estimated 268 horsepower and 288 lb-ft of torque. Infiniti says the four-cylinder should be about 27-percent more efficient than a comparable V6. In addition, while the company says this concept just shows a potential application of the engine, it's safe to say that you can expect it in the production model. With the new engine, the QX50 will also switch from to a front-drive platform, with all-wheel drive definitely an option or possibly standard; the current QX50 is based on the aging rear-drive FM platform used on other Infinitis and the Nissan 370Z. The other new tech buried in the QX50 concept's body is what Infiniti calls the "first production-ready incarnation" of its ProPilot semi-autonomous technology. The company doesn't go into great detail about what it will do except for handling stop-and-go highway traffic. We would hazard a guess that the system is functionally the same as the one introduced on the Nissan Serena minivan in Japan. It goes by the same name and can handle stop-and-go traffic, as well as maintain the car's lane position and distance behind other cars. It's another safe bet that we'll see this system in the production model. Other details about the car, such as the interior, have yet to be revealed. We're sure to see it as well as other information about the QX50's technology when it makes its full debut in Detroit. Related Video:

2014 Infiniti Q50 configurator comes alive

The G37-replacing 2014 Infiniti Q50 sport sedan launches in the not-too-distant future, and for those curious about how pricing and packages will shake out, the car's official online configurator has been launched. Here, you can build the Q50 or Q50 Hybrid of your dreams, with the cost of entry starting at $36,450 (plus $905 for destination).
Selecting the hybrid model adds $7,250 to that bottom line - mostly because the gasoline-electric version is only available in the Premium trim and higher, while the gas-only Q50 comes in a base guise. Adding all-wheel drive, which Infiniti has made available with either engine and on all trims, will set you back $1,800.
There are a number of packages available across the trims, including a $1,400 navigation pack that includes a spare tire kit, a deluxe touring pack that costs $4,700 (and includes the navigation goodies), and the upper-crust $7,900 technology package which gets you, well, everything. Put that all together on a Venetian Ruby Q50 RWD Sport like we did, and you're looking at $51,755 when destination has been added.