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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.

Renault-Nissan alliance to start autonomous EV testing

The Renault-Nissan alliance is joining the self-driving electric-vehicle party. The French-Japanese automaking collaboration, which has been selling electric vehicles to the masses since introducing the Nissan Leaf in 2010, said Monday that it will work with transportation-technology consultant Transdev on developing a fleet of self-driving EVs for testing purposes. The model of choice, though, won't be the Leaf, but instead will be the Renault Zoe. Details aren't abundant, but the group does say it will perform the field testing in the Paris area. Transdev's pedigree includes operating what it says is the world's first commercial driverless service at France's EDF campus. The company, which is majority-owned by Caisse des Depots, is no small potatoes, generating about $7 billion in revenue in 2015. Take a look at the alliance's statement here. The alliance has already been working with Microsoft on driving-technology advancements and has teamed up with Japan-based DeNA to hatch a driverless-vehicle initiative for commercial services. And in January, Nissan said its ProPilot features, which include increased self-driving capabilities, would be added to its Leaf EV "in the near future." Of course, other automakers have already jumped into the self-driving EV game. California-based EV maker Tesla has long been pushing its vehicle technology toward autonomy, and General Motors said in December that it would start field testing driverless Chevrolet Bolt EVs sometime this year. In the meantime, the Alliance is gearing up a changeover in leadership, as Carlos Ghosn said last week that he was stepping down as Nissan's CEO on April 1. Ghosn, long a champion of electric-vehicle technology, will be succeeded by Nissan co-CEO Hiroto Saikawa. Related Video: Featured Gallery Renault Zoe ZE 40 Yttrium Grey View 27 Photos News Source: Renault-Nissan Alliance Green Nissan Renault Autonomous Vehicles Electric alliance zoe

2018 Ford Expedition vs other big SUVs: How it compares on paper

With our Alex Kierstein rightly impressed in his first-drive review of the new 2018 Ford Expedition, we decided to dig a little deeper into the numbers, and we came up with the spreadsheet below to highlight how the new 2018 Expedition compares on paper to its main full-size SUV competitors: the 2018 Chevy Tahoe and Suburban (and therefore the 2018 GMC Yukon), 2018 Toyota Sequoia and 2018 Nissan Armada. We also threw in the new, even bigger 2018 Chevrolet Traverse since, as you'll see, its massive dimensions should put it on the radar for anyone who needs loads of passenger and cargo space but doesn't care as much about towing. A few notes about the chart above. First, the 6.2-liter V8 that's included with the new-for-2018 Tahoe RST trim level is the standard engine on the GMC Yukon Denali. You can apply most of the Tahoe's numbers to the entire Yukon and Yukon XL lineup. Second, though we highlighted categories where the Traverse led, we also highlighted the runner-up full-size SUV, since this was ultimately about that segment. Traverse numbers are broadly applicable to the new Buick Enclave. Related Video: Chevrolet Ford GMC Nissan Toyota SUV Comparison consumer ford expedition gmc yukon chevy traverse toyota sequoia nissan armada chevrolet tahoe ford expedition max