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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.

2013 Nissan Pathfinder: February 2013

I took the keys to our long-term 2013 Nissan Pathfinder from Editor-in-Chief Neff (who left me with an empty gas tank, for the record) directly following the Detroit Auto Show. That means that, by the time you all read this, I'll have been in possession of the Pathfinder for more time, and driven it more miles than any Autoblogger so far. I'd like to think that I've made good use of it... with one small exception.
For those of you that live outside of the Snow Belt and who may routinely ignore the Weather Channel out of cocky certainty - I'm looking at you, American Southwest - there's been some real weather in our part of the world this winter. A year ago, I'd basically packed up my shovel and my driveway salt by Valentine's Day; while the last quarter of 2012 and beginning of 2013 have seen back-wrenching piles of snow fall on and around my Michigan home. Good times, in other words, to test the all-weather capabilities of our all-wheel-drive Pathfinder.

2013 Nissan Pathfinder: May 2013

Despite the snow-capped photos you see here, our long-term Pathfinder has been the subject of some proper pre-summer lovin' here in metro Detroit (we're working on a new gallery). Now that the warm weather has hit Michigan, many of our staffers have eagerly grabbed the keys to our big, brown Nissan for road trips all over the place. And the Pathfinder has indeed proven itself to be quite the worthy long-distance hauler, as editors John Neff and Seyth Miersma have already experienced.
This time around, a couple of our colleagues from AOL Autos put hundreds of miles on our trusty Nissan. And while everyone agrees that the Pathfinder is a solid vehicle for the task of road tripping, there are a couple of specific pros and cons that have been mentioned on several occasions.