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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.

Auto News Recap For 5.13.16 | Autoblog Minute

Senior Editor Greg Migliore recaps the week in automotive news, including a look at Hyperloop One's desert propulsion test, Chrysler 300 rumors, and Nissan's purchase of Mitsubishi. Chrysler Mitsubishi Nissan Autoblog Minute Videos Original Video hyperloop

From Maseratis to rental cars | Autoblog Podcast #511

On this week's podcast, Mike Austin and David Gluckman are in a huddle room (again), because the studio was already taken (again). We talk about the all-wheel-drive Dodge Challenger GT (again), as well as the Jeep Wrangler, Maserati Levante, Miata RF (again), and then David waxes poetic on mediocre rental cars (or similar). The episode wraps up with the traditional doling out of Spend My Money buying advice, with some input from an S2000 owner on advice discussed last time. The rundown is below. Remember, if you have a car-related question you'd like us to answer or you want buying advice of your very own, send a message or a voice memo to podcast at autoblog dot com. (If you record audio of a question with your phone and get it to us, you could hear your very own voice on the podcast. Neat, right?) And if you have other questions or comments, please send those too. Autoblog Podcast #511 Topics and stories we mention Dodge Challenger GT Jeep Wrangler Unlimited Maserati Levante Mazda MX-5 Miata RF Used cars! Rundown Intro - 00:00 What we're driving - 06:11 Spend My Money - 32:45 Total Duration: 55:30 Get The Podcast iTunes – Subscribe to the Autoblog Podcast in iTunes RSS – Add the Autoblog Podcast feed to your RSS aggregator MP3 – Download the MP3 directly Feedback Email – Podcast at Autoblog dot com Review the show on iTunes Podcasts Dodge Jeep Maserati Mazda Nissan mazda mx-5 rf dodge challenger gt