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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.

US-built Infiniti Q50 engines to go into Euro-only cars

Back in March, Infiniti announced that it would be adding a 2.0-liter, turbocharged four-cylinder to its Q50 line for European and Chinese buyers. Now, we know where that engine will be built.
Nissan's Decherd, TN facility will receive the $319-million investment, which will see a separate, dedicated line for the Infiniti engines. According to Automotive News, this is more than a line running alongside the Nissan operations - the Infiniti facility will sport its own unique architecture and interior lighting, in a bid to distinguish the premium line from its mass-market parent company.
The logistics of all this do seem, on the surface, quite screwy. Building a new engine on one continent for a car built on another that will eventually go on sale on a third doesn't seem too bright, although there is a catch here. The new engine will also find its way into the Mercedes-Benz C-Class, which will kick off production in Vance, AL later this year.

Alfa Romeo Giulia Quadrifoglio and Nissan 370Z 50th Anniversary | Autoblog Podcast #600

In this, the 600th episode of the Autoblog Podcast, Editor-in-Chief Greg Migliore is joined by Senior Editor, Green, John Beltz Snyder and Associate Editor Joel Stocksdale. They've been driving the Nissan 370Z 50th Anniversary edition, Alfa Romeo Quadrifoglio and Buick Enclave, and they're pretty excited about at least two of them. Then they talk about the Subaru Forester in their long-term garage. Finally, they spend a listener's money on a used car. Autoblog Podcast #600 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 Rundown 2020 Nissan 370Z 50th Anniversary 2019 Alfa Romeo Giulia Quadrifoglio 2020 Buick Enclave Long-term Subaru Forester Update Spend My Money Feedback Email – Podcast@Autoblog.com Review the show on iTunes Related Video: