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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.

2019 Infiniti QX50 First Drive Review | A high-tech engine flies under the radar

Update: An Infiniti representative reached out after this review was published and noted that the "Park with Easy Steering" function of the Direct Adaptive Steering system was erroneously left engaged. Infiniti says this feature "reduces feel considerably at low speeds to aid in parking", and that the Easy Steering function will be disabled by default in customer cars unless the customer chooses to engage it. This seems to explain the issues our reviewer had with low-speed steering feel, although we've had other problematic experiences with Direct Adaptive Steering in a broader sense – not to mention the fact that the drive-by-wire system has been recalled several times to fix various issues, and also recalibrated in response to criticism. We hope to get another QX50 soon, and if so we'll compare the low-speed steering response with Easy Steering on and off. Even as manufacturers rush headlong into electrification and autonomous driving, revolutionary internal-combustion engine technologies are still being developed. Consider the Mazda Skyactiv-X Spark Controlled Combustion Ignition process, for example. But Infiniti's VC-Turbo four-cylinder engine, which makes its debut in the 2019 QX50, is truly a work of engineering fortitude. The engine realizes the long-held ambition among engine manufacturers to create a way to alter the compression ratio on the fly, a boon to both power and fuel efficiency. It's a brilliant bit of science that's, unfortunately, still in search of the right car. Don't get us wrong, the QX50 is perfectly competent — it's an exceedingly quiet and comfortable cruiser. However, it's no longer the driver-pleasing machine its predecessor was. That car, originally known as the EX35, was built atop Nissan's sporty FM platform, a front-midship, rear-wheel-drive layout putting the engine aft of the front axle line and giving the vehicle the athletic driving dynamics of a sport sedan. In fact, it was basically a G37 hatchback, and it was sold as the Skyline Crossover in Japan. A shortened FM chassis underpinned the 370Z, to put a finer point on it. For those more concerned with comfort than corners, the 2019 QX50 might actually be a more useful. It rides atop an all-new front-wheel-drive chassis, which means it's able to add more space for both passengers and cargo. It trades a heap of the old QX50's sportiness for comfort and packaging efficiency. If that sounds good to you, perhaps the new QX50 is the right crossover.

Genesis G70 vs sport sedan rivals: How it compares on paper

We got our first look at the Genesis G70 sport sedan today. We think it looks good, with enough ties to its fellow Genesises (Geneses?) to further establish the brand and just enough distinction to help it stand out from the crowd. But ah yes, the crowd. Although Genesis didn't release the G70's full spec sheet, it revealed just enough for us to start sizing it up to its future competition. There are certainly others with which to compare (Lexus IS, Cadillac ATS, Alfa Romeo Giulia, Jaguar XE just to name a few), but we decided to take a look at the best sellers and most competitive luxury sport sedans. (And hey, if you like this, we can always do a follow up) So, here we have the Genesis G70 vs BMW 3 Series vs Audi A4 / S4 vs Mercedes-Benz C-Class vs Infiniti Q50. Nothing like a good chart to dig your teeth into on a Friday. Note that we only compared those models that line up with the G70. So, we left out the BMW 320i and Audi A4 Ultra entry level models as well as the Q50 3.0t mid-grade model that's considerably cheaper than the German performance upgrade models we listed. All 0-60 figures are rough estimates based on several sources, models/drivetrains and OEM figures. Related Video: Featured Gallery Genesis G70 vs other sport sedans View 15 Photos Audi BMW Genesis Infiniti Mercedes-Benz Luxury Sedan consumer infiniti q50 audi s4 genesis g70 mercedes-benz c-class bmw 330i bmw 340i