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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.

A beautiful conundrum | 2017 Infiniti Q60 First Drive

"OK, this should be fun." Hands are rubbed together excitedly. It's a rear-wheel-drive sport coupe painted candy apple red. It's sleek, slinky, and uniquely styled. It's from the same folks who, in the 2000s, finally showed that BMW could be matched in the whole sport sedan/coupe game. Oh, and it has 400 horsepower. Four-hundred! With a four. And yet the 2017 Infiniti Q60 underwhelms. What looks so good on paper instead is rather conflicted, stuck somewhere in no-man's land between the traditional expectations of a performance sport coupe and those of comfier, more luxurious cruisers that isolate and pamper their occupants. It's a serious effort with serious engineering and a clear desire to be innovative, but at least in the range-topping Red Sport model we tested, it fails to come together in a way that truly excites or indulges. A great coupe should do one or the other, and ideally both. To explain, let's start under the hood, where Infiniti's all-new "VR" series 3.0-liter twin-turbo V6 makes its second appearance after debuting in the Q60's four-door sibling, the Q50. In the Q60 Silver Sport model, it produces 300 horsepower and 295 pound-feet of torque courtesy a pair of turbochargers that create 8.7 psi of boost. In the Red Sport, the knob is turned up to 14.7 psi, resulting in the oh-so-salivatory magic number of 400 hp along with 350 lb-ft of torque. A device known as an optical turbo speed sensor, special to the Red Sport, manages and maintains that extra boost, while an electric motor fitted to the valve timing system serves to quell any loss in throttle response due to forced induction. The Red also gets a second water-cooled intercooler, which, in both models, is distinctive for its more compact size, shorter airflow path, and, according to Infiniti, a resulting reduction in turbo lag and more immediate engine response. It's certainly a clear improvement on the somewhat rough 3.7-liter "VQ" V6 it replaces, which increasingly felt and sounded a little out of place in a luxury car. The new VR30DDTT, as it's so eloquently named, is buttery smooth and indeed responsive, likely capable of convincing luxury-car owners used to naturally aspirated V6s that everything's business as usual. Honestly, its character is reminiscent of a silky Honda V6. In some respects, that's a great thing. In others, it's where the Q60 starts to fall flat.

Infiniti extends long-wheelbase Q50 L for the Chinese market

Want to sell your luxury sedan in China? You're going to need a long-wheelbase model. Not because the still-dominant Chinese government mandates it, or because the customers are taller, but because Chinese buyers tend to like being chauffeured around in the back of their luxury sedans instead of driving themselves, so the priority is on rear-seat space over driving dynamics.
We've seen the likes of Audi, BMW, Cadillac, Mercedes-Benz and Volvo all roll out long-wheelbase versions of their compact and midsize sedans specifically to cater to Chinese tastes. Even Infiniti - which now bases itself in Hong Kong - offers a long-wheelbase Q70 L not only in China but around the world, and has now bolstered its extended offerings with the reveal of the Q50 L, set to debut at the Chengdu Motor Show later this month.
Set to be produced locally for the local market, the Q50 L adds nearly two inches to the wheelbase of the Q50 to the benefit of rear-seat legroom. Power comes from Infiniti's 2.0-liter turbo four offering 208 horsepower and 236 pound-feet of torque, driving to the rear wheels through a seven-speed automatic transmission with drive-by-wire steering.