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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.

Infiniti Q50 Eau Rouge portends seriously powerful future sports sedan

"If we built this car I would expect it to feature over 500 horsepower and 600 pound-feet of torque."
Eau Rouge is a notoriously difficult turn at Belgium's Spa-Francorchamps Circuit that is capable of striking fear into the hearts of the most hardened driver. Naming a car after something so terrifying, therefore, strikes us as a rather poor idea.

Infiniti Q50 steer-by-wire system took 10 years to develop [w/video]

Infiniti's Direct Adaptive Steering (DAS) is quite a novelty - the system employs no physical connection between the steering wheel and the front wheels under normal circumstances and instead relies on a computer, clutch and steering-angle actuator to guide vehicles down the road with input from the driver.
In our First Drive review of a 2014 Infiniti Q50 equipped with the system, we weren't overly impressed by the artificial feedback. But we can't help but be impressed with how long Infiniti spent on its development: a full 10 years, according to Autoline Daily in the video report below. A staggering 70 percent of the research and development time spent on DAS was devoted to getting the steering feel right, and unfortunately, our first impression suggests their results still leave something to be desired, as we found it lacked the sporty feeling a sport sedan should have.
The weight of DAS is comparable to that of a conventional steering system due to its complexity. For example, three ECUs are used in the first-generation DAS system to ensure there's never a loss of steering, but Infiniti is refining the technology and is working to simplify it to reduce weight. One day Infiniti hopes that only one ECU will be needed to control DAS. We just hope it doesn't take the Japanese automaker another ten years to get the steering feel right.