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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.

2016 Infiniti Q50 Red Sport 400 First Drive

When the original Infiniti Q50 arrived to replace the long-lived G Sedan, our reaction was lukewarm. It lacked poise, refinement, and efficiency, and we hated the Direct Adaptive Steer system. We originally thought of this steer-by-wire system as, "technology for the sake thereof." Infiniti is hoping to address these shortcomings with the 2016 Q50. It gets a new and far improved version of DAS, and a 3.0-liter, twin-turbo V6 sits atop a diversified powertrain family. And at the top of the ladder sits this: the Q50 Red Sport 400. The Red Sport's all-aluminum 3.0-liter V6 pumps out 400 horsepower and 350 pound-feet of torque, the latter of which can be called upon between 1,600 and 5,200 rpm. That low-end thrust is what's most evident out on the road – everything from standing starts to freeway passes are effortless. It's actually kind of ferocious – the tachometer needle climbs relentlessly, and the engine feels strong and purposeful all the way up to its 7,000-rpm redline. It's a refined and smooth powerplant, too, which is a tremendous improvement over the old 3.7-liter V6. The sensations the revised Direct Adaptive Steer system delivers are comparable to the average, modern, electric power-assisted setup. The bigger accomplishment is Infiniti's second-generation Direct Adaptive Steering system. Owners can choose from three steering weights and three levels of responsiveness, but steering adjustments feel more incremental rather than dramatic, so you won't be jarred if you suddenly switch from an aggressive mode to a more comfortable setup. Computer wizardry still can't match natural feedback, but the sensations the revised Direct Adaptive Steer system delivers are comparable to the average, modern, electric power-assisted setup. Make no mistake, that's a huge improvement and it means DAS performs far better dynamically, especially when you ask for its most aggressive behavior. See the differences between the different modes in the video below. Even half-throttle situations in the standard drive mode required counter-steering. Direct Adaptive Steer feels perfectly fine during everyday driving. We spent about 75 percent of our time testing a DAS-equipped car, but hopped into a non-DAS model a the short, 20-mile drive back to our hotel. DAS felt more stable and easy to track down the road – it didn't require the constant, tiny steering inputs of the traditional system.

Final Recap: Days 2 and 3 notes, quotes, and takeaways from the US Grand Prix

The Texas grass no longer rustles with 2.4-liter V8 exhaust blown at 18,000 revs, the Texas dust is no longer raised by hard-compound Pirellis. We saw a lot and learned a lot while we were there as guests of Infiniti, and after our Day 1 and race recaps, here are the bits left over from our time spent with the carmaker and Red Bull Racing, including thoughts on a "wicked" race, Christian Horner's quest for a more level playing field, Infiniti "going longer and deeper," and why Mario Andretti should get a police escort at the beginning of a race but not a microphone at the end...