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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.

2017 Tokyo Motor Show | Mega Gallery

The 2017 Tokyo Motor Show has been a big and busy one. It's also had machinery ranging from beautiful to bizarre. But there's been something for everyone. Companies such as Honda and Subaru brought performance oriented vehicles, Toyota showcased a wide array of funky and practical concepts, and Yamaha even broke away from motorcycles to do another car concept. You can check all of these vehicles out, and more in the galleries below. 2018 Honda Gold Wing: View 5 Photos Honda Neo Sports Cafe Concept: View 5 Photos Honda Riding Assist-e Concept: View 7 Photos Honda Sports EV Concept: View 5 Photos Honda Super Cub: View 3 Photos Isuzu FD-SI and Elf EV: View 9 Photos Lexus LS+ Concept: View 18 Photos Mazda Kai Concept: View 18 Photos Mazda Vision Coupe Concept: View 15 Photos Mitsubishi e-Evolution Concept: View 8 Photos Nissan IMx Concept: View 29 Photos Nissan Leaf Nismo Concept: View 8 Photos Subaru Viziv Performance Concept: View 12 Photos Toyota Century and Crown: View 7 Photos Toyota Concept-i Series: View 16 Photos Toyota GR HV SPORTS Concept: View 6 Photos Toyota Tj Cruiser: View 12 Photos Yamaha Concepts (Cross Hub, MOTOROiD, MWC-4, Motobot): View 5 Photos Related Video: Tokyo Motor Show Honda Isuzu Lexus Mazda Mitsubishi Nissan Subaru Toyota

Nissan's Carlos Ghosn taps the brakes on autonomous car progress

"Self-driving cars remain a long way from commercial reality."
Nissan CEO Carlos Ghosn shocked the automotive industry last year when he announced that his company plans to offer consumers an autonomous car by 2020. The automaker even showed off its self-driving Leaf prototype as proof. He was bolder recently with the pronouncement that select markets could have them in 2018, if laws allowed. The boss' optimism appears to be waning, though, and he's now sounding a lot more conservative about the future. While driverless vehicles are still on the way, Ghosn is hedging his bets with a more gradual implementation of several systems.