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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.

Nissan alters all CVTs to act less like a stretched rubberband

Among automotive enthusiasts, no one seems to hold a neutral opinion when it comes to continuously variable transmissions. CVTs are either praised for their ability to boost fuel economy or chided for their occasionally poor driving dynamics. Nissan is among the masters of these un-shifting gearboxes in the US, and it uses them in many vehicles in its lineup. However, for the 2015 model year, several models are getting a software update to make their CVTs a bit more like a conventional automatic.
To give drivers the option of feeling gearshifts while on the road, Nissan is adding its D-Step Shift Logic feature to the CVTs in multiple vehicles. Steve Powers, Nissan's senior manager of powertrain performance, told Autoblog the system forces the transmission to "hold a ratio and then shift" to simulate the way that a traditional automatic would. It's simply a change in software, but the company "can't do it to older CVTs," he said, because it would require changes to transmission logic, as well. According to Automotive News, the upgrade is coming to the 2015 Versa, Versa Note (pictured above), Sentra, V6-equipped Altima, Pathfinder and Quest. "We're rolling it out to all programs," said Powers.
Interestingly, buyer perception appears to be pushing the upgrade. John Curl, a Nissan North America regional product manager, told Automotive News that the decision to add the tech partially comes because some owners are bothered that the CVTs aren't changing gears. According to Powers, D-Step "avoids the rubber band feel," that many drivers didn't like. The different sensation of these transmissions seems like something consumers would notice during the test drive, or that the salesperson would inform them about. The same issue cropped up last year when the company was facing customer satisfaction problems among new buyers customers' unfamiliarity with the gearboxes.

2015 Nissan Altima pricing released, V6 gets MPG bump

Nissan has announced a range of moderate enhancements for its 2015 Altima sedan, starting with a one-mile-per-gallon increase in the highway fuel economy of the top-tier, 3.5-liter V6 engine. The six-pot now returns 32 mpg on the highway and 22 mpg in the city.
The 3.5 SV and 3.5 SL, the mid and top-end six-cylinder trims, also get NissanConnect with Navigation, blind-spot monitoring and lane departure warning. Prices, though, see a commensurate increase.
The starting price for a base, 2.5-liter four-cylinder Altima has been nudged up by $130, to $22,300, not counting the $810 destination charge. The 2.5 S model is down $130, though, to $22,560. Meanwhile, the top-end four-cylinder models, the SV and SL see their prices increase by $380 and $230, respectively.