2004 Infiniti G35 Base Coupe 2-door 3.5l on 2040-cars

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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 Q30 prototype spotted winter testing

Infiniti is the latest luxury automaker preparing to join the premium hatchback segment, and after seeing a prototype wrapped in garbage bags undergoing warm-weather testing earlier last month, we're now looking at another test mule running in the snow. Previewed in concept form at the Frankfurt Motor Show over a year ago, the Infiniti Q30 is set to share its platform with the Mercedes GLA – with which it obviously shares its proportions, but from which it will be distinguished with unique styling with trademark Infiniti design cues. It's still hard to tell much from the spy shots (heavily camouflaged as is the prototype), but their emergence at least tells us that development is continuing apace. We wouldn't take too much stock in the Volvo V60 tailing it, though: automakers often benchmark the competition, but the Q30 will more directly compete with the next V40, along with the likes of the Audi A3, BMW 1 Series and (maybe to a lesser extent) the Lexus CT 200h. Expect power to come from the same 2.0-liter four-cylinder engine used in the GLA and its stablemates as well. Production is slated to take place simultaneously in Decherd, TN, and in Sunderland, England, at Nissan Motor Manufacturing UK – one of the largest assembly plants in Europe. A QX30 crossover version better suited to rougher roads is slated to follow as well.

Production Infiniti QX50 will mostly look like the concept

At this year's Detroit auto show, we got a look at the nearly production-ready Infiniti QX50 concept. Now we get our first look at how close to production the concept was, thanks to new spy photos. The overall shape remains very similar to that of the curvy concept. However, the greenhouse looks taller with more glass. While it isn't quite as low and aggressive-looking, we're sure drivers will appreciate the small compromise for better visibility. At the front, there are more changes that are a little less subtle. The grille looks a bit smaller all around, and even looks a tad lower than the concept. The headlights also don't stretch as far back, and they aren't as narrow either. In the front bumper, the two side scoops of the concept have been significantly toned down, and now look like more traditional grilles that follow the shape of the bumper. The lower grille is more open with just a mesh insert instead of the concept's skidplate-style chrome bar. Moving to the back, we find the taillights look nearly identical to the concept's. They're very long and narrow, and they connect into a metal crease that looks a bit like a spoiler. It looks as the though the faux skidplate treatment on the rear bumper will also make it to production, but the integrated exhaust tips have given way to more conventional round tips in bumper cutouts. It also may have lost the concept's air vents on each side of the hatch. Though they may have also just been toned down enough that they don't show through the camouflage. When the QX50 hits dealers, it will be available with Infiniti's fascinating variable compression four-cylinder making 268 horsepower. The crossover will also feature a version of Nissan's ProPilot semi-autonomous technology, which has been implemented in the Nissan Serena minivan in Japan. We expect to see the fully revealed production model very soon, possibly by the end of the year. Related Video: