2002 Nissan Sentra Gxe Sedan 4-door 1.8l 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.

Porsche 911 GT3 dukes it out with MP4-12C on track and GT-R on spectacular roads

The Porsche 911 GT3 has always been a favorite among auto journalists and car enthusiasts alike, but with the introduction of the new 991-generation GT3, which is the first GT3 with electric power steering and no manual gearbox option, how does it stack up to the competition from McLaren and Nissan?
Evo's Jethro Bovingdon attempts to answer that question by pitting the rear-engine Porsche against the mid-engine McLaren MP4-12C on a racetrack and the front-engine, all-wheel-drive Nissan GT-R on some amazing, twisty European back roads. We won't give away the victor of either comparison, but we will say that, in Evo's test, the McLaren's 141-horsepower advantage doesn't give it as much of an edge over the Porsche on a racetrack as one might think, and the lack of a manual gearbox and the inclusion of electric power steering on the GT3 isn't detrimental to enjoying the car on a back road.
Watch the video below to find out which car Bovingdon prefers on road and track - we think you'll be happy to see him drift around turns every chance he gets.

Here's how to follow this weekend's 24 Hours of Le Mans

In the pantheon of motorsports, the 24 Hours of Le Mans stands as one of the great endurance challenges to man and machine. This year's event in France already looks to be one for the ages with Porsche setting record-breaking times in practice and the competition debut of Nissan's front-engine, hybrid racer. Thankfully, there's a massive list of ways to follow this automotive attraction. Reilly Brennan, the Executive Director of the Revs Automotive Research Program at Stanford University, and a friend of Autoblog, has once again assembled a helpful couch-kit to organize many of the options. Unfortunately, the old-school way of just turning on the television might be the most frustrating way to watch Le Mans this year. Fox Sports 1 and 2 are carrying about half the race, but the coverage bounces between them seemingly at random. The broadcast begins on Fox Sports 2 at 8:30 AM Eastern ahead of the 9:00 AM start and lasts there until 12:00 PM. Things don't pick up again until 7:00 PM Eastern on Fox Sports 1 for an hour, and the channels swap back and forth more from there. The Fox Sports Go streaming app offers more, but even it stops showing the race a few times. Thankfully, streaming Le Mans is easy. If you can't dedicate 24-hours on the couch, Radio Le Mans lets you listen to audio commentary anywhere with some of the best announcers in the biz. The Automobile Club de l'Ouest, the governing body for the race, also offers an official video stream in an app for $9.99. For a really low-tech solution, the official Twitter is another choice. Brennan is keeping his list updated with coverage changes. You can also check out and download the spotter's guide (from Nissan) in the gallery above. Enjoy this year's race. If you miss anything, don't worry; expect a full report from Autoblog. In fact, editor-in-chief Mike Austin is attending Le Mans this year, so follow him on Twitter for on-the-fly impressions. Featured Gallery 2015 24 Hours of Le Mans Spotter's Guide News Source: Reilly BrennanImage Credit: Nissan Motorsports Audi Nissan Porsche Toyota Hybrid Racing Vehicles