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Roller coaster or racecar, which pulls more Gs?

Looking for a thrill? You're not the only one. You'll find kindred spirits at airfields going up for a skydive, atop bridges and towers with bungees attached to their feet and standing in line for roller coasters at the local amusement park. But you'll also find them in the paddock at the racing circuit.
So what's the commonality? G-force. It's like gravity, only in each of these cases, it's experienced by human invention. But which activity subjects your body to the greatest amount of g-force? That's what Nissan set to find out.
Before putting them back in the cockpit, Nismo sent out two of its young hot-shoes - Jann Mardenborough and Mark Shulzhitskiy - to an amusement park in the UK with a camera and a g-force meter to find out if any of the coasters could produce as much lateral gravitational force as an LMP2 racing car. See what they found in the pair of videos, below.

Nissan's plan to supply US Mitsubishi dealers with family sedan stalls

Mitsubishi has quietly had some big success recently. The Japanese brand sold 77,643 vehicles in the US for all of 2014, a 24.8 percent jump over 2013. While still relatively small overall (Ford sold 74,355 F-Series trucks just in December, for example), it shows definite growth for the sometimes forgotten automaker. Unfortunately, the latest news might not help the company's future expansion. The proposed partnership of Mitsubishi and the Renault-Nissan Alliance on at least one midsize sedan for the US market is off the table, according to Automotive News. The company informed sellers that the collaboration had fallen through during a National Automobile Dealers Association meeting. "I told them that the plan has stalled," said Don Swearingen, executive vice president of Mitsubishi Motors North America, to Automotive News. "And I said that's really all I can tell you at this time." Under the original partnership, Mitsubishi was supposed to get a D-segment sedan that would have been built at the Renault-Samsung factory in Busan, South Korea. The automakers were also negotiating for Mitsu to get a C-segment four-door as a global model and developing an electric kei car for Japan together, due in 2016. While the sedan is gone, Mitsubishi isn't completely bereft of improved products in the pipeline. The Mirage Sedan is being launched in the US, and the Outlander is supposed to get a redesign for the 2016 model year. According to Automotive News, the Outlander Sport and Lancer are also due for refreshes in 2016, and a new Mirage is on the way.

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.