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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.

Common Nissan Maxima vs. Subaru Legacy breakdowns

The Nissan Maxima and Subaru Legacy are both popular sedans. Similarities can be seen in price, styling, and performance. What are some common repair problems seen in each model? When do they occur and how much do they cost to fix? What about how to pay for car repairs? Let's find out. Check Engine Light Both Maxima and Legacy owners dread the appearance of this little light. In the Nissan, it's most likely a failed ignition coil. This part transforms the car battery voltage into a higher voltage required for starting. This problem appears more often in Maximas with over 140,000 miles. The cost to replace the ignition coil runs around $400, parts and labor. The check engine light on the Subaru Legacy is more often due to a failed oxygen sensor. The O2 sensor measures the oxygen level in the exhaust and can affect fuel consumption. This part fails more frequently in models with over 110,000 miles. The repair costs around $200. Legacy Sound System Problems It's not uncommon for the Legacy to have sound system failures at 140,000 miles or more. The speakers might not work or only function intermittently. Hitting a bump might also cause the radio to shut off. Repair costs here can vary, but the typical charge is around $600. Nissan Check Engine Light Part 2 The Nissan check engine light also may appear due to oil leaking from the camshaft position sensor. Difficulty with stalling and acceleration might occur as well. The repair costs around $250 and is more frequent in models with over 104,000 miles. Big-Ticket Items Some repairs are especially costly. In Maximas with over 120,000 miles, the power steering pump may begin to malfunction. This produces a clunking or knocking sound when driving over uneven terrain. Steering might be affected with abnormal noises heard when turning the steering wheel. A Nissan Maxima power steering pump replacement costs around $1,250, parts and labor. Now, if you begin to feel your Legacy vibrating or shuddering at around 116,000 miles, it may be a transmission problem. It's more noticeable when the car shifts gears. Legacy transmission repair can be expensive, costing up to $2,000 or more. Even more costly is a Subaru Legacy head gasket failure, seen more often at 110,000 miles or more. AC malfunction, fluid leaks, and engine overheating can occur when the head gasket fails. The repair costs are around $3,000.

2014 Nissan GT-R Track Pack squares off against Audi R8 V10 Plus

The team over at Motor Trend has pitted the new Audi R8 V10 Plus against the Nissan GT-R. While both of the bright red all-wheel-drive supercars are comparably matched in power output, the similarities end there. Audi offers a mid-engine aluminum coupe with a naturally aspirated V10 that spits out 550 horsepower. Nissan shows up with a more traditional coupe equipped with a 545-horsepower twin-turbocharged V6 at the front of the car.
The Head-to-Head video takes both cars to the Streets of Willow Springs in the California desert for some track work with professional racing driver Randy Pobst behind the wheel. After a day at the track, the pair head to the local mountains for some spirited real-world driving. One dominates on the circuit, while the other earns back its credibility in the canyons. We won't tell you which coupe comes out on top, but we think you may be surprised. Follow the link below to watch for yourself.