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Weekly Recap: New bosses try to jump-start Cadillac and Lincoln

Both of America's domestic luxury brands seem to be stuck in neutral.
It's ironic that Cadillac and Lincoln got new bosses within days of each other this month. It's also a commentary on the fact both of America's domestic luxury brands seem to be stuck in neutral.

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.

Cadillac tops Tesla in Consumer Reports semi-automated driving test

General Motors' Cadillac outscored Tesla in a new ranking of partially automated driving systems tested by Consumer Reports and released on Thursday. The highly influential nonprofit organization, which tests and rates a variety of consumer products from appliances to vehicles, said it compared Cadillac's Super Cruise and Tesla's Autopilot with similar systems from Nissan and Volvo. Nissan's ProPilot Assist was ranked third and Volvo's Pilot Assist fourth. Consumer Reports said it has been testing partially automated driving systems for several years but elected to conduct a formal study intended for publication, because "we are at a tipping point where they are now going mainstream," according to Jake Fisher, director of auto testing. The organization said its tests, conducted on a private track and on public roads in Connecticut, were designed to measure the systems' ability to automatically control steering and speed in certain situations, while helping drivers pay attention and regain manual control of the vehicle when required. CR noted that any of these systems can increase driving risk if used in inappropriate situations, or if drivers become inattentive or over-reliant on them. While they can help relieve driver stress and fatigue, Consumer Reports said, the partially automated systems are "not intended to be self-driving features." The systems typically use cameras, radar and other sensors, as well as mapping data, to monitor location and traffic conditions and help keep a vehicle centered in the lane at a safe distance behind other cars. Each system has limitations. Cadillac's Super Cruise, for instance, only functions on divided highways that have been mapped by GM. In contrast, Tesla's Autopilot can be used even on small, curvy roads with poor lane markings, but "operates erratically in those situations," Consumer Reports said.The organization tested Super Cruise on the Cadillac CT6; Autopilot on the Tesla Model 3, Model X and Model S; ProPilot Assist on the Nissan Leaf and Infiniti QX50; and Pilot Assist on the Volvo XC40 and XC60. Consumer Reports said Cadillac's Super Cruise did "the best job of balancing high-tech capabilities with ensuring the car is operated safely and the driver is paying attention." Tesla's Autopilot was cited for its capability and ease of use, while Nissan's ProPilot Assist did a better job than Autopilot or Volvo's Pilot Assist in keeping drivers engaged.