Efficient diesel engine meets connected tech

The good: A diesel drivetrain gives the 2014 Audi A7 TDI impressive fuel economy for a large car. Connected features include Google local search and Google Earth integrated with navigation. Bang & Olufsen audio delivers detailed and balanced music reproduction.

The bad: The A7 TDI requires additional maintenance in the form of 10,000 mile AdBlue fill-ups. Audi's proprietary audio port requires adapter cables for external devices; a standard USB port would be preferable.

The bottom line: The 2014 Audi A7 TDI includes some of the best connected tech available today in an automobile, and those inclined to put up with a few diesel drivetrain quirks will be rewarded with significantly higher fuel economy than from the gasoline equivalent. 

In heavy traffic on the freeway, I let the 2014 Audi A7 TDI's cruise control handle braking and accelerating, and gave lane-keeping assist a try by letting the car drift over to the left lane line. Cruise control, using its radar to track the car ahead, unerringly handled stop-and-go without my intervention. And before the car crossed the lane line, the camera-based lane assist moved the wheel under my light grip, steering the A7 TDI back into its own lane.

Was I experiencing a glimpse of our autonomous driving future?

Not exactly, as the pull on the steering wheel sent the car on a drift toward Despite not exactly being the future of self-driving, the A7 has been a high-tech showcase for Audi since its launch in 2010, not to mention having an excellent body design that became much copied. For 2014, the A7 adds some driver assistance features, but its connected infotainment system is largely the same as before.

Double down on diesel
The big change for the 2014 model year, as indicated by this A7's TDI suffix, is the inclusion of a diesel engine option.

Over the last decade, Audi's parent company, the Volkswagen Group, developed drivetrain technologies ahead of the competition. The company was an early adopter of direct injection to improve engine efficiency, put quick-shifting dual-clutch transmissions into affordable performance cars, and maintained a line of diesel passenger cars as every other automaker steered clear. Audi benefited from this work, using direct-injection engines in every model and offering diesel versions of the A3 and Q7.

The A7 TDI's design employs a graceful roofline sweeping back to a hatch, making it a five-door sedan.

(Credit: Josh Miller/CNET)

For 2014, Audi doubles down on diesel, putting TDI, which means Turbocharged Direct Injection, in the A6, A7, A8, Q5, and Q7.

Like its siblings, the A7 TDI I tested was powered by a 3-liter V-6 engine, turbocharged and mated to an eight-speed automatic transmission. As is typical for diesels, the horsepower, 240 in the A7 TDI, looks small given the size of the engine, but torque, at 428 pound-feet, is through the roof. That's compared with a more balanced 310 horsepower and 325 pound-feet of torque for the gasoline-powered A7.

Given the high torque, you might think the A7 TDI would shred its tires at every start, but Audi's throttle programming lets the power come on smoothly for the most part, making the car an easy everyday driver. There are some quirks to driving this diesel. First of all, if you've got F1 aspirations go for the gasoline A7, or step up to the S7 or RS7 models. The diesel engine doesn't deliver power in a manner suitable for thrashing the turns.

Redline sits at 4,500rpm and, more importantly, peak torque hits in a narrow band, from 1,750 to 2,250rpm. The gasoline-engined A7 spreads its peak torque across a 1,600rpm power band. In practice, the A7 TDI didn't have a lot of punch to power out of a turn with. The engine was prone to surge, churning out uneven acceleration when I had the throttle down. In Dynamic mode, the surging nature of the engine even made holding a steady pace in traffic difficult.

A mess of plumbing hides the engine block under the hood.

(Credit: Josh Miller/CNET)

From the outside, the noise from the engine was remarkable enough that CNET's garage attendant asked me if there was something wrong with the car. However, Audi employs enough sound deadening to mask the engine noise in the cabin.

As with other new diesels, the A7 TDI requires a little extra maintenance over the gasoline version. Every 10,000 miles, it needs a refill of its AdBlue tank. The emissions system sprays the AdBlue fluid into the exhaust stream, where it breaks down nitrogen oxide into its component parts.

Long-range driver
Given the power delivery, noise, and extra maintenance, you might be wondering why Audi would bother with diesel at all. Fuel economy is the key here, as the diesel drivetrain in the A7 TDI gives it an EPA-rated 24 mpg city and 38 mpg highway. Audi claims a 650-mile range from the 19-gallon fuel tank.

During my time with the car, the white LED lights indicating fuel level turned off at a glacial pace. At the end of a driving course involving city traffic, 65 mph freeways, and twisty mountain highways, the car turned in a healthy 30.3 mpg. Most drivers will likely average over 30 mpg.

The hatchback allows for 24.5 cubic feet of easily accessed luggage space in the A7 TDI.

(Credit: Josh Miller/CNET)

Contributing to the city fuel economy is an idle-stop feature, shutting down the engine at stop lights. Although there was no disguising the noise and vibration from the engine's stops and starts, I didn't find the feature hampered my driving. The engine started up readily whenever I lifted my foot from the brake pedal, and the system was smart enough to keep the engine running if it was cold out.

For those that find the A7 TDI's idle-stop too annoying, it can be turned off with the push of a button.

Although the A7 TDI is more of a luxury-efficient car than a sport play, it did handle very well. Quattro all-wheel drive comes standard on all A7s, and the suspension architecture is conducive to flat cornering. When I could keep the engine up in its power band, I could feel how Quattro helped the tires dig into the turns.

Audi's Drive Select feature let me choose from Comfort, Auto, and Dynamic drive modes, or configure a custom feel with its Individual setting. Those configurations included Dynamic settings for the engine and steering response, along with the seat belt tensioner and even adaptive cruise control.

Via: Cnet.com