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"Near-Production" A4 TDI Concept e Boasts 58.95 mpg

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2009 Audi A4

2009 Audi A4

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In another "near-production" study (read: soon to be released) from VW/Audi, the firm makes an economical splash at the Paris Auto Show with its A4 TDI concept e. Using an efficiency-tuned version of the 2.0-liter diesel engine found in the Volkswagen Jetta TDI clean diesel that's been wowing enthusiasts and setting mileage records, the A4 makes due with 20 less horsepower (120 hp total) and about 22 fewer pound-feet of torque (214)--plus a few other econo-tricks--in the name of astonishing efficiency from an approximately 3,500-pound sports/luxury car. How does 58 mpg sound to you and your wallet?

The econo-tricks mentioned above are similar to those employed on hybrids and fuel-efficiency models popping up across the automotive spectrum, and include such items as the low-rolling resistance tires found on the Chevy Cobalt XFE, regenerative braking employed by the Toyota Camry Hybrid, the increasingly popular engine stop/start feature making its way into luxury brands like the BMW 3 Series, and electrically boosted power steering like that found on the new Acura TL. In addition to these more predictable fuel-saving measures, the A4 goes the distance with soft springs on the intake valves (creating less drag on one camshaft, ergo less fuel-sipping drag on the engine), and variable-rate technology on its fuel pump and A/C compressor that uses only as much engine energy as needed for those items, not one iota more.

Taking efficiency to the extreme are electrically actuated rear brakes, magnesium parts in the six-speed transmission with its economy-minded ratios, and even an insulating wrap on the transmission to heat its fluid more quickly, all in the name of reducing friction and, therefore, the energy costs of moving this slick, new A4 down the road.

Even the vehicle's electronics get in on the fuel-saving game, with the navigation system choosing the most efficient route possible, or the car's electronics running the driver through an "economy training program." Cars may soon be forcing us to get involved with driving...it's nice to think that we may be challenged behind the wheel once more, what with distronic cruise control, lane-departure warnings, and stability control taking the helm these days while many drivers are too busy texting to be bothered.

Of course, there is a performance price for high economy; 10.7 seconds to 60 mph hardly rates as exciting, though it is on par with the Toyota Prius. And with stellar mileage, suave styling, and tenacious handling courtesy of Audi's stiff new A4 platform wearing 225/50 low-rolling-resistance tires, the A4 should put the appliance-like Prius to shame. Suddenly the thought of driving an economy car doesn't seem so depressing.

Plenty of low-end torque from the little turbodiesel should make stoplight-to-stoplight easy and stress-free (much like the insta-torque of an electric motor from rest), and as long as you plan ahead for freeway on-ramps, a range of 996 miles (assuming the standard 16.9-gallon fuel tank) should provide more than adequate compensation for reduced 0-60-mph times.

Wonder what mileage-busting Australian couple John and Helen Taylor could net with an A4 TDI concept e...--Colin Mathews
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Comments (2)
  1. How is it using regenerative brakes? I thought hybrids used them to recharge their battery. What is Audi using it for?
     
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  2. Hey Mark - good question. When coasting or decelerating, it seems the Audi's alternator goes into a mode where it "operates with increased secondary voltage." This voltage spike is stored in the battery until the vehicle accelerates, at which point the electrical system releases the extra voltage back into the circuit, taking load off the engine via reduced draw by the alternator. Here is the exact wording from Audi:
    "a recuperation system that converts the energy of motion during deceleration into usable electrical energy. In the deceleration and braking phases the A4 TDI concept e operates with increased secondary voltage. At this point, it is able to convert the kinetic energy into electrical energy; it is buffered in an absorbent glass mat battery, which is a robust battery with a long life. Whenever the sedan accelerates again, the battery feeds the energy back in, thus reducing the load on the alternator."
     
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