Audi AG FSI 2L Turbocharged DOHC I-4
By Bill Visnic WardsAuto.com, Dec 20, 2006 9:10 AM

Seems like there suddenly is a lot of small-displacement 4-cyls. pushing silly horsepower. Audi AG’s turbocharged, direct-injection gasoline (DIG) 2L DOHC I-4 isn’t even the most powerful among them.

But in taking its second consecutive 10 Best Engines award, the Audi powerplant demonstrates that in the new class of power-dense, forced-induction fours, all-around versatility and refinement is at least as important as big numbers.

Engineers used to look at 100 hp per liter as a moonshot number, but these new-generation boosted 4-cyls. blow right past that benchmark.

General Motors Corp.’s DIG, turbocharged Ecotec 2L churns out 130 hp/L. Mazda Motor Corp.’s 2.3L – also employing the killer-ap combo of DIG and turbocharging – makes 119 hp/L and seems laughably unstressed in doing so.

At “just” 100 hp/L, Audi’s FSI 2L is the comparative anchor of the bunch.

Audi wins the day with superb drivability and wicked-fun throttle response that leaves its competition, not to mention a lot of larger V-6s, feeling flat. The full whack of its 207-lb.-ft. (281-Nm) torque peak being on hand from 1,800 rpm all the way to 5,000 rpm certainly helps.

Audi 2L DOHC I-4 is turbocharged, direct-injected.

The sharp throttle response is enhanced by the feeling of virtually no flywheel inertia. Your right foot whips the tachometer needle like a flyswatter.

Testers universally were enamored of this engine’s ability to deliver sparkling power and satisfying economy. No matter how hard it was driven, it seemed impossible to get less than 25 mpg (9.4 L/100 km), and a light throttle is rewarded with economy-car fuel consumption.

And typical of Audi, the 2L turbocharged DOHC I-4 pegs the technology meter. In addition to the auto maker’s pioneering FSI (fuel straight injection) DIG technology, there are more variables here than in calculus class: a turbo lag-reducing variable-nozzle turbocharger; variable valve timing; and a variable-length intake manifold that incorporates charge-motion flaps to optimize intake-air swirl.

Refinement is abetted by a pair of counter-rotating balance shafts, as does the long-stroke layout (long a Volkswagen Group preference). Engineers must have spent extra time on this free-spinning engine’s rev-limiting software, certain in the knowledge it would get a workout.

When Volkswagen AG and Audi replaced the highly regarded 1.8T turbocharged 4-cyl. (an engine that took home five 10 Best Engines trophies) with this new, direct-injected architecture, fans of that 5-valve-per-cylinder fun-motor feared nothing could replace it.

But the VW Group’s powertrain engineers upped the ante, adopting FSI direct injection (this was the first production engine to combine DIG with turbocharging, Audi claims), an aluminum block and a little more displacement.

Best of all, Audi and VW make this engine available at several price points in both brands’ model range, meaning nobody has to be rich to enjoy what is one of the most affordable performance engines in the U.S market.

bvisnic@wardsauto.com