Audi AG 2L FSI Turbocharged DOHC I-4
By Bill Visnic WardsAuto.com, Jan 4, 2006 12:03 PM

Some complain Audi AG's new A3 is too expensive either for a hatchback or an entry level luxury car.

Clearly, those critics are not powertrain aficionados, or else they would recognize an A3 starting at $24,740 is hideously cheap access to a technology-packed powder keg of an engine such as Audi's all-new 2L FSI DOHC I-4.

Like the 1.8L turbocharged 4-cyl. that came before it – itself a winner of multiple 10 Best Engines awards – the new mill combines the power density expected of a premium-class engine and the fuel economy that is virtually a requirement (at least in Europe) to compete in the luxury/sport end of the continent's dog-eat-dog B- and C-Class segments.

But Audi's new 2L I-4 improves greatly on the high standards set by the 1.8T it replaces.

While we miss the exotic 5-valve-per-cylinder configuration of the 1.8T, the 2L FSI makes up for its more-conventional 4-valve layout by sticking a fuel injector into the combustion-chamber, real estate that used to be occupied by Audi's signature fifth valve.

Direct injection gasoline (DIG) technology is the fastest-emerging power and economy enhancing innovation in the powertrain sector, and with the 2L FSI (Volkswagen AG's direct-injection acronym for Fuel Straight Injection), Audi and its VW parent are leading the pack.

Audi says FSI will be its gasoline-engine linchpin going into the future. Soon, every Audi-brand engine will feature the FSI system.

And for good reason: FSI adds new levels of power and torque, yet also delivers fuel-economy gains that, at the least, offset what typically would be lost in generating increased power.

For example, although the 2L FSI develops 30 hp and 40-plus lb.-ft. (41 Nm) more torque than the smaller 1.8T (as used by Audi), a continuously variable transmission-equipped A4 with the new engine gets 20% better fuel economy in city driving and does 10% better on the highway.

The numbers don't do justice to the effervescent nature of the new I-4. The throttle response is the last word in immediate, and this is one of those rare 4-cyls. that continually hits the fuel cutoff long before noise and vibration suggest a gearchange is in order. Twin balance shafts certainly help in that regard.

The 2L mill has a variable-length intake manifold and a superb BorgWarner Turbo Systems variable-turbine turbocharger that, when combined with FSI, all but eliminates turbo lag, just about the last remaining drawback of turbocharging.

As with Audi's excellent 3.2L FSI V-6, the only foible we've noted with FSI is brief idle and low-speed roughness when the engine is cold.

The 2L I-4 is claimed to be the world's first automotive engine to combine DIG technology and turbocharging.

If Audi's brilliant new 4-cyl. engine is typical of what happens when direct injection and turbocharging get together, we expect to see much of the auto industry follow in Audi's innovative footsteps.

Judges' Comments

McClellan: Almost seamless; responsive, powerful and fun. Can't help being a fan of turbocharging in this package.

Winter: Yeee-haaa! Amazingly smooth and vibration-free for such a small, powerful engine.

Visnic: Always feels like a cherry bomb ready to explode.

Engine type: 2L DOHC I-4

Displacement (cc): 1,984

Block/head material: iron/aluminum

Bore x stroke (mm): 82.5 x 92.8

Horsepower (SAE net): 200 @ 5,100-6,000 rpm

Torque: 207 lb.-ft. (280 Nm) @ 1,800-5,000 rpm

Specific output: 100 hp/L

Compression ratio: 10.3:1

Fuel economy for tested vehicle (EPA city/highway mpg): 25/31

Application tested: A3 2.0T

bvisnic@primediabusiness.com