Wednesday, November 02, 2005

A New Legend: 2.0L Turbo FSI

Text from Volkswagen of America.
Direct Injection and Turbocharging Deliver High Performance & High Fuel Mileage

LAS VEGAS, Nev. – How best to replace a legendary engine? Simple; build another legend!

Volkswagen faced the challenge of designing a successor to its renowned 1.8-liter turbo very simply—it built a completely new four-cylinder engine, the 2.0L Turbo FSI, and made it superior in every respect. Its unique combination of technologies not only delivers more power and more torque, it’s done more cleanly than and just as economically as the 1.8L Turbo.

Even though it’s a much stronger engine than the 1.8L Turbo, the 2.0L Turbo FSI yields comparable EPA mileage estimates: 24 city/32 highway mpg compared to the 1.8T’s EPA rating of 24 city/31 highway mpg. The new 2.0T also scores considerably higher than the 1.8L Turbo in the EPA’s Air Pollution index, earning a 6 out of 10 (and a 7 in ULEV II state configuration) for its reduced tailpipe emissions. This best-of-all-world’s balancing act is made possible primarily by the 2.0T’s singular mix of turbocharging and direct gasoline injection.

The 2.0L FSI Turbo is not just a bumped-up version of the 1.8T. Refinements from top to bottom include strengthened components in the valvetrain and a more robust crankshaft, resulting in a free-revving power curve entirely absent of turbo lag or flat spots. Its maximum output of 200 horsepower is available at 5500 rpm and holds steady until 6000 rpm, but the essential sporty character of the 2.0L FSI Turbo is better reflected in the broad and muscular torque curve. The 207 lb-ft of crank twist is available almost from idle, rocketing quickly to its peak at just 1800 rpm and then offering a gratifying plateau of power until it begins to taper off at 4700 rpm.

The result is quick response for the cut and thrust of urban traffic, an abundance of elastic mid-range yank for effortless passing, and a freely accessible top end for sustained acceleration. When it’s under the hood of the new 2006 Jetta GLI, this translates to 0-60 mph sprints of just 7.1 seconds for the 6-speed manual model and 7.0 seconds for the 6-speed automatic. The 2.0L is just as rewarding in the larger, mid-size Passat sedan, taking it to 60 mph in 6.9 second with the 6-speed manual and 7.4 seconds with the 6-speed Tiptronic® automatic.

Built around Volkswagen’s time-tested arrangement of cast iron engine block and aluminum alloy cylinder head, the 2.0L Turbo FSI’s displacement (1984 cc) results from a larger 82.5 mm bore and longer 92.8 mm stroke (3.2 x 3.7 in.). Dual overhead camshafts drive four valves per cylinder; the hydraulic lifters are maintenance free. For critical heat dissipation the exhaust valves are sodium filled, and the intake valve seats are reinforced for durability. Other valvetrain upgrades include roller rocker fingers to reduce the land width of the camshaft and roller, and identical high-tension valve springs for both the intake and exhaust valves. The engine’s bottom end was also beefed up with stronger main bearing flanges and journals on the forged steel crankshaft, and dual balance shafts counteract vibrations and harmonics developed during the four-cylinder’s normal engine operation.

The secret to the 2.0T’s blend of increased performance and undiminished estimated fuel mileage lies in the optimized combustion process. Because gasoline is injected directly into each cylinder at extremely high pressures, the air/fuel mixture burns more cleanly and more efficiently. A primary advantage of direct injection is that combustion chamber temperatures are cooler than with conventional manifold injection, which allows the 2.0L turbo to run an aggressive 10.3:1 compression ratio without fear of detonation. And because the mix of fuel and air takes place within each cylinder, it’s less affected by outside forces than in a manifold injection system. Combustion therefore is very predictable, which means engine timing can be precisely monitored and adjusted for optimum economy or performance, depending upon the weight of the driver’s right foot. Also, because direct injection results in cooler exhaust temperatures than in manifold injection systems, engineers are allowed greater scope in the design and operation of the turbocharger.

The 2.0L turbo operates in two modes. Cold-start conditions initiate a dual-injection mode for rapid heating of the dual catalytic converters. A quantity of fuel is injected on the intake stroke around 300 degrees BTDC of ignition, and the fuel distributes itself homogenously because of the long gap before ignition. A second injection, around 60 degrees BTDC of ignition during the compression phase, forms a rich mixture around the spark plug, which allows a considerable degree of retarded timing without affecting the engine’s stability. Normal mode and stoichometric levels begin quickly, when the catalytic converters have reached operating temperature, usually within 30-40 seconds.

A range of internal modifications assist this clean-burning technology to enhance operating smoothness, including a special intake port design and piston crown shape to reduce detonation “knock.” Intake manifold airflow is controlled by tumble flaps, individual plates located within the intake manifold runners, that are actuated at specific engine speeds for best air/fuel mixtures. On the exhaust side, a divider in the exhaust manifold ensures a steady flow of gases to the turbocharger and also prevents gas pressure from expanding into the other cylinders.

The North American-spec 2.0L FSI Turbo engine should not be confused with the similar European-spec FSI powerplant, which features a third mode of engine operation, stratified charge combustion, to allow short periods of extremely lean burn. In such low-speed, light throttle conditions, the very slight amount of fuel added to the mixture can result in stoichometric ratios as high as 65:1 (the normal ratio for gasoline engines is 14.7:1) and periods of exceptional fuel mileage. Because of North America’s lower fuel quality (which would require special catalysts to handle the extra NOx emissions from our high-sulfur-content gasoline), this technology is not yet available outside of Europe. True stratified combustion will be integrated into this engine, and other VW (and Audi) FSI powerplants, when the high sulfur content of U.S. fuels is decreased in the next several years.

Even without ultra-lean-burn technology, the benefits of the 2.0L turbo are clearly evident. The EPA estimates that the combination of direct injection and forced induction, when compared to a conventional gasoline engine, delivers on average 15% more power and a 10% reduction in fuel consumption. Add the character of a genuine performance engine into the equation, and Volkswagen’s 2.0L Turbo FSI is an appealing blend of sportiness and clean-running economy.

Founded in 1955, Volkswagen of America, Inc. is headquartered in Auburn Hills, Michigan. It is a subsidiary of Volkswagen AG, headquartered in Wolfsburg, Germany. Volkswagen is one of the world’s largest producers of passenger cars and Europe’s largest automaker. Volkswagen of America and its affiliates employ approximately 3,000 people in the United States and are responsible for the sale and service of Audi, Bentley, and Volkswagen products through retail networks comprising in total more than 900 independent U.S. dealers.

"Volkswagen" and "4MOTION" are registered trademarks of Volkswagen AG. "DSG" is a trademark of Volkswagen AG. All other trademarks used in this document are the property of their respective owners.

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