Audi Brings the 1.8 TFSI to the TT

30 April 2008

Direct injection in the 1.8 TFSI.

Audi is expanding its application of the 1.8 TFSI to TT line. The four-cylinder gasoline engine with turbocharger and direct injection deliver performance similar to that of larger, naturally-aspirated V-6 engines: 118 kW (160 hp) of power and 250 Nm (184.39 lb-ft) of torque available between 1,500 to 4,500 rpm. In the TT Coupé, the 1,798 cc engine consumes 6.7 L/100km (35 mpg US) and in the Roadster 6.9 L/100km (34 mpg US).

The 1.8 TFSI is one of a new engine series (EA 888) designed to deliver greater power density. The new engine family was developed by Audi for worldwide use in all brands of the VW Group. Audi first introduced the engine in the A3 line in 2006 and has since expanded its application to the A4 and A5 lines. (Earlier post.)

The 1.8 TFSI is compact, and at 135 kilograms (297.62 lb), it is unusually light. Two balancing shafts refine the engine’s running character. The toothed chain that drives the balancing shafts has also been designed for this quiet running. Another chain drives the oil pump. With its volumetric flow control and two pressure stages, it saves 0.2 liters of fuel for 100 km. A third toothed chain drives the two camshafts. The newly developed variable camshaft system adjusts the intake camshaft through 60 degrees on the crankshaft.

The exhaust camshaft drives the newly developed high-pressure fuel injector pump via a four-section cam. The six-hole injectors, which are also new, distribute the fuel precisely in the combustion chamber to achieve more efficient combustion. A two-stage injection is executed after a cold start, the first during the intake stroke, the second during the compression stroke to rapidly bring the ceramic catalytic converters, which are located close to the engine, to their operating temperature.

Fuel is injected directly into the four-valve cylinder head at 150 bar pressure from a high-pressure accumulator through newly developed, six-hole injectors. There it mixes with air that is set into a swirling motion by newly designed charge movement flaps in the intake manifold.

The integral turbocharger in the 1.8 TFSI.

The mixture is homogeneous; 14.7 parts of air are added to one part fuel. Evaporation of the directly injected fuel cools the combustion chamber, which, when combined with turbocharging, supports a compression ratio of 9.6:1. The charger is designed to react to demand so that the engine quickly reaches maximum torque and remains at this high level for long periods. The result is high elasticity at any rpm.

Combined with a six-speed manual transmission, the 1.8 TFSI accelerates the Audi TT Coupé to 100 kph (62 mph) in 7.2 seconds, up to a top speed of 226 kph (140 mph). This performance is also due to the low total weight: the Coupé weighs 1,240 kg (2,734 lb), and the Roadster 1,285 kg (2,833 lb). Both car bodies consist primarily of aluminum.

Audi also recently introduced TDI versions of the TT—the Audi TT Coupe 2.0 TDI quattro and Audi TT Roadster 2.0 TDI quattro are the first series-production sports cars to be powered by diesel engines. (Earlier post.)

The two-liter four-cylinder engine delivers dynamic thrust, with a power output of 125 kW (170 hp) and 350 Nm (258 lb-ft) of torque. On average, however, the TDI in the TT Coupe requires 5.3 liters of fuel per 100 km (44 mpg US).

Also new to the Audi TT lineup is quattro all-wheel drive for the top-selling 2.0 TFSI.