Audi Puts A Diesel in the TT; First Diesel-Equipped Series-Production Sports Cars

27 February 2008

Audi TT 2.0 TDI quattro.

Audi is introducing the Audi TT 2.0 TDI Coupe quattro and Audi TT Roadster 2.0 TDI quattro—the first series-production sports cars to feature diesel engines.

The two-liter engine generates 125 kW (170 hp) of power and 350 Nm (258.15 lb-ft) of torque, with fuel consumption of 5.3 liters and 5.5 liters per 100 km (44.4 mpg and 42.8 mpg) on the TT Coupe and TT Roadster respectively. This corresponds to CO₂ emissions of 140 g/km and 145 g/km.

The TT Coupe quattro with the 2.0 TDI accelerates from zero to 100 kph (62 mph) in 7.5 seconds and achieves a top speed of 226 kph (140 mph). The Audi TT Roadster, likewise equipped with quattro permanent all-wheel drive, requires only an extra tenth of a second for the standard sprint, and continues up to a top speed of 223 km/h (139 mph).

The new dual-camshaft, four-cylinder TDI engine uses a new 1,800 bar common rail injection system equipped with piezo injectors, whose eight-hole injection nozzles can perform up to five distinct injection sequences per cycle. This fine degree of modulation creates a modest pressure increase in the combustion chambers, resulting in a significantly reduced noise level.

The turbocharger is also part of a new generation and operates with adjustable vanes that allow torque to build up rapidly. The positions of swirl flaps on the intake manifold are controlled by electric motors in order to adapt the flow of air to the current load and engine speed. The geometry of the engine’s pistons has been modified, and the acoustics of the camshaft drive belt have been overhauled. Just as they did in the preceding model, two balancing shafts reduce the vibrations arising in the crankshaft drive.

The cumulative result of these enhancements is a maximum engine speed of 5,000 rpm and improved thermodynamics in the combustion chambers. The engine can run with up to 60% cooled EGR, reducing engine out NO_x emissions, and meeting the threshold values of the upcoming Euro 5 standard.

The engines are combined with manual six-speed transmissions with short lever travel. The housings for these transmissions are made of lightweight, high-tech magnesium materials. Relatively long final transmission ratios have been employed to bring the drivetrain in line with the character of the TDI engine.

In light of their high torque values, Audi is equipping both of its new TT models with quattro permanent all-wheel drive. The heart of this system is an electronically controlled, hydraulically activated multi-plate clutch, which is located in the rear of the vehicle for improved weight distribution. This clutch generally distributes up to 85% of the engine power to the front axle and 15% to the rear axle; in extreme situations it can divert up to 100 percent of the power to either axle.

Consistent efforts to reduce vehicle weight are also part of Audi’s efficiency strategy. The 2 + 2-seater TT Coupe weighs 1,370 kilograms (3,020 lbs) when empty, while the two-seater TT Roadster with soft top weighs roughly 1,415 kilograms (3,120 lbs). Underlying these low weights is an innovative hybrid body construction developed by Audi. Front components are made of aluminum and utilize Space Frame technology; rear components are made of steel. This solution guarantees that the frame is as rigid as possible and optimizes load distribution between the axles.