Audi is once again setting standards, this time with the new Audi TT and its TDI engine—a model that combines pure sportiness and powerful performance with sensational efficiency. The Audi TT 2.0 TDI Coupe quattro and Audi TT Roadster 2.0 TDI quattro are the first series-production sports cars to feature diesel engines. It’s a compelling union: The two-liter engine generates dynamic propulsion with 125 kW (170 hp) and 350 Nm (258.15 lb-ft) of torque, yet the TT Coupe and TT Roadster consume an average of only 5.3 liters and 5.5 liters of fuel per 100 km (44.38 mpg and 42.77 mpg) respectively—unparalleled in the sports car segment.
Audi is setting the pace with this synthesis of excellent dynamism and low fuel consumption, as it has done for many years: Since debuting in 1989 the TDI engines from the brand with the four rings have been paving the way for the world’s most successful efficiency technology and acting as trendsetters for the entire automobile industry. Today, these powerful, refined and highly fuel-efficient engines represent a modern, smart take on sportiness. The run of victories achieved by the Audi R10 TDI diesel race car at the Le Mans 24 Hours and in the American Le Mans Series are impressive evidence of the tremendous potential of this technology.
The dynamic diesel engines from Audi exert an exciting impact not just in racing but also in series-production models—and now indeed in a sports car. The TT Coupe quattro with the 2.0 TDI sprints from zero to 100 km/h (62.14 mph) in 7.5 seconds and achieves a top speed of 226 km/h (140.43 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 (138.57 mph). Both versions serve as outstanding examples of the success of the Audi efficiency strategy, thanks to their fuel efficiency ratings of 5.5 liters per 100 km (42.77 mpg), a figure that corresponds to CO2 emissions of only 145 grams/km.
Powerful, refined and efficient: The 2.0 TDI
The new four-cylinder TDI engine (engine displacement = 1,968 cc) represents a fresh take on the all-round compelling qualities of the TDI concept. Designers of the dual-camshaft, two-liter model looked to its predecessor—the most-produced diesel engine in the world—and expanded upon its major strengths: driving pleasure, efficiency and refinement.
The new common rail injection system is equipped with highly modern 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 system pressure of 1,800 bar allows fuel to form a fine dispersion, enabling precise, highly efficient combustion.
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 this progress is a high maximum engine speed of 5,000 rpm and, most importantly, improved thermodynamics in the combustion chambers. What this means is that the engine can run on up to 60 percent recycled exhaust that has been thoroughly cooled by the radiator. This results in a drastic reduction in untreated NOx emissions, with the 2.0 TDI already meeting the threshold values of the upcoming Euro 5 standard.
Dynamic road performance
The 2.0 TDI in the Audi TT Coupe and the Audi TT Roadster delivers 125 kW (170 hp) at 4,200 rpm and sends a full 350 Nm (258.15 lb-ft) of torque to the crankshaft at engine speeds between 1,750 and 2,500 rpm. Operating quietly and generating little in the way of vibration, this model delivers a hefty amount of power at the lowest rpm levels and is highly responsive to input from the gas pedal. Its supreme power development lends this engine its own unique, fascinating character—that of a muscular, smart sports engine.
The Audi TT Coupe 2.0 TDI quattro easily leaves the gasoline-powered competition behind when accelerating from a standstill. It sprints from zero to 100 km/h (62.14 mph) in just 7.5 seconds and never looks back until it reaches 226 km/h (140.43 mph). The TT Roadster accelerates to 100 km/h (62.14 mph) in 7.7 seconds and keeps going up to 223 km/h (138.57 mph).
These models—the world’s first diesel sports cars—consume an average of only 5.3 liters and 5.5 liters of fuel per 100 km (44.38 mpg and 42.77 mpg) respectively, which corresponds to CO2 emissions of a mere 140 g/km and 145 g/km. In so doing, they are setting a benchmark that represents a veritable quantum leap in the sports car segment. With the TDI engine in the TT series, Audi once again establishes its leading role on the diesel market. The brand with the four rings is advancing progress and starting at the top.
In keeping with the theme of sporty performance, Audi has combined its two diesel-engine sports cars with highly effective manual six-speed transmissions whose short lever travel allows the driver to shift quickly, easily and precisely. 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 percent of the engine power to the front axle and 15 percent to the rear axle; in extreme situations it can divert up to 100 percent of the power to either axle.