Audi is celebrating the 25th anniversary of its Turbocharged Direct Injection (TDI) diesel-burning engine. The TDI mill was introduced to the public under the hood of the Audi 100 (pictured) at the 1989 edition of the Frankfurt Motor Show.
Audi was not the first manufacturer to offer a direct-injected turbodiesel engine – that honor goes to Fiat, who introduced a direct-injected variant of the Croma sedan in 1986. However, Audi worked closely with parent company Volkswagen to democratize the concept and drastically improve it over the course of the 1990s.
Audi started developing the TDI engine in the mid-1970s in response to the fuel crisis that rocked the global economy. The Ingolstadt-based automaker saw a need for a more fuel-efficient engine to power its larger cars, and designing a new, more modern diesel unit seemed like the best way forward. Components manufacturer Bosch gave Audi a hand in the development process by providing an injection pump that built up 900 bars of pressure, allowing for a cleaner combustion process and eliminating many of the noisy rattles typically associated with older diesels.
When launched, the Audi 100 TDI was powered by a 2.5-liter five-cylinder engine that generated 120 horsepower and 195 lb-ft. of torque at just 2,250 rpms. The sedan reached an Autobahn-worthy top speed of nearly 125 mph (201 km/h) while returning 41.3 US mpg (5.7 liters per 100 kilometers) when driven conservatively in a mixed cycle. These figures were impressive for a relatively large sedan that tipped the scale at over 3,200 pounds (1,475 kilos).
Encouraged by strong demand for the TDI-powered 100, Audi launched a four-cylinder variant of the engine with a displacement of 1.9-liters in 1991. It was initially rated at 90 horsepower and 134 lb-ft. of torque under the hood of the 80, but it was later upgraded to 110 horsepower and installed in the engine bay of the first-generation A4 and A3.
Audi continued to update the TDI by making it more powerful and cleaner, as well as by launching six- and eight-cylinder versions of it. Over the past quarter of a century, the automaker’s engineers have reduced the engine’s emissions by up to 98 percent and doubled the TDI’s power and torque outputs relative to its displacement.
Today, the TDI engine is an integral part of the Volkswagen Group and it is used by Audi, Volkswagen, SEAT and Škoda in a wide variety of cars ranging from the Polo to the R8.
Photos courtesy of Audi’s archives department.