Volkswagen develops its diesel technology. Compared with more widespread common rail systems, TDI Pumpe Düse (PD) injects fuel at a much greater pressure, which leads to unrivalled power outputs along with highly competitive fuel economy. Unit injector fuel systems are being used on a wide variety of vehicles and engines. The Volkswagen Group mainstream marques use unit injector systems, branded Pumpe Düse, in their Suction Diesel Injection SDI and Turbocharged Direct Injection (TDI) diesel engines. The first Volkswagen Group TDI engine was the Audi-developed 2.5 litre R5 TDI - an inline five-cylinder engine (R5), introduced in the Audi 100 in 1989 and this variant is still used today in Volkswagen Marine applications.