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TDI (engine)

Branded engine design

  • 4 min read
  • 5 chapters

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The first TDI engine, a straight-five engine, was produced for the 1989 Audi 100 TDI sedan. In 1999, common rail fuel injection was introduced in the V8 engine used by the Audi A8 3.3 TDI Quattro. From 2006 until 2014, Audi successfully competed in the LMP1 category of motor racing using TDI engine-powered racing cars. TDI engines installed in 2009 to 2015 model year Volkswagen Group cars sold through 18 September 2015 had an emissions defeat device, which activated emissions controls only during emissions testing. The emissions controls were suppressed otherwise, allowing the TDI engines to exceed legal limits on emissions. Volkswagen has admitted to using the illegal device in its TDI diesel cars.

Overview

TDI is the combination of two existing diesel engine technologies:

  • Direct injection – where a fuel injector sprays the diesel fuel directly into the main combustion chambers. This causes a more complete combustion process than using a pre-combustion chamber (known as indirect injection), which therefore increases the torque output and reduces the exhaust emissions.
  • Turbocharging – where an exhaust-driven turbine compresses the intake air, in order to obtain higher power and torque outputs from a small displacement engine.

Most TDI engines also use an intercooler to lower the temperature (and therefore increase the density) of the compressed air before it enters the cylinder. Similar technology has been used by other automotive companies, but the "TDI" marketing term is only used by Volkswagen Group and Land Rover. Volkswagen Group uses the term SDI (which stands for "Suction Direct Injection") for its naturally aspirated (i.e. non-turbocharged) direct-injection diesel engines.

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