TDI( Direct injection Diesel engines );what it means

What does the famous acronym TDI mean? It is a commercial nomenclature devised by Volkswagen to instantly distinguish certain types of engines: let’s find out together what they are.

History of the TDI

TDI is the commercial acronym devised by Volkswagen to indicate its direct injection diesel engines , and it means Turbocharged Direct Injection.

The first TDI was presented in 1989 on the Audi 100 C3, and it was a 2.5 cc with 5 cylinders in line, 120 horses and a maximum torque of 265 Nm; the same, updated engine was installed on the Volkswagen Passat B5 (1.9 115 horsepower).

The second generation of TDI power units arrives in 1998 , with the new pump unit injector with which the pressure was regulated separately for each cylinder.

The third generation TDI instead starts in 2004: it is the common rail direct injection, which combines efficiency, power, eco-compatibility and economy.

A curiosity: the first TDI was the one just described, but the first car equipped with a turbodiesel engine of this type was the Fiat Croma Turbodiesel id (direct injection).

Differences between TDI and diesel engines

The difference is made by the nomenclature, which since its creation has been associated with the German brand Volkswagen: for this reason, TDI is also a logo, the first edition of which was developed in the late 1980s.

This abbreviation is therefore used regardless of the specific technical solution adopted for the fuel system, and there are 3 types of turbodiesel engines marketed under the name TDI :

  • Rotary pump thrusters
  • Injector pump thrusters
  • Common-Rail engines

Here are the differences and the types of displacement.

TDI: rotary pump thrusters

In these engines the power increases and consumption decreases, thanks to the timing belt that moves the injection pump, bringing diesel to the 4, 5 or 6 injectors: compared to the old pre-chamber diesels, the fuel is thrown at higher pressures and atomised more finely .

Among the engines equipped with rotary pump propellers we remember:

1.9 TDI with 90 horsepower and 110
2.5 TDI with 116, 140, 150, 155, 163 and 180 horsepower

Which cars are these engines on? On almost all Volkswagens, but not only: they are also present on Audi, SEAT, Volvo and Skoda.

TDI: injector pump thrusters

There is a substantial difference between rotary pump and injector pump engines: in the latter, in fact, each individual injector has its own pump which pressurizes the diesel fuel. The engine is therefore more bulky and requires a particular cylinder head.

Among the engines equipped with rotary pump propellers we remember:

  • 61 HP 3-cylinder 1.2 TDI (record low fuel consumption)
  • 3-cylinder 1.4 TDI with 69 HP (Euro 4), 75 HP (Euro 3), 80 HP (Euro 4 with DPF) and 90 HP (Euro 4)
  • 4-cylinder 1.9 TDI with 101 HP (Euro 3), 105 HP (Euro 4 with or without DPF), 115 HP (Euro 3), 116 HP (Euro 4, fitted to Audi A4 B7), 130 HP (Euro 3 and Euro 4), 150 HP (Euro 3) and 160 HP
  • 0 TDI (4 cylinders) with 136 HP (8v Euro 4), 140 HP (8 or 16v Euro 4 with or without DPF) and 170 HP (16v Euro 4 with DPF and piezoelectric injectors)
  • 5 TDI with 174 HP
  • 0 TDI with 313 or 350 horsepower

Common-Rail engines

This system was invented by the Fiat Research Center , and includes a high-pressure pump that sends the diesel fuel into a Rail (pipe): from this the injectors that carry the fuel directly into the cylinders start. Common rail engines are silent and guarantee excellent results, both in terms of power and consumption.

The first manufacturer to adopt them was Alfa Romeo, in 1997, with the 156 1.9 JTD, followed by the Mercedes C220 CDI e. Volkswagen instead switched to common rail gradually, starting with the 3.0 TDI V6, fitted to the Audi A6 in 2004.

Among the other engines equipped with rotary pump propellers we mention:

  • 7 TDI with 179 horsepower, then 190
  • 6 with 90, 105, 110 and 116 horsepower
  • 3 TDI V8 with 224 horsepower
  • 0 TDI V8 with 275 horsepower
  • 2 TDI V8 with 326 horsepower
  • 0 TDI with 110, 120, 140, 143, 170, 184, 190, 204 and 240 horsepower (BiTDI = biturbo)
  • 0 V12 TDI with 500 horsepower

TDI is therefore a commercial nomenclature adopted by Volkswagen, and indicates engines equipped with turbocharger and direct injection system, known for low fuel consumption and great efficiency. We remind you, however, that the various types of TDI engines are also used by Audi, Škoda, Seat and Porsche.


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