Turbocharged Direct Injection

TDI is the marketing name for diesel engines with direct injection and turbocharging of the Volkswagen Group. TDI means Turbocharged Direct Injection Turbocharged Diesel and Injection.

The TDI engine family is used in vehicles of the Volkswagen, Audi, Seat and Skoda. They were also used in previous VW - Ford joint venture Ford Galaxy and the Volvo 850 TDI. Other users were Mitsubishi ( Grandis and Lancer ) and Chrysler ( Sebring et al ).

In contrast, the diesel engines offered by Volkswagen under the symbol SDI also work with direct injection, but without turbocharging. see also: Suction


The cylinders of the TDI engines have no auricles or swirl chambers; the glow plugs are located in the combustion chamber, which is located in a generally circular recess in the piston crown. The lower combustion chamber surface compared to Vorkammer-/Wirbelkammermotor permits lower heat losses and improved efficiency; also there is no throttled ( lossy ) overflow from the pre-or swirl chambers in the actual combustion chamber. Therefore, these motors have a very low consumption. The principle requires higher pressure increases and therefore much louder engine noise. Generally, all turbocharged diesel engines on a certain starting weakness, which is due to the thrust load immediately accreting the exhaust gas turbocharger. This property, known as turbo lag is noticeable between the engine idle speed of about 1000 min-1 and the effect of the turbocharger of about 1300 min - 1 Engine speed. The TDI engines, the maximum torque is achieved at approximately 1800 to 2200 min -1.


Diesel direct injection existed before the Second World War. Today, the direct injection is the preferred method in nearly all diesel engines. Only in the area of high-speed small diesel ( Zylinderhubräume of 500 cc or less) the procedure relating to metering of fuel, the pressure generation and the quietness was problematic. These problems led to the development of pre-and swirl-chamber engines. Only the possibilities of electronically influenced fuel metering made ​​it possible to make best use of direct injection in - car standards.

First generation TDI distributor injection pump

After Fiat Croma 2000 Turbo D i.d. (1986 ) and the Austin Montego MDi (1988 ) was at the IAA 1989 Audi 100 2.5 TDI introduced the world's third passenger car with a diesel direct injection. The Audi five-cylinder diesel engine based on the 1972 Audi 80 for the first time used Audi / VW four-cylinder engine type 827 on the basis of which opened in 1976 and the first swirl chamber diesel engine for the VW Golf. The engine of the first Audi 100 TDI 88 kW (120 hp). The maximum torque of 265 Nm is available from as from 2250 min -1 and also in the lower rpm range sufficient thrust. The performance can be seen with about 200 km / h as well as the consumption of only about 6 liters per 100 km. Already the first TDI engines have an electronically controlled distributor injection pump of Bosch ( VP36 or VP37, axial-piston distributor injection pumps ). You inject at a pressure of up to 950 bar at a nominal power. As of 1991, the Audi 80 was followed with a slightly smaller 1.9-liter four-cylinder engine with an output of 66 kW (90 hp) and 182 Nm of torque.

In 1993, with a largely identical engine, the first Golf III TDI with 66 kW of power also on the market. Problem in the first TDI was the one that still hard running behavior. Therefore, the TDI in the Golf III only came with greater delay to the production stage, since the possibilities of sound insulation are much more unfavorable in its relatively small engine compartment. In addition, the very good for its time efficiency of about 38% caused a slight and late cooling water heating. Therefore, were the winter characteristics, in particular the effect of interior heating and thus of the windshield defroster is unsatisfactory. In order to still satisfy even the wintry conditions, an electrical heating element was integrated in the cooling water channel. This so-called " auxiliary heater " in the line to radiator heating accelerates the heating of the cooling water and the heating air. The alternative is a diesel-powered heater at the Audi TDI. Word spread quickly that this additional device could be extended by Eberspacher with just a little effort into a full parking heater.

Even the TDI engines of the first generation were targets of chip tuning measures, which are often overtaxed the motor mechanics. Therefore, VW and Audi later brought more variants on the market. In 1996, the 81 kW TDI came ( identified by the red I). This not only has a different engine software, but also with stronger connecting rods and pistons. This engine, first used in the Audi A4 B5 was the first car - Series engine with an efficiency above 40%. In addition, there was for many years a six-cylinder V-engine with distributor pump (radial piston distributor injection pump ) on offer.

Second-generation TDI with pump-nozzle technology

The first vehicles with pump-nozzle technology came in 1998 in the former VW Passat ( 3B5 ) on the market. These vehicles do not have a separate injection pump more. This was replaced by a cylinder-piston element, which is mounted on the injector. Both together are called pump-nozzle element. Installed it in the cylinder head. The cam exerts a third cam in each cylinder ( in addition to those for the intake and exhaust valve) force on the pump-injector, so that the fuel pressure builds up.

This system is already known from the commercial vehicle industry. Pump-jet engines operate at rated power at a pressure of up to 2050 bar, which has long been the highest pressure in the passenger car diesel engine construction. Accordingly, the efficiency and fuel economy improved. Thus, the three-liter Lupo VW and also the one-liter car is equipped with such a system. The efficiency of these motors are the three- liter car at 45 %. VW hoped that this technology the big breakthrough, which did not succeed because the system requires very tight manufacturing tolerances. Accordingly, such an engine is expensive. However, since the Volkswagen group also sells many company vehicles, meant the pump-nozzle technology a certain competitive advantage due to the lower consumption, but then what led to the spread of technology. This type of engine was phased out by the year 2010.

As of 2000, the TDI engine with 96 kW was introduced in the VW group: eg VW Passat (2000 ) and golf (2001), Audi A3 (2000 ), A4 (2000), and A6 (2001) and Skoda Superb ( 2001). In 2003, this TDI engine in the VW Sharan was blocked with 96 kW and 110 kW. Half a year later, this engine versions followed in other models such as: Škoda Fabia RS, Octavia, VW Polo, Seat Leon and Ibiza. From the year 2005, exclusively in Ibiza Cupra, a TDI engine with 1.9 liter displacement and 118 kW at 3750 min-1 offered. The maximum torque was 330 Nm at 1900 min -1.

With the Touran and the Golf V ( 2003) also came to the newer generation of TDI, now with 2 liters out ( 2.0 TDI). At that time there was only him with 100 kW (136 hp) and a short time later 103 kW ( 140 hp). This engine had, as long as it was not equipped with a diesel particulate filter ( DPF), 16 valves instead of the usual eight. Meanwhile, there is this 2.0 TDI in an uprated version with 125 kW ( here with 16 valves ) and is, for example, offered the Golf GTI, Audi A3 and Seat Leon FR TDI. This unfolds the maximum power is no longer at 4000 min -1, but at 4200 min -1.

Third-generation TDI with common -rail technology

TDI of the third generation direct injection with common- rail technology. Here is generated in a shared (common ) line ( rail), a constant high pressure during the injection timing is controlled by solenoid valves. The first engine is a V8 diesel engine in the Audi A8 1999 was equipped with this technology. Here spoke a high comfort claim against a pump-nozzle injection system. In the end proved to be the common-rail technology, which has already been used in 1997 by Fiat Alfa Romeo 156 for the first time, more comfortable and technically superior as significantly more cost-effective. The first four-cylinder engine with Common Rail for passenger cars in the Volkswagen Group was launched in 2007 in the Audi A4 and VW Tiguan to the market. The Audi A6, the Phaeton and the Touareg have been equipped since 2004 with a common-rail V6 engine and thus initiated the parting of the pump-nozzle technology at Volkswagen. Next, the Passat model has been converted to the new technology in February 2008. On the truck side of the VW LT was offered from 2002 with a common-rail engine.

VW 's largest supplier of pump-nozzle vehicles has made ​​this technology now withdrawn for several reasons, with the last 4- cylinder engines were changed:

  • The controllable injection pressures of common rail systems ( CR) reached 2007, the pump-nozzle level (PD ) with pressures of 2000-2200 bar
  • The CR can inject with its independent pump any time with full pressure, while PD is dependent on the camshaft contour, which is especially during the pre- ( running) and a post-injection ( diesel particulate filter regeneration ) is disadvantageous
  • The system costs of PD will increase more than in CR with the number of cylinders
  • Because of the large spread of CR, even in cars of the competition, the system costs can fall further in the future than in the VW - exclusive PD

Generally, common rail systems a simple structure with few components, similar in principle to an old L- Jetronic fuel injection system from the 1980s.

Meaning of the colored letters in the TDI logo

The VW TDI engines have a special feature in the design of the type lettering. So a 81 kW ( engine code AFN and ASV ) uprated version of the 66 kW ( 1Z, AHU, ALE ) was created the first generation from 1996. This showed for the first time on an adjustable guide vane turbocharger ( VTG), a different engine software and reinforced connecting rod bearings ( sputter ). Such vehicles were equipped with a " red I" in the logo. Later, the pump -jet engines came with a red "D" and "I" to do so. On the Golf IV with 110 kW (letter, among other things ARL ) was used a completely red lettering. The smaller pump -jet engines with 85 kW, 96 kW and 74 kW least had in the Gulf a silver "T" and the letters " DI " red in the type designation.

A conclusion from the lettering on the engine is possible only with knowledge of the model year. The " blue I" is often seen on transporters and indicates a very low and small TDI without intercooler out. A green " DI " is to find the three-liter Lupo.

The Seat Leon 1M there was the model topsport (TS ), which was later renamed Formula Racing (FR). These carry the 110 kW engine also a complete red TDI.

Brand TDI

"TDI" is a registered trademark since 9 August 1995 for AUDI AG in Nice class entered 12 (engines for land vehicles), as well as in various combinations. Than word - figurative trade mark for Volkswagen AG According to a decision of the European Court, it is not a brand but a " technical abbreviation ," and therefore can not be registered in Europe as a unified brand.