The breakthrough in the field of diesel engines for passenger cars was the use of direct injection. As you know, engines with injection into the combustion chamber located in the piston are more efficient and therefore more economical than engines with indirect injection. The disadvantage of non-pre-chamber combustion is the higher noise level and the problem of exhaust gas purity. These disadvantages were eliminated after introducing high injection pressures, electronic control and pre-injection systems. Direct injection was first introduced in the Fiat Croma TDI in 1988 r., however, the invention was popularized by Volkswagen. The first VW TDI diesel engine with direct injection and fully electronic control was presented to the public at the IAA in Frankfurt in 1989 r. The TDI engine heralded a real revolution in the construction of diesel engines. However, it could only be achieved thanks to this, that other manufacturers also started producing such engines. All of them have contributed to an entirely new image for the diesel engine: sometime slow, noisy and hard working – today he's snappy, comfortable and very economical.

Initially, direct injection was performed by a distributor pump. This made it possible to obtain more power from the turbodiesels (however, the petrol engines were still more powerful with the same displacement) and lowering combustion; however, the distinctive rattling noise of a diesel engine remained. The real breakthrough happened at the end of the years 90., thanks to new injection techniques. In 1990 r. the industrial implementation of the Unijet system has begun – the first variety of Common Rail, developed by Magneti Marelli, Fiat and Elasis Research Center. This phase ended in 1994 r., when Fiat Auto decided to choose the partner with the most experience in the field of diesel injection systems (The injector manufacturing tolerances were not solved). The patent was sold to Robert Bosch, in order to complete development works and implement them into industrial production. By taking over the production rights, Bosch granted the new solution, taken from the English language, nazwę Common Rail. It means common rail, strip (rail = rail). Companies using this solution call them differently, e.g. Peugeot uses the letters HDi (abbreviation of "High pres-sure Direct injection"), i.e. high pressure injection control, to Mercedes – CDI (Com-mon-rail Direct-Injection).

In this way, nine years after the launch of the Fiat Crom TDI, in October 1997 r. Alfa car hit the market 156 JTD, equipped with turbodiesel 1.9 JTD 8V Unijet with the power 105 MILES, delivering previously unattainable results. A real revolution was the Common Rail type power system used in it. Thanks to its numerous advantages, the system quickly won the recognition of most car manufacturers, and soon after its premiere it was put under the hoods of other cars (m.in. Mercedes-Benz models, Peugeot, Renault, Opel, Ford). Today, almost all car manufacturers use this solution, except Volkswagen, who decided to create in 1998 r. an alternative injection system known as PDS (not M. Pump-Duse System) the UIS (Ang. Unit Injector System). This system is about this, that a separate injection pump combined with the injector is provided for each cylinder.