The Multijet System  
 
The intoduction of the Multijet system makes the 1.9 JTD the first second generation Common Rail power unit in the world. It is based on the same Unijet Common Rail principles, i.e. high injection pressure and electronic injector control, but with a slight difference: the number of injections increases from the current two during each cycle. This allows the motor to use the same amount of diesel but in smaller quantities, this achieves a smoother combustion. The benefits are lower running noise, a reduction in emissions and an increase in performance of between 6% and 7%. This result is extremely impressive, particularly in a motor that not only represents a great technological jump forward compared to the prechamber diesel units, but it is also miles ahead of the first generation of JTD motors. The secret of the Multijet system lies in the control unit that gouverns the electronic injector opening and closure system, as well as the injectors themselves. The crucial part of the motor is the electronic control unit in itself, due to its ability to deliver a series of injections in a very closely-spaced window.
Alfa's researchers have developed the part, together with the injectors, specially for this application. It is designed to deliver the multiple injections and to assure that the designer has more accurate control of pressures and temperatures that develop inside the combustion chamber and also a more efficient use of the air intake. This enables further improvements: quieter combustion, reduced emissions and most of all increased power.