FLEXIBLE ENVIRONMENTALLY FRIENDLY ENGINES
 

The Fiat Sedici is equipped with two engines (a 1.6 petrol and a 1.9 turbodiesel unit), both combined with five or six speed manual gearboxes with precise shift and low load values. In particular, the 120 bhp 1.9 8v Multijet unit ensures outstanding power and torque values for low fuel consumption under all driving conditions: a veritable gem of automotive engineering that confirms Fiat Auto's leadership in this field. Development of the Multijet system has also allowed the Fiat Group to achieve an important new record in the diesel engine field. The Fiat Sedici Multijet engine meets Euro 4 standards and is fitted as standard with a particulate trap (DPF) that lowers fine powder pollution. This for life system does not require the use of additives for regeneration and also attracts tax benefits. When fitted with this engine, the new model can also be driven freely through areas where traffic is restricted for environmental reasons.

120 bhp 1.9 Multijet

The unit is a 4 cylinder in line engine - two valves per cylinder - with a bore of 82 millimetres and a stroke of 90.4 mm, capable of delivering a power output of 120 bhp (88 kW) at 4000 rpm and a torque of 280 Nm (28.6 kgm) at 2000 rpm. The power unit has undergone several engineering changes to increase performance and engine torque at low speeds and to reduce noise and vibration levels. The 120 bhp 1.9 Multijet unit is turbocharged via an electronically-controlled turbocharger with variable geometry turbine that helps improve power delivery while also allowing very high torque delivery even at low rpms. Suffice it to say that 90% of maximum torque is available between 1750 and 3250 rpm. These data translate into great driving satisfaction and hot performance. The 1.9 Multijet engine also meets Euro 4 standards due to its EGR emission control system that includes an electrically-operated valve managed directly by the engine control system, a heat exchanger for cooling recirculated exhaust gases and a close coupled catalytic converter. The presence of a particulate trap DPF (Diesel Particulate Filter) also contributes to the green nature of this engine. This mechanical filter is installed in the exhaust system and physically traps the carbon particles present in the Diesel engine exhaust gas. During normal service, the engine control unit records a set of data (service period, route type, temperature reached) and calculates the amount of particulate that has built up in the filter. Because the trap is an accumulation system, it must be regenerated regularly (cleaned) by burning the carbon particles. The engine control unit manages the regeneration process automatically according to the amount of carbon that has accumulated in the filter and vehicle service conditions: all this without the need for additives and without requiring any particular maintenance operations.

The Multijet system fitted to second generation JTD engines.

The underlying principles of second generation turbodiesel engines remain the same, i.e. high injection pressure and electronic injector control. But one extra feature has been added: during each engine cycle, the number of injections increases over and above the current number of two. In this way, the same amount of diesel is burnt inside the cylinder but in several portions to achieve smoother combustion. The advantages include lower running noise, reduced emissions and a 6-7% increase in performance. All this comes with a level of engine efficiency that improves car handling still further. These results are not to be underestimated, particularly because they are obtained with an engine that represents an incredible leap forward from prechamber diesels and even improves on first generation JTD engines. The secret of the Multijet engine lies in the control unit that governs the electric injector opening and closure system (and also in the injectors themselves).
 

The crucial part of the engine is the electronic control unit itself, due to its ability to deliver a series of very closely-spaced injections. Fiat Auto's researchers developed the part (together with the injectors) especially for this application. It is designed to deliver the multiple injections that assure the designer more accurate control of pressures and temperatures developed inside the combustion chamber and also more efficient use of air taken into the cylinders. This enables further goals to be achieved: quieter combustion, reduced emissions and increased performance.

The Multijet system is underpinned by long years of research. Our engineers began by resolving the problem of limits imposed by the control units. Then they went on to map the benefits they could achieve by plotting different multiple injection sequences (two secondary injections very close to the main injection; one secondary injection not too close to the main injection plus two closely-spaced secondary injections; one secondary injection and then two main injections close together after a certain period etc.) against different engine service conditions: in the idling region; with low loads and low rpm; with high rpm and moderate load; with low rpm and high load etc. The study revealed the potential of the system and showed that great benefits are achievable in all cases, though these tend to focus on one field or another according to the type of sequence chosen and the engine service area targeted. In some cases, for example, the priority is to reduce start-up times and fume levels, in other cases it is to increase torque and reduce noise while in others it is to reduce emissions and ensure a quieter drive. This research led to the production of Multijet engines, including the 120 bhp 1.9 Multijet 8v unit fitted to the Fiat Sedici.

79 kW 1.6 16 valve (107 bhp)

The Fiat Sedici may be equipped with a powerful and flexible 1600 cc petrol engine: this is a 4 cylinder inline unit with a bore of 78 millimetres and stroke of 83 mm (four valve per cylinder) that develops a power output of 79 kW (107 bhp) at 5600 rpm.  The new engine is ideal for town driving and twisting roads and was developed with particular attention to performance and fuel consumption. It owes its qualities to a variable timing system that helps optimise torque and power at any speed.

The new engine is also fitted with a VVT (Variable Valve Timing) system that allows the intake and exhaust valve timing to be varied. This system optimises cylinder filling and also allows internal EGR (Exhaust Gas Recirculation) to be implemented by making intake and exhaust valve opening overlap for a considerable improvement in emission and performance. This ensures combustion is more complete and thus improves performance. For example, the more efficient combustion allows better performance and increased torque at low speeds: the maximum is 145 Nm (14.8 kgm) at 4000 rpm, to benefit driving flexibility. A Fiat Sedici with this engine can achieve a top speed of 170 km/h and the fuel consumption figures are low: 8.9 l/100 km over an urban cycle, 6.1 l/100 km for an extra-urban cycle and 7.1 l/100 km over mixed routes. In other words, a vigorous yet frugal engine. The 107 bhp 1.6 16v engine complements these performances with respect for the environment, as evidenced by the low emission values.