CATEGORY TOPPING ENGINES
 

The New Doblò (car and Cargo) offer a diverse range of power units that enhance the model's attributes: a car that is easy to drive, comfortable, safe while in motion and easy on the environment. Different fuel systems are available: petrol, diesel and methane/petrol. This is the best demonstration of the Fiat Group's perennial commitment to safeguarding the environment and satisfying customers in terms of performance and fuel consumption.

In detail, the car and Cargo version share a 77 bhp 1.4 Fire 8v version and a 1.6 Natural Power (petrol and methane) version. And more, the New Doblò can also be driven by three turbodiesel units (85 bhp 1.3 16v Multijet and 105 and 120 bhp 1.9 8v Multijet) while the Cargo can be fitted with a 75 bhp 1.3 16v Multijet and 105 bhp 1.9 8v Multijet. In particular, the 85 bhp 1.3 and the 120 bhp 1.9 are equipped with a variable geometry turbocharger and a particulate trap (DPF). After the launch, the 85 bhp 1.3 16v Multijet and the 120 bhp 1.9 8v Multijet will also be available on the commercial vehicle.
 

	1.4 Fire 77 bhp	1.3 Multijet 75 bhp	1.3 Multijet 85 bhp
New Doblò	X		X
New Doblò Cargo	X	X	o

	1.9 Multijet 105 bhp	1.9 Multijet 120 bhp	1.6 Natural Power
New Doblò	X	X	X
New Doblò Cargo	X	o	X

o available after the launch

Diesel power units: history of a Fiat record

75 and 85 bhp 1.3 16v Multijet

The New Doblò would not be complete without the 1.3 16v Multijet, the smallest, most advanced of the second-generation Common Rail direct injection diesels. And now we welcome a new 85 bhp version with a variable geometry turbocharger. With the turbocharger, the 1.3 16v Multijet delivers no less than 85 bhp (62 kW at 4000 rpm) of maximum power and a torque of 200 Nm (20.4 kgm at 1750 rpm) to ensure outstanding performance and one of the best fuel consumption figures in the category.

The 1.3 Multijet also ensures excellent performance and fuel consumption with a power output of 75 bhp (55 kW at 4000 rpm) and a torque of 19.4 kgm (190 Nm at 1750 rpm). Apart from its different turbocharging system (the 75 bhp 1.3 Multijet is turbocharged by a fixed geometry turbocharger), the new power unit features further changes. The combustion system has been changed to increase the permeability of the intake and exhaust ducts, reducing combustion chamber swirl and altering the geometry and compression ratio from 18:1 to 17.6:1. The emission control system includes an electrically operated EGR valve managed directly by the engine control system, an exchanger to cool recirculated exhaust gases and a close coupled catalytic converter. All these devices are to ensure Euro 4 emission limits are met.

So much for the differences between the 75 and 85 bhp versions. The structure of the power unit is common to both. The unit is a 1248 cc 4 cylinder in line power unit with a bore of just 69.6 mm and a 'long' 82 mm stroke. The four valves per cylinder are driven directly by a twin overhead camshaft via finger rockers with a roller. And more. The 1.3 Multijet 16v is a true masterpiece of miniaturised technology: when clad with all its accessories it weighs just 130 kg. Its size is small (it is less than 50 centimetres in length and 65 cm high) and its component layout has been designed to take up as little room as possible.

The power unit is designed in accordance with criteria of maximum rationalism, efficiency and reliability. It offers outstanding performance and practically comes with a lifetime guarantee. It was made to last 250,000 km without any maintenance to its mechanical parts. The oil change intervals have been set at 30,000 km (the 1.3 Multijet 16v uses low viscosity oil. It is therefore thrifty with fuel and also respectful of the environment).

This compact and technologically sophisticated new power unit is also environmentally friendly because it meets Euro 4 emission limits. The version with variable geometry turbocharger also features a DPF (Diesel Particulate Filter) for the exhaust gases. 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 1.3 Multijet 16v (75 or 85 bhp) therefore represents a true technological leap that translates into a reduction in fuel consumption and emissions for the customer. Not to mention the lower noise levels (due to the multipoint injections); improved comfort (fewer alternating masses for less vibration); smooth, satisfying drive (due to outstandingly gradual torque delivery guaranteed in turn by more effective control of combustion); the flexibility and prompt responses of a diesel that is more and more like a petrol engine due to its broader rpm range (e.g. the fuel cut-off can no longer be felt over 4000 rpm) - and green attributes that allow the main benefits of diesel technology (fuel economy) to be improved as far as the environment is concerned by minimising the main defect (particulate emissions).

105 bhp and 120 bhp 1.9 Multijet

Both with 4 cylinders in line - two valves per cylinder - with bore of 82 millimetres and stroke of 90.4 mm, the former delivers a power output of 105 bhp (77kW) at 4000 rpm and a torque of 200 Nm (20.4 kgm) at 1750 rpm - the latter 120 bhp (88 kW) at 4000 rpm and 200 Nm (20.4 kgm) at 1750 rpm. Both power units have undergone several engineering changes to increase performance and engine torque at low speeds and to reduce noise levels and vibration. The 120 bhp 1.9 Multijet unit is turbocharged via an electronically-controlled Garrett turbocharger with variable geometry turbine that helps improve power delivery by 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. Like the 1.3 Multijet, both 1.9 Multijet engines also meet Euro 4 regulations, due to the EGR emission control system described above. The 120 bhp power unit also offers a particulate trap.

The Multijet system fitted to second generation JTD engines

The Multijet turbodiesel engines fitted to the New Doblò are veritable gems of automotive engineering and confirm 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. But we had been putting in a lot of hard work behind the scenes since 1986, the date that marked the arrival of the Croma TDI, the first direct injection diesel vehicle in the world. The Croma engine was an outstanding result for the time and the first major step toward automotive diesel engines with more efficient combustion. The engineering, subsequently copied by other manufacturers, meant that diesel cars were able to ensure better performance coupled with lower fuel consumption. One problem remained: excessive engine noise at low rpms and during speed transients. This was the cue for the start of the Unijet story, i.e. the quest for a more advanced direct injection system that could drastically reduce the problem of excessive combustion noise. Some years later, this research strand brought us the Unijet itself and significant benefits in terms of efficiency and fuel consumption. We reasoned that the problem could be resolved in one of two ways: we could be content with a passive system and simply insulate the engine to prevent sound waves from reaching the passenger compartment - or we could work actively to eliminate the problem at its source by developing an injection system that actually reduced combustion noise. Fiat Group engineers chose the second option and immediately chose the Common Rail principle after considering and then rejecting other high-pressure injection systems.
 

The other systems do not allow pressure to be managed independently of rpm and engine load and neither do they include a pre-injection, which are essential attributes of the Unijet system. The theory that lay behind our research was originally developed by researchers at Zurich University but had never previously been applied to a vehicle. This simple yet elegant theory is based on the assumption that if you continue to push diesel into a tank, the pressure inside will rise and the tank itself will become a hydraulic accumulator (or rail), i.e. a reserve of pressurised fuel ready for use. Three years later, in 1990, the Unijet system developed by Magneti Marelli, Fiat Research Centre and Elasis on the Common Rail principle entered the pre-production stage. This stage was completed in 1994, when Fiat Auto started to look for a partner with superlative knowledge of diesel engine injection systems. The final stage of the project, i.e. completion of development and industrial production, was eventually entrusted to Robert Bosch. In October 1997, eleven years after the Croma TDI, the market welcomed another record-breaking car: the Alfa 156 JTD. The new model was equipped with a revolutionary turbodiesel engine that was to deliver previously unimaginable results. Vehicles equipped with this engine are incredibly noiseless with all the alacrity of a petrol power unit. They improve on the performance of a similar prechamber engine by an average of 12 per cent and reduce fuel consumption by 15 percent. The Alfa 156 equipped with a JTD engine won immediate success and similar power units soon appeared on other Fiat Auto models and were adopted by many other motor manufacturers. Now the time is ripe for the second generation of JTD engines, the Multijet and multivalve units.

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. Now this line of research has led to the development of the Multijet engines that are also fitted to the New Doblò.

77 bhp 1.4 Fire 8v

The new engine offers a cylinder capacity of 1368 cc and a 4 cylinder in line configuration with bore of 72 millimetres and stroke of 84 mm. The two valves per cylinder are driven directly by an overhead camshaft.

The power unit was developed with particular attention to performance and fuel consumption, an area where the New Doblò excels in its category. This is due to the fact that the volumetric efficiency has been optimised throughout the service range due to painstaking fluid dynamic development studies on the entire intake and timing system. The result is a power output of 56.5 kW (77 bhp) at 6000 rpm and a maximum torque of 11.7 kgm (115 Nm) at 3000 rpm. This is therefore a feisty yet frugal engine due to the adoption of a drive by wire electronic throttle valve control system and, above all, the application of a new high swirl combustion chamber that is associated with a variable valve timing system managed by the control unit. This innovative system allows a significant proportion of the exhaust gases (approximately 25%) to be recirculated to the combustion chamber, thus significantly reducing fuel consumption and exhaust emissions when driving under partial load. This engine has also benefited from certain improvements that help keep fuel consumption down. For example, the timing system components have been made lighter and the valve springs are low load to reduce friction.

Another specific feature of the new 77 bhp 1.4 engine is the increase in compression ratio (11:1) and the high torque values at low speeds, qualities that have allowed fuel consumption to be kept low. This aim is also achieved through the tuning of the cutting edge engine control system that succeeds in cutting fuel consumption as far as possible while still maintaining handling, performance and low emissions. The 77 bhp 1.4 Fire power unit already meets Euro 4 legislative requirements due to a catalytic converter located in the engine compartment (and welded to the exhaust emission manifold flange using a new method) that reaches high temperatures within a shorter time period and thus reduces emissions even during the power unit heating stage. To minimise the environmental effect, the new engine is also equipped with a returnless fuel system that eliminates fuel recirculation within the tank and thus reduces vapour formation. High-performing, thrifty and clean: the 1.4 77 bhp complements these winning qualities with excellent acoustic comfort due to the adoption of a flexible flywheel that minimises the transfer of engine vibrations to the body.

Natural Power: the environmentally-friendly version

The Doblò 'Natural Power' engine, available on the Cargo and the car, offers two independent fuel systems: one petrol, the other methane (CNG natural gas). The vehicle is configured to run normally on natural gas, though the engine always starts up on petrol before transferring immediately and automatically to methane fuel. In this way, the petrol fuel system remains efficient and is only required at start-up or when the methane is about to run out. Customers can always switch to a petrol fuel system by pressing a key located on the console near the handbrake lever.

The methane fuel system is a Phased Sequential Multipoint system that allows the sophisticated electronic control methods of petrol engines to be adapted to the properties of methane. This achieves significant results in terms of handling, exhaust emissions and fuel consumption. When the engine is running on methane, it must be considered that engine power and torque are reduced by some 10% under all driving conditions compared to the levels achieved when running on petrol. The power output with the methane configuration is 68 kW (92 bhp) at 5750 rpm compared to 76 kW (103 bhp) at 5750 rpm when running on petrol. Torque is 130 Nm at 4000 rpm when running on methane compared to 145 Nm at 4000 rpm when running on petrol.

The difference between the Cargo and car versions lies in the number and location of the cylinders. The New Doblò methane tank consists of two cylinders (diameter 316 mm and length 1050 mm) located in the luggage compartment, containing methane in the gaseous state (rated pressure 200 bars at 15° C) and capacity of 126 litres (equivalent to 21 kg, i.e. 30.9 m3). The New Doblò Cargo tank, on the other hand, consists of 3 cylinders (with a capacity of 111 litres, equivalent to 18 kg, i.e. 26.4 m3) and is housed under the floorpan: this system leaves the load compartment volume unaffected. The New Doblò 'Natural Power' ensures low fuel consumption and minimum emissions in absolute safety to enable customers to drive through town areas affected by traffic restrictions. Natural Power versions also offer the same passive and active safety features as other versions powered by conventional power units: the cylinder positions and attachments are designed to overcome the most severe impact tests. The cylinders are also protected by a special steel structure covered by a mat to prevent damage. The flow of methane out of individual cylinders is governed by a solenoid that is opened only during methane operation. The solenoid unit includes devices to protect against excess flow and temperature. The solenoid is connected to the Fire Protection System (inertia switch or fuel cut-off switch).