The true heart and soul of every Alfa Romeo model is its engine. The New Alfa 156 and Sportwagon are no exception. The new models' attractive, personality-packed looks conceal a diverse range of outstanding high-tech power units that offer generous performance.

Firstly, the brand new 2.4 JTD 5 cylinder Multijet 20v delivering 129 kW (175 bhp) and 385 Nm (39.3 kgm) of torque and the 103 kW (140 bhp), 1.9 JTD Multijet 16v, both members of the latest generation of Common Rail power units, multivalve JTD engines featuring Multijet technology. These are joined by the 85 kW (115 bhp) 1.9 JTD forerunner of the Common Rail power units. 

Alfa Romeo also leads the field when it comes to petrol engines. A 121 kW (165 bhp) 2.0 JTS is available with Selespeed transmission, the first direct injection petrol engine with a specific power output of 61.4 kW/l (83.8 bhp/l). Due to its slightly modified gear ratio, the 2.0 JTS offers greater verve to place more emphasis on driving satisfaction. The 2.0 JTS is a top-performing power unit that owes its name of JTS (Jet Thrust Stoichiometric) to its specific combustion system. 

Conventional petrol engines conclude the line-up of power units available for the New Alfa 156 and Sportwagon: 1.6 T. Spark 16 valve, 1.8 T. Spark 16 valve and 2.5 V6 24 valve (available with manual gearbox or Q-System automatic transmission). 

Both represent a blend of Alfa Romeo's experience with Twin Spark technology. The performance figures are outstanding: the 1.6 T. Spark 16 valve unit achieves a maximum power output of 88 kW (120 bhp), a torque of 146 Nm (14.9 kgm) and can reach a top speed of 200 km/h. It accelerates from 0 to 100 km/h in 10.5 seconds and consumes 8.2 l/100 km over a combined cycle. The 1.8 T. Spark 16v offers a capacity of 1747 cc, 103 kW (140 bhp) maximum power, 163 Nm (16.6 kgm) of torque and a top speed of 208 km/h. It takes 9.4 seconds to speed from 0 to 100 km/h and consumes 8.5 l/100 km over a combined cycle.

Last but not least, the 2492 cc 2.5 V6 24v. The 6 cylinder unit packs maximum power of 141 kW (192 bhp), 218 Nm (22.2 kgm) of torque, reaches a top speed of 230 km/h and consumes 11.8 l/100 km, again over a combined cycle. The acceleration figures for this engine are also at the top of its category: it can speed from 0 to 100 km/h in just 7.3 seconds.

the Multijet system, the secret of second generation JTDs

Second generation turbodiesels continue to work on Common Rail principles, i.e. high injection pressure and electronic injector control. But with one difference: the number of injections increases from the two in use today during each engine cycle. In this way, the same amount of diesel is burnt inside the cylinder but in smaller parts to achieve smoother combustion. 

The benefits include lower running noise, emissions reduction and a 6-7 percent increase in performance, accompanied by an engine output that increases car handling still further. This result is extremely impressive, particularly in an engine that not only represents a great technological leap forward compared to prechamber diesel engines but is also streets ahead of 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) specially 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. Fiat's 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. 

And now this research strand has led to the creation of the Multijet engines: another first for the Fiat Group in the diesel engine field. All this has been possible as Fiat have been building up know-how in this field since 1986, the date that marked the arrival of the Croma TDI, the first direct injection diesel vehicle in the world. At that time, this represented a true engineering breakthrough that was later adopted by other manufacturers. Direct diesel injection engines offered better performance and lower fuel consumption but failed to resolve the problem of excessive engine noise at low rpms and while speeding up or slowing down.

So work began on a more advanced direct injection system and a few years later this led to the development of the Common Rail principle and the Unijet system. 
The idea first came from the Zurich University research laboratories where scientists were working on an injection system that had never before been applied to a vehicle, i.e. the Common Rail system. The idea is simple yet revolutionary: 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. In 1994, when this stage was complete, Fiat Auto started to look for a partner with superlative knowledge of diesel engine injection systems. The final phase of the project, i.e. completion of development and industrial production, was thus eventually entrusted to the Robert Bosch company.

Now our story has reached 1997 and the launch date of the Alfa 156 JTD with its revolutionary turbodiesel engine. Compared to conventional diesel power units, the JTD guarantees an average improvement in performance of 12% together with a 15% reduction in fuel consumption. These results meant that cars fitted with the engine were an immediate hit.

Now the time is ripe for the second generation of JTD engines, the Multijet and multivalve units: in 2002 with the 1.9 JTD Multijet 16v (the forerunner of this new multiple injection family), today with the 129 kW (175 bhp) 2.4 JTD Multijet 20v. 

129 kW ( 175bhp ) 2.4 JTD Multijet 20v  > image

The powerful 5-cylinder 129 kW (175 bhp) 2.4 JTD Multijet 20v, the second engine in the JTD multivalve family with Multijet technology.

This brand-new unit offers various benefits. Firstly, lower noise levels as the engine warms up. The reduction ranges from 3 to 6 decibels according to rpm and environmental temperature. Then, great power (175 bhp - 129 kW at 4000 rpm + 25 bhp compared to the 2.4 JTD 10 valve) and generous torque (385 Nm - 39.3 kgm at 2000 rpm against the 305 Nm at 1800 rpm of the 2.4 JTD 10 valve). The weight/power ratio is 7.9 kgm/bhp, a figure that confirms the true sporting soul of this 2.4 JTD Multijet-powered car. Higher performance compared to the 2.4 JTD 10v with unvaried fuel consumption. Not to mention the fact that the new 2.4 JTD Multijet 20v reduces emissions even without sophisticated exhaust gas treatment devices. 

The new 20 valve unit is derived from the tried and tested 2.4 JTD 10 valve Common Rail unit and takes the form of a 5 cylinder in line unit with bore of 82 mm and stroke of 90.4 mm. The four valves per cylinder are driven directly by a twin overhead camshaft via hydraulic tappets and rocker arms. The new turbodiesel has undergone various technical improvements to increase performance and engine torque at low speeds and reduce noise and vibrations.

For example, the Common Rail system used on the 2.4 JTD Multijet 20 valve unit includes two new strategies for automatically calibrating and balancing the diesel injected to lower noise and reduced vibration. 

CAR PERFORMANCE

Certain components of the engine are brand new: a cylinder head with hydraulic tappets, steel connecting rods and crankshaft, a piston with an internal channel to carry cooling oil to the main and connecting rod bearings that are made out of different material to the previous unit. The intake and exhaust manifolds are also new: the former is made out of a special high-strength material while the latter is made out of pressure cast aluminium. 

The electronic EGR and exhaust gas cooling systems are also new; the lubrication circuit features a new oil pump and an external exchanger (air/oil) for oil cooling; the cooling circuit comes with a new coolant pump. This long series of improvements and changes has culminated in a reliable, powerful engine with low fuel consumption.
Excellent results then, achieved through a new engine control setting; an increase in direct injection pressure from 1350 to 1400 bars; and a new turbocharger setting. 
The power units are turbocharged via a 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 3500 rpm. These statistics add up to a very pleasant drive plus really sparkling performance on the Alfa 156 and Sportwagon.

The Alfa 156 reaches a top speed of 225 km/h (on the circuit) and accelerates from 0 to 100 km/h in 8.3 seconds. The Sportwagon, on the other hand, takes 8.6 seconds to accelerate from 0 to 100 km/h. With very low fuel consumption all round: combined cycle 6.6 l/100 km, urban cycle 8.8, extra-urban cycle 5.3. The figures recorded by the Sportwagon are respectively 6.7 l/100 km, 8.9 l/100 km and 5.5 l/100 km.

Finally, the new 129 kW (175 bhp) 2.4 JTD Multijet 20v fits a new 6-speed manual gearbox. The 3-axle device is more compact than the present one and presents synchronised reverse and a clutch with automatic wear take-up. 

103 kW ( 140bhp ) 1.9 JTD Multijet

At the end of 2002, Alfa Romeo introduced its 103 kW (140 bhp) 1.9 JTD Multijet 16v, the first of the second generation of Common Rail engines in the world. The engine was adopted on the Alfa 147, 156 and Sportwagon with a sporty six-speed manual gearbox and now reappears on the New 156 and Sportwagon. 

The unit is a 4 cylinder in line engine with a bore of 82 mm and a stroke of 90.4 mm, capable of delivering a power output of 103 kW at 4000 rpm and a torque of 305 Nm (31 kgm) at 2000 rpm. 

The advantages and qualities are as described for the 2.4 JTD Multijet 20v, because this turbodiesel has also undergone various technical improvements to increase performance and engine torque at low speeds and to reduce noise and vibrations.

For example, the Common Rail system used on the 1.9 JTD Multijet 16v unit includes two new strategies for automatically calibrating and balancing the diesel injected to lower noise and reduce vibration. It goes without saying that the New Alfa 156 guarantees extremely attractive performance figures: the top speed is 209 km/h (over a circuit) and acceleration from 0 - 100 km/h is 9.3 seconds. The New Sportwagon takes just 9.7 seconds to speed from 0 to 100 km/h. All with very low fuel consumption figures. The saloon is capable of: 

- 5.9 l/100 km over a combined cycle; 
- 4.7 l/100 km over an extra-urban cycle; 
- 8.0 l/100 km over an urban cycle. The figures for the Sportwagon are respectively: 6.1 - 4.8 - 8.2. 

85 kW ( 115bhp ) 1.9 JTD > image

The New Alfa 156 and Sportwagon will again be offering the popular 1.9 JTD direct injection Common Rail turbodiesel unit. 

Introduced for the first time on the Alfa 156 (in 1997), this 4-cylinder unit of 1910 cc develops a power output of 85 kW (115 bhp) at 4000 rpm and a torque of 275 Nm (28 kgm) at 2000 rpm. Equipped with this engine, the Alfa 156 reaches a top speed of 191 km/h (on the circuit), and accelerates from 0 to 100 km/h in 10.3 seconds. The Sportwagon, on the other hand, takes 10.7 seconds from 0 to 100 km/h while its top speed is the same as the saloon.

In these power units, injection pressure is not dependent on engine rpm but is managed independently by an electronically-controlled device. It is also possible to perform a preliminary injection by means of a very short pilot injection of diesel. 

It is worth remembering that because injection supply in conventional prechamber or direct injection diesel systems is controlled by a mechanical pump (often electronically controlled), injection pressure increases as the engine rotation rate rises. This feature limits combustion optimisation and thus also performance, noise levels and emissions. 

With the Common Rail system, however, injection pressure is independent of engine rotating speed and load (accelerator position) because the injection pump generates pressure by accumulation. Because the pump and injectors are controlled by an electronic system, injection pressure and injected fuel quantity can be optimised for each engine service point. 

This means that the injection pressure can be very high and it is also possible (due to the electronic control system) to deliver minimal fuel quantities, i.e. to deliver a preliminary injection known as a pilot injection. These two features bring great benefits to the driver. The former (principle of accumulation) leads to more efficient combustion and thus improved efficiency and performance. The second feature (pilot injection) ensures a great reduction in combustion noise. 

The high pressure value also allows fuel consumption and fume levels to be significantly reduced while the pilot injection creates ideal temperature and pressure conditions in the combustion chamber to perform the main combustion. Preheating the combustion chamber greatly reduces the pressure gradient throughout the cycle that is responsible for combustion roughness and thus the metallic noise typical of conventional direct injection diesel engines. 

Multijet injectors are also adopted to ensure cylinder combustion takes place as accurately as possible. The injectors contain tiny holes that atomise the diesel fuel and spiral intake ports that impose a swirling motion on the air. 

The cylinder head is also cross-flow type for increased turbulence. Highly nebulised fuel and swirling air create a mixture that burns with great efficiency. Compared to a similar prechamber engine, the Unijet power unit improves performance by 12 percent on average and reduces fuel consumption by 15 percent - again on average.

The New Alfa 156 and Sportwagon 1.9 JTD also come with a turbocharger with performance specifications designed for reduced fuel consumption and faster responses (essentially a small turbine and reduced turbo-lag). As far as the customer is concerned, this technical solution means greater driving satisfaction that is further enhanced by electronic control of turbo pressure. 

122 kW ( 165bhp ) 2.0 JTS > image

Here is the first direct injection petrol engine with a specific power of 61.9 kW/l (83.8 bhp/l). In addition, thanks to slight gear ratio modifications, the 2.0 JTS offers a more sparkling drive with consequently greater pleasure at the wheel. An ultra-high performance power unit that takes the name of JTS (Jet Thrust Stoichiometric) from its specific combustion system, an acronym that is destined to identify an entire family of future Alfa Romeo engines. 

As far as the customer is concerned, this means a naturally aspirated two litre car that: 

- already meets stringent Euro 4 emission limits; 
- does not need low sulphur petrol but is able to use the normal petrol already on sale in Europe and the United States.

The New 156 thus confirms the first petrol engine from Alfa Romeo (and indeed Fiat Auto) with injectors that work directly in the combustion chamber. It achieves its end by interpreting the principles of stratified charge and the creation of motion in the mixture inside the cylinder in an entirely original way. 

lean burn, but not too lean

The possibility of injecting petrol directly into the combustion chamber instead of the intake duct has been known since Nikolaus Otto (who took out a patent in 1877) and has been applied for two different purposes over the years. On racing cars in the Fifties and Sixties to increase engine power. More recently (since 1996), to reduce fuel consumption. 

Recently, manufacturers have devoted all their efforts to this latter direction and gratifying results have been achieved with the stratified charge method. The principle is simple: instead of injecting all the petrol required to maintain the normal air-fuel ratio of 14.7:1 (stoichiometric) throughout the combustion chamber, only a small amount of fuel is injected that mixes with the air to form a core of almost stoichiometric composition about the spark plug. The resulting mixture is stratified or layered because it is richer where the ignition spark ignites and increasingly lean (more air and less fuel) as it approaches the outside of the chamber. 

So far the benefits of this lean burn system, usually applied in the rpm band up to 3000 rpm, have amounted to a fuel saving of some 10%. The disadvantages may be summarised as follows: 

- a drop in performance when the car is required to deliver full power (because the ducts and pistons are shaped in a certain way that is essential to reduce fuel - consumption at low speeds); 
- the need to use sulphur-free fuel that is difficult to find in Europe and practically unknown in the US; 
- the requirement for exhaust gas treatment methods (DENox) to reduce the higher nitrogen oxide emissions generated by the leaner burn. 

It goes without saying that Alfa Romeo's approach to the new technology had to be quite different. Category-topping performance and irrepressible driving behaviour have always been essential requirements for all Brand models.

But what was to stop Fiat from using direct injection to increase engine power and torque in keeping with the sporty applications of this technology. Then, they reasoned, they could bring in the stratified charge system to reduce fuel consumption within a restricted rpm band around idle speed. 

The result was an entirely original Alfa Romeo approach to applying direct injection in petrol engines. A solution that offered a compromise between the two methods pursued to date. The New Alfa 156 2.0 JTS works using a lean burn approach up to around 1500 rpm and this saves fuel, although not as much as on other lean GDIs. Above this rpm, the engine burns a stoichiometric air-fuel mixture, i.e. with a normal 14.7:1 ratio between both components. All this means outstanding performance. Much better than would be obtained using a normal indirect injection petrol unit. 

Firstly, because petrol injected directly into the combustion chamber instead of the duct cools intake air to increase the engine's volumetric efficiency. As temperature drops, the gases increase in density and their volume therefore decreases: this means that more air can be introduced into the combustion chamber.

Power unit susceptibility to knock is also reduced by chamber cooling. It is therefore possible to increase the compression ratio - in this case from 10:1 for the 2.0 T. Spark to 11.3:1 for the 2.0 JTS.

This means more power for the new Alfa Romeo engine that is, moreover, able to deliver its power unhindered because the exhaust gas treatment system used on the 156 does not generate the strong counterpressures typical of the Nox absorbers used by lean GDIs.

Direct introduction of petrol into the chamber improves power unit response speed to the accelerator control (it is faster overall than a conventional petrol engine). 

benefits: higher performance & lower fuel consumption

Compared to the 2.0 T. Spark unit, the 2.0 JTS unit fitted to the New Alfa 156 offers slightly lower fuel consumption and a generous increase in power and - above all - torque. + 15 bhp e + 26 Nm. And all this is achieved using petrol currently on sale and current catalytic converters.

In detail, the New 156 equipped with the 2.0 JTS reaches a top speed of 220 km/h (on the circuit) and goes from 0 to 100 km/h in 8.2 seconds (the Sportwagon records the same figures). The saloon consumes 8.6 l/100 km (combined cycle), 6.6 (extra-urban cycle) and 12.2 (urban cycle). Sportwagon fuel consumption is slightly higher, respectively: 8.9 - 6.8 - 12.5. 

a new combustion chamber principle

The new JTS combustion system displays two distinctive features: 

- the principle followed to generate the movement that propels the air and fuel mixture toward the spark plug inside the cylinder; 
- the range of rotation speeds within which the engine works using a lean burn system. 

In other GDI engines, the air's force drags the fuel spray into the area where the ignition spark ignites. This option is determined by a desire to achieve a very lean mixture (up to 60:1) and thus consistent fuel savings. But it brings a need to change the air's motion within the combustion chamber (charge motion) according to rpm level and this complicates the air input mechanisms (throttles, duct closure systems etc.).

On the 2.0 JTS, however, the force of the fuel spray (Jet Thrust) propels the fuel toward the spark plug as it mixes with the air. In this way, we achieve a charge that is less lean overall (the ratio remains constant at all speeds and is 25:1) and less fuel is consequently saved. But the engine's internal mechanism is far less complicated because it lacks systems for altering the air's motion.

The same process of simplification also guarantees the limitation of lean burn technology to rpm levels around idle speed (up to 1500 rpm). GDI engines that use stratified charge within a broader speed band (up to 3000 rpm) must employ modified piston and duct profiles. The resulting shape does not allow power to be optimised at high speeds.

The use of stratified charge only up to 1500 rpm, however, means that the pistons and ducts on the 2.0 JTS Alfa Romeo are hardly altered. Because their shape is more similar to those of current indirect injection engines, they are able to exploit all available power at high speeds.

The addition of an exhaust gas treatment system (Nox absorber) to remote nitrogen oxides is also only required when the lean burn range is extended up to 3000 rpm. This also dictates the use of sulphur-free fuel, i.e. the only type that will not damage the catalytic converter.

The use of stratified charge only at speeds around idle speed, however, allows the 2.0 JTS unit fitted to the New Alfa 156 to use a conventional catalytic converter system. This result is also made possible by a more extensive use of exhaust gas recirculation, which reduces the production of nitrogen oxides (NOx). 

Because Alfa Romeo engines are fitted with variable valve timing, exhaust gas is recirculated to the intake on the 2.0 JTS directly between the intake and exhaust valves (internal EGR). 

engineering: what changes

The main engineering changes on the 2.0 JTS compared to the corresponding Twin Spark engine affect the cylinder head (with Bosch injectors fitted in the chamber), pistons, camshafts and exhaust system. All these components are completely new.

The intake ports are high performance; the fuel manifold is high pressure (common rail type); piston compression ratio is higher - and the exhaust - built to Euro 4 standards - is cascade type.

The exhaust gas treatment system works conventionally despite an unconventional layout: the system no longer consists of a preconverter and a main converter located under the body. Instead it comprises two main catalytic converters built into the manifold (each connected to a double branch that leads to two cylinders). This frees up the space under the body for a silencer that is more permeable and thus more able to reduce counterpressure for fuller engine power delivery.