The Alfa GT's attractive, personality-packed looks conceal a diverse range of outstanding high-tech power units that offer generous performance. They are the best confirmation of the great sporting heart that has always distinguished an Alfa Romeo model, now and forever. The new Alfa GT is certainly no exception.

First up, the sparky 3.2 V6 24 valve unit delivers a power output of 240 bhp (176 kW) at 6200 rpm and boasts a torque curve of 300 Nm (30.6 kgm) at 4800 rpm for exhilarating performance on a sporty run but also during everyday use. The second power unit available is the 165 bhp (121 kW) 2.0 JTS. This is the first direct injection petrol unit with specific power higher than 60 kW/l (82 bhp/l) and a specific torque greater than 100 Nm/l. The third and final diesel unit is the 140 bhp 1.8 T. Spark (103 kW), a blend of Alfa's experience in Twin Spark technology, due to become available after the launch.

The Alfa GT line-up is concluded by the 150 bhp (110 kW) 1.9 M-Jet 16v turbodiesel, forerunner of the second generation of Common Rail power units.

Two manual gearboxes are also available: a six speed unit for the 3.2 V6 24V and 1.9 M-Jet 16v and a five-speed unit for the 1.8 Twin Spark and 2.0 JTS versions. The latter may also be combined with a robotised Selespeed gearbox that offers customers a sporty, comfortable and safe drive in all situations.

240 bhp (176 kW) 3.2 V6 24 valve

The top of the range power unit for the new sports coupé is the lively 3.2 V6 24 valve unit, the same adopted on GTV, Spider and New Alfa 166 models. The powerful 3.2 unit power unit, derived from the now classic V6 24 valve three litre unit, is a vigorous and, above all, 'round' engine in the best six cylinder tradition. The engineers changed the crankshaft and pistons to increase the cylinder capacity to 3.2 litres and lengthened the stroke to 78 millimetres. This change speaks volumes about the type of performance required because the power could simply have been increased by adjusting the timing, fuel system and electronics.

The fact that cylinder capacity has been increased by lengthening the stroke means that the aim was not simply to obtain out-and-out performance coupled with high power and torque peaks but also an even, gradual power delivery from the lowest speeds. As befits a car capable of thrilling performance that is suited for driving on ordinary roads as well as on the track.

The increase in cylinder capacity is naturally accompanied by a whole set of changes. The intake and exhaust ports have been tuned by applying a new timing pattern, the control unit software has been rewritten and the cooling system has been upgraded with the addition of an engine oil radiator.

The result, power output is 240 bhp (176 kW) at 6200 rpm with a maximum torque of no less than 300 Nm (30.6 kgm) at 4800 rpm. These figures are all it takes to achieve exciting performances and are complemented by a torque curve that permits high values at low speeds. The car can also travel in sixth gear at less than 2000 rpm and unleash speed spurts without changing gear. Extremely satisfying behaviour, therefore, even during daily use. The self-confessed goal of the Alfa GT is this: to offer sensations unique to a racing car yet still be perfectly serviceable for everyday use.

165 bhp (121 kW) 2.0 JTS

The 2.0 JTS is a top-performing power unit that owes its name of JTS (Jet Thrust Stoichiometric) to its specific combustion system. As far as the customer is concerned, this means a two litre car that: already meets tough 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 2.0 JTS thus represents a true technological leap for Alfa Romeo, its first petrol engine with injectors that work directly inside 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 in 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 costly, delicate 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.

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 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 also able to deliver its power unhindered because the exhaust gas treatment system used on the Alfa Romeo models 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 and lower fuel consumption

Compared to the current 2.0 T. Spark unit and other currently-available direct injection petrol engines, this 2.0 JTS unit offers slightly lower fuel consumption and a generous increase in power and - above all - torque. + 15 bhp and + 25 Nm. To sum up, the 2.0 JTS develops a maximum power of 165 bhp (121 kW) at 6400 rpm and a maximum torque of 206 Nm (21 kgm) at 3250 rpm. And all this is achieved using petrol currently on sale and current catalytic converters.

- 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.

Let's take a look at the first point. 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 noteworthy 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 Alfa Romeo 2.0 JTS 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.

Because the lean burn range has been extended up to 3000 rpm, the system requires the addition of an exhaust gas treatment system (Nox absorber) to eliminate the nitrogen oxides. Sulphur-free petrol must also be used because this is the only type that does not damage the catalytic converter.

The use of stratified charge only at speeds around idle speed, however, allows the 2.0 JTS unit 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, both 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.

110 kW (150 bhp) 1.9 M-Jet 16v

At the end of 2002, Alfa Romeo introduced its 140 bhp 1.9 M-Jet 16v , the first of the second generation of Common Rail engines anywhere in the world. The engine was adopted on the Alfa 147, 156 and Sportwagon with a sporty six-speed manual gearbox and has now been further developed for the Alfa GT, offering a power output of 150 bhp.

The unit is a 4 cylinder in line engine with a bore of 82 millimetres and a stroke of 90.4 mm, capable of delivering a power output of 110 kW at 4000 rpm and a torque of 305 Nm (31 kgm) at 2000 rpm.

The new turbodiesel has undergone several engineering changes to increase performance and engine torque at low speeds and to reduce noise and vibration levels. For example, the Common Rail system used on the 1.9 M-Jet 16v includes two new strategies for automatically calibrating and balancing the diesel injected to lower noise and reduce vibration.

It goes without saying that the Alfa GT guarantees extremely attractive performance figures: the top speed is 209 km/h and acceleration from 0 - 100 km/h takes place in 9.6 seconds. All this comes with very frugal fuel consumption. The new sports coupé offers:

• .6.7 l/100 km over a combined cycle;

• 5.4 l/100 km over an extra-urban cycle;

• 8.7 l/100 km over an urban cycle.

The M-Jet system, secret of second generation JTD engines

The underlying principles of second generation turbodiesel engines remain the same, i.e. high injection pressure and electronic injector control. With one extra feature: 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 M-Jet lies in the control unit that governs the electric injector opening and closure system (and also in the injectors themselves). The crucial element is the electronic control unit itself that can perform a set of injections that may be very closely spaced. 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 M-Jet 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.

And now this research strand has led to the creation of M-Jet engines: another first for the Fiat Group 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.

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. 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.

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.