Alfa Romeo 159 - New 260 bhp 3.2 JTS V6

The Alfa Romeo "cuore sportivo" really beats in the new V6 3.2 litre petrol engine, which delivers 260 bhp.It represents a significant departure from Alfa's previous V6 engine, as well as its natural evolution.

The new JTS engine is capable of a power delivery of 260 bhp (20 bhp or 8% more than the previous 3.2 V6); peak torque of 322 Nm at 4,500 rpm (+ 33 Nm, an increase of more than 11%); a specific power of 60 kW/l and specific torque of 100 Nm/l; a significant increase in torque at low speeds to improve the smooth delivery (approximately 30 Nm more than the previous 3.2 V6 engine, starting from 1500 rpm); maximum revs of 7,200 rpm; minimal maintenance (hydraulic tappets and timing gear with chain drive); low weight (aluminium cylinder head and crankcase); and Euro4 exhaust emissions limits.

With this equipment, the Alfa 159 can reach a top speed of 240 km/h and accelerate from 0 to 100 km/h in 7 seconds.

Main technical features

The new 6-cylinder engine of the Alfa 159 continues the strategy begun with the 4-cylinder engines, and adopts the JTS (Jet Thrust Stoichiometric) direct injection system. This is an original Alfa Romeo concept that injects the fuel directly into the combustion chamber with a stoichiometric mixture optimised to enhance performance, but also guarantees low consumption and respect for the Euro4 emissions limits.

Numerous important components have been designed from scratch and are exclusive to the Alfa Romeo V6 engine. To start with, the cylinder head is aluminium and has 4 valves per cylinder, 2 camshafts per bank with the "Twin Phaser" continuous variable valve timing (intake and exhaust) already adopted on Alfa Romeo 4-cylinder engines and now applied on a 6-cylinder engine for the first time. Variable valve timing allows the phase angle on both cams to be varied by 50°, maximising performance on one hand, because the best phase can be chosen at all engine speeds, and reducing consumption and emissions with partial loads on the other.

At the same time it is possible to optimise the volumetric efficiency of the engine over the whole operating range, exploiting the degrees of freedom offered by variable valve timing: this means a very favourable torque curve, with 90% of peak torque available from 1800 rpm (290 Nm) and maintained over a broad range (from 1800 rpm to 6250 rpm). The valves are controlled by a roller finger system, with low mechanical dissipation, and hydraulic uptake of tappet play.

Another peculiar feature is the camshaft drive system which uses a primary chain that transmits the drive to the heads via two secondary chains. Tension is provided by automatic hydraulic tensioners which need no maintenance at all during the life of the engine.

The high pressure fuel pump of the direct injection system is mounted on the cylinder head, driven by a camshaft, maintaining the pressure of the injected fuel at 120 bar by a built-in pressure regulator.

The inlet ports and combustion chamber assembly is designed to optimise the air-fuel mixture, to achieve the correct turbulence of the inlet air, forming a homogeneous mixture, for stable, complete combustion that produces fewer pollutants. The four valves per cylinder with diameters of 33.4 mm on the inlet and 28.4 mm on the exhaust guarantee suitable permeability to enhance engine performance.
The volumes and port geometry of the aluminium inlet casing have also been adapted to the high air delivery of the high revs to enhance performance. The electronic throttle assembly with a 72 mm throttle valve is mounted on this casing. And finally, the compression ratio of 11.25:1 guarantees excellent engine performance even with regular 95 octane fuel.

Briefly, the main technical features that distinguish the new 3.2 V6 engine from the previous V6 engine are:

• twin overhead camshaft with low friction drive;
• direct petrol injection;
• double continuous variable valve timing on the inlet and exhaust;
• cylinder head in light aluminium alloy;
• hydraulic tappets with automatic play uptake;
• crankcase in light aluminium alloy;
• maintenance-free timing gear drive chain;
• Poly V automatic tensioner belt to drive the engine accessories;
• throttle valve with electronic drive-by-wire activation;
• single ignition coils;
• low specific consumption and emissions;
• EOBD;
• 4 lambda probes to control emissions;
•  double knock sensor to improve knock sensitivity and to optimise peak performance;
• high performance exhaust manifold with built-in pre-catalysts; 
• minimum maintenance;
• Euro 4 emissions

The 3.2 V6 engine features an exhaust system that envisages a first group of catalysing elements relatively close to the cylinder heads to reduce the emissions level at the start of operation. Two catalysts under the floorpan and four lambda probes complete the system, so that the engine respects Euro 4 limits without adopting special systems such as secondary air or electric heating.

Another feature of the 3.2 V6 engine is the direct injection system (the fuel is supplied directly to the combustion chamber) whose main advantage is that it improves evaporation and this increases the engine's volumetric efficiency. As a result, the supply of air and petrol is both denser and colder, which allows the compression ratio to be increased to 11.25, even if Euro Super petrol is used, with an octane index of 95 RON; a high compression ratio is useful because it makes it possible to increase both the performance and the energy efficiency of the engine.

And ignition is provided by a single sparkplug per cylinder. Direct injection combined with 4-valve-per-cylinder geometry creates a mix that tends to be more concentrated at the centre of the combustion chamber. The ignition system fits a single ignition coil per cylinder.

Ports of the cylinders to control the turbulence of the air entering; a throttle valve to prevent shaking if the engine stalls, and an intercooler that is highly efficient thanks to its shape and position in the car, to guarantee the optimal temperature and density of the inlet air.

The electronic EGR exhaust gas cooling system has also been modified; the lubricating circuit has a new oil pump and an external air/oil heat exchanger to cool the oil, while the water pump on the cooling circuit is also new. In other words, a long list of improvements and changes that have produced a reliable, powerful engine which is sparing on fuel. Excellent results, achieved thanks to different engine control settings, an increase in the direct injection pressure to 1600 bar, and new turboblower settings.

The turboboost is provided by a turboblower with a variable geometry turbo that helps to improve the power delivery, but also generates very high torque even at low engine speeds. In fact, 90% of peak torque is available between 1750 and 3500 rpm. These figures translate into extremely enjoyable driving and brilliant performance: the Alfa 159 has a top speed of 228 km/h and accelerates from 0 to 100 km/h in 8.4 seconds. Fuel consumption remains low (6.8 l/100 km in the mixed cycle). A new 6-speed sequential automatic transmission isl also available with the 200 bhp 2.4 JTD Multijet 20v engine, a compact light device that incorporates the control unit in the gearbox, and was designed paying particular attention to consumption. On one hand, the use of low friction oil boosts efficiency, while on the other, the sixth speed has been designed particularly for use on the motorway.