Engines

V6 Engine (ES9J4S)

The 2,946 cm3 ES9J4S engine features six cylinders mounted in a 60° V configuration. It has changed considerably with respect to the 1996 version mounted on the XM and Xantia, especially in the design of the combustion chambers and valve gear. Friction has been reduced throughout, and the total weight has been reduced by 10 kg.
These technical advances bring the following major improvements :

• eight per cent increase in maximum power output compared with the earlier version, to 152 kW (210 bhp) at 6,000 rpm, and 6 % increase in maximum torque, to 285 Nm (29 m. kg) at 3,750 rpm, with a 10 % increase in low-end torque, to 260 Nm (26.5 m. kg) from 2,000 rpm ;

• lower fuel consumption under identical driving conditions ;

• improvement of one litre per 100 km in the standard combined cycle ;

• oil-change service interval lengthened to 30,000 km, 

• and spark-plug change interval lengthened to 120,000 km ;

• compliance with Euro 4 emission limits without any additional equipment.

Engine design changes include the following :

• variable valve gear, with the inlet camshafts incorporating variable timing ;

• modifications to combustion chambers and inlet manifold ;

• new multiple-jet injectors ;

• electronic throttle ;

• six ignition coils ;

• flexible” engine flywheel ;

• compliance with Euro 4 emission limits, with two pre-catalysts and four lambda sensors ;

• additional water / oil intercooler.

Structure

The aluminium cylinder block is fitted with cast iron cylinder liners. Four cast iron crankshaft bearings are fitted to the aluminium crankcase at the casting stage. Major design changes to the aluminium cylinder head include enhanced combustion chambers and inlet ducts, which increase power output and torque, while lowering exhaust emissions.
The new inlet manifold, in composite material, comprises six ducts of equal length. These are mounted on an aluminium distributor attached to the cylinder heads in the centre of the V. The distributor comprises 12 ducts, each with a variable cross-sectional area, and each feeding a single valve. 
This layout optimises the flow into the cylinders.
The position of the electronic throttle is precisely controlled by the computer in response to a large number of parameters, including accelerator pedal position, coolant temperature and incoming air temperature.

Rotating assembly

Improved fuel consumption and lower vibration have been achieved through extensive design studies seeking to reduce friction and to make parts lighter.
The forged steel crankshaft includes five precision-ground case-hardened bearing sections. The bearing grooves and journals are rolled in sections. In contrast to traditional rolling techniques, this process hardens the metal without distorting the crankshaft, thereby improving stress resistance.
The forged steel connecting rods feature integral oil channels for cylinder lubrication and cooling.
The pistons are 40 g lighter than those in the previous version. The flat piston tops are raised slightly in the centre, with rebates to provide valve clearance.
A “flexible” engine flywheel reduces engine vibration at high speeds. The flywheel consists of a cast friction ring on the clutch side and a sheet metal damping mechanism on the engine side.

Valve gear

The four camshafts act directly on hydraulic tappets that automatically take up any play in the system.
A phase shifter, or variable-timing camshaft, adjusts the timing of the valve gear for optimum flow into the cylinder. 
For example, during acceleration at low engine speeds, valve lead and lag take place earlier.The inlet camshafts are moved between two possible positions by means of a double helical ramp controlled by the oil pressure. The engine computer controls the oil intake through an electrovalve, in accordance with engine speed, engine load and oil temperature. The camshaft position is monitored by an angular position sensor.
 

Injection and ignition

The engine is controlled by a Bosch ME 7.4 engine control system driving the sequential injection system and coil-per-plug ignition. The new multi-jet injectors are fed from two rails with no fuel return. The fuel circuit includes a surge damper to eliminate noise and variations in pressure.

Exhaust and emission control

A pre-catalyst is mounted at the outlet of each exhaust manifold, with oxygen sensors fitted at the inlet and outlet. 
The sensors analyse the oxygen content of the exhaust gas and transmit the information to the engine control system, which then adjusts the fuel / air ratio accordingly. The main catalytic converter completes the pollution control system, ensuring emission levels compliant with the Euro 4 standard.