Nissan is introducing a version of its second-generation Murano outfitted with an enhanced version of its 2.5 dCi four-cylinder diesel. The YD25 engine has been upgraded in advance of its fitment in Murano. The 2.5-liter diesel delivers 190 PS (187 hp, 140 kW) and 450 N·m (332 lb-ft) of torque, and is mated with a six-speed automatic transmission. Deliveries begin in September.
The YD25 engine, with double overhead camshafts and a 16-valve cylinder head, features Nissan’s M-Fire technology (also used in the engines in Patrol GR, Terrano and Almera) to optimize combustion efficiency, to lower fuel consumption and to reduce emissions. M-Fire (Modulated Fire) has three main components:
Dual intake ports for the fuel, a tangential and a helical port. Under light and medium loads—i.e. when the vehicle is cruising or accelerating moderately—the fuel is routed through the helical port, giving a strong swirl action which spreads the fuel/air mix more evenly through the combustion chamber, allowing it to be burnt more completely and hence more efficiently.
Under heavy load or higher revs, the tangential port opens, its swirl control valve reducing swirl (less crucial at high revs), and increasing mixture flow to maximize power and burning efficiency, virtually eliminating output of unburnt soot through the exhaust.
Exhaust Gas Recirculation (EGR) sees exhaust gas re-circulated through the air-intake, lowering both the temperature and oxygen concentration of the mixture, thus reducing NOx emissions.
Optimized fuel-injection timing, allowing combustion to take place at a later stage in the engine cycle than is normal for a direct-injection diesel, with injection starting around TDC (top dead center).
The changes made to the engine for the Murano include a new direct injection system which operates at 2,000 bar, up from 1,800 bar. This increase in pressure means the fuel spray is atomized to an even finer degree resulting in more complete combustion.
A new cylinder head with parallel ports increases the swirl efficiency of the combustion process, smoothing the intake and exhaust flow, while a new variable nozzle turbo (VNT) with electric control rather than the previous hydraulic system for quicker responses has also been adopted.
The engine is equipped with a diesel particle filter (DPF), helping Murano to achieve Euro 5 emission standards.
The engine is offered as a single powertrain with a six-speed automatic gearbox. With a high degree of lock-up, engine responsiveness is keen and its shift logic has been programmed to make the most of the high-torque engine characteristics, but also to optimize the fuel economy.
Furthermore, the gearbox is equipped with ASC (Adaptive Shift Control), which will modify shift patterns according to the prevailing driving style, tailoring the gearbox to hold on to a lower gear during a descent for added engine braking, for example.
Power is transmitted to the road via Nissan’s advanced ALL MODE 4x4-i technology, which sends power to the rear-wheels when a loss of stability or traction is detected.