Nissan Releases the New-Look 2002 Navara
December 6 2001
Nissan's hard-working Navara ute range received a significant upgrade with the launch of a new model line-up, highlighted by the introduction of a 3.0-litre turbo diesel engine in all four-wheel drive models.
The new-look Navara range gets a comprehensive update with revisions to the suspension tuning, improved noise, vibration and harshness levels, updated interior trim and a substantial exterior upgrade.
However, the highlight of the new Navara range is fitment of Nissan's ZD30 power plant. This lightweight, compact DOHC four-cylinder displaces 2953cc and features the M-Fire combustion system.
Delivering 110kW of power at 3400rpm and 314Nm of torque at 2000rpm, the ZD30 engine enhances Navara's already impressive performance and towing capacity - now up to a class-leading 3000kgs (trailer with brakes).
The new ZD30 engine will be available in 4x4 Single and Dual Cab models. The standard transmission is a five-speed manual with double-cone synchronisers on first and second gears. Standard suspension across the range is double-wishbone front with an anti-roll bar and leaf rear suspension. Revisions to the suspension have improved ride comfort and handling.
Ventilated front disc brakes and rear drums comfortably handle Navara's stopping requirements, even when fully loaded or towing.
According to Nissan Australia's Marketing Manager for Commercial Vehicles, Mr Andrew Dimsey, the new 3.0-litre diesel is a significant step forward in the commercial vehicle range.
"The Navara 3.0-litre turbo-diesel will be the class-leader in its segment and like its predecessors will maintain Nissan's commitment to offering the best value for money proposition in each market," Mr Dimsey said.
The new power plant making its debut in the Navara range delivers a lusty 110kW of power (44 per cent more than the superseded QD32 engine) and 314Nm of torque (42 per cent more than the QD32). Nissan's ZD30 engine generates greater power, operates more quietly, reduces soot and NOx emissions while maintaining the excellent fuel economy of conventional direct-injection engines. It does so by achieving premixed combustion at a low temperature.
M-Fire Combustion System
Gasoline engines produce little soot because the fuel and air are first thoroughly mixed and then ignited and burned - a process called premixed combustion. But when this process is attempted in a diesel engine, combustion takes place all at once, raising the combustion temperature and causing the formation of large quantities of NOx. To avoid that, diesel engines burn the mixture in a diffusion combustion process - since the mixture is combusted as the fuel is injected, premixed combustion is controlled.
In order to prevent the mixture from burning instantaneously in this process, the combustion temperature is kept low, which works to suppress NOx formation. However, because the fuel is ignited before it is fully vaporised, some places in the cylinder lack a sufficient supply of oxygen, resulting in the formation of soot that causes black smoke in the exhaust.
The measures adopted to accomplish M-Fire combustion include:
In diesel engines, fuel has traditionally been injected at a point considerably before the piston reaches top dead centre (TDC) of the compression stroke.
In the ZD30 engine, the injection timing has been changed so that the fuel is injected closer to TDC of the stroke, allowing compressed air to enter the expansion stroke, thus combustion occurs after the pressure has started to drop meaning lower pressure at the onset of combustion.
As well, injecting fuel at this point allows ample time for fuel to evaporate - because it is not ignited immediately after being injected - making it possible to accomplish premixed combustion.
In designing the ZD30 engine, Nissan engineers increased the Exhaust Gas Recirculation (EGR) rate. This results in a gradual combustion process in which the mixture does not burn instantaneously following ignition, which keeps the combustion temperature from rising.
And a helical port is used to generate strong swirl motion to improve mixture formation and promote stable combustion.
High pressure distributor-type fuel injection pump
The higher injection pressure promotes better fuel spray atomisation, making the fuel more combustible resulting in greater power and combustion characteristics less likely to produce exhaust soot.
The control unit has been partially integrated with the pump to enable variation in pumping pressure to be adjusted at each individual pump - making it possible to achieve high fuel injection precision for greater efficiency and improved combustion.
Additionally, Nissan engineers ensured friction inside the pump was minimised which, together with increased efficiency in the compressed fuel line, enables the pump to generate high injection pressure with minimal energy.
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