Isuzu's next generation N and F Series trucks are the most environmentally friendly, conventional diesel powered trucks of all Japanese makes, and are now being progressively released to meet Australia's new ADR80/02 emissions standards.
The emission control technology engineered into the new Isuzu range includes a first for the Australian market, a Diesel Particulate Diffuser (DPD).
Although the DPD has been available in Japan since 2004, this is the first time Isuzu has specified it for the Australian market, and Isuzu is the only Japanese manufacturer currently offering this technology (hybrids excluded).
The majority of new light duty and medium duty trucks released in 2007 and early 2008 will be powered by engines rated to US EPA 04 emissions standards; all new Isuzus however, will meet the considerably more stringent European measure, Euro4.
While both standards satisfy new ADR80/02 emissions standards which come into force on January 1, 2008, Isuzu's Euro4 engines emit as little as one sixth the particulate matter (PM) of US EPA 04-compliant competitors.
PM is a combination of black smoke and invisible particles emitted from a truck exhaust under load, and is formed during incomplete combustion of fuel. Composed of elemental carbon, heavy hydrocarbons and hydrated sulphuric acid, PM has been linked with various ailments in many health studies.
Isuzu has used a variety of engine technologies to reach the stringent Euro4 emissions level, including variable geometry turbocharging, air to air intercooling, high-pressure common rail injection, Advanced Cooled EGR (Exhaust Gas Recirculation) systems, and as noted above, Diesel Particulate Diffuser (DPD) exhaust after treatment.
DPD – How it works
As the name suggests, the Diesel Particulate Diffuser minimises the amount of PM a truck emits via the exhaust.
The DPD, which is located midway along the truck's exhaust, combines an oxidation catalyst to clean nitrogen oxides and hydrocarbons, and a ceramic filter that traps PM.
Pressure differential sensors within the ceramic filter are used to monitor the accumulation of trapped PM. Once a certain amount of PM is detected, the ceramic filter regenerates; this is done via post-injection which elevates the exhaust gas temperature to burn off the accumulated PM.
The cleaning process is aided by precision control of the exhaust brake and exhaust throttle, which assists in raising the exhaust gas temperature, promoting PM burning.
The truck's engine control unit (ECU) continually monitors the condition of the ceramic filter, and under most operating conditions regenerates the filter automatically without the driver even knowing. However, in some circumstances, the filter will require manual regeneration.
Manual regeneration
Where the truck's operating temperature does not reach the required level for automatic regeneration, generally due to a short distance travelled or the truck's engine being frequently turned on and off, manual regeneration may be required.
The DPD warning lamp in the instrument cluster will begin to flash slowly alerting that manual regeneration will be required within the next 60 to 100 kilometres, depending on the model.
Within this distance, the driver will need to engage the manual regeneration cycle - stop the truck, keep the engine idling and press the DPD button. Regeneration takes between 15-20 minutes, during which time the truck must remain stationary.
According to Isuzu Australia Limited (IAL) Product Planning and Engineering Support Manager, Simon Humphries, manual regeneration is a process that can be easily integrated into the work schedule of the truck.
"Our local testing indicates that only a small number of drivers will need to perform a manual regeneration of the DPD at all. However, it is possible that those drivers who run regular drop-off routes and are more likely to require manual regeneration will become familiar with the cycle of their truck and regeneration will be as simple as pressing the DPD button on a lunch break or back at the depot when required.
"The 60 to 100 kilometre warning provides sufficient time to arrange an appropriate stop without impacting a driver's work schedule."
During manual regeneration, the DPD lamp will remain on, and engine idle rpm will also increase. Once regeneration is complete, the lamp turns off and engine idle will return to normal.
It is critical that the filter be regenerated within the 60 to 100 kilometre period. Nearing the end of this time frame, the DPD warning lamp will flash more rapidly (three times per second), indicating that manual regeneration must occur immediately.
If this is ignored, the 'engine check' lamp becomes illuminated and the truck enters 'limp home mode'. At this point the filter cannot be manually regenerated and must be driven to an Isuzu Dealership under reduced power, where the PM in the filter can be cleared via special regeneration equipment.
The limp home function ensures the filter is not damaged by the high combustion temperatures produced by the increased amounts of PM.
"The DPD has been available in Isuzu trucks in Japan since 2004 and is well proven," Mr Humphries said. "It is one of the main contributors in making the new N and F Series ranges the most environmentally friendly of all conventional Japanese diesel powered trucks.
"Isuzu is the first of the high volume manufacturers to introduce this technology to Australia, and our air quality will be all the better for it – every customer who chooses a new Isuzu over a competitor with US EPA 04 compliance, is playing their part in helping our environment.
"We believe that the need to perform manual regeneration from time to time in some applications is a small price to pay for cleaner air, and IAL is confident that at a time of increased environmental awareness and concern, the truck buying public will welcome and seek the technology."
DPD FAQs
Q. How frequently should manual regeneration be performed?
A. The number of manual regenerations required will vary depending on conditions. In Isuzu in-house testing, based on stop/start metro delivery applications (severe conditions for automatic DPD regeneration), manual regeneration was required perhaps once per month.
Q. Can manual regeneration be performed at any time?
A. No, the Engine Control Unit will not permit a manual regeneration unless the pressure differential is sufficient to justify it.
Q. Can the truck be moved or turned off when manual regeneration is in progress?
A. Yes, however manual regeneration will need to be performed again once the truck has been moved or restarted. To move or turn off the truck, simply press the DPD button (it will start flashing again), then the truck can be moved or turned off.