DPD=DPF
" Once again the confusion hits. first of all, I would guess "DPD" = "diesel particulate device" = DPF ="diesel particulate filter" ??
A DPF = DPD isn't affected by sulfur content!"
Now I am confused. The Isuzu DPD=DPF system uses an oxidation catalyst in front of a wall-flow filter. My layman understanding was that HS diesel reduces the effectiveness of the catalyst which reduces the effectiveness of the regen process and leads to excess PM which is picked up in the filter. HS diesel reduces temperatures reached in the regen cycle which reduces the ability of the system to clean out the filter and will shorten system life. So a DPF system needs ULSD, yes or maybe no?
The sources below are clear that a DPF needs ULSD but that might depend on the type of filter used - the Isuzu uses a wall flow filter but if you wade through the cut and paste info below you'll find mention of a Flow Through Particulate Matter Filter. This filter type won't be blocked by use of HS diesel but will have efficiency degraded. No idea if that efficiency degradation will be identified by the ECU and cause problems. Perhaps this is the type of DPF you are referring to Charlie?
A/ This from a UNEP Report from around 2009 Cleaner Vehicles: The Role of Lower Sulphur Fuels
“4.1 How Sulphur in Fuel Affects Vehicle Emissions: The Systems Approach
Reducing sulphur levels in fuels is especially important in reducing the smallest particles
and can reduce vehicle emissions in two ways:
First, reducing sulphur in fuels reduces direct emissions of both sulphur dioxide and
sulphate PM from all vehicles, old and new.24 Sulphur dioxide (SO2) emissions from diesel
and petrol vehicles and particulate matter from diesel vehicles tend to increase in direct
proportion to the amount of sulphur in the fuel. While sulphate particles may account for
only a small fraction of particle volume or mass, they are fine and ultra-fine in particle size
and account for a large fraction of particle numbers.25
Second, sulphur poisons or reduces the effectiveness of vehicle emission control
technologies for petrol and diesel vehicles, resulting in increased vehicle emissions of carbon
monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and particulate matter (PM). It
also poisons or reduces the effectiveness of new types of emission control devices such as
advanced catalytic converters and diesel particle traps, which can further reduce NOx, HC,
and PM emissions.”
“However, sulphur greatly reduces their efficiency. When a DOC oxidizes sulphur, the
resulting sulphate PM collects on the filter. This reduces its efficiency, which increases emissions,
and increases the need for regeneration, which reduces the vehicle's fuel economy.
High levels of sulphur can render the DPF ineffective or even stop the engine due to unacceptable
backpressure.
DPFs should not be used with fuel sulphur levels greater than 50ppm.”
B/ These slides from a NATO investigation into Fuel Compatibility with Euro IV Engines. Note the reference to sulphated ash or products of other ash forming components eg engine oil additives.
I wasn't planning on using the Isuzu for military purposes but you never know…..
C/ From another NATO report into problems related to HS Diesel on emission technology.
2.2.2.1 Diesel Oxidation Catalysts (DOCs)
It has been identified that high sulphur reduces the efficiency of the catalyst by reducing its
operating temperature and by increasing the formation of sulphated ash. The low operating temperature of
the oxidation catalyst reduces the formation of NO2 needed for the regeneration of the DPF.
2.2.2.2 Fuel Sulphur Effects on Diesel Particulate Filter (DPF).
HSF will cause two different types of negative effects. The first will reduce the catalyst efficiency by
reducing the high operating temperature needed for regenerating the DPF. The second one will be
caused by the oxidation of sulphur dioxide resulting in high levels of sulphated ash and total particulate mass.
Depending on the DPF design the experienced negative effects will differ as follows:
1) Fuel Sulphur Effects on Wall Flow Diesel Particulate Filter (WF-DPF)
The WF-DPF is a honey comb structure with parallel pipes. These pipes are alternating closed and
opened. The inlet pipe at one end and the outlet pipe at the other. Thus gas may only flow through the
wall of the filter. Soot particles will be collected in the inlet pipe.
Using HSF will result in an increased loading of the filter and causing frequent regenerating cycles.
Additionally, to the reduced performance of the oxidation catalyst will result in an overload and a blocking of the filter. The filter must then be replaced or regenerated externally.
2) Fuel Sulphur Effects on Flow-Through Metallic Particulate Matter Filter (M-PMF)
M-PMF is structured in a layered stack consisting of corrugation foil with shovels and porous fleece.
Exhaust gas is introduced to both up and down side of fleeces by shovels, and then soot is trapped while gaseous components pass the fleece. The nitrogen oxides produced in the oxidation pre-catalyst
cause the soot particles to be burned continuously.
As explained in Annex A,
the use of HSF will reduce the overall efficiency of the system but will not block the M-PMF.
Fuel consumption/MPG? The truck was using 16-17L/100km (14.7 US mpg) before the change and 16L/100km after the changes. I was happy to see consumption basically unchanged but with a 20% power boost which I assumed would need more fuel.