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Diesel Particulate Filters (DPF's)
Overview
Diesel particulate filters are used by a number of
vehicle manufacturers to reduce the amount of harmful particles released from
their diesel vehicles. Although very effective in most situations, they are not
suitable for drivers who do not have the opportunity to drive their vehicle at
over 50mph on a fairly regular basis.
This fact sheet has been put together so you can make
informed decisions as to when vehicles using particulate filters will be
suitable for your drivers.
What is a diesel particulate filter?
Diesel particulate filters are becoming more common on
diesel engines. They are used to reduce the exhaust emissions as required by
European legislation, especially particulate matter. A particulate filter traps
most of the soot that is produced during diesel combustion and would normally
travel down the exhaust and into the
atmosphere. Changes to new car emissions legislation, the 'Euro 5' standards,
will make particulate filters as commonplace in diesel car exhausts as catalytic
converters are on petrol cars.
Why does the filter need to “regenerate”?
A filter can hold a certain amount of soot, but not a
huge quantity, so it needs to regularly go through a process of regeneration in
order to clear out the soot and allow the vehicle to operate properly.
Regeneration occurs when the filter reaches a sufficiently high temperature
allowing the soot to be converted to a much smaller amount of ash.
To allow the filter to automatically regenerate, the
engine should be used regularly at a sufficient speed, to ensure a high enough
temperature of the exhaust gas. The engine must be under sufficient load to
ensure that the exhaust gas temperature is naturally raised. Although it may
vary from manufacturer to manufacturer, typically a vehicle must be driven at
50mph or above for at least 20 minutes in order to automatically regenerate the
filter.
During the regeneration phase, high temperatures in the
filter may cause a slight smell, especially during the first regeneration.
What happens if it doesn’t regenerate?
If the vehicle is not driven in a way that automatically
regenerates the particulate filter, it will build up an excessive amount of
soot, which, if not resolved, will reduce the performance of the vehicle and
damage the filter. If the filter does build up too much soot, a vehicle warning
light will appear to alert you. The problem can usually be solved by allowing
the filter to automatically regenerate until the warning light goes out – i.e.
by driving the vehicle at 50mph or above for at least 20 minutes.
Check the vehicle handbook for specific guidance on a particular vehicle.
If traffic conditions and speed limits do not allow the
vehicle do be driven so that the filter regenerates, it will have to be returned
to a dealer for a forced regeneration in order to clear the filter. If the
warning light is ignored and the vehicle is driven without regenerating the
filter, it will cause damage to the vehicle, which will not be covered by
warranty or maintenance agreements.
Which drivers should order these vehicles?
A vehicle fitted with a diesel particulate filter is
suitable for all drivers who have the opportunity to regularly follow the
procedure that is detailed in the vehicle handbook to allow their filter to
automatically regenerate – i.e. driving at a sufficient speed for a sufficient
amount of time.
In these circumstances, a particulate filter
significantly reduces the harmful emissions of the vehicle with absolutely no
adverse effects to performance or maintenance.
We recommend that drivers who only use their vehicle for
urban journeys or are located on one of the Channel Islands do not order a
vehicle fitted with a diesel particle filter.
Vehicles with diesel particulate filters
The majority of vehicle manufacturers now have diesel
particulate filters as standard fitment, but not on all diesel models. For
specific details of individual models, please refer to manufacturers’ websites.
Alternatives for urban drivers
If a driver is restricted in their ability to regenerate
a diesel particulate filter through driving, there are other vehicles that can
be chosen, which do not use this technology. Some models come in vehicle
derivatives with and without a diesel particulate filter, so the derivative
without the filter, typically with a smaller engine, can be chosen.
Alternatively, a different diesel vehicle without a
filter, or a petrol vehicle would be suitable. A hybrid vehicle may be ideal for
this type of urban driver.
Further information
For guidance on the operation of a particular vehicle,
please consult the owner’s manual. Alternatively, or for more information on
diesel particulate filters generally, contact our team on 01908 262662.
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All of the documents can be obtained from us in a word format, so that they can be personalised and edited to suit your company or business. This service is free of charge, on request or phone 01908 262662.
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