Members of the Birmingham MA were recently given an insight into the workings of the diesel particulate filter (DPF) by chris Manton MIMI of SMPE. Here follows a brief synopsis of what was learnt.
The DPF is a device fitted after the catalyst in a car exhaust system to collect un-burnt particulate matter – or as it is commonly known - soot. If allowed to enter the atmosphere, soot becomes a health hazard as it lodges in the lungs. A properly maintained diesel car does not reach full operating temperature until it has covered around twelve miles. Because of the claimed economy of diesel vehicles over their petrol equivalents, and the associated higher retail value, customers have purchased these vehicles for the school run and for commuting. This is not the ideal environment for such vehicles, as they never reach their proper working temperature and thus the filter becomes blocked with un-burnt fuel.
Manufacturers are aware of this and have incorporated regenerative programmes in the engine management ECUs to cover this potential problem. Briefly, additional fuel is injected into the engine to raise the operating temperature of the catalyst and thus raise the temperature in the filter to make the soot burn, and thus turn it to ash which can pass through the filter wall to atmosphere. But if the engine never reaches operating temperature…
Chris gave a great presentation and the event was thoroughly enjoyed by all.