Diesel Particulate Filter Fundamentals

welcome to automate fundamentals hi I'm

Luke in this module I'll take you

through the construction and function of

a diesel particulate filter the days of

dirty black smoke are rapidly fading due

to diesel exhaust technology evolving

over the years strict emission

regulations required diesel engines to

become much cleaner the diesel

particulate filter also known as a DPF

is a filter device fitted to exhaust

systems on modern diesel engines these

devices can be fitted before or after

the catalytic converter

they require heat to operate correctly

this is why some diesel particulate

filters are mounted directly after the

turbocharger the design of the DPF

consists of a honeycomb filter monolith

and is encased in a metal shell just

like a catalytic converter connected to

it is a differential pressure sensor

with pipes coming out of the inlet and

the outlet of the DPF will cover this


these are particulate filter materials

come in many variants the most common

materials used within a DPF are

cordierite wall flow filters or silicon

carbide wall flow filters other

materials can include metal fiber

filters metal fiber flow through filters

and partial filters common-rail diesel

engines fitted with the DPF require a

special low ash oil the purpose of the

DPF is to trap the particulates created

by all diesel engines preventing them

from entering the atmosphere these

particulates are extremely harmful to

the respiratory system the particulates

are trapped by a microscopic channels

which are within the diesel particulate

filter the particulates or soot that

attach to the walls of the channels

within the DPF are burned off regularly

in a process called regeneration

the regeneration prevents the diesel

particulate filter from blocking up

there are three types of regeneration

spontaneous dynamic and service

spontaneous regeneration occurs when the

DPF reaches 600 degrees Celsius or 1112

degrees Fahrenheit if a spontaneous

regeneration does not occur and the ECU

calculates that the DPF has reached its

storage capacity a dynamic regeneration

is initiated dynamic regeneration is

indicated when the DPF light illuminates

on the instrument cluster the vehicle

must keep going to complete the

regeneration until the light goes out if

the dynamic regeneration is interrupted

by the engine being stopped it would be

reinitiated on the next engine run cycle

if the dynamic regeneration is

continually interrupted due to a number

of short trips the DPF light will start

to flash a flushing DPF warning will

indicate that a service regeneration

should be performed service

regenerations must be instigated using a

scan tool during a service regeneration

extra fuel can be added in the form of

post injection pulses this increases the

exhaust gas temperature creating

extremely hot temperatures of around 600

degrees Celsius or 1112 degrees

Fahrenheit so we now with the

particulates to burn off if a flashing

DPF warning is ignored the soot

accumulation may reach a level where

replacing the DPF is the only possible

remedy once a service regeneration has

been performed the reading from the

differential pressure sensor will

determine how effective the regeneration

has been usually a dynamic regeneration

needs to follow our service regeneration

remember to perform the appropriate

drive cycle

if a regeneration is impossible the

diesel particulate filter must be

replaced untreated exhaust gases leave

two cylinders carrying the particulates

to the DPF they come into contact with

the microscopic channel walls and the

soot is trapped

the suit remains in the DPF until the

regeneration process is initiated

now we'll look at the DPF scan tool

parameters I'm looking at the data

because I have a flushing DPF light and

the soot accumulation is over a hundred

percent as seen here I'll carry out a

service regeneration and we'll take a

look at an injector pattern using an

oscilloscope on this scan tool service

regeneration is located in the special

functions menu once the prerequisites

are met the scan tool will initiate a

regeneration the pattern starts off with

two pilot and one main injections when

the revs increase one poly injection

disappears the post injection pattern

appears this is to get the DPF to a

minimum of 600 degrees Celsius or 1112

degrees Fahrenheit the duration will

vary depending upon DPF temperature and

may even disappear once the regeneration

is finished the normal pattern will

appear and a completed status will

appear on the scan tool this cycle

occurs over and over again whilst you

drive keeping the DPF from clogging up

with particulate matter symptoms of a

failed EPF can be warning lights on the

dash and poor engine performance a DPF

can fail by the housing cracking during

your regeneration process if the storage

capacity is too full or oil and coolant

contaminating the filter causing its a

clog that's the construction and

function of a diesel particulate filter

it's very important to understand how

the DPF works to assist you when

diagnosing remember keeping up to date

of technology is essential in today's

automotive industry bye for now