LEMON Manuals: Even more car manuals for everyone
Home >> Ford >> 2022 >> Transit Connect Titanium, Gas/Ethanol >> Repair and Diagnosis >> External Pages >> Different car >> Section 572 (Exhaust System - 3.0L Power Stroke Diesel) >> Description And Operation >> Exhaust System - Overview >> Overview

Exhaust System - Overview: Overview

WARNING: This page is about a different car, the 2021 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

DPF 

The Diesel Particulate Filter (DPF) System consists of: 

The exhaust system provides an exit for exhaust gases and reduces engine noise by passing exhaust gases through the catalytic converters and a muffler assembly. The catalytic converters also play a major role in reducing air pollutants.

The DPF reduces the pollution generated by diesel vehicles by filtering soot and ash particles out of the exhaust gases.

The PCM monitors the pressure differential sensor, DPF temperature sensors and other inputs to control the operation of the DPF system.

Soot particles can accumulate in the post DPF exhaust tailpipe. The accumulation of the soot particles should not be considered a concern, as the DPF is not 100% efficient at filtering the soot particles.

The amount of matter trapped in the DPF is monitored using the pressure sensor which monitors the exhaust pressure before the DPF. As the DPF fills with soot, exhaust flow through it is restricted.

When this occurs the pressure differential in the exhaust before the DPF will increase which will indicate to the PCM that a DPF regeneration is required to clean it.

SCR 

SCR comprises of:

The SCR (selective catalytic reduction system) improves the exhaust emissions and fuel efficiency by injecting Diesel Exhaust Fluid (DEF) into the exhaust system. DEF, is a 32.5% solution of urea in deionized water. At the inlet of the SCR, there is a port for the reductant injector which is followed by a multi-blade mixer. When DEF is introduced into the system, it atomizes and mixes evenly with exhaust gases in the multi-blade mixer. During this time, the heat of the exhaust gases causes the urea in the DEF to split into Carbon Dioxide (CO2) and ammonia. As the ammonia and NOx pass over the catalyst, a reaction takes place and the ammonia and NOx are converted to nitrogen and water. For additional information about the reductant system, Refer to: Engine Emission Control - Component Location .

Diesel Particulate Filter 

The diesel particulate filter collects the soot and ash particles that are present in the exhaust gas of diesel engines. The diesel particulate filter assembly typically consists of active precious metals deposited on a substrate filter. The exhaust gas is forced to flow through the walls of the porous substrate and exit through the adjoining channels. The particulates that are larger than the pore size of the walls are trapped for regeneration. During regeneration the temperature in the diesel particulate filter increases to greater than 550°C (1, 022°F). The precious metal washcoat promotes the regeneration of the trapped particulates through the heat-generating reaction and catalyzes the untreated exhaust gas. The substrate filter is held in the metal shell by a ceramic fiber support system. The support system makes up the size differences that occur due to thermal expansion and maintains a uniform holding force on the substrate filter.

Diesel Particulate Filter Monitor 

The PCM monitors the diesel particulate filter for leaks in the filter substrate, as well as for a filter substrate that has been removed. The diesel particulate filter requires preconditioning before the monitor is enabled. There are two tests that comprise the diesel particulate filter monitor. The first test is an efficiency monitor comparing the restriction of the diesel particulate filter to restriction values, which are a function of exhaust flow. The second test is a missing substrate monitor that ensures the diesel particulate filter has not been removed.

The diesel particulate filter monitor is enabled and runs continuously when certain base engine conditions are first satisfied. The typical monitoring duration for this monitor is 90 seconds. Inputs from the CKP, ECT, exhaust gas temperature (EGT), diesel particulate filter pressure and particulate matter bank 1, sensor 1 (PM11) sensors are required to enable the monitor. The monitor entry conditions include:

For the efficiency monitor test, as soot accumulates on the PM11 sensor, a current is generated within the PM11 sensor. The PCM calculates a monitoring time for the PM11 sensor based on the expected soot generated by the engine. At the conclusion of this monitoring time, the PCM strategy compares the current of the PM11 sensor to a calibrated threshold. If the current exceeds the threshold, a concern is present. At the conclusion of this test, the PM11 sensor operation is controlled to burn all of the accumulated soot off the PM11 sensor, and the measurement cycle is repeated.

For the missing substrate monitor test, the PCM determines a differential pressure threshold for the amount of pressure that should be measured by the diesel particulate filter pressure bank 1, sensor 1 (DPFP11) for a certain exhaust flow rate. The PCM compares the measured differential pressure value to the differential pressure threshold value. A fault filtering counter starts when the monitor begins to run. When the measured differential pressure is less than the threshold value, the counter increases. When the measured differential pressure is greater than the threshold value, the counter decreases. If the number of counts on the counter at the end of the monitor exceeds a calibrated limit a DTC sets and the MIL illuminates.

Diesel Particulate Filter Regeneration 

NOTE: Regeneration may occur during normal operation. During regeneration, diagnostic procedures may display biased values. If a regeneration occurs during diagnostic procedures, allow the process to complete before continuing diagnostics. Regeneration can be disabled during diagnosis using a scan tool.

Diesel particulates in the exhaust are trapped by the diesel particulate filter. Regeneration is the process by which the exhaust gas temperatures are increased, the higher exhaust temperatures burn off the particulates in the filter. The frequency and length of regeneration events fluctuate while both factors are determined by the vehicle drive cycle, ambient temperature, vehicle loading and the vehicle operator driving style. Under normal driving conditions, regeneration frequency varies from 143 to 805 km (89 to 500 miles) between each occurrence. The duration of a normal regeneration event varies between 10 and 40 minutes. The first regeneration on a new vehicle may not require 143 km (89 miles), it may occur at any time. The duration of a regeneration event may be reduced if a constant speed above 48 km/h (30 mph) is maintained. Driving at lower speeds and stop and go conditions may result in longer duration times for a regeneration event to successfully complete.

During normal vehicle operation the PCM estimates the amount of particulates that accumulate in the diesel particulate filter. The estimated amount of particulates is based on a number of different vehicle operating conditions, including vehicle speed, engine run time, and load. Additionally the PCM monitors the following:

Diesel particulate filter regeneration may be initiated by the PCM, manually using a scan tool, or through operator commanded regeneration (if equipped). For additional information on operator commanded regeneration, refer to Refer to: Diagnostic Methods . .

When the appropriate conditions are met, the PCM initiates a diesel particulate filter regeneration. Regeneration is carried out when the PCM calculates the particulate level in the filter has reached a level that requires cleaning.

The regeneration process initiates while the vehicle is driven and may continue for up to 5 minutes after the vehicle is stationary and as long as the transmission remains in gear. The regeneration process is interrupted if the transmission is shifted into the PARK or NEUTRAL position. If the regeneration process is not complete when the vehicle entered the PARK or NEUTRAL position, the regeneration process may continue during the next drive cycle.

The PCM may continue to initiate the regeneration process until the regeneration process completes. After the regeneration process is completed the filter is sufficiently cleaned and continues to trap exhaust particulate matter.

The following conditions are considered normal while the vehicle is in regeneration. No repairs are necessary if they are present:

To help determine the condition of the particulate filter and recent regeneration events, access and monitor the following parameters:

Exhaust Catalyst and Exhaust System 

The exhaust catalyst and exhaust system consists of the following components:

Exhaust Gas Temperature (EGT) Sensor 

The EGT sensor is a resistance temperature detector (RTD) type sensor. The EGT sensor is an input to the PCM and measures the temperature of the exhaust gas passing through the exhaust system. The electrical resistance of the sensor increases as the temperature increases, and resistance decreases as the temperature decreases. The varying resistance changes the voltage drop across the sensor terminals and provides electrical signals to the PCM corresponding to temperature.

The PCM uses the input from 4 EGT sensors to monitor the exhaust gas temperature. The EGT bank 1 sensor 1 (EGT11) is located before the OC. The EGT bank 1 sensor 2 (EGT12) is located after the OC. The EGT bank 1 sensor 3 (EGT13) is located after the diesel particulate filter. The EGT bank 1 sensor 4 (EGT14) is located after the SCR catalyst.

Selective Catalytic Reduction (SCR) System 

The SCR reduces NOX in the exhaust stream by a chemical reduction process using the SCR catalyst and a reductant injection system that introduces diesel exhaust fluid (DEF) into the exhaust system upstream of the SCR catalyst. The reductant injection system is directly controlled and monitored by the PCM.

The SCR catalyst reduces NOX present in the exhaust stream to nitrogen (N2) and water (H2O). The SCR catalyst contains a copper catalyst washcoated on a zeolite substrate. At the inlet of the SCR catalyst is a port for the reductant injector, followed by a louvered diffuser and a twist mixer. The reductant diesel exhaust fluid (DEF) is a solution of urea in deionized water. The urea solution percentage for correct SCR system operation is 28 - 35%. When DEF is introduced into the system, it finely atomizes in the louvered diffuser and mixes evenly with exhaust gases in the twist mixer. During this time, the heat of the exhaust gases causes the urea to split into carbon dioxide (CO2) and ammonia (NH3). As the ammonia and NOX pass over the SCR catalyst, a reduction reaction takes place and the ammonia and NOX are converted to N2 and H2O. This reaction takes place at up to 95% efficiency and allows the engine to run leaner and more efficiently, since the high NOX levels that are produced under lean conditions are eliminated.

Sound insulators and shields 

Sound insulators and shields are attached to the underbody and exhaust system to protect the vehicle from exhaust system heat and should be inspected at regular intervals to make sure they are not dented or out of position. If a sound insulator and shield is damaged or shows evidence of deterioration, install a new sound insulator and shield. Some exhaust fasteners must be discarded and new ones installed as indicated in the procedures. Discard any damaged or heavily corroded fasteners and install new ones as necessary. Some exhaust fasteners are of a prevailing torque design. Use only new fasteners with the same part number as the original. Tighten the fasteners to the specified torque during reassembly to make sure of correct retention of exhaust components.

There are four (4) heat shields installed on the exhaust components, that heat shields are not released for service.

scientia non olet · About LEMON Manuals