September 5, 2013, 9:39 pm
as per what jaguar have said in there x-type 2.2 auto with DPF.
i know its not a focus but the principle is the same!
Passive regeneration requires no special engine management intervention and occurs during normal engine operation. The passive regeneration involves a slow conversion of the particulate matter deposited in the DPF into carbon dioxide. This process is active when the DPF temperature reaches 250°C (482°F) and is a continuous process when the vehicle is being driven at higher engine loads and speeds.
During passive regeneration, only a portion of the particulate matter is converted into carbon dioxide. This is due to the chemical reaction process, which is only effective within the normal operating temperature range of 250°C to 500°C (482°F to 932°F).
Above this temperature range the conversion efficiency of the particulates into carbon dioxide increases as the DPF temperature is raised. These temperatures can only be achieved using the active regeneration process.
Active regeneration starts when the particulate loading of the DPF reaches a threshold as monitored or determined by the DPF control software. The threshold calculation is based on driving style, distance traveled and back-pressure signals from the differential pressure sensor.
Active regeneration generally occurs every 370 to 1250 miles (600 to 2000km) although this is dependant on how the vehicle is driven. For example, if the vehicle is driven at low loads in urban traffic regularly, active regeneration will occur more often. This is due to the rapid build-up of particulates in the DPF than if the vehicle is driven at high speeds when passive regeneration will have occurred.
The DPF software incorporates an additional trigger, which is used as backup for active regeneration. If active regeneration has not been initiated by a back-pressure signal from the differential pressure sensor, regeneration is requested based on estimated cumulative particulate emissions since the last active regeneration event.
Active regeneration of the DPF is commenced when the temperature of the DPF is increased to the combustion temperature of the particles. The DPF temperature is raised by increasing the exhaust gas temperature. This is achieved by:
- Retarding the main injection timing
- Reducing intake boost pressure levels
- Activation of the inlet throttle
- Introducing post-injection of fuel after the pilot and main fuel injections have occurred.
Control of the post-injection is determined by the DPF software monitoring the signals from the two DPF temperature sensors to establish the temperature of the DPF. Depending on the DPF temperature, the DPF software requests the ECM to perform either 1 or 2 post-injections of fuel:
- The first post-injection of fuel burns inside the cylinder, which increases the temperature of the exhaust gas
- The second post-injection of fuel is injected late in the power stroke cycle. The fuel partly combusts in the cylinder, but some un-burnt fuel also passes into the exhaust where it creates an exothermic event within the catalytic converter, further increasing the temperature of the DPF
The active regeneration process takes approximately 20 minutes to complete. The first phase increases the DPF temperature to 200°C (392°F). The second phase further increases the DPF temperature to 600°C (1112°F), which is the optimum temperature for particle combustion. This temperature is then maintained for 15-20 minutes to ensure complete incineration of the particles within the DPF. The incineration process converts the carbon particles to carbon dioxide and water.
The active regeneration temperature of the DPF is closely monitored by the DPF software to maintain a target temperature of 600°C (1112°F) at the DPF inlet. The temperature control ensures that the temperatures do not exceed the operational limits of the turbocharger and the catalytic converter. The turbocharger inlet temperature must not exceed 760°C (1400°F) and the catalytic converter brick temperature must not exceed 800°C (1472°F) and the exit temperature must remain below 750°C (1382°F).
During the active regeneration process the following ECM controlled events occur:
- The turbocharger is maintained in the fully open position. This minimizes heat transmission from the exhaust gas to the turbocharger and reduces the rate of exhaust gas flow allowing optimum heating of the DPF. If the driver demands an increase in engine torque, the turbocharger will respond by closing the vanes as necessary
- The throttle is closed as this assists in increasing the exhaust gas temperature and reduces the rate of exhaust gas flow which has the effect of reducing the time for the DPF to reach the optimum temperature
- The exhaust gas re-circulation (EGR) valve is closed. The use of EGR decreases the exhaust gas temperature and therefore prevents the optimum DPF temperature being achieved
- The glow plugs are occasionally activated to provide additional heat to assist in raising the DPF temperature
If, due to vehicle usage and/or driving style, the active regeneration process cannot take place or is unable to regenerate the DPF, the dealer can force regenerate the DPF. This is achieved by either driving the vehicle until the engine is at its normal operating temperature and then driving for a further 20 minutes at speeds of not less than 30 mph (48 km/h) or by connecting the Jaguar approved diagnostic system to the vehicle, which will perform an automated static regeneration procedure to clean the DPF.
Diesel Particulate Filter Control
The DPF requires constant monitoring to ensure that it is operating at its optimum efficiency and does not become blocked. The ECM contains DPF software, which controls the monitoring and operation of the DPF system and also monitors other vehicle data to determine regeneration periods and service intervals.
The DPF software can be divided into 3 separate control software modules; a DPF supervisor module, a DPF fuel management module and a DPF air management module.
These 3 modules are controlled by a fourth software module known as the DPF co-ordinator module. The co-ordinator module manages the operation of the other modules when an active regeneration is requested. The DPF supervisor module is a sub-system of the DPF co-ordinator module.
DPF Fuel Management Module
The DPF fuel management module controls the following functions:
- Timing and quantity of the 4 split injections per stroke (pilot, main and 2 post injections)
- Injection pressure and the transition between the 3 different calibration levels of injection
The above functions are dependant on the condition of the catalytic converter and the DPF.
The controlled injection determines the required injection level in addition to measuring the activity of the catalytic converter and the DPF. The fuel management calculates the quantity and timing for the 4-split injections, for each of the 3 calibration levels for injection pressure, and also manages the transition between the levels.
The 2 post injections are required to separate the functionality of increasing in-cylinder gas temperatures and the production of hydrocarbons. The first post injection is used to generate the higher in-cylinder gas temperature while simultaneously retaining the same engine torque output produced during normal (non-regeneration) engine operation. The second post injection is used to generate hydrocarbons by allowing un-burnt fuel into the catalytic converter without producing increased engine torque.
DPF Air Management Module
The DPF air management module controls the following functions:
- EGR control
- Turbocharger boost pressure control
- Exhaust Air Fuel Ratio (AFR) control
During active regeneration, the EGR operation is disabled and the closed-loop activation of the turbocharger boost controller is calculated. The air management module controls the air in the intake manifold to a predetermined level of pressure. This control is required to achieve the correct in-cylinder conditions for stable and robust combustion of the post-injected fuel.
The module controls the exhaust AFR by actuating the EGR throttle.
DPF Co-ordinator Module
The DPF co-ordinator module reacts to a regeneration request from the supervisor module by initiating and co-ordinating the following DPF regeneration requests:
- EGR cut-off
- Turbocharger boost pressure control
- Engine load increase
- Control of air pressure in the intake manifold
- Fuel injection control
When the supervisor module issues a regeneration request, the co-ordinator module manages the change over to the regeneration specific settings. The change over occurs during an accelerator pedal release manoeuver from the driver or after a calibrated waiting time.'