05-3 GENERAL 1. SPECIFICATIONS FOR ENGINE WITH CDPF
05-4 OVERVIEW AND OPERATION PROCESS 1. OVERVIEW As the solution for environmental regulations and PM Particla Material) of diesel engine, the low emission vehicle is getting popular. This vehicle is equipped with an extra filter to collect the soot and burn it again so that the amount of PM in the exhaust gas passed through the DOC (Diesel Oxydation Catalyst) is reduced. The CDPF (Catalyst & Diesel Particulate Filter) is an integrated filter including DOC (Diesel Oxydation Catalyst) and DPF (Diesel Particulate Filter). COMPARISON OF THROTTLE BODY FUNCTIONS BASED ON EXHAUST EMISSION REGULATION Regulated parts are carbon monoxide (CO), nitrogen oxide (NOx), particular matter (PM) and soot in the exhaust emission, and the particulars of the regulations are prescribed in the following table.
05-5 2. COMPONENTS Differential Pressure Sensor CDPF Assembly and Rear Exhaust Gas Temperatiure Sensor
05-6 3. MAJOR CHANGES The CDPF system is only installed to the D27DT engine, and the major changes comparing to the previous D27DT engine is as follows: CDPF (Catalyst & Diesel Particulate Filter) and Sensors Engine ECU The engine ECU has been revised since terminals have been added for front/rear temperature sensors. Its version is 3.2, but it is not compatible with ECU without CDPF. Fuel Common Rail and Fuel Rail (Between Common Rail and Injector) The I.D and O.D of fuel rail has changed from 2.4 mm/6.0 mm to 3.0 mm/6.35 mm. Also, the damping orifice is installed to prevent the fuel pulsation occured by fuel pressure. REXTON 2008.01
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05-8 4. OPERATION PROCESS 1) Combustion Temperature and Procedures As the soot is filtered in the CDPF, it is burnt and removed, and the CDPF is returned to the initial state to collect the soot. Therefore, the burning procedures in the CDPF can be called as recycling. The CDPF assembly is integrated with DOC (at front side) and DPF (at rear side). The DPF burns the soot with high-temperature exhaust gas (over 600 C). The rear exhaust gas temperature sensor monitors the temperature of DPF section. If this temperature is below the regeneration temperature, the ECU increases the post injection period to increase the fuel injection amount, and consequently to increase the exhaust gas temperature. Normally, when the vehicle is driven for 600 ~ 1,200 km, the enough amount of soot to be burnt is filtered and accumulated in the CDPF. The ECU increase the amount of post injection to increase the tempeature of exhaust gas up to 600 C so that the soot is burnt. The soot is burnt for 15 ~ 20 minutes.
05-9 2) Sytem Composition for Soot Combustion When the engine is running in low load range, the temperature of exhaust gas is decreased as the amount of fuel supplied is decreased. To burnt the soot filtered in the CDPF, the control system should be installed to check the operating range and increase the temperature of exhaust gas by controlling the amount of fuel supplied and and intake air. Two temperature sensors and one differential pressure sensor monitor the CDPF's operating range. According to theses sensors' information, the throttle flap decreases the intake air entered to the throttle body. Also, the fuel injection pattern is added to increase the temperature of exhaust gas for soot combustion. There are two fuel injection patterns (pilot injection and main injection). As the CDPF is installed, the post injection pattern is added. 3) Post Injection and Air Mass Control When the differential pressure sensor detects the pressure difference between the front and the rear side of CDPF, the sensor sends signal indicating the soot is acumulated and the post injection is performed to raise the temperature of exhaust gas. The amount of fuel injected is determined according to the temperature of exhaust gas detected by the rear temperature sensor. If the temperature is below 600 C, the amount of fuel injected is increased to raise the temperature. If the temperature is over 600 C, the amount of fuel injected is decreased or not controlled. When the engine is running in low load range, the amount of post injection and the amount of intake air are controlled. It is to raise the temperature by increasing the amount of fuel while decreasing the amount of intake air.
05-10 4) Throttle Body for Different Engines The throttle body is not installed in the D27DT engine (general), but is installed in the following engines: 1) D27DT (EU IV) engine 2) D27DTP (POWER UP) engine 3) D27DTP (POWER UP) engine + CDPF Both engines are equipeed with the throttle body, but its appearance and the related control system are differ.
05-11 5) Operating Procedures of CDPF The most efficient and practical technology for now is adopted to the diesel particulate filter (DPF). This system collects the soot from the diesel engine to the filter and burns the soot so that over than 95% of soot can be removed from the exhaust gas. However, the durability and the cost of additional system remain as problems. Firstly, the exhaust gas is passed through the DOC and its temperature is increased as it is oxidized. The ECU detects the temperature change with two temperature sensors. The CO, HC and partial particulate material are removed from the exhaust gas (this procedures are the sames as the ones for the conventional DOC and no sensor is required). After the exhaust gas is passed through the DOC and oxidized, most of the harmful material is removed from the exhaust gas. However, to meet the environmental regulations in the future, the soot is filtered and burnt again in DPF to decrease the particulate material further. The filtered soot is burned whenever the vehicle is driven for 600 ~ 1200 km. The driving distance can be differed depending on the vehicle's driving conditions. The soot is burnt for 15 ~ 20 minutes.
05-12 6) CDPF Over Load (Notice of Beginning CPF Regeneration Mode - P1430) 1. The CDPF system enters the regeneration mode when the mileage is around 600 ~ 1,200 km, depending on the driving condition and driving habits. At this moment, the ECU performs the CDPF regeneration process; however, the driver may not notice anything because there is no engine warning or other signals indicating such process. The control logic in the regeneration process is to increase the exhaust gas temperature by increasing the fuel injection during post injection process and controlling the intake air amount(throttle body), and no significant change can be noticed in the vehicle condition. 2. The engine CHECK lamp flashes but there is no decrease in engine torque. 3. The engine CHECK lamp flashes to inform the driver when there is an over load due to soot accumulation because the regeneration temperature cannot be reached due to low speed, even though CDPF regeneration is in process. 4. The CDPF regeneration process must be completed by driving for 15-20 minutes at a speed higher than 80 km/h to solve this problem. 5. The engine CHECK lamp flashes when CDPF is over loaded; therefore, 4) above must be performed in this case. 7) CDPF's Excessive Soot Accumulation (P0432) 1. When the vehicle is driven at a low speed (5-10 km/h) for a long time or long distance, the soot over accumulates inside the CDPF and the combustion temperature cannot be reached even by performing the soot combustion process. In this case, this DTC is generated. 2. This is more serious situation than the CDPF over load condition. Therefore, the engine power is decreased to protect the system and the engine CHECK lamp is turned on. 3. Blow the soot between the engine and the exhaust system several times and clear the DTC to solve this problem. If the same DTC is generated again, check the system according to the DTC description related to the differential pressure sensor. * This DTC is actually generated mostly due to the related system malfunction, such as differential pressure sensor malfunction.