0911201 JOHNSON WASHER, Spray plate

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(1) Diesel Exhaust Fluid (DEF) injector
(2) Selective Catalytic Reduction (SCR) system
(3) SCR mixing tube
(4) Diesel Oxidation Catalyst (DOC)
(5) Diesel Particulate Filter (DPF)
(6) Exhaust intake connection
(7) Exhaust outlet connectionClean Emissions Module Basics
A flexible exhaust pipe connects the engine to the Clean Emissions Module (CEM). The CEM contains the Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and the Selective Catalytic Reduction (SCR) systems. The CEM contains several mechanical and electrical components that reduce various exhaust emissions emitted from the engine. All the systems on the CEM are controlled by the engine ECM. Exhaust gases entering the CEM flow through the DOC first, then the DPF and SCR.
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(1) SCR Outlet Temperature
(2) Exhaust Differential Inlet Port
(3) Exhaust Differential Outlet Port
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(4) DOC Inlet Pressure Port
(5) DOC Outlet Pressure Port
(6) DPF Inlet Temperature
(7) DOC Inlet Temperature
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Air Flow through CEM Package
The first filter media that exhaust gas is exposed to is the DOC, a flow through style filter. The DOC oxidizes hydrocarbons, carbon monoxide, and soluble organic fractions as the exhaust gas flows through the filter. There are two temperature sensors, one at the inlet of the DOC canister, and one at the outlet. These two sensors are used to make sure DOC is hot enough to oxidize efficiently. The DOC outlet temperature is also used by ECM to know that the exhaust leaving the DOC, and entering the DPF, is hot enough for regeneration to begin. There also two ports on the DOC that can be used to hook up a delta pressure sensor for troubleshooting.Once the exhaust gas flows through the DOC, the exhaust gas enters the SCR mixing tube where Diesel Exhaust Fluid (DEF) is injected for the SCR. Before the SCR, exhaust gas enters the DPF. The DPF is a catalyzed ceramic filter which traps particulate matter (soot). The trapped soot is cleaned from the DPF through a catalytic reaction by heating the filter through a process called regeneration. The inlet section of the DPF cannister contains the DPF inlet pressure sensor, and DPF delta pressure sensor. The DPF Inlet Pressure sensor is used to measure the backpressure being generated by the DPF. The delta pressure sensor is used to measure soot collected in the DPF. The delta pressure sensor is measuring the pressure drop across the DPF. Since the delta pressure sensor is measuring flow resistance across the DPF, the sensor will also detect ash loading.After the exhaust gas flows through the DPF, the gas enters the SCR. The DEF injected prior to the DPF, mixes with exhaust gas in SCR to reduce Nitrogen Oxides (NOX). DEF contains deionized water and urea, which turns to ammonia when heated. The ammonia reacts with the SCR catalyst to convert NOX into harmless nitrogen and water vapor. At the inlet of the SCR cannister is the SCR inlet temperate sensor. This sensor is used to make sure that the temperature is hot enough in the catalyst for DEF dosing to occur.Engine Throttle Valve and Hydrocarbon Dosing Regeneration
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(1) Engine Throttle Valve
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(2) Hydrocarbon DoserMostly, regeneration is achieved passively, which means no added fuel to achieve regeneration. This is achieved by an engine throttle valve. The engine throttle valve is a butterfly valve located between the charger cooler outlet and the inlet manifold. This valve is the primary means of regeneration. The engine throttle valve is controlled by the ECM and is used to restrict the flow of air into the inlet manifold and the combustion chamber. This restriction increases the exhaust gas temperature and is used to control the DOC and SCR temperature to ensure emissions compliance in all operating conditions.If passive regeneration cannot be achieved due to low temperature, load, or speed, then the use of active regeneration is needed. Active regeneration is the means of injecting a small quantity of fuel into the exhaust stream to create the heat needed to oxidize soot in the DPF, and decrease sulfur in the SCR. This fuel injection process is called Aftertreatment Hydrocarbon Dosing. The engine throttle valve will always be activated as well when hydrocarbon dosing is occurring to aid in temperature increase.To regenerate the DPF at the right time, the ECM must know what the soot and sulfur levels are. The soot input is a function of delta pressure measurement across the DPF, and calculated soot model based on developed engine out soot measurements. Sulfur percentage is determined from a calculation based on operating conditions over time. There is no direct sulfur measurement. The information gathered from these inputs is converted into a percentage of soot and sulfur. The percentages can be viewed through Cat® Electronic Technician (ET).Regeneration Triggers
Soot - The engine aftertreatment system is designed to oxidize the soot in the DPF at the same rate as the soot is produced by the engine. The oxidization of the soot will occur when the engine is operating under normal conditions. The soot in the DPF is constantly monitored. If the operating conditions of the engine do not increase temperature enough to oxidize the soot, the engine throttle valve will activate to raise temperature once soot reaches a certain level. If the engine throttle valve cannot achieve the required temperature, and soot increases to a critical level, hydrocarbon dosing will trigger.Desulfation - The DOC catalyst and SCR catalyst will accumulate sulfur. This will affect the efficiency of both catalysts. A software strategy based on engine fueling and catalyst temperatures determines how much sulfur build-up there is over time. Once sulfur is above a threshold, hydrocarbon dosing will trigger.DEF Deposits - The SCR catalyst will accumulate Diesel Exhaust Fluid (DEF) deposits from the fluid being injected to reduce NOx emissions. DEF deposit accumulation will affect the efficiency of the SCR catalyst. Under normal engine operating conditions the SCR should get hot enough that the DEF deposits burn off. If the SCR does not get hot enough, and software strategy determines deposits are increasing, hydrocarbon dosing will trigger.De-crystallization - If the temperature at the DEF injector is not hot enough,