48358 Mercruiser PLUG, INTAKE MANIFOLD VACUUM HOLE

System Block Diagram
Illustration 1 g06077530
(1) Clean Emissions Module (CEM)
(2) Dosing control cabinet
(3) Diesel Exhaust Fluid (DEF) customer supply tank
(4) Compressed air supply
(5) Separate circuit aftercooler (SCAC)
(6) Air cleaner
(7) Turbocharger compressor
(8) Turbocharger turbine
(9) Mixing tube
(10) Selective Catalyst Reduction (SCR)
(11) Exhaust outDiesel Exhaust Fluid (DEF)
Note: Two tools are available to measure the DEF concentration. The two tools are the 431-7087 Tool Gp (Refractometer (DEF)) and the 360-0774 Refractometer (Brix). Refer to Testing and Adjusting, "Diesel Exhaust Fluid Quality - Test" for additional information.Selective Catalyst Reduction (SCR) refers to a method of treating engine exhaust to reduce the undesired oxides of nitrogen compounds NOx. SCR uses a catalyst which promotes a desired chemical reaction over other possible chemical reactions. The catalyst remains unchanged. Ammonia (NH3) is mixed into the exhaust, and reacts with the NOx in the presence of the catalyst to form harmless compounds (water and nitrogen). In this system, urea ((NH2)2CO) is injected into the exhaust, which quickly decomposes into ammonia under the heated conditions. Urea is used because urea is inexpensive, and does not need the special handling that ammonia requires.DEF is an aqueous urea solution (urea salt dissolved in water).A 32.5 percent or 40 percent (by weight) solution of DEF is required for the system.A 32.5 percent concentration has the lowest freezing point possible, −11 °C (11 °F), for this solution.A 32.5 percent concentration of urea keeps a constant concentration through freezing and thawing.DEF must be stored below 50 °C (122 °F) to delay decomposition.Note: The customer is responsible for providing primary filtering of the DEF from the site tank to the buffer tank. The system requires a 40 micron primary filter.Use only DEF that meets quality properties per ISO22241-1 (32.5%) or ISO18611-1 (40%). Using DEF that does not meet these specifications can result in clogging of the injection nozzle or other DEF quality related system failures.Refer to Operation and Maintenance Manual, SEBU6251, "Cat Commercial Diesel Engine Fluids Recommendations", , Exhaust Aftertreatment Fluids Specifications and Contamination Control for more information.Refer to Operation and Maintenance Manual, "Maintenance Section" to obtain locations for DEF suppliers.DEF is a non-toxic source of ammonia.DEF is corrosive. Do not store DEF in a tank or use supply lines that are made of the following materials: aluminum, brass, and steel. Use only corrosion resistant materials such as PVC or stainless steel. Any O-rings must be Ethylene Propylene Diene Monomer (EPDM).Clean Emissions Module (CEM)
Z Style CEM
Illustration 2 g06175387
Z-Flow Reactor Housing
(1) Inlet spool
(2) Inlet sensor box
(3) Lifting eyes
(4) Serial number/information plate
(5) Outlet sensor box
(6) Outlet spool
(7) Mounting brackets
(8) DEF injection nozzleU Style CEM
Illustration 3 g06175265
U-Flow Reactor Housing
(1) Inlet spool
(2) Outlet spool
(3) Outlet sensor box
(4) Lifting eyes
(5) Inlet sensor box
(6) DEF injection nozzle
Illustration 4 g06175334
U-Flow Reactor Housing
(7) Serial number / information plate
(8) Mounting bracketsCEM Operation
The exhaust gas exits the engine and enters the mixing tube, where the DEF is injected into the exhaust stream.The DEF decomposes into ammonia and carbon dioxide.The mixture of exhaust and ammonia travels through the SCR.The ammonia reacts with the NOx in the exhaust stream at the SCR catalyst to produce water vapor and nitrogen.Dosing Control Cabinet
Illustration 5 g03773465
(1) SCR controller
(2) Wiring harness connector to main DEF tank
(3) Wiring harness connector to CEM
(4) DEF vent port
(5) AC power in
(6) Breaker
(7) Wiring harness
(8) DEF outlet to CEM
(9) Air outlet to CEM
(10) Air inlet
(11) DEF inlet
(12) Wiring harness connector to engine ECM
(13) Service tool connector
(14) DEF pump
(15) DEF tankThe dosing control cabinet controls the following:
Rate of DEF flow to the injector
Compressed airCompressed air is used for the following:
Assist in the atomizing of the liquid DEF during injection into the exhaust stream
Shield the liquid DEF in the injector from the exhaust heat until spraying, so that no crystallization occurs which could plug the injection nozzle.
Purge the DEF line to the injector during shutdown to prevent crystallization of DEF resulting in a plug.Dosing Control System
The purpose of the dosing control system is to meter DEF into the exhaust stream.The dosing control cabinet houses an Electronic Control Module (ECM) that provides the basic logic.The desired rate of DEF injection is determined via a closed loop system, utilizing NOx sensors for feedback. The sensors measure the level of nitrogen oxides (NOx) entering the CEM and in the exhaust gas exiting the CEM.If the NOx sensor indicates high NOx in the exhaust outlet, the closed loop system will request an increase of the DEF flow rate.DEF flow rate is increased by increasing the frequency of the command signal to the dosing pump.The aftertreatment ECM controls the frequency of the command signal to the dosing pump.A communication adapter plug is provided on the side of the dosing control cabinet for easy connection.Injector
Injector Assembly
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