I see a lot of posts about how the exhaust system works on the new dodges. So I decided to do some research to get the facts and put it here for others to add to.
I am very interested in the aftermarket delete kits but first wanted to learn how this new mumbo jumbo works.

So here it is:





The system description

The Diesel Exhaust Fluid Emissions system uses a Selective Catalytic Reduction (SCR). This is a technology that uses a urea based Diesel Exhaust Fluid (DEF) and a catalytic converter to significantly reduce nitrous oxides (NOx) emissions. The system accomplishes this by injecting small quantities of Diesel Exhaust Fluid (DEF) into the Selective Catalytic Reduction (SCR) where its vaporizes and decomposes to form ammonia and carbon dioxide. The Diesel Exhaust Fluid (DEF) Dosing Control unit is used to control the operation and monitoring of the DEF system.
Ammonia is the desired by-product which in conjunction to the SCR Catalyst, converts the NOx to a harmless nitrogen and water.
The SCR system is equipped with two NOx Sensors and modules that are used to monitor the efficiency of the SCR Catalyst and DEF system.

exhaust-system-•-description-•-6-7l-diesel-engine.pdf

Components that are in the system

The first component of the Aftertreatment System consists of two catalyst elements, working together to drastically reduce tailpipe emissions the DOC and the DPF

DIESEL OXIDATION CATALYST (DOC)

The Diesel Oxidation Catalyst (DOC) is a ceramic flow through substrate coated with a catalyst washcoat that is integral to the DOC and resides in the front half of the assembly. The DOC treats engine exhaust gases by converting harmful carbon monoxide, unburned hydrocarbons and other compounds into water, carbon dioxide and heat.

DIESEL PARTICULATE FILTER

The Diesel Particulate Filter (DPF) is a wall-pass ceramic filter substrate coated with a catalyst washcoat. It is located just downstream of the DOC.
Exhaust gases flow from the DOC into the catalyzed diesel particulate filter (DPF) which traps and accumulates particulate matter, and further treats the exhaust gases to reduce any remaining unburned hydrocarbons and other harmful compounds.
The trapped particulate matter will be periodically removed from the DPF via a regeneration process controlled by the engine’s Powertrain Control Module (PCM).
The oxidation catalyst raises the exhaust gas temperatures to regenerate the DPF, which is passive regeneration. If the passive regeneration cannot keep up with the build up of soot in the DPF, the Powertrain Control Module (PCM) will actively regenerate the DPF to burn off the soot. Residue remains inside the DPF in the form of non burnable ash. Ash comes from the oils and other materials that are trapped in the oils and are present in the soot. The catalyst contains a large number of parallel channels, which run in the axial direction and are separated by thin porous walls. The channels are alternatively open at one end, but plugged at the other. The exhaust gases flow through the walls and escape through the pores in the wall material. Particulates, however, are too large to escape and are trapped in the monolith walls. The PCM starts the regeneration of the DPF if the soot load exceeds a performance map value. The PCM determines the load condition of the DPF based upon the exhaust gas pressure upstream and downstream of the DOC/DPF. A pressure differential sensor provides the pressure input to the PCM. During the regeneration process, the PCM raises the temperature in the DOC/DPF to burn off the soot accumulated. Under normal operation, the engine does not produce enough heat to oxidize the soot inside the DOC/DPF. This process requires temperatures above 550 ºC (1,022 ºF). After regeneration, the PCM reads the actual pressure difference at the DOC/DPF and compares it with a reference value. From this comparison, the PCM determines the ash quantity inside the DOC/DPF.

DEF fluid tank

The Diesel Exhaust Fluid (DEF) tank is mounted to the frame of the vehicle on the left side and is equipped with sub components below.
Electric Heat Exchanger
Level Sensor
Temp Sensor
Vent Valve
Fluid Limit Vent Valve

Dosing control unit

The Diesel Exhaust Fluid (DEF) Dosing Control Unit is used to control the operation and monitoring of the Diesel Exhaust Fluid system. The DEF Dosing Control Unit shares information with the Powertrain Control Module (PCM) over the J1939 Data Link.
The Diesel Exhaust Fluid (DEF) Dosing Control Unit controls the function of the Urea's "wet system" (heaters, pump, and injector). The DEF Dosing Control Unit receives a signal from the Powertrain Control Module (PCM) on when to inject. The DEF Dosing Control Unit is mounted on the DEF tank.

DEF supply pump

The Diesel Exhaust Fluid (DEF) Supply Pump has many functions. It's primary purpose is to draw fluid from the tank and build adequate system pressure for dosing into the exhaust. The DEF Dosing Control Unit provides the 12 Volt supply and ground to the pump. The DEF Dosing Control Unit provides a Pulse Width Modulated (PWM) signal to the DEF Supply Pump to control the speed and output of the pump. The DEF Supply Pump has an internal temperature sensor which reports the internal temperature of the DEF Supply Pump to the DEF Dosing Control Unit.
The Diesel Exhaust Fluid (DEF) Supply Pump is mounted inside the DEF tank.
The DEF Supply Pump:Has an operating pressure of 9 bar (131 psi).
Capable of reverse flow to evacuate system on shut-down and Electrically Heated.

DEF pump filter

The Diesel Exhaust Fluid (DEF) pump filter is has a internal filter designed to prevent foreign objects from entering the dosing system. The aftertreatment diesel exhaust fluid pump filter is a non-servicable item. If the internal filter becomes restricted or clogged, then the DEF pump has to be replaced. For DEF pump replacement go to: (Refer to 25 - Emissions Control/Diesel Exhaust Fluid Emissions, 6.7L Diesel/ASSEMBLY, Diesel Exhaust Fluid Pump/Removal).

DEF heater

Each of the Diesel Exhaust Fluid (DEF) system hoses has a built in heater to warm the fluid in the line. The line heater has power supplied to it via the DEF Dosing Control Module. The Line heater circuits are monitored on the return side of the circuit.

DEF Injector

The Diesel Exhaust Fluid (DEF) injector (1) is similar to a fuel injector, but modified to be compatible with the Urea fluid. The DEF injector is mounted to the front of the Selective Catalytic Reduction (SCR) catalyst and is designed to operate in a underbody environment.
The (DEF) Injector is mounted to the decomposition tube at the inlet of the Selective Catalytic Reduction (SCR) Catalyst. The DEF dosing Control Unit sends a Pulse Width Modulated (PWM) signal to the DEF Injector to vary the amount of fluid sprayed into the exhaust stream.

DEF fluid pressure sensor

The Diesel Exhaust Fluid (DEF) Pressure Sensor is a three wire sensor, housed inside the DEF Supply Pump that monitors supplied pressure to the DEF Injector. The DEF Dosing Control Unit provides a 5-Volt supply and ground to the DEF Pressure Sensor. The sensor provides a signal to the DEF Dosing Control Unit on the DEF Pressure Sensor Signal circuit. This DEF Pressure Sensor Signal voltage changes, based on the diesel exhaust fluid pressure supplied by the DEF Supply Pump. The DEF Dosing Control Unit uses this information to vary pump speed and maintain the 130 psi (9 bar) pressure needed for proper DEF Injection.

NOx sensors

There are two NOx modules and sensors used in the DEF fluid system, upstream and downstream. Both operate similarly to a wide band O2 sensor. The sensors are zirconium-based, multi-layer sensors with oxygen pumps. The NOx modules communicate the amount of NOx to the Powertrain Control Module (PCM) over the J1939 communication bus.
The upstream module is located on the right frame rail and the sensor is at the front of the Diesel Particulate Filter (DPF).
The upstream module and sensor are used by the PCM to monitor NOx entering the catalyst. By comparing the inlet sensor to the outlet sensor, SCR efficiency can be determined by the PCM.
The Pre-NOx sensor is mounted at the outlet of turbocharger elbow and measures incoming NOx gases.
The Post-NOx sensor is mounted at the rear outlet of Selective Catalytic Reduction (SCR) Catalyst and measures outgoing NOx gases.

Ammonia sensor

The Ammonia sensor is located in the center of the Selective Catalyst Reduction (SCR). The function of the ammonia sensor is to detect the amount of ammonia in the SCR.
The ammonia sensor is used to monitor the operation of the Diesel Exhaust Fluid (DEF) system. The ammonia sensor module shares information with the Powertrain Control Module (PCM) over the J1939 Data Link.


Emission controls

The PCM is responsible for efficiently coordinating the operation of all the emissions-related components. The PCM is also responsible for determining if the diagnostic systems are operating properly. The software designed to carry out these responsibilities is call the “Task Manager”.


Lets tear all that out and put on some stacks!!

Here are some links about some good deletes available out there!!

Found this link for EFI Live Flashscan V2 looks like a cool tool to have even looks better than a smarty.
EFILive - FlashScan V2

Found one more company who does a programmer for the late model DPF delete.

https://hsperformance.net/downloads/pdf/black-maxx.pdf


and a AFE exhaust DPF delete for any model truck:

Advanced FLOW Engineering


Dodge specific:

Advanced FLOW Engineering

 

Just a note
Anyone wanting to delete their exhaust DPF or the system all together should understand that EPA mandates all vehicles being operated on the roadways must have the emissions systems original and unaltered.
All of the shops installing the exhaust delete equipment will require a signed affidavit that the vehicle is for off road purposes only.
This is important because the feds can fine each person who operates an altered vehicle 2500$ and each shop installing them 25000$.
This also can effect the resale of your vehicle if you resale or trade in at a stealership
they won't take your truck modified as a trade.
It would make sense to keep your DPF, DOC, SCR system pieces for re-installation later.
Just so everyone reading this understands it is illegal to operate a deleted SCR exhaust on the highway in all 50 states.

 

Another case for "Big Government" (EPA, etc.) to control our lives. They should induce controls on Volcano's since they emit extremely more NOx in one eruption than we will product in a lifetime.

 

good info!
I have thought about removing just the muffler, but after reading that the system monitors the pressure in the exhaust system, before and after the DEF system removing the muffler it would change the back pressure after the system.

so it looks like if I want to change anything on you 2015 Cummins, its all or nothing!
so in 5 years, off with everything and some compound boosting!