Regen System On Trucks

[Ermengardi Atkisson]

DPFregeneration is the process that cleans the DPF. DPFs are designed using a ceramic honeycomb structure that traps and stores particulate matter from the exhaust into microscopic pores. After a while, these pores fill up, making them less effective in capturing debris.

As an exhaust component that is continually clogging from the perpetual operation of a diesel truck, this filter is built into a system where it essentially cleans itself of the buildup. The cleaning happens by burning off the accumulated soot at high temperatures, thus converting it to ash and other less harmful materials. After a successful DPF regen, the filter can more efficiently capture particles within exhaust gases and more easily pass through the airflow from intake to output, causing less stress on the engine itself.

Over time, the DPF system needs manual cleaning by a technician when the ash levels get too high. Nonetheless, DPF regeneration significantly extends the amount of time before a manual intervention becomes necessary.

This process occurs automatically, without any intervention from the driver or technician. Passive regen typically happens when you drive your truck sustained high speeds, like on highways. In those cases, the exhaust gases get hot enough to burn off the soot naturally, turning it into ash. The driver may notice a warning sign on the dashboard indicating that the DPF is passively regenerating. If you notice that light, we recommend you keep driving if possible until the process is finished.

When the fuel comes into contact with the catalyst on the DPF, it generates a high amount of heat (more than 1,100 degrees Fahrenheit), which is enough to burn off the soot off the ceramic filter. A computer sensor monitors the DPF and a dashboard indicator light notifies the driver that the regen is taking place or the DPF is now cleaning.

Regens happen because of soot build-up in the diesel particulate filter. When you lower your soot output, you can lower your regens significantly. Achieving a more efficient diesel burn is the best way to accomplish this. There are two things needed to make this happen:

Specific to diesel engines, the proper additives also restore the lubricity that has been refined out of the ultra-low sulfur diesel fuel purchased at the fuel pumps. With the proper lubricity returned to the fuel system, however, mechanical parts are then more fluid in their operations with less friction. With less friction, the amount of wear and tear is reduced, better maintaining the tolerances of machined parts for a cleaner burn and more complete combustion cycle.

Stiction is the sticky friction caused by the byproducts of burnt oil. High pressure builds heat in tight-tolerance applications and extreme heat causes the oil to burn, oxidize and create layers of sludge and deposits. Fuel injectors, pistons, rings and various other engine components are continually susceptible to this stiction buildup. All of which are the enemy of any clean and efficient mechanical system.

When oxidization, layers of sludge, carbon and deposits form throughout the engine, additives are an imperative need to clean the parts. The proper oil additives clean the gum, varnish and stiction while also lubricating everything the oil touches in your engine. But the proper additives also do so with no harsh solvents that potentially harm engine components. Specific to the DPF, the correct additives properly clean the engine parts and reduce the number of particulates clogging the DPF, thereby reducing multiple regen cycles.

The proper additives also help restore dynamic compression with an increased ring seal. The tighter seals provide improved combustion efficiency, thereby translating to not only better fuel economy, engine power and a better running engine, but also the efficiency required in the combustion cycle to prevent blow-by and added particulates flowing through the exhaust system. The proper combination of additives can provide not only a better running truck, but an extremely helpful deterrent to unexpected repairs and replacements in the future.

Regeneration, or regen, of the DPF filter, is the process that burns the soot accumulation that is inside the DPF filter. If you can no longer start a regen then you will eventually get stuck in a derate which will then lead to an engine shut down.

The regen process and how it works is something you should familiarize yourself with. In this blog post, we discuss what prevents a regen. With this knowledge, we hope it brings you one step closer to taking control of your truck.

You must listen to your gauge cluster!

The cluster has various aftertreatment signs to let you know that there is an active problem with your DPF regen system. You must also pay attention to the CEL (Check Engine Light) because if there is an active CEL then your passive and/or active DPF regen process can be disabled.

Ok, I found this quote on another post, Pay attention to boost pressure says 8-12 without DRV valve. This truck has a DRV valve and is only showing boost 1.25 PSI during regen. Towards the end of regen outlet NOx showed 510ppm, after regen and hold throttle floored at went down to 28ppm and that crept up to about 170-200.

""First go into the scr system test, There will be an scr inducement reset. Perform that, Then make sure you perform the scr learned data reset for the parts already put on. Sometimes when you have the inducment to clear on the 2010 emission products it may take 2 back to back regens. What you should do is command a regen with tech tool. Then once the regen idles up and starts on its own disconnect the com box either from the computer or from the 9 pin diag connector. You will get an communication error, Plug the com box back in and click okay and click back to go to the main screen in test. Go to sensor monitoring and select the following, Boost pressure, intake air temp, Egr diff pressure, egr mass flow, Ex gas temp, DPF 2 and 3 temp, Def pump pressure, Def doser, and outlet nox, You will want to make sure that the egr dps is staying close to its key on engine off reading which on the older style sensors is plus or minus .3, new style is .1. If that is okay, With out the DRV valve these run between 8-12 psi of boost during the regen. Make sure your t2 and t3 are running around 850+, make sure your def pressure is staying around 130 and not dropping out. Then the biggest thing is outlet nox, You will not be able to view inlet nox on this truck. We used to be able to years ago and they took that function out. Once the regen is complete, Hold the throttle pedal to the floor for about 30-40 seconds and let up, Watch the outlet nox reading. it should be below 100. The lower the better. The placing the throttle to the floor is a method to blow the extra hydro carbons out from the regen. If all of that checks out then you should be good to go and the fault should be inactive, If not then run another regen. Please let me know if you have any follow up questions on this. Thank you.""""

Thank You! we finally got it to clear yesterday. Yet I am apprehensive it may return. Earlier in our diagnoses I found a TSB stating if it had original part# NOx sensors to replace with current part number, Truck had one new part # NOx sensor on inlet and old part # on outlet so we replaced the outlet, did multiple regens again and those codes would not clear. Took Truck on another 30mile test run at highway speeds and 14miles in light went off and code cleared.

On most models , using Tech Tool you can do a Nox conversion test or a regular regen and watch the nox levels when DEF fluid is dosing. Nox inlet will be high of course and the outlet will be much much lower. Mack never told us that the levels should be though

The truck gets a SCR fault on the dash. Then not to long after, it'll do idle shutdown of course. I was reading somewhere that if you're having SCR issues then one of the problems could be your NOx sensor, and not saying which one either.

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