What is a normal DPF pressure?

[OggyOggy]

I'm interested in monitoring my DPF health. Is the pressure an accurate way to determine the health of the thing?
Thanks

 

[762vram2043]

May be too many variables to reconcile/peel apart - current and recent engine load, RPM, etc. Finding a set of reproducible conditions that would lend themselves to trending could be a challenge. A periodic run over the same road at the same speed and engine load might provide this. I recorded OBD data heading East through Big Horn Mountains of Wyoming last August which included DPF pressure. A few times (before we hit the mountains) it was relatively steady when at steady load on level road but most of the time it was all over the map. And after coming back down out of the mountains it didn't steady out at all like it had prior to hitting the mountains. I would expect the high exhaust temperatures on the upgrades to keep the soot burned off the filter on the upgrades and the light engine load on the downgrades to minimize soot accumulation but I'm certainly no expert on DPF operation. A couple days and a couple hundred miles down the road it did show a few relatively steady DPF dps while heading east through the Sandhills of Nebraska. Elevation drop during this run was gradual, about 2300 feet total. Didn't spend a lot of time trying to see if I could correlate DPF to a combination of other parameters. Also I don't believe the units spit out by the Kiwi OBD and recorded by the Torque Pro app on my phone and tablet are correct as the values indicate a huge (200+ psid) exhaust backpressure. Suspect it isn't psi, maybe mm of Hg or water??? If anyone knows I would appreciate clarification. If it's of interest, the TorquePro Kiwi3 took a data snapshot about once every 2 seconds.

 

[6V92TA]

if I remember correctly the info from the Cummins ISB serivce manual, a clogged DPF is considered to have an 11 in Hg restriction. I don't know how exactly this will correlate to what is on the Ram Truck but I suspect its close.. people who drive their truck long distances and under heavy load will get a much better service life out of their DPF than people who short trip or do alot of city cycle driving

 

[Bob4x4]

That’s one of those factoids we don’t need to memorize because we spend big bucks to buy computerized trucks to do the thinking for us

 

[Newsa]

Doesn't it also change with engine speed?

 

[Bob4x4]

Back pressure will increase with rpm/load,that is why differential pressure is used.

 

[6V92TA]

the ECM measures the pressure drop across the DPF and also measures the temperature pre cat, post cat and post DPF. the ECM doesn't measure back pressure in the strict sense, they measure differential pressure in the DPF. if someone suspects a clogged exhaust they have to measure the system using the following procedure.


quote the Cummins ISB service manual here.. QUOTE When measuring exhaust restriction, it is preferred that the measurement point be within 1 pipe diameter of the turbocharger outlet.If equipped, remove the pipe plug from the pressure tap located in the turbocharger exhaust outlet tubing or the inlet of the aftertreatment system.If the exhaust outlet tubing or the inlet of the aftertreatment system is not equipped with a pressure tap location, remove the first exhaust temperature sensor located in the aftertreatment systemOperate the engine at peak system load and record the exhaust restriction.

Exhaust Restriction Limits
mm-hg 330
in-hg 13

 

[jhenderson]

A better question might be what’s the differential pressure threshold at a given rpm and load for setting a code.

 

[6V92TA]

A better question might be what’s the differential pressure threshold at a given rpm and load for setting a code.

I know one thing, there is a timer running and if the ECM doesn't detect a full DPF after a given amount of engine hours it will initiate and run a active regen and the timing function will restet itself

 

[Bob4x4]

I know one thing, there is a timer running and if the ECM doesn't detect a full DPF after a given amount of engine hours it will initiate and run a active regen and the timing function will restet itself

That only applies to the later trucks not all the def models

 

[Wayne M.]

I know one of the parameters of delta P is to keep honest people honest. A zero reading (meaning there's nothing there) is a fault. That's pretty obvious.
To answer the OP, the only thing you can do is to start charting your algorithm and when it steps out, you'll know. Different numbers for various soot load, engine speed/ load during regen and not etc etc.
I just did a monitored regen yesterday on one of our very high hour EPA07 spark assisted Mack's, and the beginning soot load was almost 200% (yes it was in stage 4 derate). At the beginning of the regen, the delta (which is measured in PSI in Mack diagnostics) was .10-15, during the regen it went to .35, and during the cooldown, it settled at .005 PSI. This was at idle speed. We've seen them as high as .70, and that's when that number gets high, we yank the filter and bake em or look for oil contamination.

 

[Newsa]

That only applies to the later trucks not all the def models

By later trucks, do you mean 2013+?

I realize that DEF/SCR was employed earlier than 2013 in 4500 - 5500 models. So just curious when this was programmed into the non-commercial/consumer trucks???

 

[Wayne M.]

I know one thing, there is a timer running and if the ECM doesn't detect a full DPF after a given amount of engine hours it will initiate and run a active regen and the timing function will restet itself

The earliest HD truck aftertreatment DPF system I know of is the Emcon system which came out in late 05 for EPA07, and while that used all the thermal and pressure monitoring you see today, it was meant for older, sootier engines, so it tried to get a active regen off every 4 hours of runtime. The diagnostics had a actual clock, and if you had to force a regen, the second it came off a regen, the clock would start counting back at 4 hours.

 

[bob53magnum]

I got a used one with 13000 miles on it that I will sell you cheap.

 

[6V92TA]

The earliest HD truck aftertreatment DPF system I know of is the Emcon system which came out in late 05 for EPA07, and while that used all the thermal and pressure monitoring you see today, it was meant for older, sootier engines, so it tried to get a active regen off every 4 hours of runtime. The diagnostics had a actual clock, and if you had to force a regen, the second it came off a regen, the clock would start counting back at 4 hours.

first particulate traps I ever dealt with were made by Donaldson. we tested five of them in 1992.. we also tried some from a company called EZ Trap. in the same time frame, but their system required a additive in the fuel and specific injectors

 

[Wayne M.]

first particulate traps I ever dealt with were made by Donaldson. we tested five of them in 1992.. we also tried some from a company called EZ Trap. in the same time frame, but their system required a additive in the fuel and specific injectors

What was the application?

 

[6V92TA]

What was the application?

1992 Flxble transit buses. with L10 Cummins. we had 5 of them, was a test project that the FEDs paid for. Donaldson Particulate Trap was a rube Goldberg setup, two particulate traps with an electric heating coil in them and a Y pipe to them that had a diverter valve so one would collect soot while the other electrically regenerated. also required its own alternator as the setup used a large amount of electricity. you gotta remember these were L10 mechanically injected engines with the PT fuel system and this was in the days before low sulfur diesel, let alone the ultra low sulfur fuel we have nowadays. the Donaldson dual trap system was too complicated to be reliable. then another company participated ( the company was called EZ Trap) have no idea what happened to them or who bought them out. the EZ Trap was similar to a regular DPF but it required us to use an additive in the fuel and run special injectors.. I'm working on memory here , can't find any of our own info on the stuff as it long ago went to a junkyard but I did find a SAE article about NY Transit working with particulate traps in 1992.http://onlinepubs.trb.org/Onlinepubs/trr/1992/1338/1338-006.pdf https://www.sae.org/publications/technical-papers/content/920138/

 

[Wayne M.]

Wow. I heard about the ez trap. Our first try was retrofits by Cleaire and Johnson mathey DOC's. Aside from some teething, and fixing dirty, out of tune engines, it worked well.
The filter technology we have today, the interlocking blocks, really advanced things.