DPF Filter Load - What do the numbers mean?

[BillG]

I have an Edge Insight which shows the 'filter_load', but does anyone know what the numbers actually stand for? I've seen mine run up and down between 2.1 and 4.6, but I have no idea how full that is.

Anyone had an insight (or something) when the overhead showed 70%? What was the filter_load then? I'm guessing it's 1-10, but don't really know.

[slagburn]

Curious as well, it seems to be more of a counted over time number rather than a measured value.

Some with DPF deletes have reported seeing that number up in the 9s with no negative effects.

[BillG]

I've been trying to decode the Chrysler specific PIDs used in these trucks using an ELM device and a program I'm writing. I can monitor all the standard obdii params plus a number of the Chrysler specific ones (regen desoot, desox, time since regen, etc.) that I've managed to decipher, but I'm having some trouble with the filter load. Looks like it's in the 2nd, 3rd, & 4th bytes of the data portion of the custom query with mode 0x21 and pid 0x4d, but I don't know if I've found the right formula. If you combine the three bytes ( byte1*65536 + byte2*256 + byte3) and divide by 32768, and then round it to 1 decimal, you get what 'seems' to equal Edge Insight's calculation of the filter load. But I'm not certain. I've watched it go up with normal driving and down with regens, but I was hoping someone could help fill in the blanks!

Currently I'm able to monitor up to about 20 parameters at a time, and it's dumping directly to an SQL database so that I can study and graph relationships later. I've captured a few regen sessions so far, but still trying to make sense of it all.

Interesting part is how quickly the filter load changes with different driving conditions. Edge only shows a rounded number that seems to change slowly, but the raw data changes much more rapidly with more than one decimal place of accuracy. That makes it more obvious how different driving styles affect the filter load.

[Dale_K]

If the Edge reading never exceeded 5 I'd make a guess and say it's one of those voltage type sensors that reads 0-5 volts. That's a pure swag on my part.

Isn't what's being measured the differential pressure before/after the dpf? I would expect the instantaneous value to move rapidly all over the map because of the changes in exhaust volume. If the dpf remained in a constant state, say 50% clogged, the differential pressure would change dramatically when the driver put the pedal to the floor.

I wonder if regens could be triggered by conditions other than dpf backpressure. Maybe the O2 sensor acts as an indicator of NOX catalyst effectivness and triggers a regen if the ECU thinks the catalyst needs burning off even when the dpf is doing fine. I don't even know if the NOX catalyst actually needs "burning off" - this is all guesswork for me.

[slagburn]

It seems that the regens are mostly triggered (or not) by tracking temperatures in the DPF assembly, from what I've read most of the 1st generation fool boxes are just resistors that make the ECM think that the temperatures are over a certain point pretty much all of the time.

I noticed that in my Insight it lists the ReGen trigger as 4.5 but I usually get a regen at around 4.0 or a little lower, what is very interesting is that if I leave the truck parked for a few weeks I almost always get a regen within 5 minutes of getting on the freeway even if it had just completed one on the trip prior to being parked.

[jmooney]

Tracking on my Insight - the DPF load ( I think ) is a measurment of back pressure or soot build up within the filter. During Regen ( after the desoot stage) the DPF temps climb up into the 1100 degree range ( 1200 would be better but I can't get my 6.7 to generate enough EGT long enough to sustain - see old post from me on DPF and info about regen process) you can watch the DPF load drop. However, the total regen time is limited to protect the DPF itself from sustained high temps.

If you do a lot of city driving, the regen will attempt and fail ( you can track those with the insight as well). I have seen my Load score as high as 12.8 without any overhead system warning. I have seen it as low as 3.2 and still attempt to regen.

As far as I can tell there is no magic Load # that triggers regen. It does appear that if a reg cause teh load # to drop a certin % ( or # of points) that it counts it as sucessfull.

I have also read that driving with load can make the regen process more effective --- 1400 miles with a 4000lb trailer - no such luck... it tried several times but always quit mid process. I suspect that was because the DPF temps were too high during the desoot stage and the fuel simple "flash burned" as opposed to soaking into the existing soot.

BillG - does this make sense from your testing?

[BillG]

My Insight says the regen trigger is 4.5 also, but I've kept the filter load below 4 (mostly), and it still seems to always want to do a regen. I've seen it try to do a regen at 2.9! Doesn't seem to pay any attention to the trigger.

I also read that you get a better regen under load, but it hasn't proven true for me. I seem to get the best regens at 60mph (I know the TSB says 50) without a load. With a load, or even just climbing a hill without a load, the cat temps drop fast when the extra fuel is spent maintaining speed. Sounds backwards, but we're talking drop from ~1200 to 900-1100, and the filter reduction slows. Almost seems like the extra fuel in the exhaust stroke becomes rationed when that fuel is needed instead for power - just a guess ofc!

There are also two kinds of regens that I see, and they seem to alternate. One regen does about a 20 mile DeSoot and then turns off, and it increments the Regens Completed number as though it was successful. But, it does nothing to the filter load. The 2nd type does a DeSoot for about 10 miles and then switches to a DeSOx for 15-20 miles. During the DeSOx, my filter load drops. Strange thing is that this type never increases the Regens Completed number.

The 'temperature below a certain point' concept needed for a regen makes sense with what I'm seeing. If I get on the hwy and run hard, it rarely does a regen. If I go through the city and catch a bunch of lights, it almost always starts a regen! So basically it only wants to do a regen when it can't succeed! Frustrating...

I read on another forum that the Insight filter load is supposed to represent grams of soot. I'm skeptical of that though because the filter load only decreases during a DeSOx - not a DeSoot.

[slagburn]

Casual reading on the MB BlueTec NAC+SCR system (which I think is the closest to what we have) suggests that one regen cycle cleans the Nox absorber and the other burns off the soot - I have noticed that I seem to get different turbo responses depending on which cycle is running, the cycle that doesn't decrement the DPF status (my Insight software is too old to show which cycle is running) makes for little boost unless I really get into it whereas the soot burning cycle makes boost very quickly with minimal throttle input - a very informative general regen post on a Ford forum suggested that this is one ways that the A/F ratio is controlled for regen.

Here is a bizarre one to ponder - the first part of my usual drive is a 10 mile downhill highway run at about 70 - 75mph, last week the Edge EGTs (DPF) shot up to regen temperature but the exhaust manifold EGT gauge hung at around 800 (usual ex manifold regen temps are in the 1300 range) this went on for 6 miles until the DPF EGTs dropped back to normal, the regen started up again normally once I got down to the flat ground.

[BillG]

Originally Posted by slagburn

Casual reading on the MB BlueTec NAC+SCR system (which I think is the closest to what we have) suggests that one regen cycle cleans the Nox absorber and the other burns off the soot

Makes sense. I also found another Edge competitor offering a beta test of their product, and it showed three possible regen states: desoot, denox, and desox. I haven't been able to find that page since, but I know I saw it. My Insight only shows desoot and desox. I'm curious if there really are three, and if not, I wonder if Edge has them backwards (since Edge indicates desox lowers the filter load, but the filter load is supposed to be a measure of soot). The program I'm working on clearly shows the two triggers Edge is using for desoot and desox, but I haven't seen evidence yet of a third. (Although, there is so much data, truly a needle in a haystack.)

Originally Posted by slagburn

Here is a bizarre one to ponder - the first part of my usual drive is a 10 mile downhill highway run at about 70 - 75mph, last week the Edge EGTs (DPF) shot up to regen temperature but the exhaust manifold EGT gauge hung at around 800 (usual ex manifold regen temps are in the 1300 range) this went on for 6 miles until the DPF EGTs dropped back to normal, the regen started up again normally once I got down to the flat ground.

Wow, that is strange. Maybe the third mystery regen?


Anyone with the shop manuals - do they show the Chrysler specific diagnostic codes and responses for the OBDII CAN bus?

[shskr]

Originally Posted by BillG

My Insight says the regen trigger is 4.5 also, but I've kept the filter load below 4 (mostly), and it still seems to always want to do a regen. I've seen it try to do a regen at 2.9! Doesn't seem to pay any attention to the trigger.

My regen trigger never moves from 4.5.

There are also two kinds of regens that I see, and they seem to alternate. One regen does about a 20 mile DeSoot and then turns off, and it increments the Regens Completed number as though it was successful. But, it does nothing to the filter load. The 2nd type does a DeSoot for about 10 miles and then switches to a DeSOx for 15-20 miles. During the DeSOx, my filter load drops. Strange thing is that this type never increases the Regens Completed number.

I've noticed that as well.

I read on another forum that the Insight filter load is supposed to represent grams of soot. I'm skeptical of that though because the filter load only decreases during a DeSOx - not a DeSoot.

Mine seems to decrease the regen load in desox at over 1100 deg.

[slagburn]

Originally Posted by BillG

Makes sense. I also found another Edge competitor offering a beta test of their product, and it showed three possible regen states: desoot, denox, and desox. I haven't been able to find that page since, but I know I saw it.

I wonder if the Dashhawk will show the 3 possible regens... I've noticed that the online support for that product is a lot better than the Insight - mine still won't show the 2 that yours does and I updated it a couple of times.

[circ1977]

hello folks, bill im not familiar with the insite monitors you guys are using, but i can only imagine the numbers your throwing out is equivelant to what is see on my starscan . under the starscan mobile desoot screen the value is called soot load based on delta. i would assume this "value" is calculated from the two pressure readings pre and post dpf/catalyst. this value may very well be calculated into grams given the known flow rate of the dpf and the amount of grams of soot it would take to provide a given pressure difference.i've noticed during mobile desoots that the soot load based on delta will be as high as 45 on a very restricted dpf and low as 2 on a non restricted dpf.also i've always noticed during a mobile desoot that the regen always starts off with a desoot mode and then goes to desox and denox last. then back to normal mode.hope this makes things clear as mud lol.