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Duramax Fifth Generation: 2011-2016 (LML) Discuss the fifth generation (2011-2016) of the 6.6L Duramax diesel engine & associated components. Engine related discussion ONLY.

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Old 05-26-2017, 08:44 PM   #11 (permalink)
greende
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Originally Posted by Boxer1200 View Post
I've noticed with mine, if interrupted more than twice it doesn't take the soot level down as far. This results in the next regen coming sooner and therefore overall average MPG being less. When this happens , I've seen it give up around 14 grams. Not a big deal. May not even be an accurate measurement, but that's what I've seen.

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This has been my experience as well. I monitor my soot level on my Edge Insight and the level does not go down when interrupted more than twice.

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Last edited by greende; 05-26-2017 at 08:45 PM.
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Old 05-27-2017, 06:50 PM   #12 (permalink)
Ted White
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This is a subject I know a fair bit about because (a) A contact at Duramax has shared a lot of tech information with me about how the system is programmed, and (b) I run LOTS of monitored Driving Regenerations for owners in Mexico who have temporary sulfur poisoning of the SCR due to higher sulfur Mexican fuel.

It is correct that the LML will resume a regen after a key off, just as soon as the required parameters are met again, mainly DEF pressure of at least 70psi, and around 150 degs C at the SCR. Total time for a regen is about 35 minutes, so the timer pauses and then restarts, so as to ensure that the total time requirement is met.

Stops and starts at traffic lights and stop signs are not typically a problem once a regen is underway. Very little exhaust flow is required to maintain the heat so even a 5 minute stop at idle is not usually a regen killer.

Once the soot in the DPF reaches 500 degs C more or less, it is at flashpoint and begins to burn spontaneously - just like paper in a barbeque begins to burn after you bring it to flashpoint with a match. If you key off at this point there will definitely be a lot of crackling noises from the DPF. The burn will subside and the DPF will then begin to cool, but it isn't a sudden cooling, so no damage should result.

One thing that does interrupt the regen is downhill coasting using the exhaust brake. I noticed this when assisting a guy in Mexico who had a camper. We were running a driving regen on a highway out of Los Barriles which has several long ups and downs over a 10 mile distance. He had the exhaust brake engaged and every time we started downhill the exhaust system cooled and the regen stopped. Took a while to figure out what was happening, but once we disengaged the exhaust brake the regen ran normally. The exhaust flow is all but stopped when the exhaust brake is slowing the truck, so there is insufficient exhaust gas for the fuel to be injected in to from the 9th injector.

Soot load readings tend to be an approximation because they are based on the pressure differential across the DPF. This can vary depending on the amount of exhaust flowing, and how much ash is present in the DPF. Ash, as opposed to soot, gradually builds up in the DPF, increasing the back pressure in the DPF. That's why the DPF eventually needs to be cleaned out of ash, usually some time after 100,000 miles of use. The oil spec for our trucks requires low ash oil to reduce the amount of ash accumulation.

Bottom line is don't worry about it.

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Old 05-27-2017, 09:02 PM   #13 (permalink)
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Great post. Very informative.

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Old 05-28-2017, 02:11 PM   #14 (permalink)
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Quote:
Originally Posted by Ted White View Post
One thing that does interrupt the regen is downhill coasting using the exhaust brake. I noticed this when assisting a guy in Mexico who had a camper. We were running a driving regen on a highway out of Los Barriles which has several long ups and downs over a 10 mile distance. He had the exhaust brake engaged and every time we started downhill the exhaust system cooled and the regen stopped. Took a while to figure out what was happening, but once we disengaged the exhaust brake the regen ran normally. The exhaust flow is all but stopped when the exhaust brake is slowing the truck, so there is insufficient exhaust gas for the fuel to be injected in to from the 9th injector.
Whats up Ted. Good to know, as I leave my exhaust brake on all the time.
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Old 05-28-2017, 04:36 PM   #15 (permalink)
Ted White
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Just to clarify the exhaust brake situation, the downhill runs were quite long during the driving regen mentioned in my post. I don't think it would be an issue for downhill runs of less than half a mile, but anything much more than that would start to impact on the regen cycle.
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Old 06-01-2017, 06:38 PM   #16 (permalink)
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Why is the message on the DIC saying your speed has been reduced to 45 MPH or less after using high sulfur fuel in Mexico? I know a person who spends the winter in Mexico that has had this problem and almost trashed the ECM trying to fix the problem.
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Old 06-01-2017, 06:50 PM   #17 (permalink)
Ted White
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DieselDog41 please invite your friend to contact me directly about how to manage his truck while using Mexican diesel. There is no need to trash the ECM.

Here's what happens when using Mexican LSD fuel:

1.
Sulfur compounds in the exhaust gradually settle out in the SCR, reducing it's efficiency. This is called "sulfur poisoning" of the catalyst.

2.
As the efficiency of the SCR decreases, more and more DEF is injected to compensate, until no amount of extra DEF will keep NOX treatment by the SCR within spec.

3.
At this point the emissions monitoring systems assumes that either there is bad DEF in the tank, or a NOX sensor is faulty, and triggers codes P20EE and P2BAD. This inturn results in the Check Engine Light coming on, as well as a warning in the DIC about "POOR QUALITY DEF"/

4.
The key to clearing the problem and codes is to run a regeneration, which burns the sulfur compounds out of the SCR, and returns emissions to normal. Depending on the truck model year, this may happen before speed limitation reaches the second stage, or the truck can go all the way to limp mode - 5 mph.
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Old 06-02-2017, 11:09 AM   #18 (permalink)
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Thanks for answering my question.
The truck in this case is a 2013 3500HD. A mechanic in Mexico defeated enough by reprogramming the ECM and removing the DEF system that he was able to get home in MN. He had more work done on the truck and now he won't have a problem but it will never pass a smog test.
That's about all I can tell you right now.
Thanks again.
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Old 01-13-2019, 03:23 PM   #19 (permalink)
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I just installed an Edge evolution CTS 2 so now I monitor my regens. I have a few questions. My truck is my daily driver and mostly local driving. While it is not stop and go city driving it is also not highway driving at 65 -70 mph either. I have never had any DEF, DPF or emmissions codes or issues since new ( I now have 111,000 miles on it)
I'm averaging about 100 miles between regens. When the truck is in regen I notice the DPF Stat on my cts cycles on and off when I stop at lights. Is that normal?
What does the DPF Stat on/off mean? Does it mean the 9th injector is open or closed?
Today was the first day since getting the cts I was able to monitor a full regen cycle.
I was driving locally when the regen started at 41 g. First the idle kicked up from 630 to 800. It stayed like that for about 5-10 mins before the DPF Stat cycled on. It would cycle off when sitting at a stop light for a min or so then cycle back on after about a min of driving. I was able to get on the highway during regen. I was driving 70-75 mph. My soot level was decreasing at steady rate. My DPF stat would cycle off, like it was checking the soot level, then cycle back on. My soot level Dropped to zero before I got off. My soot level stayed at 0 when the regen cycle ended and didn't climb up like some have stated. My soot level was at 0 when I shut my truck off. I will see what it reads when I start it again tommorrow.
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Old 01-13-2019, 03:44 PM   #20 (permalink)
greende
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Quote:
Originally Posted by Dmax Dually View Post
I just installed an Edge evolution CTS 2 so now I monitor my regens. I have a few questions. My truck is my daily driver and mostly local driving. While it is not stop and go city driving it is also not highway driving at 65 -70 mph either. I have never had any DEF, DPF or emmissions codes or issues since new ( I now have 111,000 miles on it)
I'm averaging about 100 miles between regens. When the truck is in regen I notice the DPF Stat on my cts cycles on and off when I stop at lights. Is that normal?
What does the DPF Stat on/off mean? Does it mean the 9th injector is open or closed?
Today was the first day since getting the cts I was able to monitor a full regen cycle.
I was driving locally when the regen started at 41 g. First the idle kicked up from 630 to 800. It stayed like that for about 5-10 mins before the DPF Stat cycled on. It would cycle off when sitting at a stop light for a min or so then cycle back on after about a min of driving. I was able to get on the highway during regen. I was driving 70-75 mph. My soot level was decreasing at steady rate. My DPF stat would cycle off, like it was checking the soot level, then cycle back on. My soot level Dropped to zero before I got off. My soot level stayed at 0 when the regen cycle ended and didn't climb up like some have stated. My soot level was at 0 when I shut my truck off. I will see what it reads when I start it again tommorrow.

I have the older generation CTS. I also monito EGT#3. The Regen light does not come on until my EGT gets above 950 degrees or so. When you stop at the light, the computer keeps the idle up to (hopefully) continue regen. Most of the time the EGT cools off so the regen stops. This is what gives you the light off, light on scenario. Perfectly normal at least for my truck. I find the best and most consistent regens are with at least a little throttle as throttle position seems to give me higher EGTs.

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