2009 DPF Regeneration

[mwool]

I have a GMC 09’ 3500 HD w/@7000 miles. Is there any way to tell how often the DPF regeneration should run. Mine is kicking on 2-3 time within ¾ tank of fuel. I use a high quality fuel additive every fuel up. The last two times was about ½ tank apart and I let both run completion. What should be typical cycle times???
My driving is about ½ city and highway.
Also is the DPF regeneration a simple decision from two sensors of pressure in/out?

[More Power]

DPF regeneration is initiated based on one of the following four criteria.

Miles driven since last regeneration.
Fuel used since last regeneration.
Engine run time since last regeneration.
Pressure differential across DPF. A lower pressure differential is better. A high pressure differential could indicate a soot buildup in the DPF.Jim

[mwool]

1. Does stopping at a stop sign stop the DPF regeneration if in progress?
2. Does the DPF regeneration also eliminate any soot build up?

[More Power]

1. Does stopping at a stop sign stop the DPF regeneration if in progress?
2. Does the DPF regeneration also eliminate any soot build up?

1- Yes, stopping the vehicle will interrupt a regen. Vehicle speed must be 30-mph or greater, but the regen process will take up where it left off once DPF regen conditions are met.

2- Yes, DPF regeneration is supposed to eliminate a soot buildup within the DPF itself.

I recommend people include at least a couple of monthly runs at sustained freeway speeds of 20-30 minutes in duration, which will reduce the number of active regenerations required to maintain the DPF. Running at freeway speeds (or while towing) will produce a high enough exhaust temperature to allow burning the soot all on its own. An "active" regeneration is where raw fuel is injected into each cylinder during the exhaust stroke. This puts raw fuel into the exhaust system, where it burns and artificially raises exhaust temperature to DPF regen levels. This is one reason why the LMM produces, on average, a couple mpg lower fuel economy than earlier non-DPF equipped Duramax powered trucks.

The newest 2011 LML Duramax injects diesel fuel, through a single injector, directly into the exhaust system ahead of the DOC (Diesel Oxidation Converter), which ignites and burns hot enough to initiate a DPF regen cycle. The 2011 LML also incorporates a new technology DOC and DPF, which requires fewer regen cycles than the earlier systems - theoretically increasing fuel economy by an advertised 11% over the previous model year trucks.

By the way, the new single injector, which injects diesel directly into the exhaust system is why the LML is approved for up to B20 (20% bio-diesel). GM says the prior regen method of injecting raw fuel during the exhaust stroke presented the potential to wash the cylinder walls, and bio is reported to be more prone to this than petroleum diesel fuel.

You can read more about the LML and the new emissions system here: http://www.thedieselpage.com/duramax/LMLDuramaxc.htm

Jim

[ScottB]

Jim, If you had a choice, which engine would you prefer to own, a LMM or a LML. I currently have a LB7, 01 with 240,000 miles with no problems, except rust on the rear of the cab behind the door. Looking at a 2009 and trying to decide if I'm making the right decision. These new engines seem to be getting complicated. Thanks. Scott