DEF and Regen Discussion

[jam20ster]

As I get closer to 11, though, the truck starts doing active regens which negates any further mileage gains.

This is a great point. During my last trip home (4 hour drive) while towing 18K my truck went into regen (3-5 Min). I was very suprised at this thinking my truck was acutally working to pull the RV. Goes to show you how strong these new trucks are and that they are intended to be worked.

 

[avvidclif]

Re: maximum speed towing a 3260 fifth wheel

I thought the DEF took care of the DPF filter and the regens???? When my 09 goes into regen the MPG heads for the bottom.

 

[jam20ster]

Re: maximum speed towing a 3260 fifth wheel

DEF is urea or ammonia essentially. It is used to clean the exhaust(lower emissions). Supposed to be cleanier than gas engines when it comes out of tailpipe.

The regen takes place when the DPF filter becomes too clogged or the differential pressure between inlet and outlet of filter meets set number by Manufacturer. When your engine is under load or works the exhaust temps are high enough to naturally burn the soot biproduct of the burnt fuel(exhaust). When your exhaust temps are not hot enough (driving around city/highway without load or engine temps low) then the DPF filter collects the soot. Then upon high diff pressure it actually dumps diesel fuel to the dpf filter and ignites it which in turn cleans/burns out the soot.

So you have passive regen which is the exhaust temp burns soot while hot/under load and you have active regen which is when the filter is full and uses fuel to burn the soot out (cleaning filter).
The later is when you notice your fuel mileage go down drastically.

This is it in a nutshell hope this helps.

 

[Bob&Patty]

Re: maximum speed towing a 3260 fifth wheel

I have never had, or did not notice it, my Duramax go into regen at highway speeds pulling. A round town and no trailer....yes.

 

[alwayslooking]

Re: maximum speed towing a 3260 fifth wheel

jam20ster had some good comments on the difference between DIF and DPF. Ford actually dumps fuel into one bank of cylinders (4) on the exhaust stroke to raise the temperature to regen the DPF. I believe Dodge uses the same technique. Chevys ejects fuel in the tail pipe before the DPF, probably a better way to accomplish the objective. In any event, all three approaches use lots of fuel to remove small amounts of soot.

The biggest obstacle in achieving good millage is drag, which increases exponentially with speed. Weight is also a factor particularly if you are going up and down hills. Others have correctly pointed out that speed increases tire temperature and can lead to tire failure. If you don't have to go fast, slow down a bit. You'll see more, save fuel and keep yourself and others safer.

 

[avvidclif]

Re: maximum speed towing a 3260 fifth wheel

jam20ster had some good comments on the difference between DIF and DPF. Ford actually dumps fuel into one bank of cylinders (4) on the exhaust stroke to raise the temperature to regen the DPF. I believe Dodge uses the same technique. Chevys ejects fuel in the tail pipe before the DPF, probably a better way to accomplish the objective. In any event, all three approaches use lots of fuel to remove small amounts of soot.

The biggest obstacle in achieving good millage is drag, which increases exponentially with speed. Weight is also a factor particularly if you are going up and down hills. Others have correctly pointed out that speed increases tire temperature and can lead to tire failure. If you don't have to go fast, slow down a bit. You'll see more, save fuel and keep yourself and others safer.

I have a 2009 which has the DPF and does a regen every so often, dumps diesel in the exhaust. It was my understanding that after 2010 Ford went to the DEF fluid which eliminated the DPF and helped increase the fuel mileage due to less restriction. So how does the DEF work?


?????

 

[MikeR]

Re: maximum speed towing a 3260 fifth wheel

The 2010 and newer diesels have a catalytic converter (SCR) behind the DPF. The DPF collects particles. The SCR is for removing nitrous oxibes (NOx). The DEF is injected into the SCR vaporized and converted to ammonia, which converts the NOx to nitrogen and water. Which makes a clean diesel exhaust.

 

[danemayer]

Moved these posts from the thread on towing speed.

 

[avvidclif]

Re: maximum speed towing a 3260 fifth wheel

The 2010 and newer diesels have a catalytic converter (SCR) behind the DPF. The DPF collects particles. The SCR is for removing nitrous oxibes (NOx). The DEF is injected into the SCR vaporized and converted to ammonia, which converts the NOx to nitrogen and water. Which makes a clean diesel exhaust.

The lineup on mine is DPF, Catalytic converter, and muffler.

 

[MikeR]

Re: maximum speed towing a 3260 fifth wheel

The lineup on mine is DPF, Catalytic converter, and muffler.

The lineup in the 6.7 is DOC (diesel oxidation catalyst), DPF (diesel particulate filter), SCR (selective catalyst reduction). I would hate to have to do a complete exhaust system replacement. The costs would be multiple thosands of dollars. The above description is extremely simplified, the exhaust is a complicated assembly of hardware, sensors, electronics.

 

[porthole]

Re: maximum speed towing a 3260 fifth wheel

Some Ford specific, some common points.

Urea is not ammonia (nor urine) 32% urea - deionized water

Cab & chassis ---> DOC ---> DPF ---> SCR
Pickup -------------> DOC ---> SCR ---> DPF

The DOC oxidizes hydrocarbons and builds heat for the SCR & DPF
The DPF collects soot and other exhaust byproducts. Soot is burned off in one of 3 modes.
Any particulate left is considered non-burnable ash, which collects in the DPF, eventually needing the DPF to be cleaned (approximately 125,000 miles) or replaced (200,000+ miles)
DPF, 3 modes, passive (during normal driving), active (when you see it pop up on the dash) and manual (cab & chassis only)
DPF pressure reading is a "differential" - difference between the DPF inlet pressure and atmospheric
When active regen is initiated, the left bank of injectors are activated on the exhaust stroke to raise the exhaust temp.

SCR reduces NOx, requiring less EGR to accomplish the same
SCR , through DEF injection, atomizing, mixing, and heat cause the DEF to split into CO2 and ammonia
NOx mixed with the ammonia passing through the catalyst, cause a reaction which converts those chemicals into N2 and H2O
SCR in of itself does not increase or decrease fuel mileage. But, because SCR reduces NOx, the fuel system can be run leaner (the leaner the mixture the higher the NOx output)


Oil, quality and type plays a much bigger role then you would think with modern emissions systems. Best to use the oil recommended in the owners manual.

The system is complicated, the parts are expensive and diesels have never run so clean.