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Newbie Question bout DEF

2K views 10 replies 4 participants last post by  TW720HVY 
#1 ·
I've had this truck since December. I've got about 1600 miles on it. The first 800 miles or so the exhaust cleaning info popped up 3-4 times. Since then I don't know if it has done much exhaust cleaning? Is this something to be concerned about?
 
#2 ·
Welcome to the 6.7!

I don't know if the title and question are related. Exhaust cleaning is not related to or the same as the DEF system. The DEF is injected into the exhaust and the cleaning uses something like a glow plug to ignite diesel fuel to burn off exhaust build up. The DEF is is always going and the cleaning is a cycle based on the truck's usage/buildup.

This is how I understand it, but I am sure someone will post a much more technical answer. Hope this helps and I don't think what you have posted is anything to worry about.
 
#4 ·
You're welcome.

The DEF does help with the exhaust cleaning, so you are not incorrect. It just just two different systems with two different tasks.

When the message pops up informing of the cleaning it is only there for a second or two, I kind of wish it would give an icon during the entire cycle.
 
#6 ·
After you own that truck for a while, You will start to not notice the Active Regens, Because they are just not a big deal. You don't need to do anything special, The computers just take care of the task of cleaning up. Hence Ford gives you a 2 second message that regen is starting and you forget about it. If you watch your instant fuel mileage you may notice your mileage is down a little bit until the Regen is complete. Or you can get a display that will show that a regen is in process.

The exhaust systems on our trucks has several components, There is a CAT in the system that helps raise the heat. The Diesel Particulate Filter (DPF) collects the soot and periodically preforms an active Regen where raw fuel is pumped down the exhaust system to create high heat that burns the soot into ash that blows out of the exhaust and lands on the street, as basically dust. And last their is the Selective Catalytic Reducer ( SCR) where the Diesel Exhaust Fluid (DEF) is injected. DEF reduces the amount of Nitrates that the exhaust contains. Nitrates are created during High Combustion Temps in the combustion chamber. High Combustion temps usually happen when your turbo is pushing extra air into the cylinders.

If you install a Pyro or EGT gauge, You will see that your engine idles around 300° temp. Driving 70 mph down the hiway in 6th gear at 1500 rpm equals about 475-490° Pulling a trailer up a 7% grade = 900°. Flooring it off a red light to race a ricer next you = 1000°. The DEF fluid is injected when you have those higher temps. So basically when the truck is working hard.

Our trucks can also do a Passive Regen. Meaning that the exhaust system will try to clean as much soot up as it can using waste heat from normal driving. As opposed to an Active Regen where excess fuel is pumped in. A passive regen will happen any time the exhaust temps exceed 572° and it will last for as long as the heat is present. So towing a trailer up a 7% grade at 800-900° temps, means you have a passive regen for the entire climb up the grade.

If you tow a lot, Your Active Regen cycles will spread way out, because the passive regns are doing most of the work. If you do a lot of city driving, you will see more active regens, because you just don't get and keep the heat up over 572°.
 
#7 ·
I am sure it has popped up with you missing it. Another thing to also be aware of, the process takes about 15-20 minutes for the entire cycle to complete. If the truck shuts off in the process it is no big deal and more than likely it will start over again the next time it is running. At least this is what I noticed.

Also keep this in mind, I have noticed when it is cleaning it is also using more fuel which reduces our MPG average. I have seen it drop down .5MPG.
 
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