2023 DEF concerns
Lead Driver
Joined: Nov 2005
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Comments about DPF regen cycles have zero to do with how much DEF is used, ZERO.
Two separate systems, doing two separate jobs on the truck.
Agreed to a extent. If I'm dumping DEF in before the filter, Can it not cause the DPF to fil faster? It's funny that others have commented on DPF percentage and regen. Most of my miles are empty and my truck never gets above 65% full on the exhaust filter. It does many more regens then any of my other 6.7's
Two separate systems, doing two separate jobs on the truck.
Agreed to a extent. If I'm dumping DEF in before the filter, Can it not cause the DPF to fil faster? It's funny that others have commented on DPF percentage and regen. Most of my miles are empty and my truck never gets above 65% full on the exhaust filter. It does many more regens then any of my other 6.7's
DEF turns instantly into a vapor once injected into the SCR Cat, causing a reaction that lowers NOx, nothing to do with the soot the DPF traps.
Increased DEF injection is a good thing for the engine, because it equates to needing less EGR.
As to the increased number of regen cycles, I believe they are doing that to enhance the efficiency of the filter and make the filter work better longer.
Super Moderator
Joined: Aug 2008
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From: Frederick, MD
def injection rates are dependant upon high levels of exhaust flow. the more nox that is created the more def that is injected.
obviously this is caused by heavy work that the motor sees.
i just filled up my def and it says 4K miles, that will go down drastically when I hook up.
obviously this is caused by heavy work that the motor sees.
i just filled up my def and it says 4K miles, that will go down drastically when I hook up.
Lead Driver
Joined: Nov 2005
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No, like I said, the DEF that is injected vaporizes in the hot exhaust, no crystalized DEF is in the exhaust flow, and as far as I know, is downstream from the DPF anyway.
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Mountain Pass
Joined: May 2013
Posts: 202
Likes: 76
In the new trucks it is the first thing to be injected. The fuel comes in about 2 feet downstream. If the injector is hung open and the engine at a low power level, the exhaust may not be hot enough vaporize the fluid. Is that a possibility?
Lead Driver
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Mountain Pass
Joined: May 2013
Posts: 202
Likes: 76
Having owned 4 6.7s, I could measure the exhaust temp at the exhaust manifold on 2 of them. That being said, on a cold start and extended idle the temps could be as low as 250 or lower depending on how long it idles. And that in downstream of the turbo, so the DEF injector could be 50 degrees or more cooler that at the manifold. Do you have a dosing chart based on engine load? That would be awesome info
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Mountain Pass
Joined: May 2013
Posts: 202
Likes: 76
Can anyone that just filled their DEF tank, can you please list the miles to empty and wether your loaded or unloaded. Thanks
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Mountain Pass
Joined: Jul 2023
Posts: 161
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From: So Cal...for now
I haven't filled my DEF tank up since it had 35 miles, but as my fuel mileage has increased, so has my estimated remaining DEF mileage. When I first filled it, it was 3,500 miles with an avg MPG of 9.8 per the dash. Now with 1,300 miles on the truck it says 4,500 miles remaining with an avg MPG of 16.1 per the dash.
So that tells me estimated DEF range depends on current MPG per the dash and responses will vary based on usage of the provider of the data.
So that tells me estimated DEF range depends on current MPG per the dash and responses will vary based on usage of the provider of the data.
Lead Driver
Joined: Nov 2005
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I haven't filled my DEF tank up since it had 35 miles, but as my fuel mileage has increased, so has my estimated remaining DEF mileage. When I first filled it, it was 3,500 miles with an avg MPG of 9.8 per the dash. Now with 1,300 miles on the truck it says 4,500 miles remaining with an avg MPG of 16.1 per the dash.
So that tells me estimated DEF range depends on current MPG per the dash and responses will vary based on usage of the provider of the data.
So that tells me estimated DEF range depends on current MPG per the dash and responses will vary based on usage of the provider of the data.
That is not because it depends on fuel economy, but because as engine load goes up, NOx produced goes up, causing the PCM to call for more DEF injection to control the NOx emissions.
As a rule of thumb, DEF usage is in the range of 2% to 3% of fuel used, but I think our trucks run on the high side.
And, as I have stated before, increased DEF injection is actually a good thing, because it means less EGR is being used.
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Mountain Pass
Joined: May 2013
Posts: 202
Likes: 76
2-3% is what I expected. On our trip out west this past year, I was filling my fuel tank with 33 gallons of diesel and 3.5 gallons of DEF. Another fill up on the trip was 23 gallons of diesel and 2.9 gallons DEF. To me that looks closer to 10-12%. Luckily I can look at the open roads app and it details the fill ups at the Love's truck stops. I will run this tank of DEF as low as I can, then measure how much goes in to rule out the tank gauge
