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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N47 and N57 Turbodiesel Engine / Drivetrain / Exhaust Modifications > High DEF Fluid Use with Kerma
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      07-16-2020, 10:38 AM   #1
n00bkiller944
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High DEF Fluid Use with Kerma

Got the notification for low DEF fluid after about 3,500 miles with the Kerma tune. Was hitting close to 8-10k prior. Anyone else seen this? Is this a cause for concern.

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      07-16-2020, 11:04 AM   #2
FaRKle!
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Originally Posted by n00bkiller944 View Post
Got the notification for low DEF fluid after about 3,500 miles with the Kerma tune. Was hitting close to 8-10k prior. Anyone else seen this? Is this a cause for concern.

Thanks!
I suspect your DEF tank wasn't totally full when you first got the tune. That's probably why this refill was pretty quick.

That said, the Kerma tune does shift more emissions management onto the SCR system in order to increase power and fuel economy while maintaining emissions compliance. I also see increased DEF usage from stock/other tunes, and my data as of last Oct is below:
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Originally Posted by FaRKle! View Post
I've been Kerma-tuned for 6,660mi now and haven't observed a DEF usage nearly as high as yours.

The DEF system (passive plus active tanks) has a capacity of 18.1L. My DEF/1000mi light comes on when I'm at 3L remaining. When the first light came on after the Kerma tune I put in 12L (VW 10L jug + VW 2L bottle). My light came on again after about 5000mi. The next time I decided to completely top off the system to see how much it would take, and got 15L in there before things started spilling out. Thus my DEF consumption rate is ~400mi/L, or 6000mi before the DEF light comes on again.

How much DEF are you putting in when you fill it? BTW my driving during this period also included track time.
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      07-17-2020, 04:16 PM   #3
n00bkiller944
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Thanks Farkle. I thought I filled it fully when I tuned it, but possibly not. I will refill completely and make a note of mileage and see where I get on the next tank!
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      10-29-2020, 09:06 AM   #4
n00bkiller944
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Full fill to light on was 4,126 miles. How much is supposed to go back into the tank once the light comes on?
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      10-29-2020, 09:08 AM   #5
n00bkiller944
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Edit: Reading is hard.

"The DEF system (passive plus active tanks) has a capacity of 18.1L. My DEF/1000mi light comes on when I'm at 3L remaining. When the first light came on after the Kerma tune I put in 12L (VW 10L jug + VW 2L bottle). My light came on again after about 5000mi. The next time I decided to completely top off the system to see how much it would take, and got 15L in there before things started spilling out. Thus my DEF consumption rate is ~400mi/L, or 6000mi before the DEF light comes on again."

I put almost one whole large VW jug in there, so I believe only 8 or 9 Liters. Maybe my tanks aren't filling fully?
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      10-29-2020, 10:58 AM   #6
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You are most likely are not filling all the way. When my light came on with a countdown, I was able to fit the entire 10L VW AdBlue jug and just over a half of the other. A few times, I think the rate of pour exceeded venting capacity and fluid spewed out - making me think it is full. But letting it settle, then resuming the pour much more slowly, I was able to fit more fluid. You're full when you can see the AdBlue liquid inside the opening and it does not go down. I am sure next drive your pump will transfer some to active tank, making it less than 100%, but you will be close. So close to 15L is about right. You should be able to go roughly 6000 to 7000 miles between refills on your current tune.
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