[Nyc Dito]

So while I had my NOx sensors replaced two/three weeks ago under BMW's warranty, the technician told me I most likely needed and SCR (not under warranty). He told me take the car, drive and see if the CEL comes back and it did several days later. I cleared the code and forced a regen on the highway since soot level (according to BTool) was around 48% and soot mass was i think like 44g's. I did NOT check these levels after i received the car back from the delaership (i know). Either way soot level went down to 1% and Soot mass 0.9g.

Last night, roughly a week and half later, my light came back on with the SCR fault code again (42FC). I Checked and Soot level was 58% and soot mass was about 49g. Ash mass from the previous check went up from 48.2 to 49.4. So I forced a regen and soot level and soot mass went back down again to 1% and 0.8g.

I drive locally about 80-85% and do at least 100 miles on the highways over every weekend. Locally Im only doing roughly 12-15 miles a day, round trip. My Tstat is perfect and car drives fine.

My inquiry is as follows;

When one does a delete, wouldn't the engine continue to produce soot/ash at these levels anyway? or are these numbers exclusive to actually having the complete emission system in place?

I'm debating actually doing the deletes but wanted to know if these levels indicate an underlying issue. I understand the reason we have an emission system in the first place, and also understand many people do the deletes to get rid of such issues im facing. My Indy said we can drop the DPF to clean it or do the cleaning the BMW way (their procedure). But that wouldn't affect the SCR failing I would think.

So i'm looking at my options going forward but I really wanted to understand a bit more about this system and the ash and soot . Delete and tune which might be the consensus. SCR delete and tune? or SCR replacement and hopefully it'll last another 111k.

Any info/insight would be appreciated and thank you.

 

[Doug Huffman]

... My inquiry is as follows;

When one does a delete, wouldn't the engine continue to produce soot/ash at these levels anyway? or are these numbers exclusive to actually having the complete emission system in place?

The mass numbers are calculated from a model that assumes particular conditions. Change the systems and invalidate the initial assumptions.

 

[ChrisM011]

Without delving into specifics on diesel engine combustion byproducts, I think your initial assertion is correct: by performing any emissions system delete your are not altering the creation of particulate matter or oxides of nitrogen in the combustion chambers.


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[Doug Huffman]

Without delving into specifics on diesel engine combustion byproducts, I think your initial assertion is correct: by performing any emissions system delete your are not altering the creation of particulate matter or oxides of nitrogen in the combustion chambers.

The purpose function of emission EGR system is to minimize the production of nitrogen oxides. Delete EGR and increase NOx

 

[ChrisM011]

Thank you for clarifying, Doug. I was incorrectly assuming the delete was for DPF and SCR aftertreatment systems only. By removing EGR you do increase NOx, but decrease PM emissions.


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[Nyc Dito]

Thank you both for your replies.