N54 with Catless DPs - Emissions Readiness and MHD

[SalMoney13]

Hi All:

After scouring the BMW-related forums, I have been unable to find definitive answers to my emissions-related questions regarding my N54 with catless downpipes. I understand that the answers to these sorts of questions can be specific to a particular vehicle's problems and modifications. However, I'm not asking for specific advice related to my car and situation. Instead, I'm hoping for some generalized information that might help others who have catless downpipes and a tune of some sort on their N54.

For context: I am new to the N54 tuning world - I just purchased an 08' 535xi that was modified by a previous owner to include a Wedge tune and the typical stage 2 components, namely catless downpipes, FMIC, intake, etc. I purchased an MHD flasher and monitor license. With my Wedge tune mapped, the Catalyst, O2, and Heated O2 monitors won't set, but I don't get any emissions-related CELs.

The questions:

• For those with a catless downpipes and a tune, what options exist for getting monitors to show as either "ready" or "not available"?
  • It seems like the "Downpipe Fix" was a popular option 5+ years ago, but that option doesn't seem popular these days for whatever reason
  • Can this be handled by tuning alone?
• What does MHD Stage 0 do for monitors? Should they all eventually show as "complete" with stage 0 mapped?
  • For someone with catted downpipes on Stage 0, what options (if any) need to be selected in MHD to avoid a catalyst-related CEL?

Any advice would be much appreciated. Happy to share more about my particular situation if it would be helpful.

 

[n54praiser]

For those with a catless downpipes and a tune, what options exist for getting monitors to show as either "ready" or "not available"?

I'm FBO on MHD Stage 2+ OTS map with DP fix (car came with one) and it passes all readiness tests, including the 2 oxygen and catalyst ones. As far as I know the only straightforward way to get all readiness tests to pass is with a DP fix.

It seems like the "Downpipe Fix" was a popular option 5+ years ago, but that option doesn't seem popular these days for whatever reason

Correct, pretty much all DP fixes from all big name companies seem to have been taken off the market. I assume this has to do with legal issues as technically a DP fix on a road car is highly illegal. There are some DIYs on how to stimulate the effect of a DP fix but I don't have experience with those.

Can this be handled by tuning alone?

I saw some people here mentioning that the tests can be forced to pass with a tune but haven't seen any concrete info on this yet. I'm trying to find a way to force them to pass too as I'm planning ahead for a ST build that ideally would have single bank fueling but this setup apparently doesn't let all the tests pass. Hopefully someone can help us all out as I know we're not the only ones having this issue.

What does MHD Stage 0 do for monitors? Should they all eventually show as "complete" with stage 0 mapped?

MHD Stage 0 or even completely removing MHD doesn't have any effect on the tests.

For someone with catted downpipes on Stage 0, what options (if any) need to be selected in MHD to avoid a catalyst-related CEL?

If cats are in regardless of stage level you'd have to select the stock/catted option in the MHD flash option to allow the readiness to set. The same has to be done when being catless with DP fix. Selecting the aftermarket/catless DP option will remove the CEL but it doesn't allow the catalyst readiness to pass. So the only way to get the readiness to pass is with the cat option set to stock/catted DP in MHD, either with cats alone or catless combined with DP fix.