[winther1]

Recently the CEL light came on and bmw told me it relates to emissions.
Took my car to the garage which installed my 200-cell Wagner downpipe and they say there is nothing wrong with it mechanically.
A guy from the company where I bought it told me that the issue is due to not running a stage 2 engine map. He argues that a high flow downpipe requires an engine map like BM2 stage 2 in order to avoid damage caused by backpressure.
I never heard of this, as I though a less restrictive cat was an advantage regardless what engine map you are on. Decat is another story.
What do you think?

EDIT: oops, this should have been in the B58 section - any idea how to move?

[harkes]

I'd say no, but it is correct that the turbo (in theory) will overboost with reduced back pressure. However, I think the DME is smart enough to adjust for this on our cars.

Cool if you could share a log with OEM and Wagner DP

[thejeremyman9]

Originally Posted by winther1

Recently the CEL light came on and bmw told me it relates to emissions.
Took my car to the garage which installed my 300-cell Wagner downpipe and they say there is nothing wrong with it mechanically.
A guy from the company where I bought it told me that the issue is due to not running a stage 2 engine map. He argues that a high flow downpipe requires an engine map like BM2 stage 2 in order to avoid damage caused by backpressure.
I never heard of this, as I though a less restrictive cat was an advantage regardless what engine map you are on. Decat is another story.
What do you think?

EDIT: oops, this should have been in the B58 section - any idea how to move?

Unfortunately, wagner is not one of the DPs that guarantees no CEL. This also means that you car will not pass emissions - i.e., the catalyst monitor will not go into READY/PASS state. So no, there is nothing wrong with it mechanically, the cat in the DP just is not "good enough", so the DME detects that cat efficiency is outside OEM spec, hence the CEL and emission failure.

The guy from wagner fed you some BS. The tune is only going to make the CEL appear sooner (unless you turn it off - the CEL is usually triggered sooner the harder the car is ran) and it is in no way going to affect the emissions compliance. The whole backpressure comment doesnt hold up, either. The only thing a tune can do is prevent the CEL from appearing but it will not affect emissions compliance.

The stock tune is a load-based tune so the car will not overboost due to a DP install. Although its fairly uncommon, some people do run DPs (catted or catless) without a tune. Also, these cars run closed loop fueling, so any small change in airflow due to the DP will be handled by the DME.

Bottom line - nothing is wrong with the DP, it just throws a CEL and wont pass emissions.

[winther1]

Damn, this is bad news... Might as well have spent a fraction of the price on a decat then.
So to pass emissions I guess I have to spend a fortune on a full cat on top of this £750 Wagner pipe.

[thejeremyman9]

Originally Posted by winther1

Damn, this is bad news... Might as well have spent a fraction of the price on a decat then.
So to pass emissions I guess I have to spend a fortune on a full cat on top of this £750 Wagner pipe.

Confirm on the wagner website for B58 that their DP does not guarantee no CEL (it does not for N55 and among the fitment issues there are user-reported CELs and therefore no emissions compliance). If the website guarantees no CEL and/or emissions compliance, you can go back to wagner. If it doesn't, or it says off road use only or similar, you are out of luck.

Check your local emissions requirements. If you are allowed to have one monitor not ready for example, you may still be able to pass overall, even if the catalyst monitor fails. You can also scan for yourself and confirm it is not ready, but if you have a CEL for cat efficiency, it definitely is not. It can be not ready even if you DONT get a CEL.

[n55david]

complete bs about back pressure fyi.. any shop or mechanic that tells you that shouldn't get your business

[winther1]

Originally Posted by thejeremyman9

Confirm on the wagner website for B58 that their DP does not guarantee no CEL (it does not for N55 and among the fitment issues there are user-reported CELs and therefore no emissions compliance). If the website guarantees no CEL and/or emissions compliance, you can go back to wagner. If it doesn't, or it says off road use only or similar, you are out of luck.

Check your local emissions requirements. If you are allowed to have one monitor not ready for example, you may still be able to pass overall, even if the catalyst monitor fails. You can also scan for yourself and confirm it is not ready, but if you have a CEL for cat efficiency, it definitely is not. It can be not ready even if you DONT get a CEL.

Guess I will have to buy back the £1k bmw cat. The joys of mods

[Polo08816]

Originally Posted by thejeremyman9

Unfortunately, wagner is not one of the DPs that guarantees no CEL. This also means that you car will not pass emissions - i.e., the catalyst monitor will not go into READY/PASS state. So no, there is nothing wrong with it mechanically, the cat in the DP just is not "good enough", so the DME detects that cat efficiency is outside OEM spec, hence the CEL and emission failure.

The guy from wagner fed you some BS. The tune is only going to make the CEL appear sooner (unless you turn it off - the CEL is usually triggered sooner the harder the car is ran) and it is in no way going to affect the emissions compliance. The whole backpressure comment doesnt hold up, either. The only thing a tune can do is prevent the CEL from appearing but it will not affect emissions compliance.

The stock tune is a load-based tune so the car will not overboost due to a DP install. Although its fairly uncommon, some people do run DPs (catted or catless) without a tune. Also, these cars run closed loop fueling, so any small change in airflow due to the DP will be handled by the DME.

Bottom line - nothing is wrong with the DP, it just throws a CEL and wont pass emissions.

I'm one of those right now. Catless DP but I use BM3 to turn off the CEL. An aftermarket tune may reduce reliability at the track. I may consider running the M2 N55 tune in the future but that will be it.

[thejeremyman9]

Originally Posted by winther1

Guess I will have to buy back the £1k bmw cat. The joys of mods

Gotta read the fine print!

But as i said, check your local requirements regarding emissions monitors. If one can be not ready, you may still be able to pass. You may also be able to pass a sniffer test with the catted DP even if the car throws a CEL.

[winther1]

Got another lengthy response arguing why I am at fault for putting on the downpipe without a tune:

You've bought and fitted a Racing catalyst with a much lower CPSi than the OEM catalyst. I understand the appeal as it is so much cheaper than OEM and you can gain power at the same time, but your stock car is still running a closed-loop management system with stock software. Therefore your ECU will be expecting to see the stock readings before and after the catalyst, from a catalyst with more flow and fewer cells inside, unless you alter the other parts of the car such as software to suit, you will always run the risk of the car's sensors reading higher/lower and the Engine management system being pushed past the threshold it is happy with and illuminating an error light. It is also important to remember that as said before there are numerous other factors on the engine that can account for it not running right and that light being illuminated. That is even more likely since you have already said the stock cat was damaged.... what caused the damage to the original catalyst on such a new car? Clearly something was not happy beforehand, so has that fault been found and rectified?

This is the same on pretty much any vehicle platform in the world, not something specific to your make model, if you uprate a downpipe for a higher flowing lower cell racing downpipe setup then you should update the software to suit.
I suspect when you alter the software this will resolve your issue as long as you don't have a pre-existing problem still in existence.

[n55david]

Originally Posted by winther1

Got another lengthy response arguing why I am at fault for putting on the downpipe without a tune:

You've bought and fitted a Racing catalyst with a much lower CPSi than the OEM catalyst. I understand the appeal as it is so much cheaper than OEM and you can gain power at the same time, but your stock car is still running a closed-loop management system with stock software. Therefore your ECU will be expecting to see the stock readings before and after the catalyst, from a catalyst with more flow and fewer cells inside, unless you alter the other parts of the car such as software to suit, you will always run the risk of the car's sensors reading higher/lower and the Engine management system being pushed past the threshold it is happy with and illuminating an error light. It is also important to remember that as said before there are numerous other factors on the engine that can account for it not running right and that light being illuminated. That is even more likely since you have already said the stock cat was damaged.... what caused the damage to the original catalyst on such a new car? Clearly something was not happy beforehand, so has that fault been found and rectified?

This is the same on pretty much any vehicle platform in the world, not something specific to your make model, if you uprate a downpipe for a higher flowing lower cell racing downpipe setup then you should update the software to suit.
I suspect when you alter the software this will resolve your issue as long as you don't have a pre-existing problem still in existence.

the wide band 02 sensor sees the airfuel and the dme is capable of adjusting without any special tuning. that's the awesome plus side of having a wide band 02.

those people are just stupid.

setting a check engine light because of catalytic efficiency is completely different and doesn't change how the car runs

[SuperLomi]

Originally Posted by winther1

Got another lengthy response arguing why I am at fault for putting on the downpipe without a tune:

I'm confused. Is there another problem besides the CEL being on?

The CEL is a known side effect of running an aftermarket CAT (outside a few which are designed to make the car happy - and cost much more). Like other's have said, it shouldn't cause any problem with operation - so if you are having a problem besides just the CEL, it's likely not related to the CAT.

My understanding is all the tunes do is force cancel the CEL, they don't actually fix the reading being outside the range the car is looking for to not trigger one.

[mike@x-ph.com]

I feel things got a little mixed up with this thread.

From OP's original post, he is asking if there is any harm to running a downpipe on a stock map, as that's what he's been told.

The answer is no; there is no harm to running the catted downpipe; the person that told you so, unfortunately, does not know what they are talking about.

On stage 2, you do not get a CEL because the tune is hiding it. It's got nothing to do with the ECU or the car running better.

If you want a downpipe that guarantees no CEL without any tune, get the Active Autowerke.

[thejeremyman9]

Originally Posted by mike@x-ph.com

I feel things got a little mixed up with this thread.

From OP's original post, he is asking if there is any harm to running a downpipe on a stock map, as that's what he's been told.

The answer is no; there is no harm to running the catted downpipe; the person that told you so, unfortunately, does not know what they are talking about.

On stage 2, you do not get a CEL because the tune is hiding it. It's got nothing to do with the ECU or the car running better.

If you want a downpipe that guarantees no CEL without any tune, get the Active Autowerke.

Yeah unfortunately there is a lot of misinformation here, and the worst part is that wagner is feeding it to OP. You can see from the nonsense they are saying that they are doing everything they can to shift the "blame" to OP by make it sound like something is wrong with OPs car / OP made a mistake / etc.

The bottom line is that wagner DP is not good enough to prevent a CEL, and for some reason wagner won't simply say that. The disclaimer is on their website so i am not sure why they are skirting around the issue. It's not the first time wagner has responded poorly, as several people had fitment issues with N55 DPs due to O2 bung placement and they said things like "stretch the wire" or extend the harness to make it fit....

Having a CEL for catalyst efficiency isnt going to have any negative effect on performance, but OP should confirm that is the only code and that the emission monitor is not ready.

[BMWILUVU]

I would be very surprised if a 200 cell DP could avoid a CEL without spacers so getting a CEL witht he Wagner 200 is normal. I would not say there is no danger in running catless on BM3 even on stage 2 since it is boost based. If you are worried, I suggest having an experienced custom tuner adjust your tune. I would feel better running catless on stock than on BM3 but I wouldn't say there is no danger there either.

[winther1]

Thanks a lot for all the answers - this gives me peace of mind!
I think I will try the spacer option but also finally get BM3 stage 2.
Just have to point out that all this misinformation comes from the seller of the Wagner downpipe, not from Wagner directly.

[thejeremyman9]

Originally Posted by BMWILUVU

I would be very surprised if a 200 cell DP could avoid a CEL without spacers so getting a CEL witht he Wagner 200 is normal. I would not say there is no danger in running catless on BM3 even on stage 2 since it is boost based. If you are worried, I suggest having an experienced custom tuner adjust your tune. I would feel better running catless on stock than on BM3 but I wouldn't say there is no danger there either.

I am confused, when is there ever a danger in running catless and why would there be no danger "on BM3 even on stage 2"? BM3 stage 2 specifically calls for a high-flow (catted or catless DP), so yeah, that is the map that is actually designed to be ran with a non-OEM DP.... Also, it has absolutely nothing to do with being boost-based or load-based. All MHD maps are load based and 2/2+ are designed to be ran with upgraded DP. Your final sentence makes absolutely no sense - the BM3 stage 2 map is specifically designed to be ran with a DP, so it is even more "tuned" for the DP than the stock tune, which will rely on closed loop fueling (and other adaptations) to account for the DP. Not trying to be mean, but lets not spread misinformation.

Originally Posted by winther1

Thanks a lot for all the answers - this gives me peace of mind!
I think I will try the spacer option but also finally get BM3 stage 2.
Just have to point out that all this misinformation comes from the seller of the Wagner downpipe, not from Wagner directly.

Do not run an O2 spacer. They are not made to be ran long term and all the information indicates the secondary O2 is used for fuel trim control / primary O2 drift in addition to monitoring cat efficiency. Just tune out the CEL if you dont want it to show up.

Who sold you the wagner?

[Polo08816]

Originally Posted by thejeremyman9

I am confused, when is there ever a danger in running catless and why would there be no danger "on BM3 even on stage 2"? BM3 stage 2 specifically calls for a high-flow (catted or catless DP), so yeah, that is the map that is actually designed to be ran with a non-OEM DP.... Also, it has absolutely nothing to do with being boost-based or load-based. All MHD maps are load based and 2/2+ are designed to be ran with upgraded DP. Your final sentence makes absolutely no sense - the BM3 stage 2 map is specifically designed to be ran with a DP, so it is even more "tuned" for the DP than the stock tune, which will rely on closed loop fueling (and other adaptations) to account for the DP. Not trying to be mean, but lets not spread misinformation.



Do not run an O2 spacer. They are not made to be ran long term and all the information indicates the secondary O2 is used for fuel trim control / primary O2 drift in addition to monitoring cat efficiency. Just tune out the CEL if you dont want it to show up.

Who sold you the wagner?

I agree.

I ran an O2 spacer on my factory cat just to pass inspection. The factory cat has some issues already but a spacer was able to get it over the hump. After inspection, I swapped back to my catless downpipe.

I noticed that the O2 spacer causes the idle to sometimes get a bit wonky on start up.

[BMWILUVU]

Hey man, a post like this makes me not want to explain. Also, there is no definitive information from BMW that the secondary O2 is used in fuel trim control.

[thejeremyman9]

Originally Posted by BMWILUVU

Hey man, a post like this makes me not want to explain. Also, there is no definitive information from BMW that the secondary O2 is used in fuel trim control.

You don't need to explain anything really. Frankly most of your post made no sense at all.

I know you keep arguing in other threads as well that the secondary O2 isnt used for fuel trim control, despite the fact that MHD specifically said so (for our platform/engine) in response to a an email question about using a spacer on the secondary O2 (its buried in the MHD thread), and that it is well documented for the N54 and numerous other car platforms. I never said i am 100% sure based on XYZ from BMW for the F3x N55 that the secondary O2 is used for fuel trims (see my post - "all the information indicates"). I was very careful with my word choice so as to not imply a level of certainty above what i have. Nonetheless, it makes no sense at all to run one long term and take an unnecessary risk based on all the information we have when you can just code out the CEL. I am providing OP with information and he can make his own decision.

[n55david]

Originally Posted by BMWILUVU

Hey man, a post like this makes me not want to explain. Also, there is no definitive information from BMW that the secondary O2 is used in fuel trim control.

it's not. it would be impossible. plus lol, changing the dp in anyway would change fuel trims which we know doesn't happen.

[thejeremyman9]

Originally Posted by Phantom10R

it's not. it would be impossible. plus lol, changing the dp in anyway would change fuel trims which we know doesn't happen.

Impossible for the secondary O2? It doesn't directly control fuel trims (that's the job of the wideband, primary O2), but it supposedly is used to prevent drift of primary O2 since secondary O2 is a narrowband and is much more accurate within that small AFR window.