How to pass emissions with catless downpipes

[2015f82m4]

Short Answer:

1) Install 'spark plug' defoulers on each downstream o2 sensor (stack 2 defoulers and then screw o2 sensor into defouler.)
2) Flash back to stock tune
3) Drive car around and complete drive cycle to get readiness monitors ready (can monitor using the vgate iar pro bluetooth 4.0 obd2 dongle and car scanner elm obd2 app using the 'emissions tests' feature'
4) Once monitors are ready and pass, go to emissions and pass
5) flash back to stage 2 and remove defoulers


Long answer:

I did a lot of research on these forums and I was unable to find any definitive answers on how to pass emissions without cats. I am running VRSF Catless Downpipes, Active Autowerke Midpipe and M Performance Exhaust. I am also tuned via BM3 Stage 2. I went through emissions very naive thinking since I didn’t have a CEL i would pass. Well I guess i just expected my readiness monitors to be set to ready since my fully built evo x with no cats, big turbo, external dump passed no issues. Turns out BM3, as most tuning software’s do, disable your oxygen sensor monitors so you don’t get a CEL. First time through I failed due to my monitors not being read (As seen in attached photos)

Methods to pass:
1) Defoulers
-- I read many good and bad things about defoulers. They seemed to work 50/50 depending on the vehicle. Pro's are they are cheap and easy to install. I did see fabspeed had these super cool 'mini cats' inside the defoulers. The only thing was they are $225 for a set

2) o2 Simulators
Area 74 makes these. Cons are they are 120 and f80/f82 has 2 downstream o2 sensors so that’s $240 for a set but it is guaranteed to work.

3) Put the stock downpipes back on
Since i paid my buddy to do it, it would've cost me 250 to take off my catless downpipes and return to stock only to take them back off and reinstall the catless downpipes after the emissions testing. Pro is it is 100% guaranteed to work. Cons is that it'll cost me not only $500, but a lot of time and headache. If you can do your downpipes yourself it would save you the money but still time consuming and a pain.

I decided to go the cheapest route and buy vibrant o2 sensor defoulers off amazon which were about $23 each so $46 for the pair. i quickly realized upon getting my m4 on the lift that the only way they were going to thread on was if i took the downpipes off because there was no room to spin them on.

So plan B...go to O'Reilly's and get their cheap spark plug defoulers. Part number 42009 https://www.oreillyauto.com/shop/b/i...5/76bbf7c4bb16
I purchased two of these (2come in 1 pack) so I had a total of 4 of these defoulers. I then removed my downstream o2 sensors and stacked two defoulers together and screwed the o2 sensor in and did the same for the other o2 sensors and then reinstalled them. The idea here was to space the o2 sensor out enough so it doesn’t get a good reading of the 'post cat' exhaust gases. I saw some people drill out the first defouler the o2 sensor goes in but I didn’t do that, I left them exactly as they came.

I then flashed BACK TO STOCK tune. I know some people didn’t need to do this, they just set their monitors to on using the configure advanced settings (gear icon top right corner) in the stage 2 map in the bm3 tuning software. in my opinion, it’s easier to just flash back to stock (no need to relock the DME, you can flash back to stock and keep the DME unlocked) and then you'll need to drive around to get your monitors ready (see below)

I then used my vgate icar pro bluetooth 4.0 obd2 adapter plugged it into my obd2 port (i already had one from coding my car with the bimmercode app). then on the app store i downloaded the car scanner elm obd2 app https://apps.apple.com/us/app/car-sc...2/id1259933623 and you can go to the 'emissions test' feature and it will tell you if your monitors are set to ready or not. You will need to drive your car to get your monitors ready (see drive cycle photo). You can keep the emissions testing function open and it will tell you if your monitors are ready or not and if they pass or fail as it updates every 30 seconds or so. After driving around, all my monitors were set to ready and pass!

You can see the photos I attached, as you can see the monitors before the defouler were set to not ready and then after the defouler and flash back to stock they were set to ready and passed. I also used the 'live data' feature and selected oxygen sensor 2 (bank 1 and 2) so i could see the upstream and downstream oxygen sensor voltage. The downstream o2 sensor was a little high at .080 V as it should be closer to 0.50 V but it was steady at idle and 'flat' and not up and down which is the graph of an oxygen sensor that is bad. If you look up the graph of oxygen sensors you will see what the upstream and downstream oxygen sensor voltage is supposed to look like and read. This is where an o2 simulator comes into play. It tricks the sensor into producing the correct voltages, but in this case the defouler worked just fine by spacing the o2 sensor away from the catless downpipe.

After all my emissions tests were set to pass and were green i went to emissions testing where I passed with no issues. The only part i had 'help' with was the 'visual inspection' although it would be pretty hard for a tech to see the primary cats in the downpipes since the undertray/splash guard covers up most of the downpipes. After doing so I re-flashed my car and I plan on removing the defoulers as it will mess with the o2 sensor values with the car running since it is a wideband sensor.

[cotmfk]

I'm sure there's something about fight club in here....

[2015f82m4]

Originally Posted by cotmfk

I'm sure there's something about fight club in here....

huh?

[dtmwerksm3]

Originally Posted by cotmfk

I'm sure there's something about fight club in here....

I see what ya did there

[SilleM3]

Wow I wish I could use this. I failed for missing secondary cats. It shows not passed

[dtmwerksm3]

I'm assuming if you're completely catless you're kinda SOL or would the i02 Simulators still get you a pass? Asking for a friend.

[2015f82m4]

Originally Posted by 18LVF80

Wow I wish I could use this. I failed for missing secondary cats. It shows not passed

You realize secondary cats wouldn’t make you fail? The o2 sensors that are read during testing are your primary cats in your downpipes. The secondary cats in the midpipe do not have oxygen sensors at all therefore no data is being read by the dme. Just wanted to clear this up... do you also have your primary’s removed aka catless downpipes?

[2015f82m4]

Originally Posted by dtmwerksm3

I'm assuming if you're completely catless you're kinda SOL or would the i02 Simulators still get you a pass? Asking for a friend.

I’m completely catless. o2 simulators would work but why even do that when you can just do the defoulers like I did? I passed with VRSF catless downpipes, AA midpipe and M performance exhaust by installing the defoulers into the downstream o2 sensors

[dtmwerksm3]

Originally Posted by 2015f82m4

I’m completely catless. o2 simulators would work but why even do that when you can just do the defoulers like I did? I passed with VRSF catless downpipes, AA midpipe and M performance exhaust by installing the defoulers into the downstream o2 sensors

Gotcha, I'd rather spend the money, know for sure it'll pass and only do it once.

[2015f82m4]

Originally Posted by dtmwerksm3

Gotcha, I'd rather spend the money, know for sure it'll pass and only do it once.

well it took me longer to drive the car around after flashing it back to stock to get my readiness monitors to be ready than to install the parts. it only took about 20 minutes to install the defoulers and it cost me about $10. so in my opinion, it is worth it to try the defoulers first before spending all that money on a simulator.

[c4ss]

Great info here. I am stage 2 bootmod3 catless as well and I'm going to give this a try. I'm due for emissions and would love to have a method that doesn't involve uninstalling and re-installing my VRSF downpipes.

[blockdoc]

Originally Posted by c4ss

Great info here. I am stage 2 bootmod3 catless as well and I'm going to give this a try. I'm due for emissions and would love to have a method that doesn't involve uninstalling and re-installing my VRSF downpipes.

Would you update here? Curious to see what happens

[ronin_pdx]

You can pass emissions with secondary cats. My state doesn't do visual just emissions. sweet

[HyeM3]

Interesting, I'm curious to know how reliable this method is. I know people have success using the "mini cat" from bigdaddiesgarage which is $50 a piece so not that bad. Is there any reason to need to remove the defoulers afterwords? Why not just leave them on for those that want to do it once and be done with it?

[CachacoF80]

Kudos for your research, creativity and write up.

But I could never go through so much trouble and time invested for an emissions test...stock for me.

[Iceman1183]

Intriguing.

[c4ss]

VRSF downpipes have 3 bungs total. The longer run dp has 1 bung and the shorter one has 2 bungs. Which bung did you put the fouler into on the short downpipe? More upstream or more downstream?

I'm assuming it would be the more downstream O2 bung, as that's where it's going to be taking a reading, correct?

[2015f82m4]

Originally Posted by c4ss

VRSF downpipes have 3 bungs total. The longer run dp has 1 bung and the shorter one has 2 bungs. Which bung did you put the fouler into on the short downpipe? More upstream or more downstream?

I'm assuming it would be the more downstream O2 bung, as that's where it's going to be taking a reading, correct?

I’m pretty sure they have 4 o2 sensors. Each downpipe has an upstream and downstream o2 sensor. The only thing they test for is the downstream since they are POST CAT. Upstream o2 sensors are PRE CAT, therefore they will read the same thing if you have stock downpipes or catless, however, downstream o2 read PIST CAT, So if you have catless downpipes they are going to know you don’t have cats. The voltage reading from the upstream and downstream are going to look the same, since the air has never passed through a cat.

So to answer your question, the defoulers only are used in downstream o2 sensors since those voltage readings are what emissions are concerned with.

[2015f82m4]

Originally Posted by CachacoF80

Kudos for your research, creativity and write up.

But I could never go through so much trouble and time invested for an emissions test...stock for me.

Thanks man! I hear ya, it’s once once every two years, and the satisfaction of catless downpipes and stage 2 is worth the hassle of the bs that comes along with having catless downpipes and having to go through emissions testing

[2015f82m4]

Originally Posted by HyeM3

Interesting, I'm curious to know how reliable this method is. I know people have success using the "mini cat" from bigdaddiesgarage which is $50 a piece so not that bad. Is there any reason to need to remove the defoulers afterwords? Why not just leave them on for those that want to do it once and be done with it?

They should be removed because that is your wide band o2 sensor reading. If you get your car tuned they need to know your afr’s for tuning. I was told to remove them after so just passing on that information to everyone!

[ment4t]

Just wanted to throw in a confirmation that I passed inspection with catless Akrapovic downpipes.

My mechanic used bigdaddiesgarage.com mini-cats between the O2 sensor and the bungs on the downpipe.

I reflashed the car to OEM settings for the O2 sensors, since they were previously bypassed.

[elinstylez]

Thanks for doing the research and sharing. I'll have to try this when I have to smog my car.