Quick 02 spacer question

[Tjtubbs]

Just wondering im going to try to gut my cats soon on a 2011, do i need 2 vibrant straight spacers or just 1, or one j spacer and 1 straight? And i know it doesnt sound like its ever a gaurauntee itll work but just to give it best shot first, thanks

[dubgli]

I have an sq5 with the same motor. I've been knee deep in the spacers.

My setup is different as I moved the cats from the headers further downstream.

Many have said the vibrant J-spacers work well.

I went through three different spacers and still trying to find the right combo.

All the spacers I used will most likely get rid of the p0420- cat below threshold.

The flipside is that the spacers can be too good as in they're spacing your o2 sensor too far away from the exhaust flow. This will throw an error p013f - slow response lean to rich. (Or variants of this code)



- dubgli

[jerseyboosted91]

Literally in the same boat lol

Just gutted my cats on my 13 S4 and need to get these spacers done since my inspection sticker is up this month for NJ


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[JACKAL]

All I can say is good luck. I tried 6 different combinations of spacers including straight with various inserts and various elbows. Never got anything to work so I switched to the 034 test pipe tune to shut off the CEL and called it a day.

[dubgli]

All I can say is good luck. I tried 6 different combinations of spacers including straight with various inserts and various elbows. Never got anything to work so I switched to the 034 test pipe tune to shut off the CEL and called it a day.

Were you getting the p0420 cel or p013f cel?

Those two bound the issue, it's too exposed or too far away.

- dubgli

[jerseyboosted91]

All I can say is good luck. I tried 6 different combinations of spacers including straight with various inserts and various elbows. Never got anything to work so I switched to the 034 test pipe tune to shut off the CEL and called it a day.

Oh boy... doesn’t sound too promising for me to pass inspection haha


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[dubgli]

Oh boy... doesn’t sound too promising for me to pass inspection haha


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Just to point out, getting a tune to shut the cel off still will not pass emissions.

- dubgli

[JACKAL]

Were you getting the p0420 cel or p013f cel?

Those two bound the issue, it's too exposed or too far away.

- dubgli

Both lol. I couldn't find a happy medium no matter what I tried. I also intermittently experienced heater circuit codes. And my LTFTs were waaaay out of whack. Car typically ran rich and my fuel economy was noticeably impacted.

Oh boy... doesn’t sound too promising for me to pass inspection haha


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I don't mean to throw water on your fire and I know there are members here who have had success with spacers. I just wasn't one of them and it was extremely frustrating for me. I really do hope you have more success.

Just to point out, getting a tune to shut the cel off still will not pass emissions.

- dubgli

Correct. I took care of that part on my own, but once the downstream O2 sensors were out of the equation, my fuel trims stabilized and my fuel economy sprang back to normal. Those factors, in addition to my OCD being placated by not seeing the CEL were well worth the cost of the tune for me.

[dubgli]

Correct. I took care of that part on my own, but once the downstream O2 sensors were out of the equation, my fuel trims stabilized and my fuel economy sprang back to normal. Those factors, in addition to my OCD being placated by not seeing the CEL were well worth the cost of the tune for me.

Lol, I know the feeling. Just get the damn CEL out of my face!

However. I also know the feeling of emissions being due and my shit wont pass!! Haha. I have a year before emissions, but I'm trying to figure it out now while I got time so that I'm not throwing money at this last minute buying new oem cats and paying a shop to install everything. Then have to reinstall the upgrades.

Been there and it sucks.

- dubgli

[Tjtubbs]

Appreciate the input, but does each cat have a sensor?

[JACKAL]

Appreciate the input, but does each cat have a sensor?

Yes, each bank has its own downstream sensor.


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[rand0mher0]

I used these spacers on my wagon with gutted cats, no CEL on stock tune, all readiness monitors are good and passed. Can't go through inspection right now because all of the stations are closed but it would pass.

https://www.europaparts.com/oxygen-s...w-profile.html

[Waffles_s4]

I have three questions, so excuse my lack of knowledge on this:

1/ is the downstream oxygen sensor after or before the cat material? I once removed it, and I thought the cat material is after where the oxygen sensor is located. Am I wrong?

2/ if someone is gutting the oem cats, what do these spacers do, where would they go?!

3/ would not someone gutting their cats fail any sort of emissions no matter what? Just the smell should trigger the inspector to know the cats are not there

[jerseyboosted91]

Lol, I know the feeling. Just get the damn CEL out of my face!

However. I also know the feeling of emissions being due and my shit wont pass!! Haha. I have a year before emissions, but I'm trying to figure it out now while I got time so that I'm not throwing money at this last minute buying new oem cats and paying a shop to install everything. Then have to reinstall the upgrades.

Been there and it sucks.

- dubgli

Yeah likewise with the check engine light on being on the dash. Just knowing that it’s there is somewhat infuriating but it is what it is haha

It’s kind of annoying that I have to go every year to get the car inspected and have to deal with the stress of my car passing or failing each and every year. Makes me partly regret not getting another set of cats when mine failed but those would have just failed again and I would be back in the same boat. It’s like a double edged sword lol


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[JACKAL]

I have three probably stupid questions, so excuse my lack of knowledge on this:

1/ is the downstream oxygen sensor after or before the cat material? I once removed it, and I thought the cat material is after where the oxygen sensor is located. Am I wrong?


2/ if someone is gutting the oem cats, what do these spacers do, where would they go?!


3/ would not someone gutting their cats fail any sort of emissions no matter what? Just the smell should trigger the inspector to know the cats are not there

Not dumb questions, but here you go:

1) Downstream sensors are after the catalyst material and upstreams (primary sensors that control fueling) are just before it.

2) These spacers would go in the downstream O2 sensor bung. The purpose is the pull the sensor somewhat out of the exhaust flow giving it less exposure to the gasses and 'simulating' what it would see if the exhaust had just passed through catalyst material.

3) It depends on the emissions test. If someone is able to get a set of spacers to work and keep the CEL off, an OBD2 emissions test can be passed. However, any visual inspection might be at risk if the inspector noticed (and understood what) the spacers were for or if they caught a whiff of the exhaust while fumes. I guess it all depends on how emissions tests are performed where you live.

[Waffles_s4]

Not dumb questions, but here you go:

1) Downstream sensors are after the catalyst material and upstreams (primary sensors that control fueling) are just before it.

2) These spacers would go in the downstream O2 sensor bung. The purpose is the pull the sensor somewhat out of the exhaust flow giving it less exposure to the gasses and 'simulating' what it would see if the exhaust had just passed through catalyst material.

3) It depends on the emissions test. If someone is able to get a set of spacers to work and keep the CEL off, an OBD2 emissions test can be passed. However, any visual inspection might be at risk if the inspector noticed (and understood what) the spacers were for or if they caught a whiff of the exhaust while fumes. I guess it all depends on how emissions tests are performed where you live.

Thanks man.

So those spacers would kind of fake the real flow of exhaust gases? If so, why none of the ones stated above work properly?

Do the spacers just basically add a gap?

[JACKAL]

Thanks man.

So those spacers would kind of fake the real flow of exhaust gases? If so, why none of the ones stated above work properly?

Do the spacers just basically add a gap?

Kind of - in a system with cats, the downstream exhaust gases have significantly less pollutants and toxic gases due to the chemical reaction on the catalyst surface. Those downstream sensors are looking for that cleaned-up airflow and when they see it, they produce a *somewhat* stable/constant voltage signal of around 0.7V. Upstream sensor voltage fluctuates like crazy but downstream should be relatively smooth and stable on a car with functional cats. The image below should help clarify this:

o2 voltage signals.JPG

With the spacers and restrictors, they take the downstream sensor out of that flow by varying degrees depending on the length, restriction, and overall geometry. Getting the sensors out of the stream can simulate the effect of cats because with the sensors spaced away, they don't see as much of the exhaust flow and thus the provide a 'cleaner' signal.

The problem that I had and where things get tricky is that the ECU expects to see a voltage of around 0.7V after startup (excluding major throttle events). If you choose a restrictor or spacer that distances the sensors too much from the exhaust flow, the sensors will think the car is running lean (because the exhaust is too 'clean') and you will end up throwing lean codes even though the car truly isn't running lean.

Conversely, if you don't get the sensor far enough from the exhaust flow, you will either see a voltage signal that is too high and then the rich codes will come along OR the sensors will actually simulate the rapidly fluctuating voltage signal that the upstream sensors produce which will then trigger the P0420 and P0430 codes for poor catalyst efficiency.

Hope that makes sense and I am not trying to get all negative about these spacers because I know there are people who have gotten them to work but it's tough to find a 'one and done' because things like the bung placement for the sensor and the elbow (if you are using an elbow) orientation can all make a difference. It's definitely something that may require multiple iterations to get right.

[GID]

A few more questions to add.

1) from the engine bay, you can see the 02 sensors beneath the intake pipe as well as the driver side, are those the sensors that requires the spacers or are they further downstream those?

2) if using the j style vibrants, I've read that the smallest adapter works best but should the end of the j face towards the front or rear of the vehicle?

3) should the gutted cats be installed with the spacers preinstalled or wait to install the spacer until after the cats are I stalled?

Thanks everyone!


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[JACKAL]

A few more questions to add.

1) from the engine bay, you can see the 02 sensors beneath the intake pipe as well as the driver side, are those the sensors that requires the spacers or are they further downstream those?

2) if using the j style vibrants, I've read that the smallest adapter works best but should the end of the j face towards the front or rear of the vehicle?

3) should the gutted cats be installed with the spacers preinstalled or wait to install the spacer until after the cats are I stalled?

Thanks everyone!


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The sensors you can see are going to be the upstream ones. The downstreams are accessible from beneath the car and those are the ones that need spacers if you're removing or gutting the cats.

I can't say what the best solution is with the Vibrant spacers as I wasn't able to get even those to work for me so maybe someone else can chime in on that.

I have test pipes (so more room that you will have with gutted cats) and I put the spacers in place after they were installed. I'm not sure if there is any advantage to installing the spacers first on gutted cats but not having them in place when I put the test pipes in just gave me a little more room to work until I was ready to put the sensors and spacers in place.

[GID]

The sensors you can see are going to be the upstream ones. The downstreams are accessible from beneath the car and those are the ones that need spacers if you're removing or gutting the cats.

I can't say what the best solution is with the Vibrant spacers as I wasn't able to get even those to work for me so maybe someone else can chime in on that.

I have test pipes (so more room that you will have with gutted cats) and I put the spacers in place after they were installed. I'm not sure if there is any advantage to installing the spacers first on gutted cats but not having them in place when I put the test pipes in just gave me a little more room to work until I was ready to put the sensors and spacers in place.

Thanks. Can anyone speak to the orientation of the j style spacers?

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[Waffles_s4]

The sensors you can see are going to be the upstream ones. The downstreams are accessible from beneath the car and those are the ones that need spacers if you're removing or gutting the cats.

I can't say what the best solution is with the Vibrant spacers as I wasn't able to get even those to work for me so maybe someone else can chime in on that.

I have test pipes (so more room that you will have with gutted cats) and I put the spacers in place after they were installed. I'm not sure if there is any advantage to installing the spacers first on gutted cats but not having them in place when I put the test pipes in just gave me a little more room to work until I was ready to put the sensors and spacers in place.

Ahh that explains my ptevious question. So the sensor that is right next to the upper timing cover is actually the upstream sensor? Meaning you cannot actually see the downstream sensor from under the hood.

[FromRagsToS4]

The Vibrant J-style spacers dont work on Mertop header O2 bung location...

I have the XS Shorties 90 degree spacers and then the Big Daddy catted o2 spacer in line, on Mertop headers.

[JACKAL]

Ahh that explains my ptevious question. So the sensor that is right next to the upper timing cover is actually the upstream sensor? Meaning you cannot actually see the downstream sensor from under the hood.

Correct!

[dubgli]

Thanks. Can anyone speak to the orientation of the j style spacers?

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Base on my recent experience, having the J-spacers pointing exactly upstream should be the most limiting in terms of the exhaust gas not reaching the sensor. Having the jspacer facing the downstream would be the most exposed as in the most amount of exhaust would be reaching the sensor. You would then have to play with the in between angles and the inserts to get what you need.

Just my experience.

[GID]

The sensors you can see are going to be the upstream ones. The downstreams are accessible from beneath the car and those are the ones that need spacers if you're removing or gutting the cats.

I can't say what the best solution is with the Vibrant spacers as I wasn't able to get even those to work for me so maybe someone else can chime in on that.

I have test pipes (so more room that you will have with gutted cats) and I put the spacers in place after they were installed. I'm not sure if there is any advantage to installing the spacers first on gutted cats but not having them in place when I put the test pipes in just gave me a little more room to work until I was ready to put the sensors and spacers in place.

I'm hearing otherwise. Can someone please confirm this? I'm being told that the 02 spacer seen from the engine bay is the downstream sensor that needs the spacer. It can be installed and I installed from the engine bay, not beneath.

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[JACKAL]

I'm hearing otherwise. Can someone please confirm this? I'm being told that the 02 spacer seen from the engine bay is the downstream sensor that needs the spacer. It can be installed and I installed from the engine bay, not beneath.

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Where are you hearing this? I just looked and I cannot see my downstream sensors from the engine bay - only upstream. You absolutely do not want to put a spacer on those sensors. The downstreams are accessible from the bottom of the car. I have been under there many, many times to change spacers. I can't see any possible way of doing it from the engine bay. I see you have an A7 so I can't say with certainty that you may not be able to access them from above, but I would damn well make sure that you can see a sensor upstream of the one you put a spacer on. The upstream sensor is still on the manifold (before the 3-bolt joint that your cat/test pipe will bolt to). If you have cats in place, I honestly can't see how you could get at the downstream sensor because they are going to be downstream of the big bulge where the catalyst material is. See the image below for clarification:

The sensor just before the 3-bolt joint is the upstream. This is just barely visible from the engine bay. The downstream can be seen (partially) at the back end of the cat. You are not going to be able to get at that from the engine bay.

3.0t.jpg

[GID]

Where are you hearing this? I just looked and I cannot see my downstream sensors from the engine bay - only upstream. You absolutely do not want to put a spacer on those sensors. The downstreams are accessible from the bottom of the car. I have been under there many, many times to change spacers. I can't see any possible way of doing it from the engine bay. I see you have an A7 so I can't say with certainty that you may not be able to access them from above, but I would damn well make sure that you can see a sensor upstream of the one you put a spacer on. The upstream sensor is still on the manifold (before the 3-bolt joint that your cat/test pipe will bolt to). If you have cats in place, I honestly can't see how you could get at the downstream sensor because they are going to be downstream of the big bulge where the catalyst material is. See the image below for clarification:

The sensor just before the 3-bolt joint is the upstream. This is just barely visible from the engine bay. The downstream can be seen (partially) at the back end of the cat. You are not going to be able to get at that from the engine bay.

3.0t.jpg

Unless I'm looking at something completely different, I went out and took a picture.

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[GID]

Zoomed out for reference

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[Waffles_s4]

Where are you hearing this? I just looked and I cannot see my downstream sensors from the engine bay - only upstream. You absolutely do not want to put a spacer on those sensors. The downstreams are accessible from the bottom of the car. I have been under there many, many times to change spacers. I can't see any possible way of doing it from the engine bay. I see you have an A7 so I can't say with certainty that you may not be able to access them from above, but I would damn well make sure that you can see a sensor upstream of the one you put a spacer on. The upstream sensor is still on the manifold (before the 3-bolt joint that your cat/test pipe will bolt to). If you have cats in place, I honestly can't see how you could get at the downstream sensor because they are going to be downstream of the big bulge where the catalyst material is. See the image below for clarification:

The sensor just before the 3-bolt joint is the upstream. This is just barely visible from the engine bay. The downstream can be seen (partially) at the back end of the cat. You are not going to be able to get at that from the engine bay.

3.0t.jpg

Exactly, the one everyone is able to see is the upstream. It's the closet to the exhaust manifold, which makes sense now to me.

So if I gut my stock cats, and leave the downstream sensors as is, I will have a CEL for sure?

Ideally, we would just block the downstream sensors, and just have a device which feeds the 0.7 volts or whatever the ecu wants to see and be done with all of this. Guess that device does not exist yet.

[JACKAL]

Well it’s hard to tell from the pic but given the location it does appear to be the downstream since the upstreams are on the sides of the engine and this looks to be more central. Maybe the A7 engine bay just has a little more room than the S4. Are you able to see both sides?

[JACKAL]

Exactly, the one everyone is able to see is the upstream. It's the closet to the exhaust manifold, which makes sense now to me.

So if I gut my stock cats, and leave the downstream sensors as is, I will have a CEL for sure?

Ideally, we would just block the downstream sensors, and just have a device which feeds the 0.7 volts or whatever the ecu wants to see and be done with all of this. Guess that device does not exist yet.

Yeah, you'll throw those P0420 and P0430 codes and you'll probably notice a little reduction in power. I did anyway when I was experimenting with various spacer configurations.

It would be nice, but the simulator device you're describing doesn't exist for our ECMs. There is a company called Area74 that makes simulators (I tried them as well) and they 'condition' the downstream voltage signal because that 0.7V isn't a constant. Based on certain throttle conditions and on cold start, the ECM is looking for specific behavior from the downstreams. Unfortunately even with those simulators in place, they still weren't smart enough to fool the computer and I threw codes for those as well, usually related to slow response time from the dowstream sensors.

[GID]

Well it’s hard to tell from the pic but given the location it does appear to be the downstream since the upstreams are on the sides of the engine and this looks to be more central. Maybe the A7 engine bay just has a little more room than the S4. Are you able to see both sides?

I am, the passenger side is below the intake pipe. There seems to be a slight difference in the cat as well. In the picture you sent, the sensor is pointed downstream and connects at the collar of the cat where as my sensor is directly in the middle of the cat.

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[JACKAL]

I am, the passenger side is below the intake pipe. There seems to be a slight difference in the cat as well. In the picture you sent, the sensor is pointed downstream and connects at the collar of the cat where as my sensor is directly in the middle of the cat.

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Well if that’s the case, then I stand corrected, at least for the A7. It sounds like you would be able to get at the proper downstream sensors from the top.

[GID]

Just an fyi, this cat was pulled from an s5. Not sure when and what models had the changes if any.

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[Waffles_s4]

Well if that’s the case, then I stand corrected, at least for the A7. It sounds like you would be able to get at the proper downstream sensors from the top.

What's strange is that the sensor on that pic seems to go right in the middle of the cat, where the cat material would be, not before or after it.

Do the cats change in design on the b8 vs b8.5 on the 3.0T?

Edit: I think on my s4 the sensor is also similar to that s5. I will take a pic tonight

[dubgli]

Maybe s4 is slightly different but you should be able to see all o2 sensors from under the hood. The downstream sensors just takes a little more leaning over.

Stock cats from my sq5. Sensors are in the middle of the big section. Not sure if the catalyst honeycomb runs the whole length of the large section.

- dubgli

[Waffles_s4]

^^ my cats look exactly like that. Thats why when I removed the downstream sensors, I could see some of that honeycomb material right from the hole.

Anyone knows if the upstream sensor is connected directly to the exhaust manifold, or, there is another hole in the cat before the middle hole?

[dubgli]

^^ my cats look exactly like that. Thats why when I removed the downstream sensors, I could see some of that honeycomb material right from the hole.

Anyone knows if the upstream sensor is connected directly to the exhaust manifold, or, there is another hole in the cat before the middle hole?

Upstream sensors should be on the headers, not on the cat.

- dubgli

[Waffles_s4]

Upstream sensors should be on the headers, not on the cat.

- dubgli

Nice, what I thought as well.

So if you gut the cats like mine or yours, would downstream spacers help?

[dubgli]

Nice, what I thought as well.

So if you gut the cats like mine or yours, would downstream spacers help?

That's exactly what spacers are for.

To help you from getting a p0420 cat efficiency below threshold.

- dubgli