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2006 V70R M66, Titanium/Atacama
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Discussion Starter #1
Installed my long awaited EST downpipe and touring exhaust a couple weeks ago with fresh front and rear O2 sensors, and have gotten a CEL for the CAT after a couple days. Cleared it, and it came back again couple days later.

Looking around, I see that a spacer is recommended for the rear sensor in aftermarket downpipes, but many of the threads are pretty old and I'm not sure if EST has updated their design or not to mitigate this. The rear position essentially IS a spacer from what I can tell. Here's a photo when I was rough fitting together.

116312


And one with the sensor in as i was getting it all installed.

116313


I've also read that having too long of a spacer can cause a CEL light too, so there's a nice middle ground somewhere?

Does anyone have experience or recommendation for this configuration? If it's needed, likely have to be a 45 degree one to fit.

Thanks!
 

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Discussion Starter #2
Should probably add that I tracked my O2 sensors on a drive to work one day to make sure they were actually reading appropriately, but I'm not sure on that either. The front is pretty consistent around 1.0, but the rear is all over the place. These shots are from when the car was nice and warmed up after 15-20min of driving.

Idling, rear (purple line) does some odd slow oscillation mostly around 0.7V.
116314


Then, cruising on the highway at 100kph / 62mph, the rear reading is all over the place - wildly fluctuating between 0.2V to 0.8V.
116315


Is this normal behavior? Did I get a bad rear sensor?
 

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Installed my long awaited EST downpipe and touring exhaust a couple weeks ago with fresh front and rear O2 sensors, and have gotten a CEL for the CAT after a couple days. Cleared it, and it came back again couple days later.

Looking around, I see that a spacer is recommended for the rear sensor in aftermarket downpipes, but many of the threads are pretty old and I'm not sure if EST has updated their design or not to mitigate this. The rear position essentially IS a spacer from what I can tell. Here's a photo when I was rough fitting together.

View attachment 116312

And one with the sensor in as i was getting it all installed.

View attachment 116313

I've also read that having too long of a spacer can cause a CEL light too, so there's a nice middle ground somewhere?

Does anyone have experience or recommendation for this configuration? If it's needed, likely have to be a 45 degree one to fit.

Thanks!
Yeah I have the same combo and got the same results. I got this spacer and have not seen a cel since.

 

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Discussion Starter #4
Thanks, looks like those are on Amazon too.

Anyone have comments on the O2 sensor readings? Everything normal there?
 

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The rear sensor looks like the signal of a non functioning catalyst. When the front sensor drives mixture rich to lean and lean to rich, as is normal within a small variation about Lambda, the rear should be 0.63-0.76V. The catalyst will use the oxygen remnant in the incoming exhaust to have CO go to CO2 and HC to be come CO2 and H2O. That reduces the oxygen aft of catalyst to a small amount and binary oxygen sensor will be in the range mentioned (low O2 = higher V, more O2 =less V). An extender with a smaller hole usually can slow the exhaust gas exchange at sensor and the average oxygen level will go down as oxygen has high propensity to reduce concentration when the gas around has reduced oxygen. When the O2 level stays lower the sensor V will increase and reach the goal of ranging a small amount between 0.6V to a little over 0.7V. If that occurs the ECM will be happy. All of this is with steady throttle so the mixture is in closed loop and being emissions optimized. When you accelerate the enrichment will drop rear O2 and off throttle coast when engine speed is above 1200 rpm +/- shut off injectors and the O2 level goes way up
 

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@cattlecar good information there on normal values.

Echoing that, the cat is so small on these aftermarket DPs that if it doesnt throw the CEL right away it will in a few years. I liked this spacer for my DP. I see they are much more expensive now - I got mine for $30 a few years ago.

I like this one because you can adjust flow in case you are still getting the CEL. If you can get it cheaper maybe thats your move.

 

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Just had Hilton tune mine out when I went catless. I don’t even have the 02 installed on the car) If I put the high flow cat on I will install the o2 but it will just be to plug the bung.
 

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Discussion Starter #8
Thanks everyone, I've got one of the 45 degree spacers that IwantaS60R suggested, though from amazon.ca here:
O2 Sensor Spacer with Mini Catalytic Converter, Angular Style, Stainless Steal Design, Thread M18x1.5 (Pack of 1-45 Degree Angle), Oxygen - Amazon Canada

I should have the spacer this weekend and will report back to close this out once I've got it installed.


The rear sensor looks like the signal of a non functioning catalyst. When the front sensor drives mixture rich to lean and lean to rich, as is normal within a small variation about Lambda, the rear should be 0.63-0.76V. The catalyst will use the oxygen remnant in the incoming exhaust to have CO go to CO2 and HC to be come CO2 and H2O. That reduces the oxygen aft of catalyst to a small amount and binary oxygen sensor will be in the range mentioned (low O2 = higher V, more O2 =less V). An extender with a smaller hole usually can slow the exhaust gas exchange at sensor and the average oxygen level will go down as oxygen has high propensity to reduce concentration when the gas around has reduced oxygen. When the O2 level stays lower the sensor V will increase and reach the goal of ranging a small amount between 0.6V to a little over 0.7V. If that occurs the ECM will be happy. All of this is with steady throttle so the mixture is in closed loop and being emissions optimized. When you accelerate the enrichment will drop rear O2 and off throttle coast when engine speed is above 1200 rpm +/- shut off injectors and the O2 level goes way up
Thanks for this detailed explanation! Sounds like everything is operating normally then, just that the aftermarket cat isn't as effective as the stock one resulting in current response.
 

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Interesting. I have a Snabb catted downpipe on my VR and it does not have a spacer for the rear sensor. It's been on 4-5 years now and I haven't had a CEL or any other oddities. Apparently there are significant differences in the various catalytic converters used on the aftermarket downpipes.

 

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Interesting. I have a Snabb catted downpipe on my VR and it does not have a spacer for the rear sensor. It's been on 4-5 years now and I haven't had a CEL or any other oddities. Apparently there are significant differences in the various catalytic converters used on the aftermarket downpipes.

I posted awhile ago on another thread that o2 spacers are a crap shoot. Work for some and not others. Can’t say it enough, ALL cars are different.


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You can just disable CAT diagnostics by set CDKAT constant to zero inside your ecu BIN.
 

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Interesting. I have a Snabb catted downpipe on my VR and it does not have a spacer for the rear sensor. It's been on 4-5 years now and I haven't had a CEL or any other oddities.
Same up until the other day. I have had Contrast's pops in advance mode for the past year which I use occasionally. Have had that DP for maybe 3-4 years now.
 

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Discussion Starter #13
You can just disable CAT diagnostics by set CDKAT constant to zero inside your ecu BIN.
Do I just use a 10mm socket to do that, or...? ;)

I don't know how to write to the ECU. Assuming it can't be done with VIDA?
 

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I don't know how to write to the ECU. Assuming it can't be done with VIDA?
You can contact with Hilton or Contrast to do it. They have a software to flash ECU over DICE.
 
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Discussion Starter #15
45 degree spacer arrived on Friday, hopefully I'll be able to get it in today. All stainless, here's the one I ordered from Amazon.
O2 Sensor Spacer with Mini Catalytic Converter, Angular Style, Stainless Steal Design, Thread M18x1.5 (Pack of 1-45 Degree Angle), Oxygen - Amazon Canada

Apparently the small end cap is supposed to be "fastened tightly" so that it doesn't fall off and drop the mini-cat inside the exhaust, but it's a pretty fine thread and always turns off by hand. I'm just going to pinch it with pliers one there to hold since i don't have any high temp thread locker.

Anyway, here are some photos for those interested.

116998


116999


117000
 

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Discussion Starter #16
Installed the spacer this past weekend, super easy. I disconnected the battery to clear the system and will report back after a week or two on whether the CEL / DTC returns.

Original rear O2 installation:
117630


45deg spacer installed:
117631
 

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Yeah, let us know how it works. I am in need of one, this one looks nice.
 

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I used a curved Vibrant spacer that worked great- has three sizes of restrictors, held in by snap rings, so they don't come out. Works great, no leaks. It's available on Amazon, which is where I got it. It's a lot more (like $20) than the cheaper ones, but the curve makes it pretty low profile.
 

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Discussion Starter #19
I used a curved Vibrant spacer that worked great- has three sizes of restrictors, held in by snap rings, so they don't come out. Works great, no leaks. It's available on Amazon, which is where I got it. It's a lot more (like $20) than the cheaper ones, but the curve makes it pretty low profile.
Yeah I took a look at that one, but I wasn't sure about a 90 degree spacer given the rear port on the EST downpipe comes out at 45 degrees already. Figured it'd run the O2 sensor into the heatshield or back into the downpipe.

Anyway, still no codes showing up. So that's good!
 
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