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Is there any harm in leaving o2 spacers installed on the downpipes permanently? Does it cause issues with the tune? My car is FBO + e85
 

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Is there any harm in leaving o2 spacers installed on the downpipes permanently? Does it cause issues with the tune? My car is FBO + e85
Well... you or someone previously put the O2 "spacers" on. If they are no longer needed, for one of several reasons, it should make no difference to the performance of the car if they are physically on the car or removed. This assumes no codes are being thrown.

Alexd
 

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Yep no codes are being thrown. Just want to make sure Im not introducing potential issues by leaving them in. I guess the better question is are the post cat o2 sensors used by the ecu for anything other than emissions checks
 

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Yep no codes are being thrown. Just want to make sure Im not introducing potential issues by leaving them in. I guess the better question is are the post cat o2 sensors used by the ecu for anything other than emissions checks
Are you running anti foulers as O2 sensor extensions or are you using the Big Daddy minicat extensions? The ECU looks at the rear O2 sensor output voltage to make sure it is within a certain range, which would signify the presence of a working CAT. When you remove the CAT this changes the O2 sensor output voltage and will subsequently trip a code in the ECU. Tuners typically just disable the DTCs in the tune, but this can be problematic if you need to pass emissions because turning off the DTC's won't allow the ECU to show readiness. The Big Daddy minicat does not require that you turn off the DTC's in the tune because it filters the exhaust going to the rear 02 sensor and makes it output the correct voltage as if a CAT was still in place. People also use the anti fouler extensions for this purposes as opposed to the Big Daddy minicat, but that approach is hit or miss from what I read.
 

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Bear in mind that earlier GT-Rs just had O2 sensors on the Downpipes (like my 2012). Later models (I don't know at what year this changed) had a second set on the mid-pipe/exhaust downstream.

Not that this is particularly pertinent to your question, but it was something I didn't personally know until recently...I had incorrectly assumed that they were all similar to my car.

Alexd
 

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Bear in mind that earlier GT-Rs just had O2 sensors on the Downpipes (like my 2012). Later models (I don't know at what year this changed) had a second set on the mid-pipe/exhaust downstream.
Not that this is particularly pertinent to your question, but it was something I didn't personally know until recently...I had incorrectly assumed that they were all similar to my car.

Alexd
Every car with obd2 from 1995 on has downstream o2 sensors.
 

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Bear in mind that earlier GT-Rs just had O2 sensors on the Downpipes (like my 2012). Later models (I don't know at what year this changed) had a second set on the mid-pipe/exhaust downstream.
Not that this is particularly pertinent to your question, but it was something I didn't personally know until recently...I had incorrectly assumed that they were all similar to my car.

Alexd

Every car with obd2 from 1995 on has downstream o2 sensors.
They are downstream of the DP on a GTR though, not downstream of the midpipe cats. Assume it changed after my year?(2016)

Sent from my iPhone using Tapatalk
 

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They are downstream of the DP on a GTR though, not downstream of the midpipe cats. Assume it changed after my year?(2016) Sent from my iPhone using Tapatalk
Then, tell me if I have been doubly wrong?! The first thing I ever did to my car was to replace the midpipe...nothing else at first. I recall no sensors on the stock midpipe, or anything further through the final exhaust. An inspection underneath showed only the DP O2 sensors. What's going on here...am I blind?!

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Then, tell me if I have been doubly wrong?! The first thing I ever did to my car was to replace the midpipe...nothing else at first. I recall no sensors on the stock midpipe, or anything further through the final exhaust. An inspection underneath showed only the DP O2 sensors. What's going on here...am I blind?!

Alexd
I believe all GTRs have pre and post CAT O2s in the downpipes, which is how it is on my 09. Front O2 is the closed loop wideband and the rear sniffs for the CAT.
 

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I believe all GTRs have pre and post CAT O2s in the downpipes, which is how it is on my 09. Front O2 is the closed loop wideband and the rear sniffs for the CAT.
Boy, am I learning something then!

So, what I added spacers to on my car were the "lower" O2 sensors...closer to the mid-pipe's connection. The upper O2 sensors that you refer to as "PRE" must be out-of-sight, at least for a casual glance...or again have I been blind? (Either way...thank you for your answer)

Alexd
 

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Boy, am I learning something then!
So, what I added spacers to on my car were the "lower" O2 sensors...closer to the mid-pipe's connection. The upper O2 sensors that you refer to as "PRE" must be out-of-sight, at least for a casual glance...

Alexd
Correct... lower or rear = post CAT
 

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Yep no codes are being thrown. Just want to make sure Im not introducing potential issues by leaving them in. I guess the better question is are the post cat o2 sensors used by the ecu for anything other than emissions checks

Hi. Sorry for bringing up this old post. Ran into an issue with passing inspection due to have a Cobb stage 3 tune which does not support catalys. Passed MA inspection last year but got boned this year.Thinking about going to a stage 1 after swapping back to stock injectors. Was just wondering if you used the spacers to suppress the Cel from coming on to pass inspection? Are they just regular spacers, angled, or the big daddy minicat. Dont have the stock DP so trying to see if this will work. Thanks in advance.
 

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Hi. Sorry for bringing up this old post. Ran into an issue with passing inspection due to have a Cobb stage 3 tune which does not support catalys. Passed MA inspection last year but got boned this year.Thinking about going to a stage 1 after swapping back to stock injectors. Was just wondering if you used the spacers to suppress the Cel from coming on to pass inspection? Are they just regular spacers, angled, or the big daddy minicat. Dont have the stock DP so trying to see if this will work. Thanks in advance.



First off...I'm unfamiliar with a Cobb stage 3 tune. However any tune that turns off the O2 sensors will usually fail just because the testing requires those sensors to be enabled. In a related way, SD tuning will usually fail due to more than one sensor being disabled. Even Flex-Fuel sometimes requires re-routing connections; I don't have Flex-Fuel and cannot comment further on this.

All that being said, I believe that there's no particular reason to change your injectors; you must have a MAF Map though that is calibrated for them.
The concept of spacers is NOT the shape or whether it's built with a "mini-cat" inside it...which in my mind is only an advertising gimmick. The "spacer" device must smooth out exhaust pulses, and there is an algorithm that relates this to whether the OEM catalytic components are working...deteriorating...or removed entirely, whereby codes are thrown.

Given time, one could experiment with different lengths of spacers, shims within them with various size holes, or even stuff steel wool within the tubes (though I wouldn't recommend doing this). Again, you're trying to dampen the pulse.

It is also possible to use no spacers at all and a simple 1 resistor and 1 capacitor circuit to electronically smooth the pulse...this has been done by attaching to the wires of the O2 sensors. (As a retired E.E., I would have done this if I knew (which I don't) the hot and cold resistance of the OEM O2 sensors, from which I could calculate the R and C values needed.

There are sometimes clearance problems with spacers, to nearby heat shields, That is why sometimes an angled spacer FITS BETTER...it's not that it works better.

Alexd
 
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