O2 sensor spacers (CEL Eliminators)

2Times · 03-23-2023, 08:03 AM

Is there any disadvantage to leaving them in when getting a custom tune? I heard they can make the readings inaccurate towards the lean side but wasn't sure if that was some mythbusters stuff. Currently have the bigdaddies with mini-cat inline spacer.

Indo Rider · 03-23-2023, 10:34 AM

AFR readings are from the pre cat sensors. Are post cat sensors actually used for anything other than emissions monitoring? I honestly don't know. I wouldn't think so, but maybe someone more knowledgeable knows for sure?

Regardless, if you are getting a custom tune then you have your ECU unlocked, so you have no reason to keep the spacers installed. Just remove them and turn off the CEL in the flash.

Bill76 · 03-23-2023, 10:40 AM

Quote:

Originally Posted by Indo Rider

AFR readings are from the pre cat sensors. Are post cat sensors actually used for anything other than emissions monitoring? I honestly don't know. I wouldn't think so, but maybe someone more knowledgeable knows for sure?

Regardless, if you are getting a custom tune then you have your ECU unlocked, so you have no reason to keep the spacers installed. Just remove them and turn off the CEL in the flash.

You're right

Matt@Evolve · 03-23-2023, 11:28 AM

If you're tuning the car I would just remove the spacers.

2Times · 03-23-2023, 12:07 PM

Thank you crew. I'll go ahead and do that.

njoyRice · 03-23-2023, 12:49 PM

https://youtu.be/bmWjoudIOCk

This video helps explain it but It seems like the secondary o2s do more than just check cat efficiency.

03-23-2023, 08:03 AM	#1
2Times I'd hit it 1065 Rep 1,106 Posts Drives: G82 Join Date: Dec 2009 Location: Austin iTrader: (3) Garage List 2023 BMW M4 xd [10.00]	O2 sensor spacers (CEL Eliminators) - bad for tuning? Is there any disadvantage to leaving them in when getting a custom tune? I heard they can make the readings inaccurate towards the lean side but wasn't sure if that was some mythbusters stuff. Currently have the bigdaddies with mini-cat inline spacer. __________________ 2023 M4 xd BSM IG: MFor_YourPleasure
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03-23-2023, 10:34 AM	#2
Indo Rider Captain 555 Rep 735 Posts Drives: 135 Join Date: Apr 2012 Location: United States iTrader: (0)	AFR readings are from the pre cat sensors. Are post cat sensors actually used for anything other than emissions monitoring? I honestly don't know. I wouldn't think so, but maybe someone more knowledgeable knows for sure? Regardless, if you are getting a custom tune then you have your ECU unlocked, so you have no reason to keep the spacers installed. Just remove them and turn off the CEL in the flash.
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03-23-2023, 11:28 AM	#4
Matt@Evolve BimmerPost Supporting Vendor 1972 Rep 520 Posts Drives: F82 M4, E36 M3 Touring, Z3 Join Date: May 2022 Location: Luton, UK iTrader: (0)	If you're tuning the car I would just remove the spacers.
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03-23-2023, 12:07 PM	#5
2Times I'd hit it 1065 Rep 1,106 Posts Drives: G82 Join Date: Dec 2009 Location: Austin iTrader: (3) Garage List 2023 BMW M4 xd [10.00]	Thank you crew. I'll go ahead and do that. __________________ 2023 M4 xd BSM IG: MFor_YourPleasure
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03-23-2023, 12:49 PM	#6
njoyRice Enlisted Member 56 Rep 42 Posts Drives: G80 M3C Join Date: Sep 2022 Location: Houston iTrader: (0)	https://youtu.be/bmWjoudIOCk This video helps explain it but It seems like the secondary o2s do more than just check cat efficiency.
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