CAT removal in the frontpipe, CEL? - Scion FR-S Forum | Subaru BRZ Forum | Toyota 86 GT 86 Forum | AS1 Forum

Areddi · 08-18-2012, 06:17 AM

Hi guys,

If you remove the cat in the front-pipe, are you going to throw a code in these cars?

In my Miata there is a second downstream O2 sensor whose job is to basically verify that the CAT is there and working. The the upstream O2 sensor does all of the calculations for air/fuel etc. Therefore, if you remove the CAT, you get a code.

I live in MD so we have and OBD emissions check every 2 years, and I want to avoid codes. I want to get rid of the CAT if I can, I know high-flow is an option, but full removal would be preferred.

Has anyone confirmed whether you'll get a code or not yet?

karma003 · 08-18-2012, 06:51 AM

I would assume it would throw a code. Most cars now days have 2 o2 sensors. One to read the exhaust fumes & determine how the motors running. The second to determine how much fumes r being left out as emissions

Don@Accelerated · 08-18-2012, 07:04 AM

Removal of the front cat throws the efficiency code. Its quite annoying and when it happens you'll have idle issues not to mention power loss

Areddi · 08-18-2012, 07:07 AM

Thanks for the heads up. I will stick to cat-backs.

Kochinopride · 08-18-2012, 08:42 AM

Can't you get a CEL eliminator for this? That's what I did with my Elise when I removed the Cat.

Tainen · 08-18-2012, 03:22 PM

Hmmm... There is no o2 sensor after the 2nd cat. You will get no CEL. One before the header cat and one after the header cat.

08-18-2012, 06:17 AM	#1
Areddi Senior Member Join Date: Aug 2012 Drives: Firestorm FR-S Location: Columbia, MD Posts: 336 Thanks: 38 Thanked 86 Times in 63 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	CAT removal in the frontpipe, CEL? Hi guys, If you remove the cat in the front-pipe, are you going to throw a code in these cars? In my Miata there is a second downstream O2 sensor whose job is to basically verify that the CAT is there and working. The the upstream O2 sensor does all of the calculations for air/fuel etc. Therefore, if you remove the CAT, you get a code. I live in MD so we have and OBD emissions check every 2 years, and I want to avoid codes. I want to get rid of the CAT if I can, I know high-flow is an option, but full removal would be preferred. Has anyone confirmed whether you'll get a code or not yet?

08-18-2012, 06:51 AM	#2
karma003 auto-crosser/drifter Join Date: Jul 2012 Drives: 2013 scion FR-S black M/T Location: corpus christi, TX Posts: 255 Thanks: 321 Thanked 29 Times in 24 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	I would assume it would throw a code. Most cars now days have 2 o2 sensors. One to read the exhaust fumes & determine how the motors running. The second to determine how much fumes r being left out as emissions __________________

08-18-2012, 08:42 AM	#5
Kochinopride Senior Member Join Date: Aug 2012 Drives: 13 FR-S, 12 CLS AMG, 05 Lotus Elise Location: Edgewater, NJ Posts: 486 Thanks: 100 Thanked 118 Times in 88 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	Can't you get a CEL eliminator for this? That's what I did with my Elise when I removed the Cat. __________________ 2005 Lotus Elise (Magnetic Blue) 2012 Mercedes Benz CLS AMG 6.3 (Diamond White Metallic) 2013 Scion FR-S (UltraMarine) 2011 Land Rover LR4 (Fuji White) [winter/utility] 2004 Mazda RX-8 (Sunlight Silver Metallic) [don't even know why I bought it] Last edited by Kochinopride; 08-18-2012 at 08:43 AM. Reason: Typo

08-18-2012, 03:22 PM	#6
Tainen Senior Member Join Date: Nov 2011 Drives: First SWP BRZ-L Location: Washington Posts: 653 Thanks: 119 Thanked 281 Times in 126 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	Hmmm... There is no o2 sensor after the 2nd cat. You will get no CEL. One before the header cat and one after the header cat. __________________ First white BRZ in the country Limited SWP BRZ, 35% tint, clear bra, Nameless Performance downpipe, axelback, headers

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08-18-2012, 07:04 AM	#3
Don@Accelerated Join Date: Jun 2012 Drives: 2013 BRZ Location: Toledo Ohio Posts: 844 Thanks: 6 Thanked 1,129 Times in 306 Posts Mentioned: 9 Post(s) Tagged: 0 Thread(s)	Removal of the front cat throws the efficiency code. Its quite annoying and when it happens you'll have idle issues not to mention power loss

08-18-2012, 07:07 AM	#4
Areddi Senior Member Join Date: Aug 2012 Drives: Firestorm FR-S Location: Columbia, MD Posts: 336 Thanks: 38 Thanked 86 Times in 63 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	Thanks for the heads up. I will stick to cat-backs.

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