MY17 Exhaust questions - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

Elliotw · 09-28-2017, 04:14 AM

So I read through the stickied posted about exhaust upgrades and it was excellent. I do have two questions specific to the MY17+

Will removing the secondary cat still not throw CEL for MY17?
Are there any Hi-flow catted headers that don't throw CEL?

Thanks,
Elliot

churchx · 09-28-2017, 04:50 AM

1. Do whatever you want with secondary cats. All the sensors are before it. Also on MY2017.
2. Chance/mileage receiving CEL varies. There is no SURE way to not get one with aftermarket catted header (or O2 sensor spacer) and so on as it's not documented, how ecu decides if it should throw out depending on which readings or sequence of readings and at which specific engine running modes/temps/loads/etc. Aftermarket header vendors can do just best effort guessing, as without documentation all they can is make many prototypes (expensive), test all of them for long time (expensive & late to market & still not SURE fix), and possibly compromising performance (less competitive product). Best way to just get ECU tuned. It will disable cat readiness checks AND give extra performance gains. And if you get ecu tune with those checks disabled .. why not get catless header for best gains & cheaper price?

09-28-2017, 04:14 AM	#1
Elliotw Senior Member Join Date: Sep 2017 Drives: '18 BRZ tS, '18 GTI SE, '11 RS Location: Seattle Posts: 505 Thanks: 232 Thanked 392 Times in 224 Posts Mentioned: 7 Post(s) Tagged: 0 Thread(s)	MY17 Exhaust questions So I read through the stickied posted about exhaust upgrades and it was excellent. I do have two questions specific to the MY17+ Will removing the secondary cat still not throw CEL for MY17? Are there any Hi-flow catted headers that don't throw CEL? Thanks, Elliot

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09-28-2017, 04:50 AM	#2
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,334 Thanks: 698 Thanked 2,086 Times in 1,436 Posts Mentioned: 53 Post(s) Tagged: 1 Thread(s)	1. Do whatever you want with secondary cats. All the sensors are before it. Also on MY2017. 2. Chance/mileage receiving CEL varies. There is no SURE way to not get one with aftermarket catted header (or O2 sensor spacer) and so on as it's not documented, how ecu decides if it should throw out depending on which readings or sequence of readings and at which specific engine running modes/temps/loads/etc. Aftermarket header vendors can do just best effort guessing, as without documentation all they can is make many prototypes (expensive), test all of them for long time (expensive & late to market & still not SURE fix), and possibly compromising performance (less competitive product). Best way to just get ECU tuned. It will disable cat readiness checks AND give extra performance gains. And if you get ecu tune with those checks disabled .. why not get catless header for best gains & cheaper price?

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