P0420 and new down pipe

[tri-pedaler]

Hey all,

I’ve been getting code P0420 for a few months. Put new O2 sensors in and tried different catalytic cleaners, but to no avail. Just picked up a low mileage downpipe and plan to install it this weekend.

Anything else I should try before putting the car under the knife? And any ideas of other stuff I should address while I’m in there?

 

[atlantaM3]

https://www.oreillyauto.com/detail/.../dorman-help-18mm-steel-non-fouler/mtm0/42009

Or some such defouler will be needed for the downstream O2 sensor to clear the code.

 

[TyphoonFiST]

Hey all,

I’ve been getting code P0420 for a few months. Put new O2 sensors in and tried different catalytic cleaners, but to no avail. Just picked up a low mileage downpipe and plan to install it this weekend.

Anything else I should try before putting the car under the knife? And any ideas of other stuff I should address while I’m in there?

Whoosh* End it all

https://whooshmotorsports.com/colle...ant-02-sensor-defouler-j-style-thread-on-bung

https://whooshmotorsports.com/colle...ee-defouler-fiesta-st-focus-st-rs-explorer-st

https://whooshmotorsports.com/colle...ung-w-restrictor-fittings-for-adjustable-flow

 

[tri-pedaler]

Whoosh* End it all

https://whooshmotorsports.com/colle...ant-02-sensor-defouler-j-style-thread-on-bung

https://whooshmotorsports.com/colle...ee-defouler-fiesta-st-focus-st-rs-explorer-st

https://whooshmotorsports.com/colle...ung-w-restrictor-fittings-for-adjustable-flow

Alas, running in a street class for SCCA Autox.

 

[tri-pedaler]

https://www.oreillyauto.com/detail/.../dorman-help-18mm-steel-non-fouler/mtm0/42009

Or some such defouler will be needed for the downstream O2 sensor to clear the code.

Didn’t know about these, thanks. Since I already got a cheap low mileage stock dp I’ll install it, but this seems like a good option if the code still doesn’t clear

 

[atlantaM3]

Had to use them on a different car, as the Vibrant models were just too big for the space, could not fit both those and the sensor. The J style is huge. So the Dorman was a workable, and cheap, alternative. They come in two sizes, the short version worked for my situation.

Working well so far on my other car with a catted DP. That said, the hole in them is about the same size as the medium Vibrant restrictor, so not clear how well they would work with a decat DP.

 

[scooter123]

I am surprised Oreilly is actually selling De-Foulers, Because these are illegal under the EPA and they are really cracking down, just look at the millions that COBB had to pay out recently.

I will also note that the OEM Downpipe has features in it to form a standing wave vacuum impulse at the Turbocharger exhaust outlet. Truth is these are the best downpipes to use if you are using a stock turbo. Because that bit of tuning in the downpipe does speed the response of the turbo to the throttle and creates more mid range power in that torque hump before the turbo starts to run out of capacity.

 

[atlantaM3]

all the major parts stores near my area appear to sell such things, branded as 'spark plug defoulers' - errm, yeah. Must a 'if you know, you know' thing?

Found them at Advance Auto, Autozone, etc. too.