Borla UEL Headers sent car into a low power mode

[steve99]

Originally Posted by Carbinebbq

Thanks. I read the first part in the basic bolt on guides. The added info at the bottom was helpful. Cool. I feel reassured now. Just gotta make sure everything is bolted on properly. Then a tune when I get a chance.

2017 WRB BRZ

you probably better just getting a catless header, they will make a little more power, they cost less (no cat) .


You can still get a CEL with catted header if your unlucky.


So just wack a spacer in rear 02 of catless header about same chance at catted.


If you in an emissions hostile state then usually any change of header even to catted is not allowed anyway.


crab yourself a ELM327 adapter for $10 and a copy of android torque app or similar and you can check/clear and CEL till you get tune

[mav1178]

Originally Posted by Carbinebbq

I am asking because I am interested in catted headers, and I won't have a tune.

Originally Posted by steve99

If you change the header even for a catted one their is still a possibility that you will throw a cel code P0420

I ran the Fujitsubo catted header on my car, threw a CEL.

The 100% surefire way of not getting CEL: tune.
The 99% surefire way of not getting CEL: use a CEL fix O2 spacer.

-alex

[Carbinebbq]

Originally Posted by mav1178

I ran the Fujitsubo catted header on my car, threw a CEL.

The 100% surefire way of not getting CEL: tune.
The 99% surefire way of not getting CEL: use a CEL fix O2 spacer.

-alex

99% is better than 0! Thanks guys.

2017 WRB BRZ

[turtlefeeder]

Originally Posted by Carbinebbq

Confused now. Many previous posts say it won't run right, and now you are saying it will run fine. Not trying to argue in any way, just needing clarification. Are you taking into consideration his car is AT?

I am asking because I am interested in catted headers, and I won't have a tune. Not looking for any magical gains because I will get a tune in the future. Just want to know if the car will run normal. Kinda in it for the rumble sound first, performance later. Not trying to be a pain in the ass asking what has been asked before. Just trying to be informed.

2017 WRB BRZ

There might be no issue for a little while or it could happen right away. Base on what I know catted headers still change flow of exhaust which is why a tune is pretty ideal. Base on change in flow of exhaust gas cel might appear because the car is producing more exhaust at a faster rate than stock

[steve99]

Originally Posted by turtlefeeder

There might be no issue for a little while or it could happen right away. Base on what I know catted headers still change flow of exhaust which is why a tune is pretty ideal. Base on change in flow of exhaust gas cel might appear because the car is producing more exhaust at a faster rate than stock

It actually comparing the 02 levels seen by the 2 oxygen sensors before and after cat in header. They only measure 02 levels not flow.


air flow metering is done on intake side by the mass air flow sensor MAF


Will I get a CEL code
If you go to catless header you will get a CEL code P0420 (cat efficiency) it may thak a while to show up though.
Even some catted headers will still cause a cel code
You can try O2 spacers or de-foulers but they will not always work 100%
The only 100% way is to disable the code in the ECU usually done in aftermarket tunes.
The Cel code P0420 will stop the cruise control on your car from working, it wont go into limp home or low power mode.
Can be reset by removing battery connection or using obd tool to reset. It going to keep coming back until you disable it though.

Why you get CEL Code when changing header

Integrated in header is a primary catalytic converter. Their is the primary 02 sensor before this cat and a secondary 02 sensor after it. The ECU compares the reading from both and works out if the primary cat (in header) is working efficiently. If it detects abnormal readings it will set CEL Code P0420.
a tune for headers will disable Cel code code P0420 as well as optomising parameters for a header.


Changing any other exhaust components other than the header will not trigger a CEL code. Its only the primary cat in the header that is monitored by ECU, secondary cat in front pipe is not monitored.

[Varelco]

Kind of an unrelated question but Is the second O2 sensor used for any means of control of the engines operation or is it purely used to monitor the condition of the cat.

[jasonojordan]

From my understanding its more of a compare contrast on what the primary is seeing and does most of the judging how efficient the car is running and more of your fine adjustments. In this car mines not being used as I have the Delicious E85 module. In my old wrx I did not use one either and just controlled most of that with the tune.

[RedFRS4me]

Originally Posted by Varelco

Kind of an unrelated question but Is the second O2 sensor used for any means of control of the engines operation or is it purely used to monitor the condition of the cat.

I spent a long time trying to figure this out on my catless UEL header and a bad secondary O2. First thing I noticed is that the secondary O2 will definitely affect fuel adjustments to open/closed loop fueling. My sensor is bad and it kept sending readings like the car was running rich so it got stuck running open loop during extended cruising. I've disabled my secondary feedback via Romraider and OFT and fixed my problem. So far it hasn't caused any issues to power or driveability.