CAT free Header, Why hasn't anyone moved the bung?
 

So with the addition of catless headers, is there a reason not to simply move the rear O2 sensor behind the OEM secondary cats? End game is to add two bungs, extend the wires on B1S2 and B2S2, and move the sensors past the secondary cats. While at it, add a crossover pipe.

Thinking about OBX and error free operation without a flash.

Also, late 90's and early 2000 yoda ECM's used to use secondary O2 data to manipulate the LTFT's. Is this no longer a factor? We are talking a DD here...

Thanks in advance...

No takers? Why wouldn't this be an effective method to report real data and keep the vehicle mostly compliant as in not defeating functions one can get fined for cause one to undo should they want to sell the vehicle.

Is there any differences in the type of catalyst between primary and secondary cats??

Other than cramped location, there must be some other reason this is not being done. So what is it?

Depending on the flow rate of the secondary cats. It should be good. As you don't want the rear 02 sensors reading the same flow from the front 02 readings. Just my guess too. Then again if too spaced out readings it might detect an efficiency below threshold.

https://www.e90post.com/forums/showt...84#post8044943

I'm thinking its worth a shot to uncork the top end and get a bit more sound. I may just move the sensors now and add the headers later and never deal with a cell.

But still, why isn't this being done!??? A simple cost effective solution. 2 SS O2 bungs are what, $6? Cut a hole and weld them in! The downside is not doing a crossover now while the car is in the air air as it makes header install more painful if the spacing varies a little...

The ark exhaust does this, but you probably know that already :)

The actual cost of drilling/welding in a new bung into the midpipe AND extending the existing wiring is what made me overlook it. I just installed a simple 90 degree extension into the existing secondary O2 bung without extending the factory wiring and have been running fine since Dec 2015 (if I've remembered correctly).

Good to know. Thanks!
Even if it doesn't work, worst case is I plug them and the parts are cheap. I sure wish I could get the tech papers on ECM functionality and see if it adjusts LTFT based on data from those sensors.