Adding Headers
Team Owner
Joined: Oct 1999
Posts: 31,977
Likes: 487
From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
It is a good idea to retune the car after headers but mine did not throw codes with cats.
Pro
Joined: Apr 2023
Posts: 670
Likes: 358
From: Windsor, CT
If you get a set of post cat O2 sensors and run them as primaries, you will have better chances of not throwing any codes after a Long Tube header install. The theory is they have a better heating element. Your O2 sensors will be farther downstream then in a stock setup and can no longer rely on the heat of the exhaust to help them function reliably.
Tuning for Long Tubes has to do with telling the PCM that the O2 sensors are sitting further down the stream and you need to introduce a delay. The PCM will be seeing a delayed reaction time from its corrections, which can cause it to over and under fuel.
In my specific case, I was running rich with Long Tube headers and no tuning. 10.5-11.0 AFR rich. So tuning to clean up the fuel and change the delay of the O2 sensors is why people will say you will gain 20 HP from headers, and another 10-15 from tuning.
Tuning for Long Tubes has to do with telling the PCM that the O2 sensors are sitting further down the stream and you need to introduce a delay. The PCM will be seeing a delayed reaction time from its corrections, which can cause it to over and under fuel.
In my specific case, I was running rich with Long Tube headers and no tuning. 10.5-11.0 AFR rich. So tuning to clean up the fuel and change the delay of the O2 sensors is why people will say you will gain 20 HP from headers, and another 10-15 from tuning.
