4-1 header benefits and disadvantages?

[MuffinMan06]

I am also planning on using an FSH9 intake cam to go with it. Also, how will the car behave without a pre-cat? I am looking to use a better muffler and a cherry bomb glass pack to get a good subtle rumble without being annoyingly loud.

 

[njaremka]

The car should run just fine with a header to replace the primary cat. If you can, have the secondary O2 sensor relocated behind the second cat to keep the ECU happy.

 

[pcb]

I am also planning on using an FSH9 intake cam to go with it. Also, how will the car behave without a pre-cat?

The car will run fine without a pre-cat, but you'll get the P0421 code.

That is usually eliminated with the non-fouler trick.





Make sure it's got M18 metric threads as well as your O2 sensor bung on your header. (I kinda think that is the standard O2 sensor size?, but not everything is metric)


I know that you can use a non-fouler to eliminate the P0421 code when pre-cat if fried, and you install it on the upstream O2 sensor.

Your header may have an O2 sensor bung and you can install the non fouler and O2 sensor there.

njaremka's method of relocating the upstream O2 sensor behind the second cat makes sense to me too.
It will be monitoring the condition of the main cat instead of the pre-cat.
You probably wouldn't need the non-fouler then?

What have you done to your P5 today?

These are my 3 downstream O2 sensors... The one in the middle is my original one from my DD. They get REALLY seized and can be brutal to remove. I stripped the hex with my open ended wrech, so I cut it with a grinder and cutoff wheel so that I could get a socket on it. They have O2 sensor...

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