Hey i have a 1984 gsl se Mazda rx7 with a 13b rotary. My brother had just hooked up a new 13b for the car. We need to replace the exhaust and my question is does replacing the headers affect the computer? Also is their anyway to wire open the 6 ports so they stay open at all times? Thanks.

 

No, adding a header does not change anything in the computer, and why would you want to wire open the aux ports? That will just make your car slower from a start, and loose power on RPMs below 3800-4000.

 

The header is from a 4 port 13b, my brother thinks that if we don't wire them open there will be too much back pressure. Does a 4 port header work on a 6 port engine?

 

4-port vs. 6-port won't matter when it comes to exhaust. Any decently sized header will flow well enough.

Bolt it on, and either add a pick-up tube to open the aux ports, or set them to open electronically. Wiring them open is stupid.

 

Do you have any idea how far back from the engine the oxygen sensor goes? What does the pick up tube look like, where can i find one?

 

Stock O2 sensor placement is always as far up as possible, but with a header, you'll want it at the collection point (where the 2 pipes meet).

Go to www.racingbeat.com and look at their presilencers. The little tube sticking off the side is for the split air pipe, which is the source for air pressure on S4 NA engines. I've seen headers with a pickup welded on, but that'll obviously require custom fabrication.

 

all 13B exhaust ports are the same... two ports.

the aux ports or 5th 6th ports are for intake and unrelated to exhaust.

Perhaps he is confusing the port operation, in which if you use a crappy header or poorly designed oversized exhaust the aux ports on a '84 through 88 non turbo 13B the exhaust ports sometimes won't open... but that is an exhaust velocity issue, not a back pressure issue. RotaryRocket88 posted RB solution on how to solve that issue.