Im putting a custom single exhaust on my s4 n/a and i was wondering what size piping would be a good size to create enough back pressure to open the 5th and 6th ports with a presilencer, headers, and a muffler?

 

Good question, let's see what the 2ndgen guru's recommend. I'm a 12A kinda guy. Nikki carb. That kinda thing...lol

Mario III

 

First off, you are looking at 2 1/2" pipe.

Second, are you prepared for a really really really really really loud exhaust?

 

haha the loud exhaust wont bother me one bit. im sure itll suck driving late at night because of cops but its worth it if my ports are working right. thanks for the help!

 

Opening the aux. ports w/ backpressure on an open exhaust system is nearly impossible. RB's presilencer can accomplish it, and some headers have a small diameter pick up tube as well. I'd recommend using electronic activation, or experimenting with very small diameter pick up tubes. 1/4" or so would probably work. The split air pipe is way too big IMHO.

 

i know that just straight piping the exhaust has a very low chance that opening the ports would work and itd be ridiculously loud. thats why i was planning on buying the racing beat presilencer(with the pickup tube) and one of their headers and probably a muffler from them too. racing beat makes really good parts for rx7s and i dont want to spend money twice so im going to go with the best.

 

iv just made up a custom 2.5inch twin exhaust from extractors ta the muffler!!! cant wait ta start it!!!! ear plugs hahaha

 

yea that thing is going to be LOUD haha. i cant wait to do it to my fc