alright so im pretty sure my cats are clogged to ****. I would like to put in a straight pipe replacing the main one and the smaller ones. I search and search and search and learn about these different ways to make the ports open up without backpressure, but honestly I do not want to make something like that with all the janky fittings and stuff... i have a lot of tools and make up exhausts in my spare time. I'm positive I can make this design here:

the cat replacement pipe link


but how exactly did they go about getting the backpressure needed? I mean did they build a small box that the opening of the air line goes to?

help me out here... i can even start production of something like this if there is interest.

 

i made a custom straight pipe back to some good mufflers...
but I used the thang that is on the stock piping for backpressure.
Then I rebuilt and took out those stupid aluminum cans in the LIM, so it didn't really matter.

 

ok.. so you just cut the backpressure air pipe thing off the stock pipe and welded it on to the new pipe? that sounds easy enough... did 5/6 open up at 3600-3800 still?

 

its 3/4 that open up there...
5/6 open up with backpressure...
and they didn't open as easily... like if they were opened it was FOR SURE that i was racing...
but then again, the performance benefit from the lack of backpressure made it more than worth it.

 

cool deal. i'll give it a shot later today. you know what diameter the pipe is there? and the diameter of the smaller runners with small cats to the y are?

 

i would be interested but i have a T2 so the backpressure isn't a big deal to me since we don't have secondary ports, i just want to remove the cats and install a pre-silencer to quiet the thing down, hopefully something i can swap in and out when it is time to smog. let me know if you go into production of these, if you ask me it looks like most places overcharge for a couple of angled pipes. only reason i 'might' consider paying for a RB setup or other is because most muffler shops just won't fabricate you a "check" pipe for your cats because it is modifying emissions.