Exhaust thread...
 

Ok, my mufflers are rusted out and I want to give my car some extra power and a good sound- but I don't have $1000+ to spend per muffler LOL..
I was thinking of a cat-back system, maybe even get a header-back system installed..now my problems are- should I keep the cats? If I lose the cats, should I block off my emissions crap? I was thinking of super- or turbo-ing this out as well so I wasn't sure about piping size- should I stay OEM or bump it up a bit?
I am really torn between just going back stock mufflers or if I should dish out the extra $ for something worth it. I am also puzzled over the backpressure 5th/6th port operation concept- an explanation of its inticasies would help.. Any suggestions?? Thanks!

Just save your dough and pop for the RB setup. It is set up to work with the s4's aux port activation.

whats the RB setup? how big of an exhaust pipe is the 'limit'? i dont have a cat on mine and still have a stock header, but i do have an apexi muffler - so i was thinking about going to a larger size pipe from the header back....

thanks for the response but I could have assumed that a high end- rotary-specific manufacturer would be a good option- I am looking for more info like "apexi n1s are too open/not open enough/just right" etc.. or something else specific, and was hoping for an explanation of the 5th/6th port operation not simply to know that "so and so will work with your ports", anyone say corksport or racing beat or mazda trix re-a or on and on- I know these will all work, they are out of my price range right now..

Or you could have actually utilized the search function of this forum. This topic has been covered to death.

The search function is incredibly convoluted and overrated- I couldn't find SH*% and I have been searching for an hour. WHY DOES EVERYONE ASSUME THAT JUST BECAUSE SOMEONE IS ASKING A QUESTION THAT HAS ALREADY BEEN ASKED THAT THEY DIDN'T TRY TO FIND AN ANSWER!!??!
besides, I am obviously not the only one who can't find an answer about this through the search..

+1^^. not to be a dick, but there are tons of threads on this. anyway, the s4 (unlike the s5) system uses exhaust backpressure to activate the 6pi system. basically there is a pick up tube coming out of your catylitic converter (called the split air pipe) that diverts a small amount of exhaust to the 5th and 6th port actuaors thus opening them at a certain threshold. this is a slightly faulted system to begin with as you must be under load and therefore cannot check the actuation of the system in neutral in your driveway, plus the fact that the ports open at different time depending on the gear and the load. there are a few different ways that you can mod the system (to run off the air pump or an electric pump) and they are all fairly cheap+easy to do and have PLENTY of documentation both on this forum and on other sites (fc3spro has a good write-up) so there is no real reason for you to worry about modding the system if you find an exhaust you like and it doesn't have the pick-up tube (i.e. NOT a racing beat). still tho, you may wanna check the functionality of your actuators as many people's dont work on their 20 yr old cars. but as mentioned before, if you dont wanna have to mod the system you can buy the rb pre-silcencer and use it with their header or as part of a custom exhaust. i am actually thinking about using it with their header and then using another brand cat-back. since the presilencer bolts to the stock y-pipe, any other bolt-on cat-back should also bolt right up to the presilencer.

I have stock mufflers for $100 shipped. They have less then 1000 miles on them. PM me if interested.

you should stay stock.

Can you give me some links to the 6 port mods? I cant seem to find them..
also, whats so great about staying stock? BTW, I have a brand new engine- are you suggesting I stay bone stock or just keep the exhaust the stock SIZE? I know I could make some gains with a header and an AFC..which are next on my list.

I would say, go 2.5in. Its one of the biggest sizes you can go NA(on any car) that will give you the best gain and no loss of power. The 5+6th ports need like 3-5 psi to open up so most anything will do.

As far as brands of catbacks, id say make your own. I'm making one myself. I bough some 2.5in pipe from summit, and have a friend with a welder. So oneday we are gonna weld it up. All in all, its gonna cost me less then 50 bucks(I already had 2 mufflers). It should be less then 140 to build your own(if you buy flanges, pipe, mufflers, and dont have to pay a welder)

https://www.rx7club.com/2nd-gen-archive-72/how-air-pump-auxilary-port-activation-330310/

http://www.rotaryresurrection.com/2n...elec6port.html

http://www.rotaryresurrection.com/2n...actuation.html

sorry, it was rotaryresurrection that had the write-up, not fc3spro

ok....i was at home depot the other day and they could get me a "dump/vent valve" bc they didnt know wtf it was. does anyone have a picture of theirs? is it just a open/close valve that u leave cracked?

:lol2:

Attn: Rotary Ressurection...
 

I read through these, I have a couple of questions- the air pump method is cheap and effective, but I cannot (or haven't yet) been able to figure out how to put vacuum on it at low rpms until the trigger at 3800-4k..
It seems that the electric pump has an advantage since it can apply vacuum at low rpm and pressure upon activation of the pump (maybe even if you could get it to have built up a resevoir of pressure and when the vacuum solenoid opens the pressure immediately opens the ports instead of the buildup lag- maybe its unnoticeable just an idea:scratch: ) yet the need for an rpm switch SUCKS, since I don't have the budget for one even used- is there no other source of power or ground at the necessary 3800-4k range that would suit a splice to activate the relay for the pump? Nothing that runs through the computer? Maybe even if it needs an additional relay wired in to keep from spiking the ecu?
Hopefully kevin will read this, perhaps he's already thought of this and nixed this idea...maybe not.
Crazy- temp switches are cheap, you'd think you could get an rpm switch at a budget price since you can get $10 timing lights...

"maybe even if you could get it to have built up a resevoir of pressure and when the vacuum solenoid opens the pressure immediately opens the ports instead of the buildup lag- maybe its unnoticeable just an idea"

i'm not sure if i am reading this rite but are you saying that you want the ports to open earlier than stock? if you are, i think you have a misconception. some people DO forgoe the 6pi system and just wire the ports open. this however causes a significant drop in low rpm torque (not sure of the numbers, but its significant enough that mazda spent time and money in R&D to develop the 6pi system. conversely, if you keep them shut, then you lose like 25 horses up top, or so i hear. as far as your other questions, i dont really kno what to tell you, i still have working actuators and stock exhaust, so no personal experience here. hopefully kevin will chime in!

No, no no no, I was just saying since they should open and close quickly from what I have read that having a blast of 5psi loaded ready to go when the vacuum solenoid opens would open that 5/6 ports up very quickly, as opposed for waiting the 2-3 seconds (i am guessing, maybe an additional 500-1000 rpm increase in my mind) for the electric air pump to come up to speed and produce enough pressure to open the ports. Thats what I am saying- and when RPM drops the signal dies and the actuators get a vacuum and close the 5/6 ports up fast as well..
but you probably wouldn't get any benefits from it unless you are trying to shave hundredths off of your quarter mile or something..

but the main question was about any power or ground that can be used as an rpm signal- I am thinking, maybe the ground for the secondaries could ground out a relay with 12v on one side and air pump/ground on the other and switch the pump on? The secondary injectors have power all the time but get ground from the ecu at 3800, right? maybe when they kick in would be a good time to open the ports- that's what I was getting at- using another signal reference for rpm/relay as opposed to buying an rpm switch for $100+?

Actually- I realize I sound dumb, now that I think about the secondary injectors being a good circuit I forget that ground is not constant after 3800 it pulsates at the speed the injectors fire! Man, can't believe I missed that before posting ^ lastnight..it would need a constant power or ground activated by the ecu or other circuit at 3800-4k rpm- are there any? Maybe a transistor could be utilized, PNP..but what could cut power to the resistor after the rpm drops again? I guess what I need is someone to figure out a simple rpm-activated switch that can be soldered up at home with parts available at RadioShack, and I am thinking THEN the pulsations on the ground of the secondaries could be used to power a relay for the elec air pump through some more simple circuitry than the multi-function MDS RPM switch and others....I gotta hit my electrical engineering books tonight..
I am definitely thinking if I want to do some exhaust work my first step is to get my 6pi sys working- when I got my car back from the mechanics I had a vacuum line attached to my actuators, since I put the split air line back on correctly there has been no change in performance- which hints that my 6pi isn't even opening- probably those leaks in my system..get the ports working on electric triggers and do whatever you want to the exhaust is what I am thinking- doesn't require high back pressure any longer to activate the ports right? So 2.5" all the way back, headers, straight pipe, etc.

hi zzzoomzoom. i am on dfw's with you. i am wes.pro5


i have a racing beat and it is reasonably priced. it also isn't too loud.

can someone tell me what a dump/vent valve is and whatit looks like? the guy at home depot had no idea what i was talking about.

a dump valve is just a valve that dumps air- there's a pic of a setup in the links provided by TOUCH, the forum post not rotary ressurections site..
but you can use any valve that opens and closes airtight I would guess- even a toilet valve or something- probably best to get a valve with a 90* on/off knob, maybe a nylon socket valve probably would be ideal..

Don't waste money on an AFC for your NA.

before i bucked up and got my racingbeat was gonna get the corksport header and a race pipe racingbeat presilencer then finish it off with the apex n1 cat back all 2.5in but the racing beat is so worth the money it has the perfect sound and the true dual all the way back not to mension its goes on perfect. if you dont want to spend too much you shoould look on the forum, e-bay, or craigslist

p.s. looks goooooooooood (not my hunk-o-shite car)
http://a949.ac-images.myspacecdn.com...f0b886b53c.jpg

Header, 2.5" high flow cat, 2 mufflers of your choice, something SS in and out, borla, magnaflow, or something stock replacement.

Relatively quite, good sound, works with aux ports, pass emissions, inexpensive.