I'm wanting to build an exhaust for my Naturally Aspirated S5 FC with stock ports. I have a general idea of what i want for an exhaust, but am also seeking feedback from people who are more knowledgeable and experienced with exhaust performance. My goal for this exhaust is not so much a full race exhaust but rather something that does give power gains and looks good at the same time. Do note that this exhaust is for my daily driver but none the less, noise level isn't much of a concern. As of right now, my plans are to buy an aftermarket header(undecided and short on funds for header), then running 2.5" piping keeping it as straight as possible and welding it to a Magnaflow 2.5" in/out muffler with a 3"flange on the opposite side(note: this muffler will be before/by the rear differential), and will connect to a 3" Titanium Resonator with a 3" Titanium extension pipe.

i was shown this thread today, and basically made me rethink my exhaust setup which is how i ended up with the idea i have now:
https://www.rx7club.com/naturally-aspirated-performance-forum-220/informative-exhaust-tuning-what-part-system-actually-tunes-883371/

Please let me know if you have any suggestions for me, I'm open to ideas so let me know. Heres pictures of my Magnaflow and Titanium Resonator i plan to use:

 

i think you're on the right track...

basically you've picked the 2 mufflers, and pipe diameter, so all you have to do is pick a header length, and maybe collector too, if you've got room.

2.5" is a good diameter, and with 2 mufflers it might not even be loud

 

im still not fully understanding how a collector works, or even looks like to be honest. im gohna google it but if you could fill me in i'd appreciate it. pictures would help too

i have this 3" stainless steel cat replacement, would this work as a collector? again i dont know how a collector works, so maybe this is too big anyway?

 

This is a collector:



Many aftermarket FC headers come already collected (each individual exhaust port's pipe merging into one single exhaust pipe). The only one that does not come collect that I know of is Racing Beat's Road Race header.

 

i did a quick search and i ran across what could be the headers i would want to use for my setup. its off of someones thread and he states:

"Now available at the shack, the MAX POWER header! This new product has been in testing for some time to insure maximum power/torque output with longevity in mind as well. This finished product ending up being made from 16 guage 304 stainless to minimise cracking. The primarys are 1-7/8" to a 2" merge collector to a 2-1/2" to a 3" collector, while the exit size is 3". They are available with or without the crossover tube, as well as 12A or 13B. Also, an o2 bung or EGT bungs can be added for optimum tuning. These headers are guaranteed to make more power than any other production run header sold!!! These headers are built to win races and break records!!"

of coarse i'd be using the header with the 2.5" collecter but none the less, here's his pictures and link to his thread:



https://www.rx7club.com/general-rotary-tech-support-11/race-exhaust-sytems-828749/

 

better yet, here is the link to rotaryshack's website:

http://www.rotaryshack.com/customheaders.html

gohna be honest, i saw the price and wanted to cry lol talk about pricey!

 

Yep! Honestly if you're running stock ports, I would be surprised if there was anything over a few horsepower difference between all of the off the shelf headers. If that few horsepower is worth the extra $350 for Rotary Shack's headers (assuming those are the optimal headers designed for stock FC ports), then by all means get them!

 

well yeah of coarse im not expecting a huge marginal difference in HP gains with headers, but i am looking for some gains over stock. I am rethinking getting the rotaryshack headers. i think i'll just go with what i can afford sooner, a used set of RB streetable headers. it just seems that the rotaryshack is probably something i should consider once i have some sort of porting done to my car. i emailed rotaryshack last night asking for a price quote and which porting the header was designed with

 

When I was researching headers, I came to much the same conclusion. Instead of the Racing Beat collected 13B header, I opted for the Corksport header. During my research I read several threads saying that the primaries were too long in the Racing Beat for a short primary setup, and too short for a long primary setup. Since Corksport's primaries were shorter, I figured that they would be a better short primary header than Racing Beat's.

However, I urge you to come to your own conclusion.

 

RB picked a header length that gives you about the same tq peak as the stock parts do. iirc its about 31"

most race cars used 24-26" long headers, which will move the tq peak higher.

the RB length is great on the street, it gives a broader flatter powerband, shorter header might give a couple more peak hp, but it'll have less low end.

the long primary setups are like 90-120" so we're not really talking about those at all.

 

honestly i wouldnt mind doing that either. do you by any chance have headers you might want to sell? if not i'll just go the cheap way out (temporarly untill i have funds) and purchase a pacesetter header off of someone that was selling one to me for 40 bucks. i just the old out and the new in lol but definitively want to avoid using the stock header

 

My setup is on a similar engine. It's a rotaryshack header, shortened a few inches, to a 3" magnaflow spun cat, to a 3" magnaflow main cat, back to a small 5" diameter resonator, to an oval summit racing muffler.

The primaries are a little on the short side but I needed them to be (racing class rules) and with this setup the exhaust is not loud at all. 87dBA at 50'. Very tolerable.

If you can, I would retain the catalysts. It just makes the car so much more pleasant to drive.

Haven't dynoed with my latest setup, but the car pulls very well.

John

 

I will have a used set of wrapped Corksport headers that I used on my car for sale in a couple weeks, but they'll be a far cry from $40.

 

when you refer to keeping the catalysts and making it more pleasant to drive, are you refering to the smell of fumes and noise level?

 

well shoot me a pm, lets work out a deal

looking to run a new setup?

 

i want your opinions on a Racingbeat S5 Presilencer. anyone know if they effect performance?

also, since i will be running a catless setup will all my ports still open?

 

You can get the noise level down and improve the quality of the sound with the right mufflers / presilencers. But you can't get rid of the smell without running cats.
It's worth it.

 

Since you're running an s5 N/A engine setup, your cats open from the computer telling them to open, not backpressure like the inconsistent s4 N/A system.

RB presilencers are amazing at cutting down noise without hurting power.

 

i definatley think that running cats will be something i will do later on, without a doubt

but for now, i think im going to try a catless setup and see how i hold up lol

cats arnt too restrictive right?

 

oh good! so do S5's even have that air valve pump connected to the cat?

im soo glad i opened this thread, its been so helpful. Thanks for the suggestion bro

 

The cats I listed are cheap. Even if you just run a main cat, it won't cost you much and it will be worth it. Unless you want your eyes to tear up every time you stop for a traffic light. And your clothes to smell when you drive your car.

 

I also recommend using a cat in the system, although it will hurt power more than a presilencer will. However my reason is different then SoloII///M's reason for running a cat. Just by running a single main cat, you will cut down on the hydrocarbon emission into the atmosphere by great amounts.

 

+1, main cat alone will pass smog = eliminate the stinky, and hardly cost any power on a stock port engine.

my stock exhaust S4 na only has about 3.5 psi of backpressure in the exhaust @redline. that's stock too, stock manifold with 2/3 cats (it was 4.5, i found one cat to be melty), and stock cat back.

with larger piping, less restrictive mufflers, and a header, you should be able to flow a lot more...

 

well since i am a low on funds, i'll focus on getting the header and presilencer first. Do you guys recomend the bonez high flow cat? seems like they really withstand the rotary heat quite well.

 

I recommend the Bonez and thats the brand I just picked up for my car.

Here is the website I ordered it off of. http://rx7.com/store/rx7/fcexhaust.html