I was thinking about getting a straight pipe, about 2.5inch, straight back from the exhaust manifold to the rear passenger exhaust exit. No muffler, no cat.
Now, give me your advice as to why this would be a good/bad idea for a street ported n/a 13b dd.

And if you say it would be bad, please give me other suggestions as to what to do.
I've searched the forum and I've weighed the consequences of going straight pipe with no mufflers.
Sound is really the only negative I could find.
It is an s5 as well, I know the s4's aux ports are actuated by the back pressure of the exhaust system, right?

 

everyone's going to have their own opinion about going straight pipe but aside from the sound, the smell of the exhaust is going to be overwhelming in traffic.

i say if you wahna try something you should go ahead and do it, you can always reinstall the old exhaust(:

 

+1
That's sort of the other thing I figure.
I just want to hear that noise in person. lol.

 

Straight pipes with no muffler will be entirely too loud for a street car, as this configuration is banned at most race tracks due to the noise. You will need at least one good muffler intended for rotary engines, and a presilencer isn't a bad idea.

Also, 2.5" is too large for an NA, and power will suffer. For best performance, you will need to stick with an inside diameter of about 1.75" for the primary pipes. If you like, you can gradually incerase the diameter as the exhaust piping travels to the end of the car. See the Racing Beat guide for custom exhaust:
http://www.racingbeat.com/mazda/perf...gurations.html

 

Terrible idea for a car that's going to be driven on public roads.

Get a REAL exhaust that's intended for street use. There are SO many choices out there for catback exhausts...generally the less money you spend the louder it will be.

 

Yeah seriously I drove my car with a straight pipe to a magnaflow muffler and it was still retarded loud. I had a girl in my car once and literally told me to stop at an intersection and let her out lol

At least get a presilencer along with a good muffler if you want to keep your hearing

 

thats the thing about rotaries and performance engines if you want to get the most out of porting the exhaust will have to be well designed.
a good starting point on a street port is 1.50 with a less restrictive cat and a decent muffler
then you can alter it as you go along
my 86 n/a set up was a 1.50 to the cat 1.75 to the muffler with a street port and it sounded sweet at idle but roared at high revs, and dynod the highest of all the other straight pipe settings i tried w/ cat and muffler. i did get the r/b duals but never dynoed it(since it was stolen before i could) so i wouldnt know if doubles are better.
its all about balance and if you want to hear your car as if it had a straight pipe run it with only the headers to satisfy your craving.

 

You'd stop driving it within a few days, if not hours. You wouldn't be able to do anything, and you'd get pulled over a lot.

 

Well, not everyone would. Of course I didn't have much choice. Long story short I drove my TII around with only a downpipe for a month and managed to not get any tickets, but my ears hurt every day. I will never do it again. A straight piped NA would be of similar volume. Don't do it. It'll set off car alarms, it'll **** everyone off as if you're a Harley ***, it'll practically abort passers by's babies. Don't do it.

 

i have a 2.5 inch straight pipe with a muffler. After driving it for over a year, i havent been pulled over, it has decent power, its ******* loud, and it sounds ok. (comparing to civics)

but nothing beats racing beats, they are the best way to go. good sound, good performance, good everything!

I am only staying straight pipe because i cant afford racing beat yet. I say run a straight pipe, if you like it keep it, if you hate it, go back to stock and save up for racing beat.

 

The turbine wheel reduces the noise by about 6db, which works out to about 30% less noise than an NA when driving down the street. This is why NA cars are so loud when the owners install mufflers intended for turbocharged cars.

 

I figured downpipe only with turbo versus full length straight pipes would be pretty comparable considering the exhaust came out right under the pass seat as opposed to out the back. I believe you that the NA's can be louder, but either way it's way too loud.

And when I drove it downpipe only, I didn't baby it... I came up to a Camaro with a rumbly exhaust and when he heard me he got on it, so I did, too and I couldn't even hear him right next to my rolled down window

 

You would need earplugs to drive it. I had a 2.5" straight through to an Apexi 3" muffler and it was insane. Needless to say I got ticketed and had to go back to stock.

 

throw some free flow mufflers on and call it a day thats what i did....... i havent gotten pulled over yet. tho some say i sound like a jet.........

 

My S5 n/a is straight piped to a ebay single exit 3" catback with foldgers can(muffler) on the end. Putting the silencer insert in there makes a world of difference for street driving. Its obviously still loud but I can now hold a conversation inside of the car.

A friend with a 12a powered S3 is truly straight piped, from the header to bumper, just pipe...now that is ******* LOUD.

 

I actually thought that 2.5 inches was the standard exhaust size for a ported n/a.
From what I'm gathering here my current exhaust system is probably good enough until I go turbo.
I've got a stainless steel custom exhaust that is about 1.75inches with a high flow racing cat and two mufflers? I'm not for sure what brand but my brother said they weren't cheap (they look like stock mufflers).
I was thinking a straight pipe, no cats, no mufflers to really open up the exhaust, but if it is really that unbearable on the street I won't bother.

 

what silencer did you use? was it just a ebay silencer, just asking because i need one

 

i drove my tII 13hours straight with a straight exhaust, and keep it that way for 3 years. really was not that bad. but it was a turbo so not as load as an n/a will be. i have a duel setup now, i would never go back to a straight pipe.
my non turbo supra will make my head hurt if i drive it to long and it has a straight through muffler and resonator on it. i would think an n/a rotary would be louder than that

 

I'd think anything, so long as it didn't fall apart from poor craftsmanship, should be fine for a silencer. The exhaust temp is WAY lower at the tailpipe than at the manifold.

 

I would atleast throw a cat on. Straight pipes are fun if you don't drive the car that much, but yours is a dd. I'm sure you'll grow out of having a loud car, or atleast I did...

 

either that or you'll mysteriously start asking people to repeat themselves more often

 

yea i would have to say i have a precat with stock manis but race piped from there to free flow muflers and when the mufflers had the silencers in them it was nice but not loud enough for me, althought this is not s DD but a fun around car, if i was you just use muffler that have there own silencers and just take em out if it aint loud enough for you, then if u want them qieter just put em back, takes 2 screws, one per pipe