Exhaust related question
 

so my frirst payday with my new job is wednesday... and i decided i am finally gonna give my baby the muffler she has been waiting for.. (yes my car LOL)

i got a 2 inch catback system... (had muffler too but EPA didn;t like it so i had 2 take it off... currently running stock)..

want i want is a muffler that isn;t restrictive yet quiet...

e.g my previous one was a noname brand straight through muffler... which sounded BEAUTIFUL... but i lost alotta low down torque (understanbly..)... while higher end i did notice much better accelerations...

what i want is something that wont drop low down torque too much... but yet keep the high end acceleration good...

what i was told was with N/A engines u have to match up the intake of the exhaust with the tip size... so 2 inch inlet = 2 inch outlet... this true?? to keep a good level of bak pressure or somefin??

also the quietening thing... like stock mufflers have 4 sections it goes through from intake to outlet correct?? which makes it very restrictive...

so am i best goin with 2 sectioned muffler??? because that way i can have it quietish... keep the low down torque to a decent level and top end good as well??

okay enuff of my essay... is my thinking correct??? or am i just rambling horse poo poo???

From what i understand its
Exhuast Design that is key, Then i guess the size would come into play. Also if you were to really beef up your intake system and Engine i am sure you could optimize and go large diameter but hey just theory

Exhaust backpressure is NEVER desirable in and of itself. It is simply an unwanted byproduct of the need to keep the exhaust pipe diameter small enough to maintain sufficient gas velocity to obtain maximum extraction of the exhaust gas from the combustion chambers. This is why too large a diameter exhaust pipe actually impairs performance on a NA engine. Diameters somewhere between 2" and 2.25" are in the ballpark for our engines. For example, Racing Beat's cat back for 3rd gens utilizes 2.375" tubing.

Reference: The Scientific Design of Exhaust and Intake Systems, Third Edition, by Philip H. Smith and John C. Morrison

Do you have the sedan?
Honestly, I can't see how just a muffler/axle-back exhaust is going to make any noticeable difference in torque output. Sorry, I can't see it happening.
Which means it's all gonna come down to how you want it to sound. Personally, I like my Racing Beat axle-back. It's quiet enough, a nice rumbling note at idle and louder than stock at WOT.
I don't know what your options are in Australia, but I bought mine directly from the Mazda dealer. It was the "performance Exhaust" NOT the Mazdaspeed exhaust, which is an entirely different animal. Mine is very similar to the MP3 axle-back and was made by Racing Beat. Maybe you can find a used one? I dunno, you could check with the dealer first.

hey... LOL sif i ma do just an axel back.... i have a catback exhaust system ( just had 2 change thr muffler to stock one because of EPA issues... cat back pipe is around 2.1inches or somefin)...

i want to get a better muffler now because it was payday for my new job today hehe :D:D and its about time i got a proper muffler...

racing beat hey... will look into that.... my exhaust shop said they can custom make one up for me... (which they did for my friend... and sounds great and flows great too)...

magnaflows any good?

Racing Beat, all the way...but don't expect big performance gains. BTW, some mazda's used backpressure to actuate the six ports (in the 2nd gen. N/A RX7), but this system didn't work well from the factory, lol.