another dual exhaust thread..

ninjajim4 · Post by **ninjajim4** » June 16th, 2005, 12:18 pm

hey gang,

well, i'm looking to get a new exhaust system put in, and i'd like it to be dual exhaust for aestetic reasons, though i realize i'll be losing out or breaking even on performance.

from what i've read, the way to go seems to be one cat, two mufflers? i am thinking 2.25 piping to the cat, and then maybe 1.75's on the way out?

also, i am looking to swap to a klze in the not too distant future, so i am hoping on getting reccommendations as to what to do now, what to wait for after the swap, and hopefully if there is some sort of middle ground that i can do now that will work nicely with both motors, but that's probably wishful thinking... would getting a high flo cat for the k8 be a waste, like some have been saying?

and one last one... i'd like for this ride of mine to have abit of a growl, but i still want be able to have a conversation in the cockpit. magnaflow seem like a good pick?

thanks for your input

hgallegos915 · Post by **hgallegos915** » June 16th, 2005, 12:52 pm

what is your reason specifically for doing this? :s its gonna look like a rocket and sound like a truck. Is it a ze?

mitmaks · Post by **mitmaks** » June 16th, 2005, 12:53 pm

I would add x pipe too

ninjajim4 · Post by **ninjajim4** » June 16th, 2005, 12:58 pm

because i have this bumper:

http://pakfeifertuning.com/store/images ... _neu_4.jpg

and it looks like crap with only one exhaust, IMO. and i want to make sure i'm getting actual emission outta both exhausts, since i'm not interested in something PURELY aestethic.

i'd avoid it sounding like a truck if i could, but i'm afraid it WILL look kinda like a rocket

ninjajim4 · Post by **ninjajim4** » June 20th, 2005, 12:47 pm

well i got back from the exhaust shop with nothing done at all -- as it turns out there's just no room for a second muffler, because of the spare tire compartment.

i know i've seen ppl with two mufflers so how did they accomplish this?? the guys at the shop suggested cutting out the compartment altogether and welding a flat sheet across, but i dont want to sacrifice the trunk space or go through a lot of effort for what is essentially a completely aestetic mod.

any comments, explanations or ideas? thanks

Post by **Custommx3** » June 20th, 2005, 1:35 pm

Im not sure if most of you know this or not, but we have a semi-dual exhaust system already.

"From the mazda SAE K series design papers"

By adopting the semi-dual exhaust system in which two exhaust pipes have almost the same length, torque was raised in the desired, mid speed range

Nd4SpdSe · Post by **Nd4SpdSe** » June 20th, 2005, 1:40 pm

ninjajim4 wrote:i'd like it to be dual exhaust for aestetic reasons

hgallegos915 wrote:what is your reason specifically for doing this?

I though it was pretty obvious

Custommx3 wrote: By adopting the semi-dual exhaust system in which two exhaust pipes have almost the same length, torque was raised in the desired, mid speed range

Those almost look like a concept for headers

Flashpoint2 dual exaust is just T-ed off near the end

PATDIESEL · Post by **PATDIESEL** » June 20th, 2005, 1:49 pm

If going dual exhaust you need two things to make it happen and get good performance out of it. First you HAVE to cut the spare tire well out. There is no way around it. You need the room for piping and the second muffler. Secondly you need to get a "X" pipe or cross pipe like Mitmax said. This will even the flow of exhaust out so that one muffler isn't doing all the work. Race cars and well tuned properly set-up street cars use them. What you do is use one high flow cat, the nafter the cat you split the pipe into two seperate ones then about half way down the car you have a "X" pipe that connects the two again and lets the exhaust gas pressure equal out between the two. Then after the X pipe you place your two mufflers at the bumper. As for pipe size let the guys at the exhaust shop help you decide. You'll want to get a common X pipe size so that you don't spend a fortune on a custom one. As for mufflers, the Magnaflows I've heard on ZEs are pretty loud, I'd get a 2 chamber Flowmaster, they are pretty quite when cruising and get mean with WOT. Good luck and post pics of the final product if you go ahead with the project.
PS, this is NOT an astetical mod, it is performance, and if you treat it as astetical you'll be sorry with the results. Spend the few extra dollars and get a good result.

ninjajim4 · Post by **ninjajim4** » June 20th, 2005, 3:06 pm

wow, thanks for all the informative replies, guys.

I'll be sad to lose that spare tire well, but if that's what it takes..

Pat, I've read up on the few posts there are regarding this, and I don't think anybody has said that there is any performance to be gained from doing this mod -- hence my hesitation to start sacrificing trunk space. if that's not the case, then i think i'd find myself a little more willing.

i have two questions before going further though. is all this something i should hold off on until the ZE gets swapped in?

and if i were to hold off, this will make ppl cringe... but is there enough space under there to not mod the trunk and just have one muffler, two tailpipes? again, that'd be just for the looks.. and it'd be just for now.

PATDIESEL · Post by **PATDIESEL** » June 20th, 2005, 9:10 pm

as for a gain in HP for having twin pipes. It should be the same as a single if done properly. The thing is what is properly? No one knows since not many of us do a twin pipe set-up, but I'd bet you will loose a few ponies. Maybe 10 at most. Talk to a GOOD exaust shop and they will let you know more than any of us could ever tell you.

jschrauwen · Post by **jschrauwen** » June 20th, 2005, 10:06 pm

Tatsu always seems to have a pretty good handle on the dynamics of exhaust systems.

Chronicle-Rod · Post by **Chronicle-Rod** » June 21st, 2005, 5:16 am

If you just want it for looks, cut the second exhaust so it'll fit and wire it up. It won't be functional, but if you're just going for looks anyway...

Otherwise, yeah - you have to cut out the spare tire compartment and sheet metal it over. For me it was an easy decision, with the larger rims I'll never run a donut anyway.

Nd4SpdSe · Post by **Nd4SpdSe** » June 21st, 2005, 9:23 am

PATDIESEL wrote:as for a gain in HP for having twin pipes. It should be the same as a single if done properly. The thing is what is properly? No one knows since not many of us do a twin pipe set-up, but I'd bet you will loose a few ponies. Maybe 10 at most. Talk to a GOOD exaust shop and they will let you know more than any of us could ever tell you.

This may not be related to backpressure, but it'll be good for explaing a proper exaust setup

ninjajim4 · Post by **ninjajim4** » June 21st, 2005, 1:54 pm

[quote="PATDIESEL"]as for a gain in HP for having twin pipes. It should be the same as a single if done properly. quote]

this is why i am against going balls out for this mod. a lotta work and money to end up with a different look but same result (at best).

does it much make a difference (perfomance-wise) if there are two tailpipes coming outta the muffler instead of one? i wouldnt think so, but then my opinion doenst count for much since there is absolutely no knowlege behind it.

georgechicken · Post by **georgechicken** » June 21st, 2005, 2:05 pm

Wow.. I disappear for a few weeks, and this is what I come back to find... <breaking out the paper towels>... lets clean up some mess here...
First, As Chronicle-Rod took the words right from my feeble head and spurt them here, if you're doing it for aesthetic reasons, then just slap a second muffler and tailpipe up there without altering the rest of the exhaust. That's not a smartass idea, either. That is honestly my recommendation. However, I get the feeling that someone is hellbent on having a fully functional dual exhaust system, so I'll take you down that road... First, You'll have to have an exhaust shop either fabricate a collector pipe assembly (the part shown in the drawing that Barry--custommx3-- added a few posts back) or you'll replace the exhaust from the exhaust manifolds all the way back. As PATDIESEL said, if you treat this just as an aesthetic modification, you'll regret it. The only way to make it happen without butchering the performance of your engine is to just slap on a non-functional second muffler and tailpipe. Altering the factory exhaust is going to destroy your low end power/torque, especialy if you go the route of a true dual exhaust using 2" piping (or more). As to why, refer to the "Backpressure FAQ" thread at the beginning of this forum. It is marked as 'sticky', so it always stays at the top. My final observation goes a bit like this.... I can't imagine that you'd be swapping in the KL-ZE for aesthetic reasons (if you ideed ARE, then make a trip down here to Nashville so that i can slap you.

)... Something tells me that you would swap a ZE into your car for more performance... If you're willing to spend the thousands of dollars to make a ZE fit and work, then why would you dump insane amounts of money into something that will only compliment your bumper while seriously taking away from the same performance that you're going to pay out the nose to gain? It seems a bit wasteful and ignorant to me. DO read the Backpressure FAQ thread though. It will enlighten you (I get the feeling that you, as well as many others) have a grave misunderstanding of 'backpressure' and what an exhaust system is for in the first place. After reading that thread, you may then get a clearer understanding for why the dual exhaust that you're chasing is going to be a bad idea.
One last thing... I'm NOT saying that a dual exhaust would not necessarily be cool on the MX-3. As a matter of fact, our favorite moderator (well... close) Barry Clark (custommx3) and I spent several hours outside of the Mazda Farm (his garage) one recent night talking about what it would take to make a better-tuned exhaust system, and make it into a dual setup at the same time... When we stopped discussing it, whatever we came up with sure sounded cool (envision a side firing exhaust setup, bringing each pipe out either just behind the front wheel or just in front of the rear wheel... I dont remember which it was), but would be a ROYAL pain in the a-- to build (it involved fabricating longer exhaust headers and eliminating the collector pipe setup, and God only knows what else)... Do let us know what you end up doing. I'd be interested to see how someone would build their own dual path exhaust system, and moreso how it performs. Good luck!

Daniel