6MPS Exhaust options

[Yeldarb]

You can save yourself a few dollars by re-using the std rear mufflers.

Having the DP done at a separate time won't cost the earth either.

I did a full TBE excluding the rear mufflers on Penguin740's car. It has a note under power, but very minimal at idle, if at all. It is a full 3" system with 1 cat and 1 resonator.

A little off topic but could you do a similar "y" piece on a GENII?

[mazda6mps]

Thread is a bit old, but i thought i'd chime in about the CPe dual cat back exhaust system i got from MPS garage.

Start up - loud and deep, to the point where if you are in an enclosed area, your ears will hurt, and you will set off sensative car alarms - but i love the sound at start up, it travels right through you and you know the car is alive;
Idle - relatively decent and quite, deep tone again - very pleasent;
Crusing - drones, to the point where even my girlfriend ended up turning up the stereo to drown out the drone - i've since laid some dynamat and some shielding within the boot, and the noise is still quite dronie;
WOT - very loud, head turning loud actually, to the point that if there were cops around, they would probably pull you over, so i haven't done WOT for a while now.

I don't have a dump pipe done yet, but apparently this only increases the loudness of the whole system.

I will probably have to spend some money on fitting a resonator/hot dog just after the stock CAT. I think the drone and the loudness is attributed to the muffler straight through design, but hopefully what i want to do will help with some of the droning.

Quality wise, the welds are good, the quality of the stainless is good as well. The only beef i have is those f**ken clamps and the slot design - install is not fun, getting all the pipes slotted in place, and unless you tighten the clamps with a rattle gun, you are going to get exhaust leaks - so i might at the same time as getting the extra resonator fitted, have the guys doing my exhaust work fit proper flanges where the clamps are so at least I can get a nice seal to the system.

[rogwick]

Hey mate, most of the drone would be coming from the pipework in combination with the mufflers. Although stainless may look great it carries a lot of noise and resonance with it. I have a coated mild steel exhaust complete with two resonators. Drone is minimal - none in my car. Provided on cold start it sounds like a beast, can't help that. The different between a mild steel and stainless is...if you to grap a tool (spanner or something metal) hit the catback on the stainless you would hear a loud "ting" on the mild steel more of a "clack" hence where the sound and noise comes from. For stainless being more expensive I decided on a mild steel option. See how you go after fitting one or two resonators as that should help!

[Doug_MPS6]

Contrary to popular opinion, the stock mufflers are not that restrictive. This was averred to by Genie who looked at mine when I was debating a revised setup and trialling the CP_e 3" SS arrangement. The DP is the biggest single improvement you can make to the exhaust. Genie also held that the 3" all the way through setup was, if anything, overkill. It's easy to do the sums on the relative cross sectional areas. 1 x 3" feeding into 2 x 2.5" or 2.75" is just fine.

Straight through mufflers such as the CP_e will be too noisy for civilized use, so I elected to stick with the existing ones. There is no difference in internal noise experienced when running at any road speeds, but a healthy note on-song to an observer, I am told. The mild cackle from a cold DP getting lots of rich fuel on first start of the day, but it settles down in 15 seconds to completely quiet.

[ppham]

Bumping this old thread.

I'm considering a similar setup to what has been discussed here - 3" Downpipe, 2.5" or 2.75" custom catback with 'Y' split and retaining stock mufflers.

I want to know what sort of difference i can expect from either going for a 2.5" or 2.75" mild steel catback. And would 2.75" somehow enhance gas flowing or improve the mating capabilities? (3" downpipe feeding into 2.75" catback into 2.5" stock mufflers)

I should add, I'm aiming for power gains but without the affects of droning. I've also heard that changing the downpipe would increase top end power, but you lose on bottom end. Is this true? Can anyone confirm this?

Thanks for help in advance!

[kmh001]

Keeping the stock mufflers is the smart way to do it. As Doug indicated, they are not restrictive and there is plenty of evidence about that.
The system described by 2XS is the way to go. The key to getting the design right is how you approach the Y piece. I recommend doing the DP as well, then go with a matching 3 inch pipe to the rear diff and use a 15 degree merge collector with a pair of 2.25 inch mandrel bent pipes swinging around to the mufflers. I had a cpe DP installed a while ago, then after a long search I recently found a fabricator with the skill and equipment to make up the mid-pipe exactly as I described above. It only cost $420 for the mid-pipe in SS and the results are impressive. The DP and this mid-pipe work extremely well together. It's probably the most cost-effective mod I have done on the MPS.

[ppham]

Hey kmh001. I've read some threads lately about exhaust options for the MPS6 and your name keeps comeing up on alot of them lol. Your comments are the main reason why I am going for the exhaust system stated above.

But there are no comments about the pipe size options for the catback, they only suggest a 2.5" or 2.75" will do the job. I want to know the reasons for this and what the gains and drawbacks (if any) for going a larger pipe, i.e 2.75" or 3". Maybe someone can explain the differences and benefits of 2.5" vs 2.75" vs 3" catback exhaust system.

And by going for difference pipe sizes, for example 3" DP to a 2.5" catback, would this cause any leaks (or any problems) in the connection? I'm getting the impression there would be a gap, so might leak due to size difference.

From my understanding, you have a full 3" system up til the 'Y' split (like Penguin's?). What are your reasons for the 3" piping on your current system? Did u add any resonators to the system? What are your experiences with this setup in terms with power gain, droning and scraping? My concern for the 3" pipe is scraping as I'm currently lowered.

I notice u have a VersaTune. I'm going for the same thing once i get my exhuast system figured out (last piece of the puzzle)

[kmh001]

My reason for choosing 3 inch is because a respected engineer in the US tested a few configurations and proved that this one gives the best gains. If I remember correctly he also tested 2.5, 2.75 and 3.5". The 3" pipe works best and fits fine - my car is lowered. The stock mufflers are acoustically tuned to suit the car so there is no need to have power-robbing resonators and there is no drone.

[kevstewart]

This thread had made me want a new system... I already paid £440 for this bad workmanship:

[bd581]

Oh my god!
How can people like that still be in business?
I would be parking my car at the shop and showing every customer that came by until it was fixed. that's just shocking