NEW PHOTOS AT BOTTOM OF FIRST PAGE 4/25/11
ok, so its time for me to upgrade my exhaust.
Im doing a full SS catback (already have aftermarket header) 2.5" od the whole way with a cutout that will still go through the tips when opened.

this is the original cad drawing (i didnt connect everything, it was just for conception and angle on the bends i would need)
even though the system is convoluted, it follows the same path as the stock exhaust, but with smoother bends, and better flow


PIPE CAME IN!


i went with 2.5" in/out vibrant ultra quiet resonators. Even thouth they are straight through, i can screen into these things, and it is of "inside voice" level on the output. and im running three with the valve closed.


inside the vibrant ultra quiet


new tips
dual 3.5"out magnaflow corvette c2 style tips


started cutting last night
quick mock-up, obviously no final cuts, just showing flow pattern to a friend


closeup of the bottom bend


made the t and ive already finished the rest of the bends, the ones post cutout are not shown.

 

this is quoted from my club forum by john (he has a garage.. were college students... and he took some pictures)
This is my first exhaust, and i did every cut without help, and the only help i received designing the system was from juston in atl as to what resonators/mufflers to use.
(im brad, Richard is in the welding gear)


well i started polishing it up a bit, but still to go, i have to run the 4 foot section of pipe, put a kink in it to get it to go into the middle brace correctly, and then weld in the last resonator just after the header. We also have to finish measuring and cutting the pipe for going out the back of the mini, as well as welding up the exhaust hangers.

and here are a few after i polished it up a bit

 

Can't wait to see/hear a video clip of the final product on your ride. Looks pretty unique.

 

Awesome. Love seeing this kind of homebrew!

 

Looks pretty good, could you fit those ultra quiets end to end in the tunnel if there wasn't the battery box in the way?

 

interesting project

where did you get the valve ? any info on that ?

 

Very nice!
Looks like a professional job all the way.
Great engineering!

 

Keep the pictures coming , cant wait to see the finished product.

 

finished the welding today. had to hammer in the bottom bend on the bottom right.. shame as it was so pretty, but it was starting to melt my bumper.
and sadly, it came right back off the car, as i am now looking for a solution to take another 20dba out of the equation, as it is too loud for my personal preference with the cutout closed, or to sell it for close to what i have in it.
~500 obo. (raw materials were that much, welding was done by me and a friend)
It is extreemly smooth sounding though, one of the smoothest ive heard on a mini. It doesn't have any of the typical 4 banger exhaust sounds when revving, has a deep tone, and burbles like crazy on lift off.
its fairly quiet (you can hear it, but not obtrusive) when not under load, but when you get on it, i couldn't even begin to hear the supercharger till ~5000 rpms or so, and i have an alta...
pictures will be up soon

 

Hmm interesting. I was curious how loud it would be with just 3 resonators. Didn't get any videos or sound clips?

My friend who was head of NVH engineering (noise, vibration, harshness) at Ford Motor Company told me the simple rule of quieting down the exhaust of the car:

Volume Volume Volume.

Meaning, the exhaust and its mufflers need internal volume to cut down on the emitted noise volume. That's why the stock "two-ball" exhaust is pretty quiet- those '*****' have a ton of internal volume. That's why all stock exhaust mufflers are always so massive and bulky..

So as a very rough calculation, lets say 1 of these Vibrant 1141 resonators = ~243 cu in of volume.
One of the "mufflers" that Vibrant sells (1102 model in this example) = ~575 cu in of volume.
So, a single muffler will likely quiet it down by more than two resonators.

I doubt you can fit a full size muffler in there with the current routing, but its just some food for thought on your next design (or modification of the current one).

 

I did a little digging today, and i can fit, post cutout and resonators (in the loop around the battery box) a magnaflow 11366 muffler. It is a center out offset in 11" long case that is a 4x9" oval. that comes out to be 1244 cu in. and not straight though, the vibrants were 678 cu in and straight through.
Thoughts?

 

I definitely think all that noise is lack of a true muffler. I would wager that the relationship between volume and noise is highly non-linear and fraught with all sorts of caveats. Certainly that has been UCONN has found whenever we start researching the process behind designing our own muffler for the SAE car.

If I were in your situation, I would try it.

 

Yes it should be a big improvement, especially in the 'cut-off open' state.

Yes it is definitely non-linear response.. the volume/volume relationship is just a general rule of thumb. Fabricating exhausts using the typical "hack and paste" method of building custom exhausts, giving basically random (you get what you get) exhaust tones. The OEMs can use CFD to tune their exhaust frequencies with muffler baffles and resonators to get a specific exhaust tone.

If lower overall noise is all you're after, I've seen race teams use tuned resonators to cancel out a certain band of frequencies that was much louder than the rest of the exhaust noise..

 

I know you're probably stuck on which direction to go at this point, so I figured I best provide a link on how to properly go about this sort of fabrication:

http://www.ninja250forum.com/index.p...24495#msg24495

Cheers,

--Rich

 

love custom exhaust

 

Any updates? Videos?

 

My 1st setup on my custom exhaust was: stock exhaust manifold + custom exhaust (Vibrant Ultra Quiet resonator 2.5" + 2x Vibrant Ultra Quiet muffler/resonator 2"). It was freaking loud (very deep tone)! When I was in car enthousiasts meeting place, I asked to a friend (who came with his Corvette C6) to rev my car to allow me to hear the sound. Within the 3 next seconds a crowd of over 15 people walked to our way to find out which car made that sound. I asked to my friend to turn off the engine and get out from the car right away. This crowd thought the sound came of the Corvette C6 just beside my car.

So, Soccerbummer1104, your car will be a "monster car".

 

thought id post a little update. Exhaust was too loud, so I finally got the (hopefully) last muffler in a while ago, and will weld it in this weekend (time permitting)