Only taken about 5 years, but finally fabbing center exit exhaust I sketched out..
 

The 16-gauge, 304 stainless Burns Stainless components I bought like 5 years ago are finally taking shape into the center exit exhaust system I always wanted so I can sell my car with piece of mind... LOL

https://photos.smugmug.com/Cars/Stil.../O/Burns-1.jpg

https://photos.smugmug.com/Cars/Stil.../O/Burns-2.jpg

My younger brother is the welder, so many thanks for his help in this...I need much more practice at welding to do anything decent. I do everything else though: the actual cutting, prepping, and finishing of the pieces.

This is the last custom design mod I'm doing to the car before selling it and am currently in the middle of the process of creating it. Have from stock flange to differential section of the tubing done and test fit, and the differential to tip tubing done seperately and test fitted to the other section. Need to weld the two sections together, add in hanger by the differential, weld on rear tip mounting brackets for the spherical bearing locating turnbuckles, and attach the turnbuckles to a custom bracket mounted to the bottom 2 heat shield mounting locations. I think it will look more proper than a dual exit exhaust for a car with the fake diffuser panel removed - plus able to add in a real, functional custom diffuser if so desired using the 4 stock muffler mounting donut locations as mounting points.

Using a Burns race muffler only, and it's located where the stock resonator would be. Of course had to do a start up test with the part to the differential completed...really like the sound. Not really any louder than the SRT system I customized, and seems deeper toned. I think the thicker 16 gauge tubing was the right way to go. Once completely done and can take it out for a test drive I will know for sure how it sounds, but I am more than pleased with how the SM-250-350-17 Burns race muffler with scrubble sounds.

https://photos.smugmug.com/Cars/Stil...O/OI000754.jpg

https://photos.smugmug.com/Cars/Stil..._174908-X4.jpg

https://photos.smugmug.com/Cars/Stil..._175331-X4.jpg

https://photos.smugmug.com/Cars/Stil..._185546-X4.jpg

Ended up not really needing the 90 degree bend segment in the design, though did use its straight portion to attach to the factory flange section to get the muffler where it needed to be. So the only bend pieces needed were the two 15 degree and two 45 degree bend sections. Will probably be this coming Friday when we will actually be able to get back on and hopefully complete this custom center exit catback exhaust.

It looks as though you're going to have it go right underneath the rear diff. Are you worried about bottoming out with it? Even at stock ride height (which I fully support) that's a gamble. I love this idea though, I want to see more

That picture underneath the car is with the tubing temporarily rotated downwards as far away from the differential as possible so I could start it and let the car fully warm up, then rev it to see what it sounded like. The true routing actually goes off to the driver's side of the differential just like factory and most aftermarket exhausts. Plenty of clearance. I'll have better pictures and video clip when finished.

Just finished (for the most part - going to shorten and straighten out the tip later to align with bumper better and not stick as far out):

https://photos.smugmug.com/Cars/Stil...O/OI000755.jpg

https://photos.smugmug.com/Cars/Stil...I000757-X3.jpg

https://photos.smugmug.com/Cars/Stil...O/OI000758.jpg

https://photos.smugmug.com/Cars/Stil...O/OI000760.jpg

https://photos.smugmug.com/Cars/Stil...O/OI000761.jpg

Short video clip:

https://youtu.be/mJ_9Vaez9Hc

Time to install the Centric rotors, Winmax W3 pads, and 949 racing 50mm steering column extension now...

Wow nice work. I've been doing metalfab for sixteen years. I'd let you do mine. Very nice.

Great job? Nice design and superb assembly. K

Just reworked the aluminum turnbuckle bracket and used 3M automotive tape to bond it to the underside of the trunk after cleaning it well where the outermost sections that touch the aluminum angle are...

https://photos.smugmug.com/Cars/Stil...O/OI000762.jpg

https://photos.smugmug.com/Cars/Stil...O/OI000763.jpg

https://photos.smugmug.com/Cars/Stil...O/OI000764.jpg

Nice work!

:thumbsup:


humfrz

Well my brother is the one who welded it, but I do like to design things along with fabricating parts and shaping materials for custom projects. I converted one of the bedrooms in my house to a work room - created a custom drop-down exhaust system with sealed plenum in the attic from ceiling to outside vent and wired up the room for the TIG welder and lots of LED shop lighting. Can weld, solder, paint, or coat wood with polyurethane in that room, temp and humidity controlled with great ventillation.

Also helps to have the right tools - part of the reason it took me this long to finally do it is I knew I wouldn't be happy with the Harbor Freight grinding chop saw that can't hold a precise angle in a cut. Finally broke down and bought the 12" Makita chop saw and an Evolution stainless cutting blade... so nice to use! Makita jig saw was used to cut/shape the aluminum bracket, and that was 'recently' bought last year for help in remodeling the kitchen (cutting the butcher block countertop for the sink and induction cooktop.) It also worked great when I was helping my brother put up hardy plank on his house recently.

So just test drove it.... definitely too loud, NOBODY will want to buy this car from me with that exhaust on it as is. Burns does have a very probable solution with their 2 stage quiet muffler (P/N SM-250-450-17-2S), didn't want to go that route if I didn't have to because of cost...we're talking a ~$600 muffler here...but I really like how the design of the exhaust turned out but it absolutely needs it to be quieted down (the test drive just now was starting to hurt my head and I could tell my ears were getting fatigued.) Diameter will increase to 4.5" but that should still have plenty of room in the tunnel and have adequate driveshaft clearance. Man, I really hoped the race muffler would have worked (seemed promising before the test drive.) Not sure what the lead time will be on the 2 stage muffler, but it HAS to be ordered.

Oh well, that's how things go sometimes...

P.S. drove it again for an extended period with hearing protection this time (Etymotic ER20XS) and level was acceptable...so if can reduce it 15-20dB it will be good enough.

It looks great! Nice Job.

You can always find a quieter muffler that isn't $600 and also throw in a resonator in there to get rid of the drone.

The tunnel area is the only place available for muffler or resonator placement for a center exit exhaust like this, there may not be enough room for both. MAYBE a 12" total length resonator could fit if redo the section immediately upstream of muffler - but it would basically be resonator and muffler directly butted up to each other.

As for muffler, don't think anything over 4.5" diameter is a viable solution, so am very limited in choices. I'm inclined to go with the 2 stage Stage Burns quiet muffler as it should work to reduce sound level acceptably along with taming some resonances, will have even deeper tone than currently, and is a direct swap out for the Burns race muffler installed. Went with Burns Stainless to begin with because wanted a specific type of sound, just unfortunately looks like it requires the more expensive muffler to keep sound level and drone reasonable for street use. Can always see about trying to squeeze in a resonator later if needed as well.

I dig center exhausts on these cars. A buddy fabbed a Focus ST muffler on his BRZ: https://www.instagram.com/p/Bl2-dJmF...ns_share_sheet

Really like how that one looks. :party0030: And mesh screen covering the bumper is not something I was thinking of but looks nice...