While waiting for the headers to be ceramic coated, I turned my attention to the cat-back system. I had ordered all the parts several posts ago, so they were simply waiting in their boxes for their turn to shine:
The system starts at the collectors with a pair of 2.5" x 6" stainless flex joints from Yonaka (p/n YMEFP256) braided inside and out. These will allow the cat back systems to be semi-isolated from the headers and will lessen the stress, vibrations, and movement transferred between the two halves of each system:
Immediately downstream of the flex joints are the catalytic converters. I bought these Magnaflow MPE-59926 converters after seeing them on a few of V8 Archie's cars, so if you're reading this Archie, thanks for the idea!
They're a honeycomb style, full flow universal converter. What I liked about them was their compact size at only 4" in diameter at the widest:
The last pieces of the puzzle were these compact SuperPro Street 9326 mufflers from Spin Tech. I'm not sure how well they'll muffle the racket from the headers, but they were perfect size-wise. The case measures 4" x 6" x 9" and has a 2.5" inlet with dual 2.25" outlets.
After studying the strange weld patterns on the case, and peering inside, each muffler has three large diameter tubes welded vertically in a staggered pattern inside the case. The tubes have been slit along the vertical with one edge curled outward and the other inwards, making a sort of loose spiral.
Some of the airflow entering the muffler gets caught by the open edges of the spirals and gets spun around into the center of each tube and exits through some perforations in the tube walls.
The rest of the airflow bypasses the spirals and flows along the inside perimeter of the case, passing through some perforated grates, and mixing in a final chamber with the exhaust exiting the spiral tubes. There doesn't seem to be any steel wool or other fibres inside. These things might be a little loud.
With the parts in one hand and the plan in the other, I started building the system by slicing the mandrel bent 2.5" diameter tubes with my handy-dandy pipe cutter:
I made a few modifications to my plan when I realized I'd have to raise the exhaust outlets to make them exit the rear fascia at the correct height. Things were getting tight so I gained a bit of space by shortening the inlet and outlet extensions on the mufflers. Here's one of them getting introduced to the chop saw:
Making the cat-back system was a no-brainer compared to the headers. Here are all the pieces mocked up on my work bench:
When I was happy the parts measured up to the dimensions on my drawings, I tack welded them together to test fit them into the chassis:
I needed to be sure there would be enough room longitudinally, and there was... just barely! Here I've got some Vise-Grips supporting the weight and some magnets spacing the tubes away from the very back wall of the trunk. I may yet have to make some modifications to the rear wall of the trunk, or get some shorter flex joints, but for now it looks things will work out:
Here's the worm's eye view of the system (moments before thanking the evolutionary process for not giving him ears):