The rear is starting to look pretty wicked. Everything after the catalytic converts is 3.5” titanium. The muffler assemblies are fully welded and the rest is tacked. The first step was to connect the catalytic converters to the mufflers via titanium pie cuts. A titanium flex bellow was used to absorb linear growth caused by thermal expansion and to help decouple vibrations.
The flex bellow is visible on the upper tube
Once the upper tube was completed, the muffler outlets were connected to the X-pipe. The challenge was to determine the exact location of the X-pipe and to keep it there during fabrication. The solution was a piece of 1/4” plywood. The leading edge was clamped to the underside of the billet chassis piece that crosses under the transaxle and two vertical supports were fabricated from right-angle aluminum to affix the trailing edge to bosses on the transaxle. Slots were milled in the supports to enable granular adjustments. This provided a stable platform to locate the X-pipe and enabled the X-pipe to be precisely tilted (the tips will be tilted upwards). This worked much better than a floor stand because everything moved when the car was raised/lowered via the lift and there was no chance of knocking over the stand or dumping everything on the floor.
Plywood platform to support the X-pipe while fabricating the connecting tubes. Plumb bobs, squares and digital angle finders were used to get everything symmetrical.
Merge collector (left), bell housing (top middle) and four primaries joined by a flange crossing under the oil pan (bottom middle)
Merge collector (left) flowing into a transition cone (middle) leading to a catalytic converter after which pie cuts flow into the bellow
The X-pipe is connected to the muffler outlets. A mock exhaust tip on the left side.
The final step was to connect the mufflers to the X-pipe which required a fair number of pie cuts of different centerline radiuses (CLRs) and slip fittings to enable the muffler assemblies to be removed/installed.
The cat-back system required 82 pie cuts, 6 mandrel bends and 4 straight sections. When V-bands, bellows, slip fittings and transition cones are taken into account there are 113 welds with a 3.5” diameter. That results in a whopping 1,242” or 103.5 feet of welding!
The next steps are to integrate the cutouts, finish weld everything, add hangers with vibration isolators to the X-pipe and fabricate a heat shield between the X-pipe and transaxle.