I cleaned up one of the factory cats just with a wire wheel on the bench grinder. I will use these to replace the 4" fake ones that are welded in the mid pipe I bought with the headers. Notice how it is double walled so the pipes are more restrictive than they look.
My idea of moving the cat from under the transmission pan and further along was not to be. They will not work correctly that from the heads due to lack of heat. So I had to try and find a way to fit the bigger 5" factory cat under the pan it wouldn't end up hard against it. My solution was to weld in some 3" to 5" eccentric reducers.
You can see the amount of clearance I would gain as when flipped the other way, I would gain an inch of extra clearance.
I prepped the cats ready for welding the 3" exhaust to on the right one, and for the 3-5" eccentric reducers on the left. Just after taking this photo I picked up the left one only to find parts of the centre falling out! This one had a small dent from when they used a fork lift to move around the Jeep at the auction house as they lost the key fob. Seems that was enough to damaged the ceramic brick inside so it is a throw away now! O'well, I will just have to upgrade to the Kooks high flow cats which are the only ones which wont set off a CEL. Also means I don't have to use the reducers now either as they will clear being 4" round.
Surprisingly the new Corsa X pipe just bolted straight up to the end of the OBX mid pipes that came with the headers.
I did run into a problem the the wheelbase difference that the hangers above the axle ended up under the cross member. Also were the wrong height as want the pipes up higher than stock.
To solve the hanger problem I was able to kill both problems at once. I heated up the hangers with a propane torch and then using a long tyre lever, bent them backward away from under the cross member and getting the height I wanted at the same time.
I needed some stainless steel welding wire to do the exhaust with. As a 5 kg roll was nearly $200, wanted to buy just a 1 kg roll as don't have much to do in stainless. My welder was not made to take the small 1 kg mig wire rolls, so made this up just from some 5/8" all thread. Didn't have any nyloc nuts so used some teflon tape on the threads so I could adjust the spool tension.
The tips stick out a bit far I think even though the bed will hang out past the rear cross member by a couple of inches still.
I had just enough straight pipe before the bends where the resonators slip on to cut an inch off and get the tips closer in. Think they will be perfect like this now.
The tips do line up nicely in the centre though but will have to shorten up the hangers about 3" so that they end up behind the cross member.