Catalytic converter compatibility

[Marc_986]

One of the final hurdles to get my car back on the road is the exhaust. For reference, I have build a G87.21 into the back of my 986 so the stock muffler doesn't fit. I got one of the 'sausage' shape at a local breaker and it does fit behind the gearbox. However, at least the right side exhaust pipe doesn't match up (not even nearly). The car has in its life taken a hit on that rear side, so I already noticed some dents in the pipe. More careful inspection today revealed that the catalytic converter is deformed significantly. The section where it goes from converter diameter back to the pipe diameter is forced inward, giving an odd shape and offset.

Likely my best way forward is to get at least the right side cat (left side is welded up to the U-shape pipe, not sure whether that was part of the previous 'fix'). Are all 986 cats compatible? Or do I need to narrow specifically to the 2.5 model (as I have)?

I don't intend to run the car for many more years in the current form, so I guess a used one would be fine. Ebay prices are crazy, can get a new one (DesignTek) for that money which I might be able to resell afterwards. Any ideas or input?

[edit] for the compatibility question it probably good to mention that my sausage style muffler came from an S model.My car is a '97 2.5.

[JFP in PA]

If memory serves, the 2.5L engine had slightly smaller diameter exhausts.

[78F350]

I'm far away from home and my Boxsters today, but I'm pretty sure that the O2 sensor wiring is another consideration. I don't think that the stock 2.5L sensors will reach the bungs on the later model exhaust. At least on the US models.

[Marc_986]

Thanks all. I have ordered a new cat for the 2.5 specifically. Didn't really want that, but my sources couldn't provide and Ebay is too expensive (about same price as new aftermarket).

Next step is to get the old thing off. The joint to the exhaust manifold is welded up, see pictures below. So my idea is to grind the old cat pipe off near the joint. That will allow me better access to the three holes so I can try and drill these straight out. I did try a little part with a small diameter drill, but it really didn't want to start cutting. Any idea on my plan or better proposals?



And just to see the damage to the cat, the arrow points to where the whole tapered section is dented in. It also might have a little hole, but I didn't try to push it through.

[Marc_986]

Last Thursday I returned some parts from the wreck and had some discussions on this exhaust. His suggestion was that likely it isn't welded, just totally rusted to bits. His advice was to use a pneumatic hammer with a sharp chissel and get some force between the flanges.

So that's what I did today and after some careful and later less careful hammering they did indeed separate! So tip for anyone who has to do the same job. One leftover part of a bolt remained on the manifold side. Once I had this one broken off I could tap the last bit out.

The remaining job was to get the O2 sensor removed, but that went quite well after getting enough heat in it with a torch. Now I just need to file the slightly damaged edge of the manifold flange while I wait for the new cat to arrive. Overall with this little tip it was a lot less work than I was afraid off