Exhaust trim

 The other job for this weekend was sorting the exhaust. It needs three tasks;

• Adding the exhaust end trim to make it IVA compliant.
• Adding a heat shield round the cat so it doesn't melt the fibreglass body or the passenger.
• Ensuring the gasket faces are aligned to reduce leaks.

The third task here was the last thing to do, and I need to bolt up the manifold properly first to have any chance of getting things lined up. So it's not included for this weekends work.

First thing was the exhaust trim, and it started badly. I don't know what the trim was made of, but it wasn't ferrous and it was as thin as paper. It was also the same thickness as the exhaust, or at least that's what I initially thought. A quick visit to the nearest car place gave me some ideas on what to do, basically an aluminium sleeve over both sides, rivetted in place and with some exhaust paste to make it airtight. The airtight bit wasn't vital here, it's right at the end of the exhaust anyway. The emissions test probe would go in further than the join so it's not as if I'm cheating the emissions test. 

That's where it got a bit weird. Cutting both the exhaust and the trim to length I found that the exhaust got narrower. So narrow in fact that the trim piece actually slotted over the exhaust! Of course, at this point I'd cut them both to length, so having it slip over wasn't a good thing at this point.

Having said that, it did still work, and refitting it to the car gave me a good guide on how much it would stick out. IVA has a certain limit, and aesthetically I wanted it peeking out every so slightly anyway. So I continued with the same job, although I used hose clamps rather than rivets. I may swap those out in the near future, but they're not visible anyway.

Once the body trim piece was positioned and screwed in place, I think it's come out really nice;

The fixings aren't visible, and it has just the right amount of 'peek' to be what I wanted. I particularly wanted the slight angle on it, I think if I'd have tried to go for 'perfectly aligned' I'd have never got it right and it would have looked worse just being slightly out. At least this is purposefully at an angle. 

Unfortunately the deviation from the initial plan killed several hours of useful time so I wasn't able to get to the shield. However, using the hose clamps on the above does show how I can do it. The cat isn't that much thicker than the pipe itself, as shown in this aerial photo;

So my plan of using aluminium brackets rivetted to the shield, then hose clamps front and back of the cat will allow me to fix it well. I might add a couple more brackets mid point to keep an air gap between the shield and the cat, but they won't need to be fixed. Then again, just thinking about that I am wondering whether having unfixed brackets will give me a nice 'buzzy' sound on the exhaust when it's running. Perhaps just front and rear brackets then. I could put a crease in the shield, that would increase rigidity considerably. The size of the sheets means I need two side by side to cover the length of the cat, but I have some capacity to include some folds either side. Just checking the hose clamps show they'll work well, if a bit fiddly, and there's definitely scope for folding. 

Oh, and there is the centre section of the exhaust trim that I'm still not convinced about. It can still be removed, but for the time being I'll leave it in. Again I'm not going for a race car so I am assuming the reduction in size isn't going to be a major influence on performance.