Targa Miata
July 20, 2012 - I've had enough with hot transmission tunnels.
The exhaust heat was actually enough to melt the heat shielding on the tunnel. So I decided to delete the catalytic converters. They're the source of most of the concentrated heat right beside our legs.
Now, it says in the Open Class regulations that the car has to run cats if it came with cats. In the OE location, too. Obviously, the latter isn't really possible due to the engine swap. But I overheard that at least one of the other Open Class cars was in Open because they had removed theirs. Racing gossip, of course. But I decided to ask.
The answer was "run them if you can, but we know you build legal cars so we'll understand if it can't be done for heat and packaging reasons". I've always been very careful about sticking to the regulations, and I'm glad to see it's been noticed. Then again, I'm probably the only person who's ever required about the minimum required length of the tow rope...

Anyhow, I cut the cats out of the car and replaced them with pieces of straight pipe. I discovered while doing this that one of my cats had actually been damaged at some point. Quite a while ago from the looks of the battered core that came out of it. Interesting.
With the cats gone, the car is noticeably louder. It has more ground clearance, too. It's too early to tell if it's going to be cooler, but taking that broken cat out of the exhaust can only be a good thing.
entry 1048 - tags: exhaust, cats
July 20, 2012 - Here's what the core of the cat looked like once I got it out.
That's a piece of broken ceramic core cat on the left. The round one is a metallic core cat, which is probably why it simply bent and banged up instead of shattering. It's a pretty compressed little unit, though - it's about 1.5" smaller in diameter than it was originally! It's just about small enough now to slip into the 2.5" pipe. I'm thinking it just kept on getting banged around inside the housing and eventually got smaller. Good failure mode I suppose, it didn't clog anything the way a ceramic one can.
The housing had an impact mark on the bottom. Not that bad compared to some of the other stuff under there and it probably pre-dated the skid plates, but the cat had taken a hit.
entry 1049 - tags: exhaust, cats