Project Miatabusa part 12 – Why You Can’t Make Aluminum Exhausts, And Why I Did It Anyway

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Here's a tip for either V-band. Never, ever use power tools. Even relatively slow electric power tools. The stainless locking nuts gall really easily. Boo… 

Luckily, I had a few of these less-sexy industrial V-band clamps I salvaged from an obsolete piece of test equipment a few years ago. I never throw anything away… 

This Vibrant Technology race cat goes at the bottom of the downpipe. The compact size makes it easy to package (if we weren't concerned about the heat, we could have even put it in the engine compartment), and the light weight and high flow construction make it easy to think about the puppies and the horsepower at the same time. 

The catalyst chemicals are coated on the surface of this thin corrugated stainless steel. Compared to conventional ceramic-core cats, the steel-core cats have a higher void ratio with larger cells and more airflow space per square inch.

The cat is so small I was actually able to install it about a foot forward of the cutout where the factory cat lived. This will light the cat off a hair earlier, but it also leaves that catalyst space for a silencer. 

Since I hadn't expected the cat to be so small, I hadn't planned on using a silencer here. Luckily, I'm a pack rat, and had saved this factory RX-8 silencer from an earlier project. The RX-8 silencer is a beautiful, high-flow perforated core that's about 2.7″ ID, with high temp packing (it has to handle a rotary after all) and a thin, spun-stainless shell. Good stuff. 

By comparison, the hole density on the Vibrant aluminum muffler isn't nearly as high, but I suspect the aluminum wouldn't be strong enough if it was. Hell, it probably wouldn't even be strong enough to withstand the drilling of the holes.