After several false starts, I finally managed to remove the old exhaust system on the 325is and install the new cat and muffler I’ve had since August. All of the DIY postings I’ve read on e30 exhausts have said the same three things: 1. Don’t try this without a lift; 2. This thing is long; and 3. It’s heavy. Right on all three. You can do it with the car on jack-stands, but be prepared for a lot of up and down work. It helps to have a couple of extra stands to support the exhaust; an extra jack to move it up into position; and a skateboard to help guide the exhaust under the car.

Bolted together, the old cat and muffler weighed in at 60 lbs. The new one came in slightly lighter at 55 lbs. The mufflers are essentially the same, but there have been some changes to the mid-pipe over the last 20 years. Catalytic converters are much more efficient and much smaller now. The old one also had an elaborate heat shield that rotted away.

The e30 exhaust system has basically three parts. A pair of very short exhaust headers (which I didn’t remove); a mid-pipe with the O2 sensor and cat; and a pipe and muffler section.

I’m not sure I understand the basic design principles involved though. The BMW 6 cylinder engine has two exhaust headers. The new pipe has an X-pipe at the O2 sensor, but then the two pipes continue to the cat. Before the cat, they go through a Y-pipe and enter a larger diaper tube into the cat. That larger pipe is perhaps 2 1/2 inches in diameter; the other pipes about 2 inches. Then there is another Y-pipe and back into two smaller diameter pipes to the muffler. Why not a Y-pipe at the O2 sensor, then a single pipe all the way back? That has to be a lighter design.

I guess I don’t have to understand it to appreciate it. The new system sounds great and seems to have a bit better throttle response, so the redesigned cat must be more free flowing. Also when I walk up to the car, I don’t have to look at the old crappy muffler any more. Yeah.