I have a 91 Civic STD all stock. I bought a new muffler since it was getting time to replace the original one. I bought a 91 Civic Si muffler since I was told it was interchagable. The muffler shop broght it to my attention that it is not. My muffler uses a flat gasket at a flat joint between the downpipe and the muffler. The Si uses a round gasket that apparently fits half in the muffler side and half in the pipe side, therefore would not fit. What else do I have to replace to get this to work? Downpipe for an Si? What about a cat? I have been told that the STD Civics had the cat on the exhaust manifold as opposed to the underside with the DX and Si, but my car has the heat plate underneath (I assume the cat is behind it). Is the cat on the manifold or underneath? I have a DC Sports header ready to go on and a cat from a 91 DX and a DX downpipe in a storage locker. Will this combination work? Do I really have to chage out the whole exhaust system just to put an Si muffler on?


Modified by johnclaunch at 5:46 PM 6/27/2005

 

bump

need info

 

The cat is under the car on the 90-91 models. Also i got an after market axle-back designed for the si to work fine with my std mid pipe. Just takes some ingenuity

Not sure if the cats are the same size on all the hb's, so you may or may not be able to just swap out the mid pipe section.

 

your exhaust has probably been changed once already thats probably why its like that it should be the same