My stock system on my ej8 civic coupe (2000) is rusted. What system that looks stock and quiet but has a better flow? What piping diameter is appropriate that won‘t hinder performance?
Really, there isn't much you can do exhaust wise that will be a sleeper for a civic. Only a very expensive exhaust system will actually give your civic a decent tone or you will sound like all those other ricers on the road. Also got to think with all the extra sound you produce you may gain a full 10 horsepower max. If you really don't care about sounding like a ricer and people with real power laugh at you then you can go as far as just replacing the pipe with maybe a 2.25 inch pipe, which will give it a little deeper tone. Get some aftermarket headers either high flow cat or take it out all together if you have no emissions and run straight pipe to a good muffler. I wouldn't really go past 2.25 inch pipe only because you will probably begin losing torque after that and these little engines don't have much torque to begin with and doesn't push enough air to need a bigger exhaust pipe size. I think 2.5 might be just a little much, but it may work.
