I own a 2001 honda CRV that's DOHC 4 cylinder with a 2.0-liter engine, its Front-wheel drive. It's a 5-speed automatic I've done a cat delete and rebuilt the exhaust system excluding the cat. I have a Magnaflow performance muffler and a 2 1/2 foot long cherry bomb resonator what size exhaust pipe should I go with to finish out the exhaust the rest of the way out the back of the car. my exhaust system is currently 3 1/2 feet in total length. I want to make it split into a dual system behind the rear axle and add dual exhaust tips in as well so it's quad exit exhaust. I'm trying to figure out what exhaust manifold and downpipe to use along with what size exhaust pipe to use to finish it out I was thinking 2.5 inches in diameter but I'm unsure should I go bigger or smaller? please help...

 

From the manifold and back to the Y, the pipe size should be 2.5-inch, the same size as your mufflers inlet and outlet. To keep a constant velocity in the branches from a 2.5-inch inlet you should go with 1.75-in branches. Theoretically. But 1.75-in exhaust pipe is virtually unobtainable, so I would just stick with the common 2-inch for the branches. The gas will slow down and expand as it enters the branches, but it should still be pretty efficient. You probably won't have many options with the tips.