4.0 WJ pre-cat exhaust diameter/exhaust idea

**the88thpianoman** · 09-22-2008, 08:05 PM

I've heard but I just want to verify that the exhaust pipe diameter before the cat is 2.5" and after the cat goes down to 2.25" Is this true, or is it 2.25 the whole way?

I ask because if it is 2.5" then it makes more sense to me to get a 2.5" cat and muffler and then (if it'll fit) replace everything behind the muffler with the 2.5" pipe that I have from my 4.7 parts Jeep. Any reason why this won't work, or could I be about to assemble the cheapest 2.5" exhaust on JF?

**the88thpianoman** · 09-23-2008, 01:07 PM

bumpity bump

dmolaver15 · 09-23-2008, 01:42 PM

yes, the pipe before the main cat is 2.5" and then it's reduced to 2.25" after the cat. Why? i'm not exactly sure..
but i did exactly what you're thinking. 2.5" hi-flow cat, 2.5" flowmaster, and rusty's 2.5" mandrel bent tailpipe. Sounded MUCH better.

but i like obnoxiously loud things, right now i'm running no cat to a glasspack to a sidepipe right before the back wheel