i know everyone is probly sick of seeing exhaust questions but i hope one more doesnt hurt. i have a 3.9L v6 im gonna run a flowmaster 40 single in dual out muffler. i measured my exhaust pipes now and they are 2.5" should i run 2.5 in and 2.5 out or should i run 2.5 in and 2.25 out. if ne one knows which would be best let me know thanks.

 

going buy the millions of other people that have asked this question. I would go with 2 1/4" so you still have enough backpressure.
________
UGGS

 

<snort>
backpressure eh?

I'm out.

 

lol dont blame ya for bein out on this one horatio. like you said ppl will never understand backpressure is bad but anyways the 2.5 that you measured is probably the OD/outside diameter of the pipe when people say to run 2 1/4 exhaust they are talking about the ID or inside diameter of the pipe. run the same size pipe thats on the truck now dont make it smaller or you'll restrict your airflow and you wont be able to get proper velocity for your exhaust and your combustion chambers wont be clean for the next time around hindering performance

 

thanks im not looking for really detailed explanations of whats gonna go on. i didnt need to know about back pressure of valocety. god knows u guys have all argued about that enough on here. i just wanted simple yes or no answere if it'll work. im gonna do what dodgedakota98luver said and just stick with the size of the stock pipe. thanks

 

yes, go with the 2.25" dual outs. this may still be to big.

open up any exhaust too big and your torque will drop which will hurt your fuel economy.