Ok i've already got true duals on my 4.6 as we speak. I had them done in 2.25" pipping originally thinking i might tow. Well i've made up my mind that my truck will never see a trailer at all. So i wanted to know would i benefit more from 2.5" piping all the way? I would redo my system completely with new flowmasters again (love the sound) and with an H pipe.

Also would it be possible to expand the openings of a set of highflow cats from 2.25" to 2.5"?

 

Just my personal opinion ..... and you know what they say about opinions ..... but I would keep it 2 1/4" throughout. Plenty of diameter for a mild to moderately modified 4.6.

Chech out this thread for some insight.

Good luck.

 

keep it 2 1/4
add an x-pipe

 

www.dynomax.com/techsupport.stm
scroll down

 

wow that guy lost nearly 20rwhp with his 2.5" setup. I guess its safer to stay 2.25".


Now will it be any kind of problem with the engine running a 2.5" off the manifold's to 2.25" piping all the way. Will it cause to much backpressure now that the exitint diameter is larger then the new opening diameter of the downpipe?

 

So what would be considered the ideal diameter pipe for a 4.6? Mine currently has 2 inch i.d. and someday when the system needs replaced I want something that improves performance but doesn't come with a lot of noise. Current system is stock except that when I bought the truck the dealer had the pipe changed to exit behind the wheel instead of in front of it.

Maybe I should ask what the ideal type of system is?