Re: Resonator
Reply #2 –
My answer is what I picked, and why. Only a O-pinion. Everbody got one.
The smallest inside diameter pipe in your exhaust system will be the effective "restriction" regardless where it is positioned.
When we got our coach the exhaust was 4" pipe from turbo to OEM muffler, then a 5" tail pipe (which was not original).
I elected to switch to a MagnaFlow resonator part #12771, which is 4" in and 4" out. Downstream of the resonator, I used adapter to go from 4" to 5" simply so I could retain the existing tail pipe. The 5" tail pipe offers no performance advantage.
I picked MagnaFlow cuz I had used their products on several hot rod cars and liked their signature sound and their quality construction.
Whatever resonator you decide to use, be sure to verify the (smallest) inside diameter (bore). You might find there is little internal size difference between the different inlet/outlet sizes. I know in the case of MagnaFlow, the 4" in/out model and the 5" in/out model both have a 4" core, so there is no point in going to the bigger, more expensive size. This may not be the case for other brands.
Just something to check before you plunk down your cash...