Cat back exhaust

[frose]

Installed a 12 or 14 inch Magnaflow muffler on the 05 stock exhaust some time ago. I recently picked up a used manaflow cat back system with an 18” muffler. When I took it to the muffler shop to be installed minus the 18 “ muffler, I was told that it wouldn’t help as the stock exhaust 3” was plenty big for the engine. Your thoughts, will the addition of the cat back 3.5” help?

[Doug Allen]

The stock exhaust is 2-1/2", not 3".

[Chuckster]

Just installed a Magnaflow cat back system last weekend. Didn't expect to increase horsepower and don't think I did. Sure sounds great though! The stock tubing to the muffler is 2.5 inches, the new tubing is three. I think I'll pick up some horsepower from the cat back system once more things are added.

[hdflstf]

The stock exhaust is 2.5" in the areas where it is dual. At the area before the muffler it is 2.75" which is a bit of a bottleneck when compared to the dual 2.5". The cross sectional area for the 2, 2.5 is 9.8 sq in whereas the single 2.75 is 5.9 sq in.

So yes a true dual exhaust would help (at least a little).