The current exhaust on the Mustang has a fair amount of drone on the highway. I love the sound of the exhaust but when we take any type of road trip you can hardly hear the radio or have a conversation. I've done what is possible with Dynamat and other stock style sound deadeners leaving the option of replacing exhaust components. I've hesitated to this point as I hate to give up the current sound but I want it something that any member of my family would not hesitate to go for a long trip due to the drone.
Before replacing the exhaust, I attempted to use a decibel measuring application on my phone while driving around in the Mustang. I expected to give me some objective measurement on how much (if any) the new exhaust is. However, with idle, driving on the highway, driving at 2,000 under load, and going 60 with it in neutral the application measured the sound at a fairly consistent 75 db. The only way I can explain the fairly consistent db is if it is just the certain frequency of the drone which is annoying.
Before replacing the exhaust, I attempted to use a decibel measuring application on my phone while driving around in the Mustang. I expected to give me some objective measurement on how much (if any) the new exhaust is. However, with idle, driving on the highway, driving at 2,000 under load, and going 60 with it in neutral the application measured the sound at a fairly consistent 75 db. The only way I can explain the fairly consistent db is if it is just the certain frequency of the drone which is annoying.
This past weekend I began the project of replacing my current Dynomax Super Turbo mufflers (Part# 17733) with a set of Borla Pro XS (Part# BOR-40358). Removing the current exhaust with the rear axle in place was a challenge as the current mufflers were essentially crimped on by the exhaust clamps requiring much of it to be removed in large pieces. I worked on it some Saturday morning and again this afternoon and everything is now apart.
Once it was apart, I noticed the Borla muffler inlet and outlet are actually a little larger than my 2.5" exhaust. They slipped on rather loosely such that I really did not think a good seal would be possible. I rented an exhaust expansion tool (EverTough 067097) from O'Reilly and used it to slowly open up the size of the exhaust pipes until the Borla mufflers slid on with a bit of resistance. I then used it on the Dynomax mufflers to essentially create a dolly inside the muffler inlet and outlet so I could return them to a round shape so they could be used again if I desired.
The new Borla muffler is a straight through design which I hope does not make it incredibly loud.
I shined a light down into the Dynomax muffler but it is a little hard to tell what exactly is going on inside. The center inlet runs exhaust through a perforated tube and then to one side using a flow director at the opposite end of the case. It seems to run in a large circle inside back around to the side where it has the offset exit. Its hard to see how it is able to flow this way without the center inlet getting in the way of the exhaust exiting. I searched for a picture of the internal design and found someone took one apart to find the following. My case seems identical except perhaps a little longer.
