Text and Images by FM Staff

If you blindfolded a musclecar enthusiast and took them for a ride in a 2005 Mustang GT, it is likely they'd conclude they were in one based solely on the sound of the exhaust. The throaty rumble of the Mustang V8 is as hallmark as its' running pony emblem. This however isn't by chance. Sound Quality Engineers at Ford's Advanced Engineering Center study and design sound for all aspects of a Ford vehicle, but particularly for the Mustang V8 exhaust. For the 2001 Bullitt Mustang, Ford engineers digitally mastered the Mustang's signature raw V8 sound on computers from the 13 minute chase video. They then computer matched the sounds to prototype engines by tuning exhaust system components.

It goes without saying then, that for the all new 2005 Mustang, exhaust sound was high on the list of priorities for Ford. This is evident in the exhaust system delivered on the car from the factory. The new '05 GT has arguably the best factory exhaust system placed under a Mustang. The manifolds are better flowing than preceding designs. There are only two catalytic converters leading into a fairly straight and restriction-free crossover pipe. The piping is all 2.5" mandrel bent stainless steel. The dual exhaust system ends with a decent pair of mufflers mounted under the rear bumper. The factory system is high quality, and sounds pretty good. However, as with most things stock, there is always room for improvement. Let's face it, when it comes to exhaust sound, enthusiasts want more growl, a deeper bark, and to be set apart from the masses.

Video 1: Watch a clip of the bone stock 2005 Mustang exhaust system. It sounds better than Mustang's of years past but still lacks authority. The slash cut 2.5" tip however looks hideous, and reason enough to replace.

Designing out Drone
When exhaust technology company Flowmaster went to develop a system for the '05 Mustang they faced a challenge. How to improve upon a factory muffler that flows as well as their popular 40-series muffler, and how to do it without creating a resonance frequency that will annoy the driver during part throttle driving. Even though the 05 Mustang has a very simple and easy to replace muffler system, Flowmaster deliberately waited until after the release of the car to come out with their product. Other muffler companies simply grabbed universal mufflers from their product lines, welded up a tip and hangers, and marketed the product to anyone willing to pay for it. Low and behold we're hearing from unhappy owners complaining about severe resonance problems with their "straight through" style mufflers. The dreaded 2000-2500 rpm exhaust drone will cut through even the quietest of new car cabins.

"Many of our competitors overlook the fact that a rear mount muffler with no tail pipe after the outlet will resonate. It may seem like a simple kit to develop, but in actuality it is much more complicated. We went through six design changes on our '05 muffler before we were ready for anyone to hear it." commented Kevin McClelland, head of R&D at Flowmaster.

In fact, while at a glance one might assume the Flowmaster '05 mufflers are just their 40 series muffler with '05 specific hangers and piping, the reality is the internals of this 5" x 10" muffler are completely unique for the new Mustang GT. Still the trademarked Flowmaster chambered design, the actual numbers, shapes, and positions of the baffling are a closely guarded secret. Of course Flowmaster expects some of their lowbrow competitors will eventually cut the unit open to copy the design, a problem they face with all their mufflers. However they combat this problem with American build quality and materials that the cheap offshore manufacturing operations simply cannot "knock off". A trained ear can actually hear the differences between cheap Flowmaster look-a-likes and the real deal. Continue to Installation and After Video