Although they're considerably...
Although they're considerably longer than the mufflers we're used to seeing on an '05-present 'Stang, DynoMax's new VT muffler looks good on Chris' Shelby. To ensure perfect fit and positioning, David Chappelle of Chappelle's Exhaust and Kustom Shop replaced the factory exhaust hangers with a set of his own custom pieces, and used DynoMax clamps (PN 36438) to secure the 55-degree coupling tubes he created for the muffler-to-exhaust-pipe union.
As far as we're concerned, nothing beats the sound of a late-model Mustang's V-8 engine, at idle or at full growl. Over the years, Mustangs have become identifiable by their sound alone. Seriously, how many of you instinctively turn your heads to "find" the 'Stang that you hear rolling down the street, long before you see it?
Aftermarket exhaust manufacturers have developed mufflers and full exhaust systems that include larger tubes, headers, and more, which increase performance, and in many cases, add even more distinction to the "Mustang sound." However, while the bark of a mean-sounding exhaust is pleasing to the ear, the resonant drone that is inherent with some aftermarket exhaust systems certainly is not. The drone we're speaking of is the deep, steady, monotonous noise that is heard inside a Mustang's cabin.
Drone typically rears its ugly head right at the rpm where you typically cruise down the freeway. Turning up the stereo's volume is one method of escaping exhaust drone, but that tactic isn't always effective. The key to eliminating drone starts with the mufflers themselves. The trick is finding a way for them to resonate less without sacrificing performance or sound quality.
It appears DynoMax Performance Exhaust has come up with a remedy with its all-new VT mufflers (PN 17159; $99 each). The VTs are high-flow, stainless-steel performance mufflers, specifically designed to control drone thanks to Continuous Roving fiberglass and an exhaust-pressure-actuated valve mechanism that redirects exhaust flow during low-rev cruising conditions.
While the two features eliminate the resonance you normally hear inside the car, one of the valve's main qualities is that it does not hinder performance. The valve automatically adjusts when you plant your foot on the go pedal, allowing gasses to flow at more than 840 cubic feet per minute, with a strong, powerful and unique sound.
Our normal M.O. is to bolt-on exhaust pieces and see how they measure up in the power department by loading a Mustang on a chassis dyno before and after installing aftermarket mufflers. This time we're doing things a bit differently as the mufflers' sound is our focus.
Through the following photos and captions, see how David Chappelle of Chappelle's Exhaust and Kustom Shop in El Cajon, California, outfits Christopher Howard's '07 Shelby GT500 with the DynoMax VT mufflers, as well as the results of our decibel test, which proved to be quite interesting.
With the DynoMax VT mufflers...
With the DynoMax VT mufflers installed, this is the decibel reading taken inside our test Shelby GT500 with the engine running at 2,500 rpm....
The audible difference between factory-original mufflers and DynoMax's all-new VT silencers is almost eerie. The big deal with the VTs is not what you hear coming from the mufflers-it's what you don't hear.
Prior to and after installing the new pieces on Chris Howard's '07 Shelby GT500, we used Scoshe Industries' handheld decibel meter (PN SPL1000) to conduct pseudo-scientific (interior-windows up, accessories off, meter positioned in the center of the car; exterior-shop silent, meter positioned in the center of the rear bumper, 5 feet from tailpipes) tests to determine exactly how "loud" the 'Stang is inside and outside its cabin, with the engine running at an idle as well as 2,500 rpm.
A breakdown of our findings is in the chart. However, given the fact that we had three hours' driving time (yes, El Cajon is quite the trip from Los Angeles) after our project was completed, we really need to add our personal impressions of this interesting muffler design.
....and here is the VT silencers'...
....and here is the VT silencers' audible output outside the cockpit at the same rpm. (Outside measurements were taken with a Scoshe SPL1000 decibel meter positioned 5 feet from rear bumper.)
While a Shelby's OEM exhaust hardware already is relatively quiet, the DynoMax VT cans are even quieter than the stock pieces. In some instances during our long freeway-speed cruise home, your tech editor found himself checking the tachometer or rolling the window down to confirm the engine was still running. On the outside, during strong freeway-on-ramp/lane-change-or-passing bursts of throttle, the VTs literally open up and emit the muscular growl that one would expect to hear coming from a late-model 'Stang.
We enjoyed the quiet. However, we understand that "the louder, the better" is a motto that many Mustang enthusiasts swear by when it comes to exhaust. DynoMax offers curious 'Stang owners a chance to try the VTs, and with its Performance and Sound guarantee, give the mufflers back after 90 days (for a full refund of the purchase price) if no-drone technology isn't to your liking.
| OEM Idle | OEM 2,500 | VT IDLE | VT 2,500 | Diff Idle | Diff 2,500 |
| Int DB | 68.80 | 78.00 | 65.20 | 76.10 | -3.60 | -1.90 |
| Ext DB | 86.20 | 92.10 | 80.40 | 89.70 | -5.80 | -2.40 |
David Chappelle of Chappelle's...
David Chappelle of Chappelle's Exhaust and Kustom Shop of El Cajon, California, puts a final welding zap on a custom exhaust tip on Chris Howard's '07 Shelby GT500. Because DynoMax's new "universal" VTs are slightly longer than OEM cans, installing them on an S197 involves specific custom tubing fabrication (for now). DynoMax engineers are working on a true bolt-on VT muffler system for late-model Ponies, and hope to bring it to market in early 2011, if not sooner.
After taking baseline interior/exterior...
After taking baseline interior/exterior baseline decibel readings-at idle and at 2,500 rpm-the Shelby is raised on a drive-on hoist. Then David (right) and Phil Christy remove the factory mufflers. The purpose of this project is not to see how much power a 'Stang will gain with the VT mufflers. For this exercise, we're comparing the idle-/2,500-rpm noise/drone levels of the factory mufflers against those produced with DynoMax's all-new VT mufflers.
The fully welded stainless...
The fully welded stainless steel, 2 1/2-inch VT (bottom) measures 16 inches in length; it is a full 2 inches longer than DynoMax's Ultra Flo welded (top) cans and stockers, as well.
This closeup photo and cutaway...
This closeup photo and cutaway illustration details the internal specifics of a VT muffler. The centerpiece of this setup is a stainless-steel, spring-triggered valve door, which remains closed at idle and low-rpm cruise speed, and then opens as exhaust pressure increases.....
....VT mufflers' flow characteristics...
....VT mufflers' flow characteristics are similar to their more aggressive siblings thanks to their straight-through, unrestricted design. VTs are said to be capable of supporting up to 2,000 cfm and 2,000 hp.