[pikapp]

Originally Posted by 65sohc

I remember the Dynamat display at a local stereo shop. They had two sheet metal panels, similar to doorskins. One had a piece of Dynamat maybe 4x4 inches. When you whacked the naked sheet metal with a small hammer it made the typical ringing sound. When you hit the Dynamatted panel it just made a dull thud with no reverberation. As I think about it, a carpet lies on top of the panel and absorbs some of the sound energy passing through the metal. A product like Dynamat is permanently affixed to the panel so that it must change the vibration characteristics such that the panel itself generates less sound. Most of the objectionable exhaust noise is not coming out the tailpipe but is the result of harmonics of the various pieces of hardware. Ford designed the exhaust system to allow maximum actual exhaust sound with minimal obnoxious harmonics which I think is why there is no insulation in the trunk area. It isn't needed. My Mustang overall is much quieter than the last two cars I had-a 94 Supra Turbo and a 2003 Z4. I'm no expert on this stuff. I've never even used Dynamat (though I have a big roll ready to plaster all over my '65), but I think that is the concept.

I agree that Ford did lots of research into the exhaust system of the mustangs and the results is obvious, but once you change the exhaust out for example to..Flowmasters or other after market mufflers or add headers, x-pipe, etc...you're gonna get some unwanted resonance and vibration inside the car, hence the quest for a vibration/resonance deterant. I was about to order the QuietCar stuff, but figured I'd take the cheap route 1st. If it did what I needed it to do, then I saved some $$. If it comes up short, then it cost me nothing and I'll fork over the $$ for good stuff. I'll admit, the mustang was very quiet with the stock muffler, but it didn't appeal to my wanting an aggressive sounding mustang. By wanting that sound I accepted the unwanted guests--vibration & resonance. Now I'm just trying to make them more livable with.

[65sohc]

Originally Posted by stlwagon

Great idea. My SLPs are driving me nuts at 2000 rpm.

It would be interesting to have the car on a dyno, or at least a hoist and run it to 2000 and see exactly where the noise was coming from. It might have to do with a pipe hanger, a shield nearby, a bolt or screw, a specific panel, etc. One or both of the pipes might be resonating and the hangers are transferring it to the chassis. BMW did a show on the new Z4 Coupe where they ran it for 24 hours much of the time at full throttle listening for noises. They discovered that an unwanted noise was coming from the glove box latch, so they redesigned it and the noise was gone.