Exhaust Fluttering Noise

[td2185]

I have been try to resolve this unpleasant exhaust noise that accures at cruise and de-excel. Would this be a common problem with the cobra exhaust with a particular engine and side pipe manufacture combination. I would also be interested if anyone would know the origin of this exhaust noise.

[Ron61]

I am not exactly sure what you mean by flutter, but you could have a leaking exhaust around one of the header ports or even in the collector area. And no, that would not be a common noise in any Cobra that I have ever been around. Can you tell if it is on just one side or not? With the car warm and at idle go put your hand close to the end of the exhaust pipes and see if you can feel any change from one side to the other such as a miss would cause. I once had a strange noise but it wasn't exhaust as I had crossed two spark plug wires and they just caused enough of a misfire that it sounded funny. When I stuck my hand down by the exhaust pipe ends, I could feel that one side was different and that side had the crossed wires.

Ron

[undy]

..bird-in-a-sidepipe.. Unfortunately there's no tweetment for it..

Check your valve adjustment (on that side especially) too.

[td2185]

The noise is coming from the exhaust turn out exit. Sounds like a flag flapping in wind or boat with rear exhaust sitting in the water with exhaust half exposed. The 514 engine is properly tuned and runs perfect and no exhaust leaks. Have tried exhaust cones inside the sidepipes to smooth out the transition from the collector to the sidepipe. This reduced the flapping/flutting noise some.

[Madmiles442]

If it only happens during deceleration, just taking your foot off the gas and letting it come down, at the same rpm every time, it sure sounds like an exhaust leak somewhere. At the header or header/collector.

[rattlesnakepete]

I experience what you are describing nearly everytime I drive on the street. I have even captured it on video tape when using stereo microphones in the cockpit of the car. It took me a while to develop a hypothesis but I believe it comes from separation of the two cylinder banks achieved with side pipes, i.e no cross-over tube. To me it is like alternating pressure waves on each ear drum that are not in synch. I would imagine that different firing orders would impart different rythms as well.

I like it myself and like to consider it a good sign that my engine is healthy and happy provided the ryhtm does not change drastically under similar conditions.

[Silverback51]

It could be as simple as the side pipes.

I just swapped my stock SPF pipes for some Stainless Specialities pipes and there is a definent difference in the sound when I let off the throttle. And it is what could be described as a fluttering sound.

[ceslaw]

I also put on a set of Stainless Specialities side pipes on about a year ago and noticed the same thing. Sort of a metalic flutter sound when decelerating. Not really that loud, not a backfire. Car runs great, so can't see any reason to be concerned. It was not there with the stock side pipes, but they were so loud I doubt i would have heard it anyway. By the way, the Stainless Specialities pipes are really nice.