ynasef

I have a 67 mustang with a new 3" Flowmaster exhaust system. Its sounds great and I like it. However, there is a resonating sound or droning sound that comes from the exhaust! It comes and goes while idling but as soon as I tap the gas pedal, it disappears. Also, at certain speeds or random times the sound comes and goes. Everytime I get into the car and drive around my ears feel deaf and get a headache. I took it to a muffler shop and they told me to change the mufflers to a stock muffler, but its not guaranteed! So what should I do? Please help. Magnaflow?

TexasAxMan

Flowmaster's drone, you can either get used to it or change it. I'd go with Magnaflow, but that's just my opinion ...

scottybaccus

Same ol', same ol'....

We ditched the flow muckers on my pal's car. It picked up in the quarter, stopped droning and sounds Bad ***!

Grab yourself two DynoMax Super Turbo mufflers. They are cheaper, sound better, make more power and you will never buy anythig else once you use them.

urban_cowboy

I have a 3" dual exhaust system with full tube headers and Flowmaster 40s. Mine does the same thing as it sounds like yours does. If you get the throttle in just the right place, it makes a terrible racket, but has a different tone at a position above or below that strange spot. Flowmaster mufflers are chamber mufflers and they are prone to drone...it is pretty commonly discussed topic and yes flowmasters are call dronemasters because of that. I personally like the sound at both idle and WOT just not that rattle during that strange throttle range.

My theory on the drone coming and going is that it is caused by the exhaust gas pulses and their spacing when they hit the muffler. If you read about exhaust system tuning, these same pulses cause reversion, scavenging, and all kinds of things both good and bad. Racecars, especially F1, Indy, and Nascar, will tune exhaust systems to take advantage of the pulses and minimize their negative affects at the rpms and throttle position they plan to run. Street cars really can't do that and their restrictive systems hurt performance...the only good thing is due to their restriction, the pulses stack up, which helps create a little more torque on the lowend, but what a terrible trade off for what it does at all other rpms.

I have not proved this as I have not installed one yet, but I think an H pipe would cure the drone issue even it did not improve performance. It would allow the pulse to escape another way thus altering their spacing and helping eliminate the drone in the chamber. The downside is they kill that distinctive true dual exhaust sound.

Also, moving away from a chamber muffler fixes the issue as there is not a chamber for the pulse to resonate in. Many stock mufflers are a single pipe snaked through a case of insulation thus...no chamber. Glasspacks are a straight flow through muffler with insulation packed around the exhaust tube...still no chamber.

A third solution is installing a set of resonators that more or less reflect some of the sound pulses in addition to the muffler which is absorbing them.

Here is a pretty good article.
http://www.nsxprime.com/FAQ/Miscella...austtheory.htm

If an H pipe does not fix my issue, I will probably pull the flowmasters off and opt for something else...the problem is almost all mufflers hurt power so finding one that does not affect is much but has a drone is a trade off, I guess. Performance verse sound. From my experience, the two are mutually exclusive. Glasspacks perform probably the best next to no muffler, but the popping and sound level is a negative...at least to some people.

JMD

I know I live in the dark ages, but imo.... long glasspacks will fix the drone....

jspagna1

Straight exhaust is going to be loud as hell. You definitely need to run an H-Pipe or X-Pipe. X-Pipe being the quietest of the bunch. H-Pipe being the cheapest and easiest to install.

2+2GT

You should absolutely put in a crosstube. As close to the engine as possible. You'll get quieter operation and more horsepower.

ozarks06

What he said.

frdnut

Are you running tailpipes?..If not they will help with the drone and quieten it down a bit as well.

crunchyskippy

I've got 2.5" Flowmaster 44's with an H pipe. I still experience somewhat of a drone at idle as well, however it does not bother me terribly. As I stated before, I like the Flowmaster sound (and I realize I'm in the minority).

It sounds like your idle speed is creating a resonating frequency that annoys you the most. Perhaps you could speed up or slow down your idle to tune it out. I don't believe it would take very much adjustment to move the frequency resonance. It may be worth a 30 second try.

Good luck.