Stainless Exhaust Without Drone?

Discussion in 'Classic Mustang Specific Tech' started by 2manyfords, Jul 7, 2013.

  1. Looking for a stainless exhaust that does not have a drone at cruising speeds. Car is 66 with 302 and full length headers. Want good value also. Seems the biggest complaints of aftermarket systems is drone.

  2. I always thought that the drone came from the muffler manufacturer. The pipe material should have no impact. Chambered muffs, I.E., flowmaster 40 series are known for having a sweet spot that sucks...
  3. That is correct. Some of the Magnaflow and Borla have a slight drone(depending on the muffler type) but its not nearly as bad a Flowmaster
  4. Drone in my opinion is simply an acoustic oscillation that occurs at a frequency to where the exhaust pulse pressure wave travels down the pipe, hits the atmosphere (end of the tailpipe or another discontinuity) and reflects back. think of a guitar string. there will be a frequency where an exhaust system resonates with the total exhaust system length the biggest impact to the RPM where it occurs. the biggest problem is when that frequency of oscillation occurs at an RPM where we cruise (if it occured at 4000 RPM, then 99% of people would never notice). the muffler design can help attenuate the oscillation to reduce the amount of audible drone.
  5. I should have clarified, agree material does not affect drone. Just want to limit my choices to stainless as I want maintenance free. Also want a system that exits out the back. Found a Pypes system that looks like a good deal but read the fit might not be that great?
  6. I have installed Dyno Max on my 69 Cleveland. The fit was perfect, I can't speak to the drone because driving to date has been limited.
  7. I put the Pypes universal Intermediate X pipe with cutouts on mine. It fits good for a universal one.. But if you want to tuck it up nice and neat, you will have to do some fitting.

    That said I am not disappointed with it.. Especially since it only cost a 150ish.. Was a great deal.

    If you don't want any drone, go with a turbo muffler.. I used to have Dynamax Super turbos, and it had a deep mellow rumble at idle, and quiet cruise, not too loud at full throttle.

    It is the entire system that makes it drone, not just the muffler. I currently have flowmaster 40's right now, and I don't get any drone.. Not saying you or anybody else wouldn't though. I do believe the X pipe has a lot to do with it. I noticed a different sound when I changed my H pipe to the X.
  8. It's not just the exhaust length, the muffler has a large influence and the chassis design does too. The new Camaros have really bad interior resonance problems with aftermarket exhausts of various kinds due to the chassis. Fox3 Mustangs do as well, especially the hatchbacks, although not to the same extent.

    IMO, Flowmasters earned the name "Dronemasters" because they have a lot of open volume inside that makes them act as a sort of Helmholtz resonator in the audible range. Toss in some constructive interference and you get very high amplitude waves in the band of frequencies we hear as drone.

    One way to get rid of the drone that I have heard is quite effective is to weld closed-end resonators on each leg of the exhaust. They can be perpendicular or parallel as long as it is 1/4 wavelength of the target frequency. The target frequency is easy to find: simply get a clear audio recording when the exhaust is droning, open it with free audio software like Audacity, select a short section of audio, go to Analyze > Plot Spectrum, and there will be spikes on the graph at that/those frequencies.
  9. Just went through this. Installed a set of Pypes Race Pro's on my car and it's quite docile at cruise and light throttle. I wouldn't say it's 100% drone free but then no aftermarket muffler is. Anyone who tells you otherwise is either lying, or doesn't understand the terminology.

    That being said....the exhaust is outright violent sounding when you slam the pedal down. So much so, I'm considering welding a set of high flow cats into the system to mellow it out some. But at cruise....she's very livable. The Pypes Race Pros are designed a lot like Mangaflow XL's. The best part about them, is that they're almost half the price by comparison. I got mine for about $60/each.

    These replaced a set of Flowmaster 2-chamber style mufflers BTW. Even with the O/R H-pipe vs the stock 4-cat set up, the chambered mufflers were still considerably more obnoxious at cruise. I'd rate the Pypes a 2.5/10 on the "drone" scale, vs. about an 8/10 for the Flows.

  10. i indicated exhaust length has the largest impact. not the only impact.

    i installed a straight through Magnaflow on my truck. it had a bad drone around that seemed to peak around 1800 RPM (when up to temperature). I made my own closed end resonator and made it adjustable so I could tune it to the exact frequency range. I've made various lengths and also diameters to test the impact. So I know it works.


  11. And I disagreed. Nothing more to it than that.