What makes Flows drone from 1800-2000rpm? They don't drone anywhere else...

Discussion in 'SN95 4.6L Mustang Tech' started by Craig Mack, Dec 3, 2003.

  1. I just got some flowmaster 40 series mufflers welded in with 22"x3" chrome tips a few days ago. Needless to say, I love it. Coming from a Maxima, it's refreshing to have such a powerfull exhaust note. But, what the heck makes these flows drone from 1800-2000rpm? It's very weird, (to me at least) becuase they are quiet up until 1800rpm, then I get a LOUD drone for 200rpm, then they get quiet again. What is it about those RPM that are soo different from the others that make it drone? It doesn't make sense to me. If it was a steady increase to the drone, and a steady decrease, it would make more sense, but the drone hits you out of no where...

    Oh, and what makes the 96-98 Cobras lope at idle? My Maxima had a very steady idle, whereas this Cobra seems to lope up and down just a hair, causing a very subtle off and on vibration in the cabin.

    As a side note(s)

    I can't wait to get rid of the stock H-pipe. I have heard Cobras with flows and offroad H-pipes, and to me they sound really boring. I like an exhaust that has a pronounced echo and burble, and while the h-pipes are deep, they just seem too monotone for me. Hopefully the X-pipe will give me the polyphonic echo I crave! Thus far the Flows are doing a good job.

    Coming from an Import, my exhaust is like heaven to me. Whenever I hear a 4 banger fart by with a loud exhaust, I shake my head in disgust and become even more thankfull that I have twice the cylinders and 3 times the displacement. :flag: I was driving with my mom to pick up my car from the tint shop the other day, and she got mad at me for making fun of a ricer with a HORRIBLY farty exhaust. She says that just becuase I don't like it doesn't mean someone else won't. "One mans trash is another mans treasure, and maybe they think your Cobra sounds like trash Craig"...... :nonono: I told her she needs to stop being soo nice and start ripping on them a bit. :D
  2. Bla, I cant stand drone... any cruising speed in my car creates drone, but I just turn up the stereo :flag:
  3. I believe the scientific term is "harmonic resonance". Basically what it mean is that in any air funnel they come a point where the air is moving at an exact speed to create an additional boost in air velocity. This is why the sound appears and disappears so quickly.

    I'm sure someone else will be better able to explain it to you.
  4. When the exhaust passes through the muffler, the shape of the muffler, the speed of the exhaust gas exit and the obstructions and bends cause some resonation. Each muffler design will resonate at a slightly different rpm. Some are very quiet (stock...no drone) and some designs are louder and you will get drone.
  5. The flowmaster 40's drone is not objectionable with good comments previous
    to my post. When you hit that 2000rpm note going about 45mph or so in 4th
    or as i have done in 5th with cruise going 70mph is not objectionable...almost
    sort of a purr that is to me really relaxing to listen to. Scrap your stock h
    and go with drgas x pipe. It and flows are a marriage made in heaven imo. Mark
  6. Well, I'm not sure if my car has a lope but it does sound nice, but maybe the difference you are thinking of is that a dohc mustang has a v-8 and the maxima doesn't? Or does it? i think its a 6 cyl. :shrug:
  7. This was the case for me until I got my Magnaflow x-pipe, it's loud as soon as you step on the gas! :nice:
  8. Get a Pro Chamber. :nice:
  9. actually, i'm almost certain the stock muffs dont drone because they are not the same size to each other, hence canceling out the drone
  10. I think your right. I know they made something uneven down there on purpose to decrease sound.

    Thanks for the explanation guys.

    Mr Dohc: The Max is a DOHC 24v 3.0L V6. It was also a sedan, so it's understandably going to have smoother features, and the idle was no exception. You can hear it in the exhaust (on my cobra) that the car lopes a littttttle bit. It has a deep moan at idle and will emit slightly unstable pitches every now and then. It's not a problem, I'm used to it, I just thought maybe Ford uses a fairly aggressive cam from the factory, which is what causes the lope.