Drone?????

[cleanmerc01]

what is this drone you speak of in exhaust. my exhaust has seen better days and has rust holes in the flowmasters. i called the shop today and they said it be about $425 for whole new exhaust. guy said the mufflers are some knock off flowmaster 40 series but better they stainless. i didnt ask about the drone sound cause i have no idea what it is. i was also thinkin about having the exhaust to stop at the rear end with turn downs what is the pros and cons of having it stop at the rear end???

[slymer]

drone is the rumble inside the cabin area when running down the road in cruise. it basically is undesired noise... unless you like drone (which some of the guys here do).

[cleanmerc01]

i guess if i have the exhaust stopped at the rear en with turn downs i would have quite a bit of drone then. i just wondering cause it would be about alot cheaper to stop there. also where could i get maurader tips at??

[zoomie]

drone isnt a rumble its more like a solid whaaaaaaaa sound alot like a 60 hrtz freezer hum only a shit load louder and deeper, and its very annoying

[marquisman]

yea, its the constant humming sound you get at a steady RPM while driving. it affects everyone differently

[SVT98t]

Marauder tips
www.innovativeinterceptors.com

You can have them add a u-pipe out of the mufflers and have them come out the sides right in the front of the rear tires.

-ryan s.

[v8only]

it only happens at certain rpms...for 5.0 mustangs it's right at 2100 rpms....I find it the most beautiful sound on the planet....dual flowmasters reverberating.....it's the exhaust singing to you it's melody. I never quite understood why someone wouldn't like it, that's the very reason why you get an aftermarket exhaust. When I was younger I literally burnt out an entire clutch going up a 10 story parking structure just so I could hear the drone bouncing off all the parking structure walls....lol I was new to driving stick. man, you should have seen and smealt the smoke coming from that clutch when I got to the top. Don't go with "knock off" flowmasters...the only muffler that sounds like flowmasters are flowmasters.

[P72Ford]

Drone is great in something that you don't drive every day, in my opinion.

On the truck in my signature (which is my driver) I have a Cherry Bomb Extreme (aptly named) and an electric dump tube. The exhaust is dumped under the bed, right before the rear wheel.

My truck resonates (drones) so bad that is buzzes the interior trim at any engine speed below 3000. When you romp it, the sound cleans right up and it sounds like a hot rod.

I used to have tailpipes on it, and it wasn't nearly as bad. I will probably go back to at least a single tailpipe this summer.

BTW, the Cherry Bomb Extreme is a single chamber 'muffler' which is about 12" long, total. The case is 6" long. Like a Flowmaster 10 series.

I will also let you know that Flowmaster mufflers are not the end all of performance mufflers. There are alot better performance options out there, but for your car which has a basically stock engine, they would be fine.

[v8only]

I buy flowmasters specifically for the sound. I've been through about every type of aftermarket muffler and keep coming back to flowmasters.....flow is good enough for me....give or take a couple of hp doesn't matter to me.

[1987cp]

My (limited) experience is that drone has absolutely NOTHING to do with the mufflers. I tried Flowmasters (loud, turned heads on the street), Super Turbos (quiet), and generic economy turbo-style mufflers (also quiet), and each droned about as badly as any other when I had 2.5" exhaust all the way back. For now, I've crutched the situation by using smaller tailpipes (2.25" someone else had custom-bent), which somehow switched the drone around so it doesn't bother me as much (saves my hearing, plus my non-car-enthusiast passengers don't complain about it). I also rode with a member who's not around much anymore who had (at the time) a 2" system with NO mufflers, and for me it was very quiet inside the car (little to no drone). Nearly the same thing with my P72 when it came into my possession with original Flowmasters and 2.25" tubing - the actual exhaust note was pretty obnoxious, but relatively little drone/resonace inside the car.

My opinion (which some guys will refute) is that anyone not bothered by exhaust drone simply has low hearing sensitivity in that part of the sound spectrum. Either that, or mine is abnormally high among car enthusiasts.

Solutions I've heard of for exhaust drone basically involve some sort of resonator. Some guys at SBFtech were talking about actually installing a separate resonating tube off the side of the tailpipe, cut to such a length that it tends to cancel the soundwaves that bother you the most. It's along the lines of a Corsa muffler, which has nothing in the actual path of exhaust flow but effectively has sound-cancellation tubes of various lengths to produce what they call "broadband sound cancellation". The idea is that even if the actual exhaust tone is quite loud, there is very little in the way of the resonance that drives passengers crazy and causes low-frequency hearing loss for the driver.

[Jon]

I have the exhaust on my LTD exiting right under my butt. Just the factory system with the muffler cut off. Had to do that to replace the gas tank.

There is a bit of a done at highway speeds...but I love it...also, once you roll up the windows, its quiet enough you can have a decent conversation.

I know of that sound the 289 mustangs sound at 2100rpm and personally i cant stand it. It just buzzes the hell out of my ears and makes my head want to explode. However, driving it is different than riding in it. And when driving it, it doesnt hurt as much as when im riding in the backseat.

Ill let you know a tercel wagon has that death drone too. Had to cut the muffler off cause I bent the hell out of the pipe when offroading. Unbolted the pipe from the cat...and now at 2800 rpm...aka 57mph Theres a drone...and its worse when you roll up the windows. Really ricey sounding and just plain OW to my ears. getting a 90* bend to fix it by making the exit smaller.

[1987cp]

I have the exhaust on my LTD exiting right under my butt. Just the factory system with the muffler cut off. Had to do that to replace the gas tank.

There is a bit of a done at highway speeds...but I love it...also, once you roll up the windows, its quiet enough you can have a decent conversation.


Again, depends on your sensitivities. I drove a stock SEFI lowpo with open exhaust after the cats for about a week, and for me it was way beyond horrible. Even tried wiring some steel wool across the openings just to tone it down a little while I figured out what to do about replacing the Y pipe that had just rotted off.

I've been in a Civic with a nasty drone, so I agree that it's hardly a V8-specific phenomenon.

[1980c10]

In the marq with 1 5/8" headers, 2 1/2" h pipe, and slp loud mouth 1's dumped at the axle. Between 50-60 mph it is absolutly mind numbing, it's like there is a pressure on your head, kinda like you're underwater. It's terrible.

But... 100% worth it because it sounds so nasty when you unleash it. It really sounds awesome at WOT.

[SVT98t]

On my Marauder, I replaced the stock 3.5" res tips with 4" resonator-deletes.
It does make a difference in drone.
It has a sweet spot around 2k and then again at 4k. It wonderful. And that's all with stock exhaust!

-ryan s.

[torquelover]

1987cp's car with 2.73s had hideous drone/boom in OD at low revs. Actually eye watering for some in the back seat. I used to have passengers start pleading with me to either speed up or downshift.

[1987cp]

Interesting. Guess with the 3.27s it was hardly ever spinning that slow. And that's with the 2.25" exhaust I said was fairly low on drone despite being wheelie loud out back, correct?

Speaking of which, keeping a 2.5"-equipped car up in the revs via deeper gears (say, 4.10s) and a looser converter (maybe 2500 or higher) might help the occupants experience less drone despite it being pretty horrible when it happens?


Incidentally, when I had my side-exit setups (exiting in front of the rear wheels), it was loud but no drone. And you can get away with that in Indiana (or so my experience dictates).

[cleanmerc01]

i have single exhaust and i havin my buddy weld new exhaust on. i was wondering how i am i going to do this dual set up? am i going to need to get another cat and o2 sensor? or should i just run the way now with a 1 in 2 out muffler? i want to have it exit right in front of back tires. any help will do. we have mandel bender and welder so we can make all bends.

[Leafsrule16]

Your exhaust is dual all the way back to the muffler where the two pipes meet into one muffler and go back as single. Just buy two mufflers of ur choice (remove the second set of cats too or it wont sound good at all), buy an h-pipe, tail pipes and a few feet of piping and your set. Weld your tips on too if you want some.

[gadget73]

Yup, just buy the stock replacement dual exhaust parts. It just bolts in, easy as you please.

[v8only]

The problem with the stock dual exhaust is that it's WAY too restrictive. The dual exhaust connects right after the cats up front, which is dual 2.5"...then the pipes get restricted down to 2" or perhaps smaller.....You'd probably be best sourcing some dual exhaust stuff from a junkyard cruiser, then using it as a template and cut out the smaller diameter piping and have dual 2.5" stuff welded in.

[slymer]

2" all the way to the manifolds on my 88... 2.25" all the way for my 93. 2.5" all the way for my Mark (mustang stuffs under the hood).

[TomO]

I guess everyone can have their own definition of drone, but I've always thought of exhaust drone as describing a resonant effect of dual exhaust. Here's my theory. Resonance is a natural frequency at which an object vibrates. Think of a tuning fork as an example -- a tuning fork tuned to the note of "A" has a resonant frequency that makes an "A" note (I think it's somewhere around 400 Hz, but I don't remember exactly). If you put a "A" tuning fork against a violin or guitar or other stringed instrument and play an "A" note, the tuning fork will start to vibrate because it's the resonant frequency. But if you play any other note, the tuning fork will not vibrate much. With a muffler, resonance is the frequency of the exhaust pulse or speed at which the air inside the muffler vibrates to make a louder noise than at other speeds. I'm not sure what causes it, but I think it's when the wavelength of the exhaust sound is some multiple of the length of the chamber in the muffler. This can cause a louder sound because the wavelengths and muffler chamber interact so that the sound is sort of amplified by itself. That's why with some old cars that have rattles, you will won't hear the rattle until the engine reaches a certain speed -- when the engine speed reaches the resonant frequency of the rattling part. Another way to think of it is to imagine a big tub of water. The resonant frequency of the tub is the frequency that it takes a wave of water to bounce from one side of the tub to the other side. Imagine the tub is a muffler. Imagine your hand moving back and forth as the exhaust frequency. If you move your hand back and forth real slowly, the waves are absorbed between your hand and the sides of the tub and everything's cool. But if you slowly increase the speed of your hand moving back and forth you will eventually reach a speed at which your hand is moving back and forth at the same speed that a wave naturally bounces between the sides of the tub. At this speed, your hand moving back and forth is amplifying the natural wave frequency of the tub and you will notice that the wave gets really big and starts splashing out of the tube. This is resonance of your hand moving back and forth and the tub's natural resonant frequency.

Now think of an exhaust system. The exhaust pulse varies with the speed of the engine. The system has a natural resonant frequency. This resonant frequency of the exhaust system is usually accentuated in a dual exhaust system with two mufflers of the same size. That's because the resonant frequency of both mufflers is the same and when one muffler starts resonating, it will amplify the resonance of the other muffler and vice versa. This seems to be particularly true with systems that have a cross-over tube (balance tube) and performance mufflers that don't have resonance chambers (like turbo mufflers etc.) There's a certain range of engine speed in which the resonant frequency of the muffler is reached, which causes both mufflers to resonate. It sounds like a loud hum and it occurs only near a certain engine speed.

[Mercracer]

..... There's a certain range of engine speed in which the resonant frequency of the muffler is reached, which causes both mufflers to resonate. It sounds like a loud hum and it occurs only near a certain engine speed.

No drone I have ever experienced was the effect of having duals resonating against each other. Aftermarket exhaust will often cause parts of the car (and people's homes, etc) to resonate due to the stronger unharmonious vibrations coming from it...
I have never seen someone try so hard to justify loud exhaust and the often irritating drone it causes by blaming it on "just physics".......:lol3:

[1987cp]

He does seem to be thinking partly in the right direction, but if drone were ever caused by "resonant frequency of the muffler" (which I suspect rarely if ever even really exists, at least within the frequency ranges that typically cause objectionable resonance), it would: a) go away when substituting a different muffler with completely different design (and if you're thinking of resonance inside chambered mufflers, it'd be nonexistant when using a dissipative type muffler), and b) be unaffected by the experiments guys have done by constructing auxiliary "tuning tubes" based on the resonant length of the tailpipe.


+10,000 on resonance of parts of cars or of nearby buildings.

[gadget73]

strictly speaking, it is just physics. Annoying as hell, but it is just physics.

Apparently drone is more pronounced when both sides of the exhaust are identical because the whole system will resonate at the same time. Some vehicles specifically use different length mufflers and different diameter pipes to make this not happen. If you've ever ridden in a stock Lincoln Mark VII, they do not drone at all. Different mufflers, one tail is 1 7/8", one is 1 3/4" or something. Replace that with a conventional cat back with 2 matching mufflers and tailpipes of larger and same size pipe and you get that typical Fox 2100 rpm drone. Use 2 different mufflers though, and its mostly not there.

Interestingly, Panthers with a Mustang H pipe have the same drone points as a Mustang does. can't help but think the pipe up front has something to do with it.

Anyway, the stock dual exhaust pipes are not a significant restriction with a stock motor. The stock mufflers blow, but the H itself isn't really an issue. Tailpipes aren't spectacular and could do with an upgrade but the mufflers are probably the easiest thing to upgrade. Most people aren't gonna want the stock mufflers anyway, too quiet.

[johnunit]

Wasn't there something posted here about a person who had cancelled out drone on a mustang by having a pipe going nowhere T off of one of the tailpipes? It seems it was the same length as the length of tail pipe after it, and was capped off. It's resonance cancelled out the resonance of the tailpipe past it, and having those resonances cancelled out stopped the other tailpipe from having a "partner" in resonation.

[1987cp]

Yep, that's precisely what I was talking about. Seems the original thread was on Corral.net, and it's referenced in a thread here (started by me, IIRC) and one at SBFtech.