exhaust drone

A

Anonymous

Guest
Ugh!

I just spent some dollars and bought a new set of Pacemaker dual headers with the jethot coating. On the aft end I had installed two Flowmaster 40s w/an H-pipe in between.

I sounds fantastic driving around the city.

On the highway, things change. Between 60-70mph, all you can hear is a terrible headache-inducing droning sound. It's way too loud and it makes my ears ring for a long time after. Above mph it quiets down again. I don't know what rpms this is happening at because I don't have a tach.

I spoke with the local Falcon mechanic today and he said he had the same problem years ago with a similar setup. Does anyone know exactly what causes this and HOW TO FIX IT?

I wouldn't mind getting quieter mufflers if I knew it would solve the problem. At this point, I'm ready to do anything because its just undriveable on the highway.

Thanks for listening.
 
Ahh, the Flowmaster drone..... Some people actually like that noise.... :unsure: (I'm not one of them).

Without buying new muffs, two things may help. First, a crossover H- or X-pipe will soften up the sound. Or, second, you could stick resonators in the system and see how that sounds. The muffler shop should have some small ones that will fit onto the tailpipes.
 
Noise travels in pipes like it does in a flute or a trumbone. High or low pitch based on size.

Becasue the general rules are that small single pipes create a higher pitch, the as you go to large single, the exhast tends to rumble like a trombone at various points. Going to two similarly large size pipes is even worse, as the drone is worse.


My recomendations on this forum are to

1) run the smallest diameter V8 exhast system (1.875 to about 2" internal diameter),

2) run dual mufflers of a good size at the back.

3) Then use an X pipe.

In my opinion, the easiest system basically runs a dual out header system like Offenokee Comet's, but it has a modification.

The two pipes co-join in a proprietry X pipe just past the crossmember.

http://img.photobucket.com/albums/v223/ ... meteX2.jpg

It is the easiest way to ensure the pulses cancel out the rumble and drone at the 1500 to 2500 rpm level.

Essentially, the rumble or drone happens when big pipes allow the pressure waves to reflect. When that happens, you loose low end torque, and the gas expands too much, and looses its motion, and its ability to scavange. At 4500 to 6000 rpm, it'll be fine, but the restriction and backpressure comes from mufflers, not the X pipe or the right smaller pipe diameter. The idea is to use the smallest pipes that work. On the street, they will work much better! As an exapmle, one 165 hp four cylinder engine only needs a 1.875" internal diameter pipe, one resonator or large two element primary muffler, and then one other 300 cfm muffler at the back. A 330 hp engine could just get by on twin 1.875" pipes if there were two mufflers over 300 cfm. Chuck all the other info into the rubbish bin.

Sound wise, the various kinds of exhast system with only mufflers at the back are the worst for an unobtrusive sound on the street. If one or two glasspack resonators are added at the front, they always help, but our in-line sixes have no space for them. Note, if glass packs are placed backwards with the serations pointing to the tail of the car, they produce little flow loss, but help deaden the drone.

The X-pipe idea works better than any other option, becasue the pipes on a six in line have to branch out from one side, and go under or around one side of the tranmission or cross member.

Take a copy of the picture, and have your exhast man install one.

Another set-up with superb results is wsa111's set-up. It will do the same thing...reduce the drone.
DSC_0007.jpg



information from many sources says that people are too eager to go for big single or big dual pipes. A six cylinder street engine in the 150 to 250 hp area only needs two 1.875 to 2.0" ID pipes, and two mufflers which individualy flow 165 to 290 cfm at 25" H20. Fitting an X-pipe is preferable to fitting two resonators because packaging four mufflers is pretty hard to do.
 
Welcome to Flowmasters!

I have 50 series and get the 2000 RPM drone. Not bad at highway speeds because of the matting I have. I actually can't hear them at all at 65MPH. I still am thinking of putting some resonators in the system becuase I like the sound otherwise.

Slade
 
I’m curious about this Flowmaster drone. I would like to ask a few questions of our members that run the Flowmaster to see if there is a common exhaust pipe configuration that causes this drone (exhaust turbulence frequency / back pressure).

How many of our members have this Flowmaster drone with the single exhaust?

How many of those with the drone have the dual outlet header with the “Hâ€￾ pipe or Crossover? Is the Crossover the cause?

Are there any members who use the Flowmaster that do not have the drone and what exhaust configuration are you using?

There are enough members that are using different configurations here that may provide a “Cureâ€￾ if the correct exhaust configuration is identified.

Doesn’t it make you what to say, Hmmm I wonder?

Have fun, Ric.
 
I think alot of the drone has to do with the 40 series mufflers.
I have a single exhaust with a 40 series flow and I have the wonder full drone.

I also had dual 50 series with an H pipe and turn down before the rear axle, with the turn downs angled 45 degrees at each other.
I had no drone.

I think the drone has something to do with the 40 series muffler and how the pipe after the muffler is routed..

Nathan
 
The "drone" is a resonance within the muffler itself. It sounds just like someone blowing across the top of a jug. At certain engine speeds, the exhaust pulses cause a sound inside the muffler that is exceptionally annoying to most.

It's a function of the internal volume of the chambers which is why 40 and 50 series react differently to the same exhaust flow.
 
My drone occurs between 2800-3000 rpms. I just give it a bit more gas and drive right through it. The drone doesnt bother me, but somthing is loose on my exhaust and it rattles in time with the drone and is very annoying :D :D

Mine is dual out pacemakers, "H" pipe, dual 2" pipes back to 40 series Flows which exit out a GT rear valance.

I really like the sound! ;) 8) 8)

Later,

Doug
 
The '66 Pontiac I bought has older 40 series on it and the drone around town is annoying. Flowmaster's website says the new 40 series don't drone, but I won't be buying them to find out. I too think it is the muffler cans and not any particular configuration. Rap on the cans and they ring.

I like the sound of a good exhaust, but all I can hear at certain rpm's is the drone. BTW the engine is 400 ci with stock manifolds and duals. It has a crossover pipe up front.
Doug
 
Hi.

Well, I did just that: I brought it back to the muffler guy and he welded in two bullet-shaped resonators. Worked very well to clean up the drone, and the system is quieter on the whole. I'm quite happy. You can still hear the drone very briefly at 60-61 and one other spot also, but it is much more driveable.

The only problem now is the RATTLE. For speeds at 10-20mph there is a definate and loud rattle sound. It doesn't happen in neutral and barely in Park. Only in Drive.

The muffler guy swears its not the pipes, but it didn't make the sound until I had all the stuff put in. Grr..
 
spankmeister7":hz520g9r said:
The muffler guy swears its not the pipes, but it didn't make the sound until I had all the stuff put in. Grr..
Click to expand...

Get in it and raise the car on the lift.
Stand on the brake and put it in drive and tell him to fix it right.


Drone is also fixed by using two different size and shape of mufflers, one each side.
 
im getting a 40 put on tomorow and i think ill do just fine with the drone cause my glasspack does that at certain rpms (mostly lower speeds) and it makes the music from my speakers warble... i dont give a shit, if it sounds badass! :D
 
Same here. Just installed single out header 2 1/4" pipe with 22" glasspack all the way out the back dumping just in front of the rear bumper and I get a loud drone in the low to mid rpm range, but sounds great once I open it up past that drone.
Now I'm thinking I shoulda went with 2" pipes and maybe a smaller muffler. Originally I had the stock system with a Walker muffler and it was a dog. I got a whole lotta of top end once I went with the new pipes.
 
Drone is because your exhaust acts like a pipe organ.

You can change the resonant frequency by adding a leg to the exhaust pipe, capped at the end. That will kill the drone.
 
You must log in or register to reply here.

Similar threads

DoctorC
Exhaust note change - stock to headers
Replies
6
Views
2K
StarDiero75
StarDiero75
XMFalcon221
Exhaust crossover - priority on sound
Replies
6
Views
2K
xctasy
xctasy
M
FAST EFI Installation on 200 Inline 6
Replies
11
Views
19K
thesameguy
T
A
brnt exhaust valve or blwn headgasket or neither??
2
Replies
27
Views
3K
mugsy
M
Back
Top