[70f400]

70 firebird 455 RA4 cam, pypes cross flow Rare 2-1/2 RA factory header.

I have a deafening drone from 1500-1800 rpm. Is there another 2 in 2 out mufler I can try that will work with the pypes set up or should I try and remove the x pipe? Any other sudgestions

[b-man]

Maybe try installing resonators on the tail pipes?

[70f400]

would placing the resonators before the muffler in the straight section of the pipes accomplish the same thing. after the mufflers there is little room for this with stock chrome tips.

[melwff]

i had the same issue, massive drone at 2K which is cruising at 40mph. Switched from Pypes mufflers to Dynomax VHT. 71 GTO 455 HO same exhaust as yours including manifolds.

[b-man]

Originally Posted by 70f400

would placing the resonators before the muffler in the straight section of the pipes accomplish the same thing. after the mufflers there is little room for this with stock chrome tips.

The factory did use 2 very small mufflers in that location in 1st-gen Firebirds, so I would assume they were for dampening resonance.

[PontGuy]

I have the Pypes crossflow system with X and RARE manifolds on my 74 455 and have absolutely no drone at all. Only difference is the cam. And the more I read through these drone threads I am coming to think that the cam might be a factor. Placement of the X could make a difference too. I had a shop install the T/A system and they placed the X a bit more to the rear than I would have.

My Lemans has the 2-1/2" Pypes X with Dynomax mufflers, also with a 455 and RARE manifolds. It has just a bit of drone with the top up, but not enough to be even noticeable with the top down. I installed the system myself and the X is pretty tight toward the front of the car.

Years back when I still had a 350 in the Lemans it had a terrible drone with Flowmasters, to the point where we could hardly talk over it. I added resonators before the mufflers and that toned it down a good bit but it was still aggravating. Based on my experience resonators are not a sure-fire solution.

I've not heard of any direct replacements for the Pypes crossflow muffler, and since my T/A with the same system does not have any drone I am not sure that replacing the muffler would solve your problem. I think I would try moving the X a bit before removing it or adding resonators. I never heard of anyone trying that and it would be interesting to find out if it made any difference.

[70f400]

That would be interesting to see. It is just behind the cross member now. How far back is yours?

[PontGuy]

They put it maybe 18" behind the trans crossmember. Not the way I would have done it but they said they wanted to make sure I could get the trans out easily, and they did do a very neat job. And it doesn't drone.

The other big difference is the cam. I have an XE268 in the engine now. The engine came that way and a swap is on my to-do list because it does not match up well with the 9.5:1 CR. I'd hate to put a good cam in the engine and then have a drone problem though.

[rexs73gto]

Last year I had in my car the 455/462 with the Dynomax trubo mufflers with an X-pipe & it had no drone at all. Also the 21/2 " Rare RA IV exhaust manifolds with the E-heads. My X-pipe is set so the start of the x is just behind the cross member & then the pipes go into the mufflers. No drone at all that way. I do believe its because the placement of the X-pipe behind the cross member that cures the drone.

[PontGuy]

My X-pipe is set so the start of the x is just behind the cross member & then the pipes go into the mufflers. No drone at all that way

That's the way I did my Lemans and no drone problem with mine either.

It just seems strange that we are putting identical exhaust systems including manifolds into cars with very similar engines and getting different "drone" results. I've read a lot of people having drone with the 2 muffler Pypes system, though I am not one of them. But this is the first I've heard of someone with a drone problem with the F-body crossflow system.

[70f400]

If the drone is a harmonic then there is a lot that plays into this. lifters,( Rhoads) rocker ratio(1.5) X placement, and compression ratio (9.75)all effect the end sound at the tail pipes. By changing anyone of these I guess you can get a frequency that causes this a harmonic that rattles your brain!

[PontGuy]

That's what I was thinking. And if so moving the X even just a bit might change the harmonics? A shot in the dark, but I never heard of anyone trying that and it would be interesting to find out if it made any difference.

[71GP76TA]

When I bought my 2009 Challenger R/T it had 2 chamber Flowmasters that droned really bad. I removed those and installed 1 chamber Flowmasters and moved them further back... It still droned... A couple of weeks ago I removed the mufflers and welded a piece of pipe in place(no mufflers on car now).... and eliminated most of the "cruising speed" drone. Its still loud(very loud ) when you put your foot in it... But at 1800-2000 RPM cruising it just gives off a slight rumble/drone..

[rohrt]

Posting this again for edification. I spent a few hours in the archives to find who had and eliminated their drone.

Long story short->Just because one person had success don't mean anything for you. There seems to be some magic why some have drone and others don't and even more magic why some are able to get ride of it doing something and other do the same thing thing it doesn't work for them.

The most success I have seen for anyone that is documented is with the VT mufflers. There are only a handfull of guys on the board that had issues with them and took them out. Most other have had great success.

My VTs are still in the box


_____________________________________________
Drone

Description is very important.
Drone vs to darn loud exhaust
Drone from vibration or from pulse wave amplitude

Most drone at 1800 to 2000 RPM

Had drone
Raven mufflers
Flow Master 40s
Spin Techs
Magnaflow
DynoMax Utraflow
Goerlich Xcelerators


Read one guy that use two different mufflers and drone was gone another thread where two case lenghts were changed it didn't help at all.

Read one guy changed a cam and drone went away. I changed my cam and the drone didn't change at all


http://forums.maxperformanceinc.com/...t=Drone&page=2

CCass- post 27
Race Pro
Magnaflow
DynoMax Ultra Flow
Goerlich's Xlerators

All are the SAME design mufflers. Therefore they will sound, flow and drone just about identical. They're fairly quiet except for wide open throttle. However there will be a drone (resonance) at light throttle around 1800-2500 rpms depending on gears, motor power etc. It's pretty much unavoidable with a straight through muffler. Things that will reduce the drone are as follows:
X-pipe
insulated exhaust hangers
resonators
That's about it. Some bodies seem to create more drone than others.

The only style muffler that elminates drone must have a flow path that runs down the muffler on one side, back up the middle and then back down the other side.
Dynomax Super Turbo is one of the best. Pypes has just introduced a Turbo Pro muffler that is very similar but is welded case stainless. However, it is only available in 2.5" offset offset.


aronhk_md-Post 28
I went with the Goerlich Xcelerator 123's after talking with Tom Hand. His report on the 3" in and out 18" version was they flowed 97% of what a straight 3" pipe would. I was having trouble getting through inspection in DE with 101-102dB (they measure at 2500 rpm) with a set of 3" Spin Tech 14" body mufflers. Come to find out those SpinTechs only flowed 78%!!!

The Goerlichs dropped me to 95dB at the same rpm. But they also got rid of the drone I had with the old mufflers between 2200 and 2500 rpm. I can now talk to someone inside while driving, and as of right now theres still bare metal floor.....no insulation or carpet yet. Plus I know they are putting less backpressure on the turbo. The new 18" mufflers required some patience to fit into a 2nd gen bird but I think they are worth it. The car still sounds great, but NOBODY thinks theres almost 1100 hp there (soon to be over 1100....hehehe).



http://forums.maxperformanceinc.com/...ighlight=Drone

Wrenchmen - post 28
I had the same issue with the dreaded drone!

I installed a 2 1/2 system with X-pipe and spin tech low profile mufflers, the drone
was terrible!...just around town it was not a problem, but long drives and the drone
made it very annoying and hard to talk to someone else.

I loved the sound of the Spin Techs, so I tried everything I had read about on eliminating the drone without replacing the mufflers.

A I made sure the system was loose and not binding, I had to fabricate my own tailpipe hangers to acomplish this....result...No improvement!

B I experimented with exhaust tip length, exiting well beyond the rear of the bumper and several areas in- between...result....No improvement!

C I designed my own exhaust tips, similar to what diesel engines are using now,
result....No improvement!

D I cut both front pipes right after the turn downs and installed short flex pipes from jegs, totally isolating any ridgidness of the exhaust system from the exhaust manifolds/engine....result....No improvement!

I finally gave in and replaced the mufflers...Drone is completely gone. I used a pair of DynoMax VT's. I think they are a little too quite at idle, but the drone is gone!

I believe that engine build specifics and parts used play a big part in whether or not an engine is prone to having drone issues.

I was thinking of trying some other ideas out there to eliminate the drone without a muffler change, One idea was a type of dampner (not sure if thats the proper term) Ford uses on some of its exhaust systems....like the one pictured at this link.......
..http://www.mustangmonthly.com/howto/.../photo_06.html

Also, I read of people using a "J" pipe in the exhaust system to help with drone,
something like this at this link,.....http://www.performancecarweb.com/showthread.php?t=144
Forgot to add that I also gutted my interior, added peel n stick to all floor sheet metal and up the rear sides including behind the rear seat and under the package tray.

I also hung a very heavy piece of jute type insulation behind the rear seat back.
All that work did not seem to make any noticable difference to the exhaust drone inside the car.

Almost forgot to mention that in my drone free quest, I purchased a pair of Hedman Hot Tips,
small 9" resonator chrome tips...litlle glass pack exhaust tips.
like here...http://www.jegs.com/p/Hedman/Hedman-...69187/10002/-1
Bolted them on and guess what...absolutley no drone. BUT my car now sounded like crap! They really drastically altered the sound. For a while I would just bolt them on when we were taking a long drive, but that got old real quick and also in a short time, the chrome peeled.

As you can see, I did a helluva lot of stuff to try and eliminate the drone AND keep a decent strong sounding exhaust note. I am happy with the DynoMax VT for now.
Another added benefit is they seem to not reject as much heat onto the rear floor and into my car as the SpinTechs did. The SpinTechs rejected a ton of heat, and I would think that means they didnt flow as much as the DynoMax VT's do.


Sorrotica-post 31
Upon doing a little searching on the internet about exhaust drone I found 2 things that people are praising to stop it. One of the things Pontiac did on the production line and I could never figure out why one muffler was longer than the other on dual exhaust Pontiacs and now I seem to have stumbled upon the answer.

If the right and the left sides are different the sine waves don't amplify as they are not the same frequency, so Pontiac engineer in their wisdom made the mufflers different lengths and sizes so the sound waves didn't mirror each other. It also seems that X pipes make this phenomenon worse, just switching one muffler may cancel out the drone.

Another fix was to build a pipe that looks like an H pipe and install it behind the X connecting both pipes together. The pipe is not open in the middle though it has a barrier wall inside the pipe and is not in the middle, it is about 1/4-1/3 of the way from one end causing unequal length chambers for each pipe also causing the waves to be at a different frequency. It seems v6s are even worse than V8s are and this is how some of the HP V6 guys fix the drone and it also works for V8s. They call it a center resonator chamber and it looks fairly easy to build and install.

http://www.allfordmustangs.com/forum...s-p1010351.jpg

http://www.allfordmustangs.com/forum...s-p1010356.jpg

Some other info was the J pipe, resonators, a glass pack towards the end of the system tailpipe area, the weights that ford uses welded on the pipes at different points and different length arms and possible different size weights. The main theme here is to make the system not mirror the other side so the waves change. It evidently can be accomplished in a variety of ways. I hope this may be of some help in enlightening about what causes this problem.

After thinking about this center resonator chamber if I were to build one I would also maybe vary the pipe diameters as well as the wall in the middle to make them as much different as possible, the shorter side 1 3/4 pipe and 2 1/4 on the long side.


http://forums.maxperformanceinc.com/...ighlight=Drone

VAB5 post 11

I'm so flippin happy right now! '69 LeMans convertible with a 350 2BBL. I have a Pypes 2.5" X-pipe setup. I started with 14" Street Pros (drone), went to Dynomax Turbo 14" (drone), swapped out ONE side with an 18" Dynomax Turbo (drone) to replicate how the factory did it. Unbearable drone right in cruising range with each setup. Can't hear the radio/fillings are coming loose drone. Made we want to sell the damn car.

Got the VTs installed today. What a difference. No more drone. Taking the car on a club cruise this weekend, and I'll report back. But so far, I have no complaints.

Don't have to sell the car! ;-)

[71 T/A]

Yep I tried the VTs for my 72 Formula and there was no drone but car slowed down noticeably from the Goerlichs. I reinstalled the Goerlich Xcelerators, the car is quicker but there is some drone around 1800-2200 rpm.

[leeklm]

Not sure how common this is, but here is what I ran into... Car was loud anyway with flowmaster 40's on it (RAM manifolds and H-pipe). But then I blocked off the heat crossover on my iron heads and the drone was much worse.

I then drilled a 3/8 hole in each of the crossover plates, and the drone went away (or at least back to normal for a flowmaster 40). Talked to my engine guy, who said he has run into this in the past.

Something to consider.

[455rebel]

Went from 2.5 cherry bomb style generic mufflers that exited just in front
Of the rear end with 22 degree turndown,horrible drone 1400-1900rpm.
To dynomax that won the muffler shoot out, same position same 22 deg
Turn down, drone almost all disappeared , except slight drone only
About 1400 rpm. Best hundred dollars I ever spent!

[70f400]

I had to do something about the exhaust. Ordered new parts for fuel delivery system including a tanks inc efi gas tank which well have 8 AN lines in and out. No way the transverse muffler was going to allow that to happen. I had a local muffler shop look at what I could do and hopefully limit the drone. The old guy recommended Flowmaster delta 40's. I took a chance and I am glad I did. No drone great sound and you can whisper in the car and still be heard ( with windows up and A/C on.) roll down the windows and it sounds like a muscle car but not too annoying. Ground clearance is not great but he was able to tuck them up tight and back towards the rear wheels. I like it so far.