[VAB5]

I installed the Pypes 2.5" system with X-pipe on my '69 LeMans, along with the Dynomax 14" turbo mufflers. This is supposed to be a relatively drone-free setup, but I get horrible drone at idle in drive, and at various other RPM points. Skull-rattling drone.

I have a theory about what's causing the drone. I have the '69 bent trumpet tips, and they exit well before the back bumper. I'm thinking that the hollow area back there creates a box for resonance, and that's why I'm getting this awful drone at several speeds.

Thoughts?

I'm going to install the 2.5" Pypes turn-downs, which are longer and should exit beyond the bumper. I'll report back my findings. I hope I'm right!

[Sirrotica]

Anytime the exhaust can hit the floor it's going to be louder than if it exits away from sheet metal. The sheet metal acts like a speaker and amplifies noise. Put your head inside of a 55 gallon drum sometime and see how much noise gets amplified.

[ericwy]

Make sure the exhaust is isolated from the body by the exhaust hangers.
I replaced very quiet 14" Midas "golden turbo" style mufflers with louder better
flowing 14" Dynomax super turbos. But I also rehung the system using proper
mounts with isolators in the OEM locations. Made a huge difference. The system
is louder overall on the outside, but no drone on the inside.

[rexs73gto]

I have the dynomax 16" mufflers the turbo style & I to have an X-pipe in the proper plce according to the placement sheet. It stops at the rear axel, 2 1/2 " pipes & at just about any speed I get drone. I have hush mat with insulation & carpet. It's so loud at times I can't hear myself think. It's all mounted with the factory mounts in the rubber hangers but It is still very loud. I think it may have to do with the X-pipe more then the placement & the way there hung. I think this becaue before I had an X-pipe it was not as loud as it is now. I think maybe the X-pipe scavanging process is the reason it's louder & has the drone now. Am I out in left field or can I be right?????

[Sirrotica]

Any exhaust I have seen an X or and H usually quiets a previously separated system down although it does change the tone. I had a separated system with turbo mufflers under the back seat area and stock type tailpipes on a 75 T/A and it was a major headache to drive on the interstate with. I was going to try an H pipe to change it but never got around to it.

I do believe it would have gotten rid of some of the noise because I had built 2 systems on 2 other T/As just using the pellet type catalytic convertors on both sides and no mufflers and with an H pipe it quieted both cars down so they weren't objectionable on the road.

I feel if it's too loud and objectionable with an H or an X pipe you just flat out have the wrong muffler. Another nice feature with the H or X is they give more bottom end that you can feel (seat dyno) over true duals.

[2002Z4CSS]

I have the 2 1/2" Pypes Stret Pro system with "X" pipe on my car and there is no droan heard. Usually if you do get a droan it is while driving in high gear.

[FrankieT/A]

I have an X pipe and flowmaster 40 series muffs and have a little drone at about 2500 RPM on the highway, but only at that one speed. A couple hundred RPM more or less and it goes away. 71 TA with factory style tails exiting like factory.

[rohrt]

One of my favorite topics.

My observation based on the fleet of pontiacs that me and my brother have.
My theory on Possible Drone Causers:

Larger the exhaust more susceptible
Convertibles more susceptible
strait through mufflers more susceptible
shorter mufflers more susceptible
shorter exhaust systems more susceptible
Larger displacement engines
X - pipes???

I have some cars that have drone and some that don't

[ericwy]

I am no acoustics expert by any means, but from my minimal research its about resonant frequencies of the pipes which is determined by the length and diameter.

An analogy is a guitar string. If you pluck a string it resonates at some frequency based on length, width, and tension. If you very lightly touch the string at the mid point (like when tuning) and pluck the string again the resonate frequency shifts up (probably doubles) and the sound is much higher.

I installed an extra pair of hangers about midway between the collectors and the splitters. The location is in the drive shaft tunnel. They are not there to support the
exhaust pipes, but to help snub the resonate frequency of the length of pipe.

There's alot more going on inside an exhaust pipe than a guitar string, but I figure the frequency of the pipe that's transmitted to the body shell through the hangers adds to drone. If you can influence that frequency (double it) the resonance will occur at 4000 rpm rather than 2000 rpm cruising rpm.

[drtracer58]

ericwy you are saying you don't have any Drone ????

[quicksilver97ta]

Originally Posted by rexs73gto

I have the dynomax 16" mufflers the turbo style & I to have an X-pipe in the proper plce according to the placement sheet. It stops at the rear axel, 2 1/2 " pipes & at just about any speed I get drone. I have hush mat with insulation & carpet. It's so loud at times I can't hear myself think. It's all mounted with the factory mounts in the rubber hangers but It is still very loud. I think it may have to do with the X-pipe more then the placement & the way there hung. I think this becaue before I had an X-pipe it was not as loud as it is now. I think maybe the X-pipe scavanging process is the reason it's louder & has the drone now. Am I out in left field or can I be right?????

Are you saying you dont have tail pipes? Probably not what you meant but, tail pipes do wonders to quiet the cabin compared to without them.

I had some Race Pro mufflers which sounded really good outside the car, not too loud either. But the straight through design made alot of drone inside the car. I switched to some Dynomax Super Turbos, they have an 'S' design inside, somewhat noticable difference outside the car but a big difference inside the car. This is a 3" system with headers and an X.

[rexs73gto]

Sirro says he put on a converter on each side of the exhaust, that in itself will stop almost all noise because by putting on a conv. you are simply putting on a super quite muffler. Cats are designed to no only collect gases but to quite a system so that system doesn't really count because were running exhaust with no convs. I have 2 1/2 " exhaust with larger mufflers then some which I wanted to help quite down my noise level , but it still has the drone. I have 3.73 rear gears so at just about any speed I hear it. I will try tail pipes next. I forgot to say I run Ram Air exhaust manifolds too. The new 2 1/2" style. My car has the x-pipe & should be qiute but it's not. When I had my last set of headers with real duels no X-pipe & walker turbo mufflers I didn't have any drone. Is it now just the mufflers were buying that are causing the problem drone??? It seems everyone on here has some form of drone with teh new exhaust were installing. Are the muffler were useing now seem to be noisey for the sake of a little extra hp?? I want to have exhaust on my car that allows me to hear myself think while I drive. Can anyone help in give me an idea on which muffler to use for that. I din't have this problem with the past exhaust without an X-pipe. ANY IDEAS?????

[quicksilver97ta]

Put the tail pipes on before you do anything else. I thought my exhaust was louder with more drone than systems I used to have several years ago but I think the reality is that I am just getting older. Not that I'm old but I'm not that teenager or twenty-something I used to be! LOL!

[Silver Judge]

Tailpipes should make a BIG difference !

[ericwy]

Originally Posted by drtracer58

ericwy you are saying you don't have any Drone ????

No drone at cruising rpm which is about 2k with my OD. It gets pretty loud at 4k. I had horrible 2K rpm drone with the "quieter" midas mufflers. Same 2.5 " pipes and x-pipe before the mufflers. I got rid of the solid metal hangers that attached the tail pipes to the body (above the axle and at the splitters)

Still had some drone after replacing with new rubber isolated OEM style hangers so tweaked and adjusted the system so each hanger supported the same weight and made sure it all hung "loose". This helped reduce 80% of the drone. I then added the mid pipe hangers to the tunnel. The bracket hangs about 1/4" above the pipe before clamping it to the pipe. So its just barely it tugging upward on the pipes at that mid point. That semed to eliminate the rest of it.

The 14" Dynomax STs are much louder than the midas mufflers but there is no arguing that the cabin is much quieter inside than it was before.

[Sirrotica]

Originally Posted by rexs73gto

Sirro says he put on a converter on each side of the exhaust, that in itself will stop almost all noise because by putting on a conv. you are simply putting on a super quite muffler. Cats are designed to no only collect gases but to quite a system so that system doesn't really count because were running exhaust with no convs. I have 2 1/2 " exhaust with larger mufflers then some which I wanted to help quite down my noise level , but it still has the drone. I have 3.73 rear gears so at just about any speed I hear it. I will try tail pipes next. I forgot to say I run Ram Air exhaust manifolds too. The new 2 1/2" style. My car has the x-pipe & should be qiute but it's not. When I had my last set of headers with real duels no X-pipe & walker turbo mufflers I didn't have any drone. Is it now just the mufflers were buying that are causing the problem drone??? It seems everyone on here has some form of drone with teh new exhaust were installing. Are the muffler were useing now seem to be noisey for the sake of a little extra hp?? I want to have exhaust on my car that allows me to hear myself think while I drive. Can anyone help in give me an idea on which muffler to use for that. I din't have this problem with the past exhaust without an X-pipe. ANY IDEAS?????

Just a FYI, dual pellet convertors by them selves are about as quiet as glasspack mufflers, they are not quiet by any means and they sound obnoxious, at least to me. The factory used a regular stock muffler to quiet the exhaust because cats by themselves are much too loud. This was in the late 70s and in Pennsylvania where I lived and had my garage/service station at the time required catalytic convertors in order to pass the yearly state safety inspection.

For the late model T/As at the time (75-79) that people wanted to improve the performance of, the answer was 2 1/4 pipes with dual cats and with 390 Torino tailpipes the exhaust exited at the quarter panels where the stock T/A splitter ends could be welded on the Torino tailpipes. The cats were the only thing to quiet the exhaust, no mufflers, no resonators. This was before X pipes were known about, but H pipes did a lot to bring the performance up and get rid of the crackle from the twin cats and make the car quiet enough to not attract unwanted LEO attention. Most of these cars also had headers and it really helped from the performance standpoint and because the cars had dual cats they were legal in the eyes of the law.

Re-jet the Q jet, recurve the dist and we'd also use either the cast iron intake or a Holley street Dominator intake. They surprised more than one musclecar and they looked stock but were a little louder than stock, they surely didn't run like a stock T/A though..................

I believe that Detroit had problems with drone long before we did and their answer was resonators to kill the objectionable tones. I believe if I were to design a system today it would have Aero mufflers and Aero exhaust resonators as they both increase flow while getting noise under control. I just do not like loud obnoxious exhaust, I got that out of my system when I bought a set of cherry bombs when I was 16 and accumulated tickets from loud exhaust and attracted too much attention from cops. The Areo company went out of business, however the patents were purchased and are now again being produced:

http://www.jonesexhaust.com/products.cfm?ProductTOC=23

[rexs73gto]

I think it may be I'm getting older to but I like the sound of a good exhaust but I can't stand the loud drone inside the car. I have never had it with this car ever, & I bought my car new, so that right now means I've had my car 39 1/2 years & it sounds worst then it ever did.

[wrenchmen]

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

Never got around to the above experiments, just replaced the mufflers and moved on
to my next dilemma!

[FrankieT/A]

The drone is not from the actual installation in my opinion but rather the sound waves. So I don't think hanging weights on the exhaust is gonna help. I would think weights would dampen vibration in the system causing metal fatigue. When you use an S type turbo style muffler it actually lengthens the exhaust system. The exhaust system thinks the muffler is triple the length. The drone is from sound waves getting out of phase with each other. The exhaust as a system needs to be tuned, just like the analogy ericwy used. Sirrotica is right about resonators to a degree. I was in the muffler business for some years and really the only cars that had resonators for the most part were the luxury cars, but i feel that was mostly to reduce noise further and not because of drone(Brad, thats just my opinion). I can tell you that back in day( before Dr. Gas and his X pipe) putting in H crossover eliminated drone a lot of the time. From all posts of this thread, the only people that were successful at eliminating drone changed to a different muffler. Turbo mufflers use a parabolic system to cancel out sound waves instead of just a packing to absorb noise. Back in the day I used turbo mufflers because Flo Masters weren't invented and I used to blow out exhaust manifold gaskets(Ram Air III manifolds) left and right. It was driving me crazy!!! When I put on the Flo Masters I never blew an Ex. gasket again. I like the way they sound so I put up with a little drone.

[chrisp]

Would like to take a poll as to who has sound deadener on the floor and who does not , i believe this may play a role in the drone / interior resonance .I have the peel/stick foil faced & have 40 series Flowmasters on a 461 roller Kaufman headed tri-power 64 GTO , no drone @ all tailpipes exit behind tires @ the side .