The Great Flowmaster Super44 drone experiment of 2012.

Yes, I really like them and get lots of compliments on the sound. Never had any Flowmasters so I can't say how they compare.

It might be more old school than what most are after. Wanted to avoid the high frequency, tinny noise you hear a lot.

I also liked the exterior sound of the Magnaflows -- just couldn't tolerate the drone.

Kept "popping up" on Scooper's threads 'cause I wanted to know why he didn't warm up to the glasspack resonators. I understand there probably isn't room on the driver's side with a Maverick fuel tank. That's another good reason to go to the Mustang tank, IMHO.

 

I would have a better chance fitting glasspacks BEFORE the mufflers as a resonator. Think that would make a noticeable difference?

I wonder if my truck has no resonance because (in part) of the catalytic convertors? Maybe they act as a resonator?

 

I have been reading a lot on the internet about drone, and I have found two interesting facts.

1) Most people don't even know what it is, and assume it is just exhaust sound that you can hear inside the vehicle. There are several youtube videos showing "drone" and they have none, just loud exhaust.

2) Many people scrap and rebuild their exhaust systems in a semi-random fashion until they get a setup without drone, and often, they can eliminate it by utilizing a variety of fixes (better hangers, better mount locations, resonators, better routing, etc.).

 

New iPhone 5 is using my idea about the microphone and noise cancellation.. They thought of it without me lol

 

Converters definitely act as a muffler. Huuuge difference on most converter equipped cars when removed..

 

Your factory pipes etc. are tuned to that truck and engine combo. Thats why you have little to no drone. Its also why the hemis especially 2010 and up have a noticeable drone when they enter MDS 4 cylinder mode. The exhaust is tuned for eight cylinder firing pulses. Even with all the money and ressearch they spend on NVH its not possible to tune for both frequencys. Exhaust design,hangers etc are important yes. They wont get rid of the drone from our flowmasters chopped at the axle though. Gotta go out the back.

 

If your truck sounds decent and without drone.. study the design. First thing you'll notice is the factory hangers being exremely flexible in all directions. That alone reduces vibration transfer as it isolates the system from the body.

Then.. as to the location of your cheapy hangers.. you're ust adding insult to injury there. Just imagine your unibodies floorboards are a type of speaker cone and any vibration transfer gets amplified as such.

In my experience.. "drone" is caused by 2 distinct scenarios and is generally a combination of the 2 in most situations that are problematic like this one.

First one being sound waves getting back under the body as I mentioned earlier. Sound waves can and will travel in all directions if the tailpipe is located anywhere near a "soundbox" such as the wheelwell or rearend tunnel and will become amplified and change tone at various RPM. Hence the drone pattern changes associated with varying RPM and why some speeds are worse than others. Very easy to diagnose a sound wave reverberation issue by simply running a makeshift tip extension of around 6-8 inches. Looks like hell.. but I'd bet small cash that the issue will be lessoned to at least some degree. Also consider that side exit exhaust is prone to more of these issues than rear exit would be due to the waves coming back around towards the driver.. especially when the windows are down.. and/or the sound deadening/window seals are less than optimum. Such as these old cars would have.

Next.. and most typically seen.. is the vibration transfer from placing the hangers in the wrong position(as you apparently have done here) and/or using too stiff a hanger(which is the most common mistake for cheaper DIY projects). And if you think it's bad now?.. try runninmg solid hangers and see what that floorboard sounds like! lol Been there.. done that.. when I was green.. rushing through a job without the right parts.. or just to get the car quickly on the road again if the exhaust is being done in stages. Truck beds are notorius for sound/vibration amplification too even though they are seperated from the cab. Just goes to show what vibration/sound wave transfer can do to an otherwise decent exhaust system. IMHO, and no disrespect or salt in wounds intended here.. you've just received a crash course in what not to do.

So, in a nutshell.. changing mufflers on problematic systems can help drone somewhat.. or even completely in milder cases.. by changing the actual frequency..and therefore the amount/degree of vibration and at what RPM they occur.. but will do nothing to completely eliminate drone if the other design factors are not considered. And thinking that one muffler is superior to another or cannot be made drone free is simply horsepoo. Never seen a muffler that cannot be made drone free.. including the small cased 40 series Flowmaster's that people are so quick to blame.

Also.. you're right to assume that the headers will increase drone or at least change the tone to some degree. The above remarks answer the reasons why. Vibration transfers and sound/tone changes get amplified with tube type manifolds and OEM's ofetn use shrouds with hi-temp unsulation to help maintain heat in the header and reduce vibration/tone changes. Especially luxury cars. This is another reason why I always use header wrap and premium gaskets whenever possible. thicker/softer graphite gaskets at the flange and collector.. such as the thicker Remflex gaskets.. can and do reduce the problem.

You're also right to assume that the use of a flex pipe will help reduce drone associated with vibration to slight degrees as well. OEM has known this for quite some time now and it's not just about reduction in flexing of welds/flanges/gaskets.

If you think of the exhaust as a large tuning fork(and it surely is).. and do what you can to reduce the tendency to exaggerate/amplify vibration and sound wave reverberation.. you'll be able to run ALMOST any muffler you want without drone. Period.. exclaimation point.. end of story.

 

Do you still want pictures or is the mystery of how the glasspacks fit solved by knowing about the Mustang fuel tank?

 

That is pretty much the way I started thinking of it today. I spent time under my truck and noticed the type of hangers used, and am now looking for similar rubber and weld-on/bolt-on hangers, as well as stabbing in a chunk of flex pipe.

I would love to see a picture. I am having a hard time imagining how you stabbed an 18" long piece of straight tubing anywhere behind and above the axle, regardless of the gas tank.

Currently looking at the following types of items...I could bend the rod to fit around the pipe for support, and weld to pipe and bolt to frame.

 

Not 18" -- used 12" blanks. I'll post some pictures soon.

 

I just say 18" since the tube is 12" with 2-3" at each end for flanges.

Unless I am not getting your gist and am way off on what I am thinking about.

 

No flanges. The blanks (glasspacks with no pipes attached) are welded directly inline in the tail pipes. Each blank replaces a 12" section of pipe.

 

Glasspack Resonators

The DS side is closer to the fuel tank than it needs to be but it hasn't been a problem. It also would have more clearance if I didn't have the tailpipes tucked up under the rear valance. Wanted the tail pipes barely visible from the rear.

Also, if the DS shackel were put in the other way there'd be another 1/2" of space for the pipe.

When fighting the drone, I put temporary extensions on the tailpipes to move them out past the valance a few inches to see if the barely-past-the-valance tail pipes were causing the drone. Didn't make any difference. Just thought I'd mention that in case someone is thinking the short tail pipes were the cause of the drone.

 

WOW!!! That is TIGHT!

I get what you are saying about just the blanks, now.

I need a couple of couplers, and two of those hangers you have, and ready to start cutting and re-routing.

Haven't found the hangers yet, but found the rubber isolators. Might be able to hook the isolators right up to the frame, if I look at it again. Into clean clothes for the night, so will have to look at it later.

 

Just installed this on my phone, but should have used it before I took the exhaust all apart so I could compare before and after and after-after, etc.