The Great Flowmaster Super44 drone experiment of 2012.

I told you adding pipe after the mufflers would change the sound, like tuning a guitar. Wouldn't listen though. See, us old folks do know things after all....

 

Adding pipe only quieted down the exhaust sound, but not the resonant drone. It still drones horribly, but now it is so quiet, I may as well have factory mufflers on it.

 

My friend has Flo-Pro "V-Force" mufflers on his Maverick. They are a modified version of a Flowmaster. They are loud and have that aggressive, raspy tone of the Flowmaster, but without the "drone", and they are supposed to flow better than the FM. I highly recommend a set of those with full tailpipes out the back. His exit over the leafsprings behind the rear wheels. Of course having proper mounts and hangers will also keep drone to a minimum.

http://www.flopro.com/vforce.html

 

Yea, I've never changed the exhaust. I used a Summit X pipe kit and the two turbo tubes, the pipe coming outta them is only a foot or so (at most) long, angle cut, they end under the rear housing. It's loud as **** at speed, but its OK by me. Nice raspy sound when you let off the gas.

 

I think the drone in the flows come from their solid steel constuction.

 

Either my exhaust shop mounted mine just right or i just got lucky but my 40 series flows have no drone what so ever.It's a little loud inside but very tollerable,some insulation under the carpet would probably help alot.

 

My next step in the experiment was going to be wrapping the outside of both mufflers with fiberglass welding blanket and seeing if the drone was controlled. But, I cannot seem to find the blanket.

I have moved twice since I used it last, so no telling...

If that worked, then my final solution would have likely been header wrap.

 

Linus had it last I saw

 

Probably not the direction you were thinking...

But if you could get the drone to be constant, you could: record an audio sample of it -> Flip the phase -> send it through your car stereo
And with alil tweaking, it should cancel out a bunch of the noise
(in theory..)

If the drone is only happening between certain rpms, you could try to figure out a way to use you tach as a triggering device for the reversed phase audio to play in the car, and to shut off when no long at those rpms
(in theory..)

Never heard of anyone trying this, but it should work
(in theory.. lol)

 

That WOULD work!!!

Except I have no audio system yet.

 

there are several possibilities for the problems here.

First of all.. baddad is correct in that many non-packed steel mufflers can exhibit this same tendency. Some use thicker case material and/or actually utilize gusset type dividers/walls to increase the rigidity of the case which can help but not eliminate the tendency. The higher the compression ratio.. the worse it will get as the pressure and the sound waves give the case an even harder workout even in normal light duty operation.

Automakers have long studied NVH and known about the need for resonance tuning aids. They do in fact work very well and some of the most expensive luxury cars in the world currently use the techonology. Even my old 1990 Infinit Q45 had them located in a few places, including the muffler, and simply going to the junkyard to find some good isolators and dampers will help much more than many realize. I typically use them on any car that I need to be quite and refined sounding. Even my V6 Accord has 2 of them since my wife likes near stock sounding exhaust without any vibration or resonance with the windows down. Hard to tell much difference on that particular car.. but they do slightly chnange the tone a bit. I've also talked with a few old timers that used to weld springs onto the exhast system and then shoved hard rubber plugs towads the tops of the coils. Newer technology is probably better tuned for specific ranges and would be better than an old spring for sure. lol

Then there's the tailpipe length of the exhaust to consider. This is the biggest area to improve things, IMHO. While the exhaust gas itself may tend to get shot out and swept away at crusing speeds.. we know that the sound waves travel in all directions. If simply aiming the tail pipes exit angle to move sound waves away from the undercarriage worked so well.. everyone would be running lighter and freer flowing mid-pipes with turndowns, right? That obviously means the shorter "cooler looking" snub nosed tips will inevitably cause the waves to travel under the floorpan, rearend/gass tank, and even wheelwells(as in your application) depending on the proximity of the tailpipe exit.

So, in my experience so far with building and helping design many exhaust systems through the years.. it's not usually the mufflers specific sound that causes the drone. It's the exhaust systrem as a whole(mounts included).. and every nook and cranny under the car that catches the stray waves and transfer it as vibrations.. which can often be heard more than felt.. that causes the reverb and tones that bother some of us.

But if you isolate the exhaust with highly flexible "factory style" mounts(unfortunately.. the cheap parts store stuff is not in that classification).. maybe even run a few isolators(most properly designed "hey!.. look at me" hotrod exhausts don't need them, IMHO).. and then run the tailpipes longer than usual.. the sound is quite pleasant and without drone... regardless of what the mufflers natural tone sounds like.

Case in point.. my latest exhaust "street build" on my 85 s10 Blazer. Temporarily drove it with mufflers and stubs with that horrible flowmaster reverb.. you know.. that nasty tinny sounding reverb at light cruising. Was so bad that you either had to go slower or faster to get your hearing back. Then I ran it the rest of the way out the back and cut my tailpipes long to figure where the final cut would look good since I had an angled cut on two seperate planes to consider as well because they're angled outward and upswept to keep em' tight and match my rear roll pan body line. Truck sounded quiter than it ever had. Cut my tailpipes to what I thought looked cool and some of the reverb was back again. Not as bad of course.. but the sound waves were definately getting back under the truck a bit more again.. and even sitting still idling sounded meaner and deeper toned. Then I made some 3.5 inch tailpipes to tack over my 3 inch and again left them longer to more easily eye my final angle cuts. Well, guess what.. the reverb completely dissapeared again. Cut my angles again with slightly longer tailpipe length this time around.. and the sound came back slightly again. Even had my 11yo son stand at the end of the driveway and confirm whether or not I was crazy as I slipped them on and off multiple times. Neighbor across the street heard us talking about it and said he could tell from 200 feet away as well. Then I had my boy take them on and off while I sat in the truck listening for the difference. Easily perceived from in the cab.

In the end.. the best we can do is to run the pipes out where it's convenient while keeping an eye for aesthetics in the process. But in my experience, getting the tip length right can tune the cruising sound more than most will ever realize. At least until they've driven around with 16 inch tailpipes to do before and after tests.

PS.. while I myself still use flexpipe for mocking header/exhaust routes.. it certainly doesn't help the stray sound waves and tuning of the resonant frequencies. If you really want to test my "too short a tailpipe" theory out?.. add an 8 inch piece of pipe and drive the car a again. From there you probably need better mounts as well since vibration transfer causes everything else to vibrate which just adds insult to injury in most cases. Sound deadener on floorboards and trunk isn't just for the stereo guys and can do wonders for exhaust frequency modulation too.

 

Tmi..................................

 

Not TMI. Actually a good write-up with lots of good points.

Thanks for taking the time to share all of that.

 

I have yet to see groberts post a "less than 4 paragraph" comeback to any particular problem, hence the TMI post....................