How to Reduce 2 in 2 out muffler drone?

[BoxsterGT]

Anyone know of an insert that could be fitted to the tail pipes to reduce the drone at highway cruising speed?

Not a "supertrapp", but something to slide into the pipes while street driving and of course remove for the track.

Does Ben at M&K make anything like this?

Len

[Joe Bob]

I would suggest a baffled set of tips....the ricer aftermarket sites may be useful....

The look may not be to your liking. Most Sport Muffs have the option of capping the twin tips and running a single outlet on the side in the stock location.....maybe that mod would be a better alternative?

[Greek55]

What kind of 2 in 2 out muffler is on there now?

[BoxsterGT]

Its an OE 74 911 style polished SS Dansk muffler. I love the sound at the track, but it drones badly at 70 mph on the highway. Some sort of baffle that could be removed would be ideal.

Len

[Joe Bob]

Try capping just one tip.....

[Wavey]

Ditto to mikez. Almost all 2-outs drone.

[Buckterrier]

Ben @ M&K does have baffles and will cut them to size for you. May try it myself.

[berettafan]

strange, my 2/2 (homemade Leistritz) doesn't drone at all. screams like a mf'r but no droning at all. is on a 2.4 which perhaps makes a difference.

[Wavey]

IMO, it's not whether they're baffled or not, it's the the fact that they're 2-out. My GT3-type dual center out drones with both outlets open, whether they're wide open or have reducers in them. Reducers are bolt-in inserts that reduce the outlet size by about 50%. Drone disappears with one outlet completely blocked and one completely open. Do a search and you'll find that almost all dual-outs, from any manufacturer, whether single-in or dual-in, get comments about droning.

[Buckterrier]

Wavey, do you have a picture of your capped GT3? I have the same muffler from Ben.
Thanks

[tobluforu]

Originally Posted by Wavey

IMO, it's not whether they're baffled or not, it's the the fact that they're 2-out. My GT3-type dual center out drones with both outlets open, whether they're wide open or have reducers in them. Reducers are bolt-in inserts that reduce the outlet size by about 50%. Drone disappears with one outlet completely blocked and one completely open. Do a search and you'll find that almost all dual-outs, from any manufacturer, whether single-in or dual-in, get comments about droning.

What Wavey said as my MK drones like crazy at a certain rpm (dual out) and my home made bassani (dual out) droned as well until I added mini glass packs to it. Muffle it more and the drone will go away. I had an idea to basically mangle my old heat exchangers. I was going to cut the pipes from where the three pipes collect, weld in mini glass packs and mate them where the stock muffler would attach and go from there, but the HE’s are toast and not worth it. This would enable a person to retain the looks of the muffler and not have to cap one side/baffle, etc..

[Wavey]

Mark - I just pulled the blockoff, getting ready for some dyno runs tomorrow. I'll get some pics of the blockoff parts I made when I put it back together.

[Buckterrier]

Awesome, thank you much Wavey.

[76911]

I have a pair of baffles from Ben for my M&K 2 in 2 out They work well for the drone on the street. I leave them out for the track.

[kenikh]

MK mufflers drone the worst, factory sport mufflers the least...my guess is that the internal gas routing is the cause, not the tips. My factory sport muffler drones at 2500 RPM, then settles in after that, while the MK seems to drone at 3500 RPM.

Baffles will be the only way to solve this without opening the muffler.

[jhelgesen]

I've got a 1 in two out on a 3.2 that drone's from 2500 to 3000. Would using a factory pre-muffler help, or installing a glass pack or racing muffler in the cats place (for those of us that can run without a cat)?

[rfloz]

I have a 1 in 2 out M&K. 1 in to maintain smog-ability and two out, well, just because.

Anyway, I asked Ben to make up a muffler that would allow RSR type exit pipes, i.e., two 2 1/2" pipes straight back out of the muffler, about the width of the engine cover apart. I believe Ben welded up an extra long box to do this.

So, knowing the 2 out would be a little loud, I had TRE install some baffles. I don't know if the baffles are Ben's or TRE's. The are basically 6" long sections of 2 1/2" pipe necked down to 2", with perforations (maybe 1/4") running down the necked down part of pipe.

Well, the sound was a little loud, but bearable. Except, the pipes made a whistling/Tweety Bird sound that was just awful. After trying to grind away parts of the baffles to minimal effect, they were removed. No more Tweety Bird! However, the sound level was just a tiny, teensie bit - LOUD!

Oh, and the ironic part, no drone in any of the above variations. Go figure.

So, I too am looking for a solution, but more to lowering the sound level, not the drone.

I really don't want to cap off one pipe. My thought at present is a necked down baffle w/o the perforations might help. Say to 2" or even 1 3/4". At least on the driver's side. That side because the single entry pipe is nearly a straight shot out the driver side exit pipe.

As an afterthought, such a baffle in one side might help with drone, too, since the sound out of the two pipes would be a little different.

[rfloz]

Originally Posted by jhelgesen

I've got a 1 in two out on a 3.2 that drone's from 2500 to 3000. Would using a factory pre-muffler help, or installing a glass pack or racing muffler in the cats place (for those of us that can run without a cat)?

FWIW, my setup currrently includes a pre-muffler (for track use only). As stated above, no drone, but I have not tried it with either a bypass ot a cat.

[Gunter]

Originally Posted by kenikh

MK mufflers drone the worst, factory sport mufflers the least...my guess is that the internal gas routing is the cause, not the tips. My factory sport muffler drones at 2500 RPM, then settles in after that, while the MK seems to drone at 3500 RPM.

Baffles will be the only way to solve this without opening the muffler.

+1.

All 2-in/2-out drone at mid-RPM.

I tried MK, Dansk...............and it was excruciating.

Didn't like the "plug-the-second-tip" approach. What's the use of having 2 outlets if one is blocked? Just bling. plus the drone doesn't completely go away.

Because I value my hearing, I went with a 2-in/1-out Dansk.

[cdrik915]

I've got a Dansk complete exhaust 2 in 2 , 84 mm out , and absolutly no drone at any rpm.

Is it not possible that ssi heater boxes touch somewhere on the motor and create this boring sound ?????