My '87 3.2 has a Fabspeed euro-style premuffler & Dansk 1-in-2-out (84mm outlet pipes) with the outlets on the corners, not together below the rear license plate.

I doesn't drone, but above 3200 rpm it is too loud for relaxed highway cruising with the windows & sunroof open, IMHO.

Sure, I use earplugs (the partial attenuating kind, so I can still hear horns, sirens, etc.), but that's not a great solution for non-track use. More importantly, the exhaust volume can draw undesirable attention (i.e. the attention of those who "protect and serve") exactly when I don't want it.

I tried baffles, without success. In fact, those gave me a "drone" when I didn't have it before.

I'm looking at different ways to conveniently put a butterfly valve or cap in/on one side, for occasional use.

The blockoffs posted by Wavey look like a good approach, combined with a remote cable actuator (like the muffler cutouts on my old '67 Camaro, back in the day). I just have to find a good spot in the curved Dansk outlet pipes.

-Dan
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black/black '87 sunroof coupe, f/r spoilers, fabspeed, dansk, sw chip, euro ride height, mod rear bumper, CDR220, etc.

On the question of horsepower, I once ran my cap on one side of my flowmaster on the dyno, and then uncapped for the other pulls. The cap cost 7 HP.

Tried that (see post above), a bit quieter but no difference in droning.

Or the electronic version. Have one, thinkin' about it!

http://forums.pelicanparts.com/uploa...1269265184.jpg

Thanks Ed - I'll check that at the next dyno session, after I get my a/f straightened out.

You weren't the only person to opine on the subject spanky.

SmileWavy

Got it, Buckwheat:D

Wavey - Can you suggest a source for that butterfly valve?

BTW, I agree that almost all 2-outs drone, at least based on most that I've heard.

I think my 2-out is unusual in that it doesn't drone, perhaps because of the location (corners, not center) and shape (kind of an "S" curve) of the outlet pipes on this style of Dansk muffler. Perhaps the outlet pipes being "angle cut" at the ends, not straight cut, (which is a feature of this Dansk muffler) even has an acoustic effect.

This also means it has more of a "muscle car" sound at idle & low rpm's. Sounds ok, but not as suitable to a 911 as I would like. I've even had people ask if it had a V8 engine transplant! [shudder] [cringe]

-Dan
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black/black '87 sunroof coupe, f/r spoilers, fabspeed, dansk, sw chip, euro ride height, mod rear bumper, CDR220, etc.

Otay;)

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About $150 a couple of year ago. Come in several diameters.

Ed - was the engine out, or was that a road dyno?

I ask b/c the dual cowhorn style mufflers don't "add any hp" relative to the stock single outlet mufflers. For years, I've been thinking I might cap the RH side of my Monty, tho I've never gotten around to it (mainly b/c I don't drive much on the fwy).

I'm thinking that the internal construction of various muffler brands might differ, and perhaps cause the differences in relative hp...

It was a chassis or road dyno. I run B&B headers to the muffler.

Thx - I wouldn't be surprised at 7 hp variation run to run on the same motor...

OTOH, if anyone knows what the guts of a Monty look like or has more info...

I think the tq was even more. The others were all pretty close-we thought it looked like the cap made a difference.

I guess I should have said my problems disappeared. ;)

cappng 1 tail pipe and the problem does go away. It is simply a harmonics issue with a dual outlet . single outlets have zero drone

You could always try these, but they are pricey! Dynatech 72-32520 - Dynatech Vortex Insert Cones - Overview - SummitRacing.com

A friend tied 4 stainless pot scrubbers and fastened them inside his dual out and they supposedly reduced the resonance.

Understood, but I would rather live with the drone (don't drive car much), then live with the look of a muffler with a cap on it.
Do the org. sport mufflers drone?

Unfortunately, 3" seems to be the smallest diameter they make. My pipes, e.g., are 2 1/2".:(

How about if the two pipes, in GT3 Cup configuration (next to each other, straight out the center) were attached to the muffler using a "collector" of sorts, so the exhaust was all dumping out one hole and just split with the pipes? Has that been tried?

In that same idea, does the GT3 drone? If not, why?

THAT is a great idea! Maybe 2.75" to 3" at the muffler, split to a couple of 2.25" or 2.5"?