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In 1994 my mechanic got 2 bb mufflers directly from bb. One was a sport version and a standard version. I dont know if there was ever two versions or just bs to sell product. What I do know I have been around to see all different setups since the 90's , Ive seen/heard bb headers with diff exhausts with no drone. My wrench owns his own shop so time and testing is done. I just go with my experince and mech's word. Inmop it could be other factors. Hopefully it works out.
Old 12-28-2009, 11:53 AM
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Check your local noise statutes or requirements....the zorks aren't exactly quiet...they're a bit too noisy for me, but I know several folks who run them and like them.
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Old 12-28-2009, 11:54 AM
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I am not planning on running a zork permanently, just for testing and trouble shooting. I know for a fact that the zork will be too loud for me.
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Old 12-28-2009, 12:05 PM
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Max Sluiter
 
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Just a thought from a lurker...

The drone getting worse over time sounds to me like an exhaust leak/crack getting progressively larger.
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Old 12-28-2009, 12:19 PM
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i run B&B headers on my car. Used to also have a twin outlet B&B muffler that droned to no end. I replaced the muffler with a dynomax straight thru design and no more drone...
Old 12-28-2009, 12:22 PM
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If you have decent computer sound and speakers, turn it up and check this exhaust sound video.

YouTube - Porsche 911 Exhaust Sounds

Specifically listen to the 1991 turbo accelerate, and at 3:52 mark I can hear some resonance really change the pitch of the exhaust. Is this similar to what you are hearing?
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Old 12-29-2009, 08:57 AM
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Quote:
Originally Posted by William930t View Post
If you have decent computer sound and speakers, turn it up and check this exhaust sound video.

YouTube - Porsche 911 Exhaust Sounds

Specifically listen to the 1991 turbo accelerate, and at 3:52 mark I can hear some resonance really change the pitch of the exhaust. Is this similar to what you are hearing?
Sounded to me like the wastegate opening.
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Old 12-29-2009, 10:22 AM
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I am definately not ruling out the possibility that the drone is coming from the headers. Since no one else seems to have an issue than it most likely is the headers or some other problem.
I am guessing something is broken or bad gasket as there should be no drone whats so ever as there is no refraction inside the system
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Old 12-29-2009, 03:10 PM
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If the droning gradually increased over a few months or whatever I would check to see that the sound absorbtion packing hasn't gradually blown out of the muffler or melted.
If that happened, and it just recently happened to someone that lives near me with one of these mufflers and there's a post about it here the muffler would gradually become louder and if there is a droning at certain rpms than the pitch of the exhaust may be hitting the resonant frequency of the engine bay sheet metal, or possibly the floor pan and rear bulkhead firewall.
If sound absorbtion material has been removed from the floor or behind the back seats to lighten the car, that will just make it louder and more resonant at certain frequencies.

What do you use for sound absorbtion material in your mufflers?

Chopped fiberglass packing blows out of 4 cylinder glass pack mufflers in no time from the exhaust pulses so long strand fiberglass usually stays in place in those applications.
I've also heard of stainlees steel wool fibers being used. Not sure if I've heard of carbon fiber being used in muffler packing.
Old 12-29-2009, 03:30 PM
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I crawled under the car while a friend gassed the car and I could here no indication of an air leak. The car really is not that loud when standing beside it or when listening to it drive away. It sounds really good. So it is really just an annoying drone. I am no expert but I find it hard to believe that a bad gasket or even a crack in metal would create a drone. Maybe a very loud exhaust but not drone.

Also I wanted to make it clear that the drone has increased over time, but seems to have stabilized.
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Old 12-29-2009, 03:49 PM
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Could your drone have something to do with the muffler mounts coming loose and simply vibrating at a certain frequency? Or the muffler itself touching....or almost touching...something that it shouldn't be?
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Old 12-29-2009, 04:24 PM
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Quote:
Originally Posted by mark houghton View Post
Could your drone have something to do with the muffler mounts coming loose and simply vibrating at a certain frequency? Or the muffler itself touching....or almost touching...something that it shouldn't be?
definitely could be a mounting issue. I need to get the car in the air and do a thorough inspection.
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Old 12-29-2009, 04:54 PM
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My mufflers do not drone, I guarantee that. If we find this drone is caused by my muffler I'll refund the purchase price.

The muffler body is a straight through design with no baffles. The sound travels with the exhaust and does not bounce back or around. If some of the sound deadening material is removed the muffler will simply get louder. My hooligan mufflers have no sound deadening material at all with no hint of drone. I use a dual out hooligan for special occasions as it gives all the great turbo noises at 1/2 the volume of a zork.

It is mysterious that a drone has developed. Usually it is there from the beginning if it is going to occur at all.


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Old 12-29-2009, 06:58 PM
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I realized my wrench was scoping out his entire bb exhaust sys.Drone... and I think he had a solution. I noticed he inserted round bumper stops b/t the muffler and bumper. I would have to chk were they are exactly.

Last edited by wjfk32; 12-29-2009 at 09:08 PM..
Old 12-29-2009, 09:03 PM
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So this is a sheet metal ringing/clacking, not an exhaust drone? I think of "drone" being an unpleasant resonant pulse of the exhaust gas sound waves caused by constructive waves superposition at certain frequencies (rpm). This is sometimes called "beat frequency" and is the bane of twin-engined airplane pilots.
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Old 12-29-2009, 09:48 PM
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Quote:
Originally Posted by JFairman View Post
If the droning gradually increased over a few months or whatever I would check to see that the sound absorbtion packing hasn't gradually blown out of the muffler or melted.
If that happened, and it just recently happened to someone that lives near me with one of these mufflers and there's a post about it here the muffler would gradually become louder and if there is a droning at certain rpms than the pitch of the exhaust may be hitting the resonant frequency of the engine bay sheet metal, or possibly the floor pan and rear bulkhead firewall.
If sound absorbtion material has been removed from the floor or behind the back seats to lighten the car, that will just make it louder and more resonant at certain frequencies.

What do you use for sound absorbtion material in your mufflers?

Chopped fiberglass packing blows out of 4 cylinder glass pack mufflers in no time from the exhaust pulses so long strand fiberglass usually stays in place in those applications.
I've also heard of stainlees steel wool fibers being used. Not sure if I've heard of carbon fiber being used in muffler packing.

With being the owner of M&K I have had the luxery of trying all kinds of sounddeadening materials. Ironically I used chopped fiberglass on my prototype turbo conversion when I did that 6 years ago. It still had the fiberglass in it when I sold the kit last year at this time to another pelican. With other testing I found that fiberglass matting works well and the stainless wadding does work as well though the most effective is the longer strand material similar to home insulation. it holds up the best. now these examples are with straight through designs and if it were to melt out there is something real bad going on with the car those type of heats should be no where near a turbo charged engine. but that is just my experience with many different combonations and many many miles
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Old 12-30-2009, 05:23 AM
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My suspicion is that something has changed or moved causing some resonating to occur. It is not my intent to try to harm Brian's reputation. The quality of the muffler was top notch and the guys at Evolution Motorsports were very impressed with it. I did have an EGT drilled into the headers as well and that was done a month or so after the initial installation. I am confident that I will figure it out and I am not worried since I know Brian stands behind his product 100%. I am moving to a house in two weeks that has a lift and will be able to really do some trouble shooting and even provide pics at that time. I will keep you all posted.
Thanks for all your advice and help.
Steve
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Old 12-30-2009, 07:45 AM
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The car in Florida that burned out the sound deadening material is the first and only time this has happened. That car had a turbo failure and saw EXTREME heat. The sound deadening material crystallized and was spit out which essentially left him with a hooligan muffler.
That burned out muffler did NOT drone, it simply got louder in a short time. This is what alerted the owner that something was going on.
I spoke with both the owner and the mechanic who were complaining that the muffler had gotten progressively louder in over a year's time. Because my muffler failed I sent him a new muffler body at no cost. I was horrified when I received the burned up muffler and immediately called to report something very bad was going on with his car and he should not drive it until fixed.
These mufflers are made of 321 stainless and can take more heat than 304. Normal heat will turn them bronze over time, this one was purple. I inspected it and found no issues at all with the structure.

(The tailpipes pictured with the burned up muffler were not on at the time, this is a package I put together to re-sell it after being re-packed)

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Old 12-30-2009, 07:45 AM
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Steve, we posted at the same time. I wanted to remove any misunderstanding concerning the burned up Florida muffler.
I know you are simply trying to figure out what is going on with your car. Droning is completely unacceptable to me as it ruins the driving experience. Yes I will stand behind my products should we find they are the culprit. These things aren't made in China, we can fix problems and are only a phone call or email away. That goes for product sold by Pelican as well. Anything that has my name on it will be supported.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 12-30-2009, 07:54 AM
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Thanks Brian, I have no doubt. I am very happy with your product. I will figure this out since it has taken some of the fun out of driving the car. I will contact you and send you any pics you would like when the car is in the air. I am confident this will be sorted out.
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1986 930 Slant nose Black/black RUF
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2001 Ferrari 360 Spyder Rosso/Tan
1969 Carrera Widebody TurboKraft Custom (Mexico Blue)
2001 E39 M5 Imola/Black-red interior
Old 12-30-2009, 07:59 AM
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