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PostPosted: April 30, 2016, 2:15 pm 
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It is not reversable. If it were reversed, I doubt it would do anything.


MV8, I just can't figure it out. How does the exhaust flow thru this? what's confusing me is you say it wouldn't work backwards, but it also sounds like the inner tube goes straight thru....

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PostPosted: April 30, 2016, 2:52 pm 
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Cory,
all it would take to hold it in is one screw through the pipe, preferably into one of the bells.


Marcus,
If it were reversed, it would not be as effective. The outer chamber would have no outlet.
The center pipe has two slots covered with divergent ducts, asymmetrical to the center pipe.
Flow bounces off the closed end cap to flow over the same ducts which form another divergent duct to reach the slotted end cap.

I'm going to make a back pressure tester to compare noise to back pressure. I will be able to test while driving also.

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PostPosted: May 8, 2016, 1:42 pm 
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I took the car out for it first long drive today, the exhaust is the quietest it has ever been, you can actually drive it, your not constantly in noise control mode. I added a SuperTrapp end cap, and a Vortex cone just before the muffler

Graham


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PostPosted: July 26, 2016, 9:48 am 
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For big HP with super quiet exhaust, it's difficult to beat Cadillac CTS-V mufflers. I've heard one of those 556-horse supercharhed 6.2s uncorked, no way any other street engine is any louder. But the main reason they didn't make the power of the 'vette version was the cam, not the muffs. The ZL1 Camaro used the CTS-V cam, but 'vette mufflers, and only made 580 HP, so a 14 HP loss is what, 3% at worst?


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PostPosted: July 26, 2016, 10:25 am 
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Dave1976 wrote:
Fso a 14 HP loss is what, 3% at worst?


Betting that HP loss graph isn't linear. So under 300 hp, probably less than 3%?

EDIT -- looking at the prices for this stuff. OWWWWWW!!!!!

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PostPosted: July 26, 2016, 11:40 am 
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FastG wrote:
I took the car out for it first long drive today, the exhaust is the quietest it has ever been, you can actually drive it, your not constantly in noise control mode. I added a SuperTrapp end cap, and a Vortex cone just before the muffler
Graham

I had such a negative experience with a SuperTrapp setup that I can't bring myself to ever use one again. I remember my thought at the time, "they've created a product that has the amazing ability to both restrict power and be loud at the same time."

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PostPosted: July 26, 2016, 9:54 pm 
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FastG wrote:
I took the car out for it first long drive today, the exhaust is the quietest it has ever been, you can actually drive it, your not constantly in noise control mode. I added a SuperTrapp end cap, and a Vortex cone just before the muffler

Graham



Glad to know of another success. Did you try it with only the cones?
I'm still waiting to drive my car to test out my giant mufflers.

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I've heard one of those 556-horse supercharhed 6.2s uncorked, no way any other street engine is any louder.


Rotary for sure. I've done a dyno day where there were several LS cars, some with open exhaust. Loud for sure but when they ran the one big HP turbo RX7 everyone able to fled the building covering their ears.

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PostPosted: June 6, 2017, 1:11 am 
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Just got home from doing some sound testing with my car in its new, quieter form. Got 2 flybys of 90dB, and one (erroneous?) of 98dB. I'm surprised by how loud it still is when WOT. I think exhaust length is the biggest factor now. I did build a pair of cone inserts with a 1 5/8" hole which I will run at autox, but did not test on my car. I did test them on a friends LSx camaro though. Saw a 8dB reduction and I would say we were 5-10ft closer this time. I was pretty impressed by how much of a difference the cones make even just stuffed into the tail pipe. Even at idle it was much quieter. Granted, the 1 5/8" hole was not enough to maximize his power, but he doesn't need 500hp to do autoX.

I think I am safe once I stuff the inserts in my car. If not I will aim the tips upwards away from the sound meter. I intend for my my S/C to get a little louder at some point too so may need to build a second cone set. Oh, and one plus from the giant mufflers on my car is that it sounds much better. Honestly the best sounding 90° V6 I've ever heard. Still nowhere near as sexy as the LSx though......

Thanks again for the help. I will post after I try autoX. They can still shut me down even if I am below dB if it "seems" too loud. Basically if they hear sound reflecting off the trailers, and clouds they get concerned. Nothing against them, they are doing what it takes to keep the last autoX pad in the area.

Cheers.

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PostPosted: July 24, 2017, 10:24 pm 
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Update: I've done my first event in the car and am totally OK for sound. To the point that even when my right exhaust tip/insert fell off*, the sound levels were fine. It's quiet enough that no one even considered to check my levels. I do have a backfire on decell I should seal up, but no one brought it up.

Thanks again for the help. I'll probably just pull the inserts out and loan/give them to my friend with the loud Camaro to try.

Cheers.


* fell off is not really the right description: Got hammered off from repeated cone-impacts is probably more accurate :mrgreen:

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PostPosted: March 19, 2018, 2:01 pm 
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In my sports car racing days, I always carried a "turn down", an exhaust extension with a turned down tip cut at an angle that could be added when needed. This could be installed in the necessary direction to accommodate the sensor locations at any given track. When in doubt, aim it down to break up the sound wave pattern. Some tracks are a huge pain in the ass (Laguna Seca and Lime Rock Park come to mind).


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PostPosted: March 19, 2018, 2:50 pm 
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From http://www.norcal-saac.org/ot/soundadvice.htm. While this was written specifically for 60's-style Cobras, everything still applies to us. Full credit is given to the original author, Tom Georgalos.

Summed up: the bigger the muffler and the smaller the exhaust diameter the better.

-------------------

With the sound restrictions getting tighter at Laguna Seca and for that matter all tracks, we are continually looking for better ways to quiet our cars. The sound meter requirements over the last 10 years have been tweaked more and more. Each time the meter was tweaked tighter we seemed to know what to do and how to quiet our cars just that much more. We started around 103 dba, then went to 100 dba, then 95 dba. When the meter hit this last mark of 95 dba we started to separate the men from the boys. The race cars with high strung motors were the most difficult to tame. Technology came around with the Flowmaster muffler, which seemed like a miracle. This muffler didn't cut down on power, it enhanced torque, and it made the limit. Now we are at a new low limit which is being strictly enforced, and this is as low as 90 dba. By the way these readings at Laguna Seca are taken at 50 feet. Most other race tracks take their readings at 100 feet. Quite a difference!

We don't claim to know the exact solution for quieting the car on the racetrack, but are in a panic to perfect our readings. The advice we offer below is merely some findings that we offer to you. We would love to take advice from anybody and share it with others. Many cars in our group pass with flying colors, we will try and list their formula. We are also in search of other techniques all the time which we will try for the future.

Exhaust Systems That Don't Work.
•Open exhaust, obviously doesn't work!
•Glasspack mufflers do not work!
•3 inch pipe Flowmasters don't work!
•Flowmasters with center inlet or center outlet don't work!
•3 inch pipe or larger Brand-X mufflers don't work!
•Shorter than 28 inch LoBaks don't work!
•Race style LoBaks don't work!
•Borla mufflers without catalytic converters or without a secondary muffler such as a Supertrapp don't work.
•Monza style exhaust or European high performance mufflers on Ferrari's, Porsche's, etc., don't work.
•Stinger type of exhaust on Porsche's & Mazdas, commonly known as expansion chambers, don't work.

•Diameter of Exhaust System
2 1/2 inch pipe is the absolute largest pipe that can be utilized to make strict sound limits. Naturally 2 1/4 inch or 2 inch would even be quieter. This even applies for necking down of side pipes.

•Length of Exhaust Pipe
The longer the pipe the quieter the system. Exhaust all the way out the back of the car is going to be quieter than side exhaust. Some believe routing both pipes, if dual exhaust is used, to the drivers side of the car, helps divert sound away from the sound meter. This can only be a crutch until sound is read on both sides of the track.

•Flowmaster Mufflers
Large three chamber Flowmasters (approximately 16 inches or longer) with offset in, offset out 2 1/2 inch pipe seem to get you just below the limit. On certain days this system may be right at the limit, especially if the atmosphere has any moisture present. Crossover tube is essential. Try part # FLO-42553. This is the quietest Flowmaster that they have currently. It will not sacrifice power up to 400 HP. This will satisfy most of our needs. By the way, Flowmaster has found their mufflers are quietest at wide open throttle. They seem to smooth out the exhaust flow and that's when they really do their job well. The latest versions of Flowmasters are aluminized to hold off corrosion. By the way we are on about the fourth generation of Flowmasters currently. You may have the old ones.

Flowmaster offers complete Cat-Back systems, which may interest owners of late model Mustangs & Corvettes, etc. Contact them for your application. They also have developed new bolt on aluminum heat shields which incorporate stainless steel straps. These might be just the ticket for vehicles with converters, which generate more heat. Great safety item!

•LoBak Mufflers
Street LowBaks 32 inch or longer seem to get the job done, keeping with 2 1/2 inch pipe & a crossover tube. Stay away from the race version of the LowBak. Some have reported 24 inch LowBaks working with fairly healthy motors and keeping well below the sound limit. These seem to be the answer for sidepipes for Cobra's, yet must incorporate an additional Supertrapp attached to the end. Nevertheless this is far less restrictive than just Supertrapps.

•Supertrapps & Supertrapp Mufflers
Supertrapps definitely work! They are more restrictive than most of the race style mufflers, but they allow you to stay on track with no black flag. You can tune them on the spot for the most power possible. Supertrapps seem to be the real answer as a secondary muffler system. They are the assurance you need to tune your car quiet when all else fails. Supertrapp mufflers with the plates on the tail end are less restrictive than just the plates by themselves. These may warrant looking into for side pipes and Cobra's.

•Catalytic Converters
These act more like a muffler than can be imagined. A stock Mustang GT with catalytic converters will register down in the low 80's for decibels. If your car was designed to work and run with catalytic converters, it will be just fine. Catalytic converters definitely help and work! Don't take them off! If you take them off you place yourself in the same position as the vintage cars. That is, constantly trying to find a solution. If your car is tuned for catalytic converters, stick with them! They don't give up that much power. There are some companies that offer Hi-Flo catalytic converters that claim 50 -100 % gains in flow, which mean less back pressure. This would be the avenue to pursue while still keeping sound levels down. One such company is Random Technology in Stone Mountain, GA., with their Super High Flow converters 404-978- 0264. Another source is M & M Distributing, Mesa, AZ., who carries Mor-Flow Converters 800-408-2287. Dynomax is a most recent developer of hi-flow converters. They are cheap and affordable. A final source for aftermarket high flow converters is Summit Racing Equipment at 330-630-0200.

•Stock Mufflers
Most stock street mufflers seem to work, these are somewhat more restrictive than the so-called performance mufflers. Remember, 2 1/2 inch pipe. Don't forget the crossover tube! Naturally 2 or 2 1/4 inch pipe would be even quieter!

•Walker/ DynoMax Turbo Mufflers
Turbo mufflers, as mentioned, seem to work. Aiming the exhaust to the ground in front of the rear axle causes a resonance & may cause you to be over the limit. Once again don't forget the crossover tube and out the back is the best method of quieting the car within the limit using turbo style mufflers. One of the better known brands is Dynomax, although this information could be applied generally to all brands. The Dynomax seems to be very efficient for dollars spent, robs very little horsepower.On very high strung motors or race motors, 2 1/2" Dynomax may be just over the limit. It may take 2 1/4" pipe to actually do the job. In the Dynomax line, stick with Super Turbo models, nothing less. The Ultra Flo model will not work.
Dynomax offers complete Cat-Back systems, which may interest owners of late model Mustangs & Corvettes, etc. Contact them for your applications.

•Borla Mufflers
Beware of using Borla mufflers without catalytic converters! See above. We have not seen anyone claim to conquer Laguna with Borla's by themselves. Using Borla mufflers, with 2 1/4" pipe may be the way to make them work. We know they work with catalytic converters and or Supertrapps on the ends. Let someone else try them first as a primary muffler. On the plus side these are stainless steel, carry a great lifetime warranty, and naturally these mufflers claim great power gains.
Borla offers complete Cat-Back systems, which may interest owners of late model Mustangs, Corvettes, & SHO's. etc. Contact them for your applications. We are confident that these systems with catalytic converters would pass the sound limits.

•Edelbrock Mufflers
Edelbrock has come out with a new line of mufflers. They are referred to as the RPM Series Mufflers. We don't have information on them yet, but know they have been vintage racing with two or three sets of them in the development stage. They claim good torque benefits, little horsepower loss, and many of the advantages of Flowmaster mufflers. These mufflers are stainless steel, and offer lifetime warranty like the Borla mufflers. They claim to be quieter than Flowmasters, yet we can't attest to the power relationship. We will report when more information is available.
Edelbrock offers complete Cat-Back systems, which may interest owners of late model Mustangs & Corvettes, etc. Contact them for your application.

•Bassani Mufflers
This really seems to be a popular addition to my information. This company makes an X-pipe bolt on fabricated crossover for the late model Mustangs, including the 4.6 liter variety. Their mufflers are good and adequate especially when used with the cats. Quality and fit really seem to shine with Bassani.

•Mandrel Bent Pipes
There are many companies forming mandrel bent pipes lately. This enables one to go with a small diameter tubing, utilizing quieter readings while still keeping up good flow characteristics. A normal 2 1/2" pipe system with normal muffler shop bends will reduce down to around 2.5 square inches of exhaust flow. The mandrel bent tube will maintain 3.14 square inches throughout. This is commensurate to other pipe diameters.

•Latest Attempts and Technology
The latest race muffler set-ups are proving that single exhaust systems are the most advanced. They offer virtually no penalty of power, yet quiet things down. Consult your muffler manufacturer. Along the lines of two devices, we saw a Flowmaster system with either Lobaks or glasspacks welded in- line to help cure the problem. This worked! The system was 3 inch, sort of an exception. The motor was a 377 c.i. Windsor stroker!

Harley Davidson motorcycle pipe baffles. We have seen these inserted in the end of the exhaust system to help quiet the system a bit more. Naturally you will need a straight shot of pipe at the end to incorporate this.

•Reducers and Trick Pieces
If you are fabricating an exhaust system and want the smoothest transition of exhaust gas possible.

If you are fabricating a single exhaust system and want to blend in two pipes with the smoothest transition possible.

•Some Other Factors
Noise is noise! It doesn't have to be exhaust sound to be noise and trip the meter. Here are a few of the things that might play havoc with the sound meter, while you are aiming at the exhaust system.

• Quick change rear-end, like a Franklin
• Flex fans for the radiator
• Gear drive timing sets
• Weber carburetors with velocity stacks
• Mechanical fuel injection with velocity stacks
• Turbo charger swooosh!
• Cam timing. Who can tell us what is the best type of cam to run for sound? Lots of duration or little duration?
• Compression ratio, the more you have, the more the bang.
• Exhaust leaks, holes in pipes or bad connections, etc.

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PostPosted: March 20, 2018, 11:32 pm 
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> as low as 90 dba

Back in the 1980s Germany tightened the screws on noise. The motorcycle companies had trouble meeting the new TUV standard. After doing some research, they found out that the main problem wasn't the exhaust, but... the chain. Several companies went to narrower final drive chains, which were quieter.

Another area the OEMs had to address was tires. Dunlop had addressed tire noise in automobiles as early as the 1950s, but as an NVH issue. When treads moved from sipes to blocks, tires got noisier, but OEMs handled that with rubber bushings and sound deadening. But that didn't address exterior noise...

The speed-event guys - Silver State, Maxton, etc. - often comment that they can hear oncoming cars from their wind noise long before they can hear the exhaust note. Not much you can do about noise from form drag, though.


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