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 Post subject: Quieter exhaust
PostPosted: December 7, 2011, 8:14 pm 
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I saw this article on GRM and it reminded me that I'd seen a test on a muffler like this a few years ago on some V8 powered cars where it really shone.

http://www.motoiq.com/magazine_articles ... -slow.aspx

It's a large case muffler, but for those cars with noise issues, it might be worth at least investigating.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 9:20 am 
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Original equipment Harley big twin mufflers are quiet, so much so that the bikes frequently do not leave the dealership before they are removed.

The chrome is very good quality. The pipe size is 1-3/4. Realize that a 1-3/4" pipe only 3 feet long has better flow than a 2" full length exhaust system.

These takeoffs are dirt cheap. They can be found on Ebay for about $20/pair. The clamps are stainless steel. I think they cost about $10 each at the dealer if the seller does not throw them in for free.

The oem muffler can easily be modified for more noise and less backpressure without removal, by drilling a hole in the aft end, then opening up that hole as required. With two mufflers, one can experiment and get it wrong or have a muffler for track and a muffler for street use.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 1:23 pm 
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Im not sure if I could bare telling anyone I have harley mufflers on my car


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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 2:52 pm 
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The Harley mufflers I have in my garage wouldn't flow worth a darn for a car. The final output is through a very small diameter pipe section.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 3:37 pm 
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The Harley mufflers I have in my garage wouldn't flow worth a darn for a car. The final output is through a very small diameter pipe section.


That may be a mistake we're making. Look at the HP numbers for the big sport bikes and think how much they must flow at their rated RPM.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 4:08 pm 
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There is more to flow than the size of the hole at the end of the system. The entire system determines the flow. There is no miracle muffler.

The harley mufflers start out quiet and are easily adjusted to be louder with a unibit and extender, rather than starting out loud and getting replaced. One can take a hole saw and make the hole as big as the logic dictates, but then we are back to the same problem.

There is nothing wrong with trading a few hp at the top of the rev range for less noise at all revs.

The earliest originals had short systems, but they added a tail pipe in the late 60s that extended all the way back and has 3 bends. Maybe it was just regulatory, but just adding a proper tail pipe will add some muffling and get the noise away from the drivers ears.

Also, Walker sells 3 universal "sound fx" round mufflers in 3 diameters and lengths, ranging in price from $20 to $45. Part numbers: 18263, 17193, and 17902. All are for pipes 2 inches and larger.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 4:22 pm 
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This has brought up a point. I need to address the loudness of my rotary. I can get a pair of Harley mufflers here for ~25 per pair. they will have 60K+ miles on them. How can I tell if they have been modded?

Anybody run two mufflers top/bottom style with a "Y" feeding them both?

Most of the Harley mufflers I have seen, the tips do not turn outward but would end up shooting directly at the rear fender. Don't know how that would work out. Still......... I'd be willing to chance the change if I could get the noise level down.

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 5:10 pm 
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With no mods, there should be either no hole or a very small one off center in the middle plate.

The center forces the flow to the outside chamber through the baffling, then back through the baffling to emerge at the center after the middle plate. For more noise/reduced back pressure, holes can be drilled in either the middle plate or the outer cone. A hole saw can also be used to separate the center baffle assembly and pull it out for modification, then re-insert it and weld the cut.

I think staggered duals would look better with sportster mufflers which can be modified in the same way, but they are much smaller and less effective as mufflers. They are also dirt cheap.

I have both on hand if you want measurements. I found these photos with a quick search online.

One way to filter the mufflers on ebay is to search for "harley touring muffler". Some newer mufflers have a crossover pipe port so ask the seller to make sure you don't buy those.


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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 5:28 pm 
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Measurements of both touring and sportster styles would help. OAL and diamater muffler dia. including the inlet size ( I think 1-7/8" ID ?). I'd probably be looking for the touring styles as my primary goal is QUIET. I'd like to stay no more than 36" OAL including any "Y" pipe I may have to include. I'll also have to add an O2 bung on this side of the header/muffler joint. Ideally I'd like an exhaust tip turn-out too. My wish list is getting longer as I type. :D

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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 6:18 pm 
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Sportster/Tourer
Length: 19/29.5
Overall OD: 2.75/4
Inlet ID: 1.75/1.8

Measured inlet IDs with a dial indicator. A small copper tube connected to a pipe bung welded into the exhaust tube ahead of the muffler could be used to check pressure during acceleration. The copper tube is long enough so the rubber hose slipped on the end doesn't get hot, and the air isn't circulating through the tube and hose to the guage, so the guage would not be affected.


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 Post subject: Re: Quieter exhaust
PostPosted: December 8, 2011, 10:07 pm 
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Thanks for the measurements. I'm gonna have to try this.

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 Post subject: Re: Quieter exhaust
PostPosted: March 9, 2012, 5:57 pm 
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Racing Beat pre-silencer and silencer squeezed in as small a space as possible. Hope it is under 100 db at full throttle.


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 Post subject: Re: Quieter exhaust
PostPosted: March 9, 2012, 7:49 pm 
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Hmmmm Rotary. ...
Don't you mean pre-igniter and igniter? :rofl:

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 Post subject: Re: Quieter exhaust
PostPosted: March 9, 2012, 11:29 pm 
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locofinn wrote:
Racing Beat pre-silencer and silencer squeezed in as small a space as possible. Hope it is under 100 db at full throttle.

The problem is that more and more tracks have sound limit a lot lower that that - Laguna Seca in CA is 92 dB, even some OEM cars will trip that. What a lot of people don't realize is how loud engine intakes can be.

Turbos muffle both :wink:

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 Post subject: Re: Quieter exhaust
PostPosted: March 10, 2012, 12:57 am 
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I'm using a stock Suzuki GSXR1000 muffler on my GSXR1000 engine and the noise was unbearable above 5,000 rpm at WOT under load!

I tried a pipe out the back of the car and the noise still hurt my ears above 9,000 rpm.

http://dmr-architect.com/~locouki/exhaust-out-rear.html

I have an article on my website how I fixed the problem,

http://dmr-architect.com/~locouki/baffle-muffler.html

I'm quite sure the noise is not completely caused by the muffler itself but a combination of the header and connecting pipe size/length -before- the muffler (remember this is an absolutely STOCK muffler that was used on the Suzuki GSXR1000 motorcycle). The moral of the story for me is that the muffler itself isn't the whole story for sound level [at least] on a BEC.

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