I am over the sound limit for our local facilities and have a few questions regarding modifying my exhaust with an additional muffler.

The motor is a mildly modified Honda B series with limited room in the gearbox change extension tunnel.

My current exhaust system consisting of a 4-2-1 header leading into 2.5” SS tubing with the sound level being modified by an Magnaflow 4” round by 14” body muffler, followed by another short section of 2.5” SS tubing dumping by way of a turndown under the car in front of the rear axel.

There is room to add another muffler in the tunnel similar in size to the one I am already using.

1.) Should I go with another of the same muffler, Magnaflow 4” round by 14” body, I am already using in an attempt to reduce the sound level further with in the current muffled frequency range ?
2.) Or go with another brand with the hopes of attenuating the sound levels in a different frequency range? Some thing like this http://66.223.106.208/Ultralit....html
3.) Or best plan, an in expensive means to analyze my exhaust sound, frequency, and levels then search for a muffler designed to reduce sound levels in the frequency range where I am exceeding our local limits?

 

Put one of the magnaflow ovals in the stock location. The bigger the oval the quiter it will be.

 

Noise abatement FTL... I have seen down turn tips that help, but not much

 

OOPS... I see you have a down turn already

 

May I ask what your sound level was? I run a B18A1 totally unmuffled and am under the 103 dB regulations in the Midwest.

If you are happy with the Magnaflow, then I would stick to the Magnaflow. My next 2 suggestions are assuming that the MagnaFlow has the same concentric tube design as the link you gave (I am not familiar with the MagnaFlow design).
- If you are barely over the sound limit, then I would replace your 4" OD existing muffler with a 5" or 6". The larger diameter will reduce your sound further (as BrianZ mentioned).
- If you are not that close and need more muffling, then get a slightly different length MagnaFlow (12" or 10"). The different length will cause the attenuation frequencies of the 2 mufflers to offset and allow 1 to damp out where the other does not.

 

Hello mc-integra111,

My sound level was right at the 100dB, this is with a B17.

The muffler looks like this



Magnaflow does not make a 5" round, they do make a 6" however it would be to large for the tunnel.

The Magnaflow 4" round does not come in different lengths but the Burns Ultra Light does come in different OD and lengths.

I am happy with the Magnaflow however my real question is will I achieve greater sound attenuation using two different types, shapes or styles of mufflers or two of the same?

 

I was debating on getting one of these and just bolting it to the exhaust exit.
http://www.pegasusautoracing.c...=4305

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by DB2-R81 &raquo;</TD></TR><TR><TD CLASS="quote">I am happy with the Magnaflow however my real question is will I achieve greater sound attenuation using two different types, shapes or styles of mufflers or two of the same?</TD></TR></TABLE>

Unfortunately, that question depends on far too many things to know for sure. Although if it were that simple a part of my job wouldn't exist.

The concentric tube muffler design is very good at not increasing the back pressure, thus not affecting performance. Their noise reduction qualities are minimal, which is why you see larger overall diameters to help reduce noise further. In the interest of maintaining performance, I would stick to finding a muffler with the same concentric tube design, having a slightly different length than what you have, and with as large a diameter as you can fit. You could also try to get a glasspack, as the packing will help to reduce the sound even further, although the addition of the muffler itself is a much bigger effect than just the addition of the packing.

Thanks for the noise level reading. You didn't mention what the limit is, but there is a track in Michigan that has a 75 dB limit. If you have a limit like this, you will need a full muffler to get this low.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mc-integra111 &raquo;</TD></TR><TR><TD CLASS="quote">...but there is a track in Michigan that has a 75 dB limit. </TD></TR></TABLE>

Sheesh....75db! Where is that, downtown Detroit? I'd thought Laguna Seca was overbearing with a 92db limit but 75? Whoa.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ponyboy &raquo;</TD></TR><TR><TD CLASS="quote">Where is that, downtown Detroit?</TD></TR></TABLE>

Waterford Hills, about 40 miles outside of downtown.

 

Hello mc-integra111,

Our Pitt Meadows, Mission, Vancouver area limit is 95 dB.

Waterford Hills, magic place, spent my childhood in Royal Oak and many wonderful weekends at Waterford Hills in the 60's and early 70's.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ponyboy &raquo;</TD></TR><TR><TD CLASS="quote">

Sheesh....75db! Where is that, downtown Detroit? I'd thought Laguna Seca was overbearing with a 92db limit but 75? Whoa.</TD></TR></TABLE>

holy crap, dont yell too loud. . i know in my area you have to be like over 110Db I think, and that just at the lot that belongs to a hs stadium. :-p

 

Yeah, at least one of the racers at Waterford has pointed out that some riding lawn mowers in the residential area are over 75 dB.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mc-integra111 &raquo;</TD></TR><TR><TD CLASS="quote">Yeah, at least one of the racers at Waterford has pointed out that some riding lawn mowers in the residential area are over 75 dB.</TD></TR></TABLE>

That's the level of a stock C5 Corvette at ~3,500 rpm, in neutral at 50 feet, 75 dB.

A Lawnmower is typically measured at 90 dB.

Hell, Freeway traffic is ~70 dB, most motorcycles are 85dB unmodified.

 

All excellent points. I think that sound restriction is the reason why I personally don't think Waterford is going to last long term as a road race track.