Noise Testing Results (Muffler Comparison)

[Daves]

One area all teams can work together in is by sharing with each other which mufflers are able to pass the noise test. This would save us all much money and frustration because we would not waste money on mufflers that fail. Here are the results of our 2003 car at Detroit:

Engine: Honda CBR600F4i
Testing speed: 11,000 rpm
Muffler: Supertrapp
Noise level:
18 plates: 123 db
14 plates: 115 db
11 plates: 115 db
11 plates with 1 piece walmart steel wool: 118 db
7 plates with 3 pieces steel wool: 105 db

Our engine did not like the steel wool, though. Therefore, we ended up using a stock Honda 600 carbon steel muffler. We also bought a Honda 1000 stainless muffler, and it was almost identical to the 600.

Engine: Honda CBR600F4i
Testing speed: 11,000 rpm
Muffler: Honda
Noise level: 102 db

110 is the limit, and every 6 db is twice as loud. Therefore, the muffler can only be slightly over twice as loud as stock. Sadly, most aftermarket mufflers are much louder than that. Please post your results here, as I am considering buying mufflers by the following companies:

Akrapovic
Arata
Arrow
Bos
Devil
Erion
G Force
Hindle
HP racing
Jardine
Kerker
Laser
LeoVince
m4
Micron
Micron
Quill
Scorpion
Two Brothers Racing
WRP
Yoshimura

[Charlie]

Yoshimura Zyclone Ti, CBR600F4i, 109.8 dB http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

-Charlie Ping
Auburn University FSAE (http://eng.auburn.edu/organizations/SAE/AUFSAE)
5th Overall Detroit 2003
? Overall Aussie 2003. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Matt Ahl]

Supertrapp EAR, F4i, 109.7 dB.

We tried the Supertrapp IDS and couldn't get it to pass on a lab grade instrument and went back to the EAR. Supertrapps dissipate sound differently so they are generally louder up close that they are far away relative to other mufflers. So the car will sound quiet on the track, but do poorly in sound.

[Sam]

last year we ran a stock muffler off an R6, we passed at 101db i think, quietest at comp. was pretty heavy though. this year i picked up a carbon pipe off a wrecker. no idea what brand it is, no idea how loud it will be, but it's light http://fsae.com/groupee_common/emoticons/icon_smile.gif

Sam Graham
Engine Group Leader 2003
UQ Racing

[Ben Beacock]

We ran a stock GSX-R muffler and measured 108.9db at 11000rpm

the muffler was rated for 89db (printed right on the side of it)

Ben Beacock
Co-Manager
2004 Gryphon Racing - University of Guelph

[Daves]

Ben, the 89 db rating is for a distance like 50 feet away, not 1.5 feet away. If you do the math,

89db @ 50ft.
+6 *1/2
95db @ 25ft.
+6
101 @ 12.5ft.
+6
107 @ 6.25ft.
+6
113 @ 3.125ft.
+6
119 @ 1.5625ft.

So 108.9 db was pretty good (fewer than 119 db) if it was rated for 89 db.

[Daves]

And I forgot that the muffler db rating is not taken at the same rpm as at FSAE. I believe it is rated for a much lower rpm. Therefore, no amount of math will help you in choosing a muffler. You must go with experience or someone else's experience (hence, this thread).

[Kevin Hall]

We tried making our own out of Carbon/Kevlar, and packin it with f'glass packing. It was a straighthrough design, and we ended up needing some magic plates on the end to get it to work.

Last year, we went to a Ti Hindle pipe for comp. When the engine was cold, we were 112, but once it warmed up, we had 106. Pretty good as far as I could tell, and the pipe is REALLY light.

Hindle is a great company, and they sponsor well. Our hats off to them!! If you contact Lee Hindle through email at i n f o @ h i n d l e . c o m , tell him I sent you, and he's bound to have a good deal for you. Couldn't find a better company if I tried.

Kevin Hall
University of Saskatchewan
'03-'04 Team Director

[fsae_alum]

We ran a carbon fiber Yoshimura that we cut in half to make shorter. We got it from a salvage yard and was crushed about 1/3 of the way down the length. We just cut it in half, put the end back on and ran with it. We squeaked by in 02 by 1 db! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif By the way that was on a F4i

In spite of...

[Bam Bam]

Holy throw money at the problem batman!!

Just make the bloody thing

muffler glass pack $25
aluminium sheet $2
Rivets 20 cents
perforated tube $4
a little bit o welding and PRESTO! Instant muffler.

You can make these things enormous and they're still lighter than most $700 mufflers. Just don't run an aluminum one at WOT on the dyno at 13 grand for any length of time.

[fsae_alum]

Throw money at the problem? Not quite what you'd think at first glance. That Yoshimura CF muffler didn't cost us anything but about $.10 in rivets and about 15 minutes in labor. Since it was damaged beyond being able to use on a bike, it was free with with one of our car kits! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif Looks good and sounds good!!

In spite of...

[Matt Gignac]

alum, you'd still have to put that yoshi muffler in the cost report, and 700$ dollars for something you don't really want on the car but have to have there is excessive in my opinion. We made ours ourselves out of cf and stainless steel, total cost of 125$ in the report

[fsae_alum]

Yeah...I hate that damn cost report... We reported half of it since we only used half of it! I'm not saying our choice was better or worse than anybody elses...juas that we did it that particular way and it worked for us, that's all. Had we had the time, I'm sure we would have made one ourselves too. Yeah..our cost report was horrible but that's a completely different story!

In spite of...

[Daves]

This exhaust header is an interesting concept, and it yields tremendous power gains to stock bikes.

http://www.hardracing.com/Exhaust%20Systems/MicronSerpent.htm

http://www.hardracing.com/images/clip_image01.jpg

[Richard Lewis]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> We ran a stock GSX-R muffler and measured 108.9db at 11000rpm <HR></BLOCKQUOTE>

We did the same, and it took us 3 tries to pass. Stock GSX-R, 11000rpm, 108.9dB.

-------------------------
UVIC Formula SAE Team
http://members.shaw.ca/drax77/Formula%20UVic%20Sig.jpg
http://uvic.fsae.ca

[Matthew]

we built our own straight though muffler:
first try 111 db
repack 1: 117db
repack 2: 107 db

(10500 rpm)

-Matthew Hetler
hetl0020@umn.edu

[Lyn Labahn UW-Madison]

We passed sound with a little over 109 with a Vance and Hines SS2-R muffler. It was repacked with some special packing that I found. As a side note I believe this to be the slimmest commonly availible muffler you can buy. It is around 3.5 inches, which is crucial for us because we run the muffler under the a-arms.

As a rant, the sound test is complete and utter bullshit. Hardly any Gixxers could pass the test because the RPMs were so high. Many schools that passed the test(with Gixxers and other engines) were not at the proper RPM, as per my ear tachometers. Anyone else notice this?

2002/2003 Team Leader
Best overall average finish of the new millenium http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Richard Lewis]

Yeah I thought it was unbelievable that we failed twice with a stock muffler... Our car is no louder than the street bike, and it really isn't louder than many cars/bikes on the road with exhaust tweaks.

ANd now that I think about it some more, we were over 109 as well, not 108.9 as I had origionally posted. I remember that we just sqeaked in.

-------------------------
UVIC Formula SAE Team
http://members.shaw.ca/drax77/Formula%20UVic%20Sig.jpg
http://uvic.fsae.ca

[Mi_Ko]

This is my first reply in this forum.

We used an single Akrapovič (Made in Slovenia) muffler for the 2001/2 and 2002/03 formula SAE europe (Formula Student) competition on a honda cbr 600 engine (y. 93).

y 01/02 - 109.9 db
y 02/03 - 109.2 db

The rpm were to low I think (only 1/4 of throttle - 4000 rpm). But the judge said they are o.k. - thank good.

2002/03 Team Member - Formula student Europe

[Daves]

While researching, I came upon the mufflers that the CART Formula Atlantic Toyota cars are required to use. They are made by Coast Fabrication in California (coastfab.com). They are quite inexpensive considering how much some FSAE teams pay for mufflers:

(Prices in US$ I think)

Inlet Outlet Length Part No. Price Weight

2.5" 2.5" 17.13" 25X25FATLSS $170.46 2.61 LB

Go to http://www.coastfab.com/ultralights.html to see their other mufflers.

[MikeWaggoner at UW]

Anyone doing flowbench testing when they do their muffler comparos?

UW FSAE
The views of Mike Waggoner are not necessarily the views of the UW FSAE team.

[Mechanicaldan]

We ran a '99 Kawasaki ZX-6R with a Muzzy oval carbon and passed right at 110 dB. 3.5 lbs of eye candy.

Cyclone Racing
www.cyclone-racing.com/fhome.htm (http://www.cyclone-racing.com/fhome.htm)
Iowa State University
Project Director

[Hot Rod JayRad]

Hey so i was wondering how some teams went about designing thier own mufflers? Is there any good books on muffler theory?

[mangel83]

A very old post this one, but what the hell... it's good to know what some mufflers are rated, if you know how they're tested. Yoshimura's RS-3 are rated 95 dB (20" away, at 45 deg from the tip, and at 4000rpm), we ran a 03 GSX-R600 with this same muffler (brand new) and we were rated around 115 dB in our first try, we repacked the thing and passed in the sencond attempt. But if you only base your selection on this you are leaving an important factor out of the equation: the header. We tested this muffler in a bike with our same engine and the stock header and with our super-sentive ears we didn't notice any difference, but the sound meter said the bike was around 6 dB quieter.

[Dallas Blake]

This is very true. Last year at competition we had a header that was less than ideally constructed. Any little leaks contribute quite a bit to noise. Another thing to look for is where the muffler joins to the header. Make sure there are no leaks there. Also worth an attempt is tuning your muffler for attenuation resonance. Gordon Blair's book highlights the equations for predicting natural frequencies of different muffler types. It would be worth an attempt to tune your muffler to resonate at the noise test RPM (in the case of a side resonant chamber this would correspond to maximum attenuation)

Noise has always been an issue for our team. We just got ourselves two brand new mufflers, a stock and a white brothers for a predator 500. The white brothers is rated at 102dB for GNCC (which has the same noise test reguations as us) so we'll see how it reacts to a 600I-4 versus a 500single.

[Wesley]

I don't claim to be an expert in acoustic theory, but I have read Blair's section on muffler tuning/modelling, and also numerous other sources about band-pass and band-stop filters.

If you tune the length of the muffler to resonate at the test frequency, you will not attenuate anything. A chamber forms a band-pass filter, which will pass its resonant frequency and dampen those that are not harmonics.

[Dallas Blake]

Wesley,

There is more to tuning the muffler than the length, you must consider the number of holes, size of the holes and volume of the chamber.

Most bike mufflers are a dual chamber, one chamber of which is a diffusion chamber (with the packing) and one is a side resonant chamber. A side resonant chamber provides maximum attenuation at its resonant frequency (Page 718-719 of design and simulation of four stroke engines) the second chamber

the diffusion chamber provides zero attenuation at its resonant frequency

[Wesley]

I apologize, I should have clarified.

A straight through chamber (in addition to a diffusion chamber) provide zero attenuation at its resonant frequency.

A side chamber, (or Helmholtz resonator) will provide max attenuation at its given frequency.

We just got our muffler built based on a brute-force MATLAB program that tested varying elements, such as those you named - % area of perforation, packing density, chamber volume and cross sectional area, tube cross section, and final chamber resonant frequencies. Needless to say, it passes sound. (It weighs 40 jillion pounds, but it works)

I should have specified - an expansion or diffusion chamber. I consider Helmholtz resonators to be that - resonators, versus a straight chamber, though in a platonic sense they are also chambers. My apologies.

[Chris Allbee]

its 9 pounds and its just the test piece for crying out loud! We'll replace the all-steel muff with carbony bits and aluminum where we can.

[MikeDutsa]

We ran a hindle TI 18"x3" on a cbr600f4i, 112db. we ended up putting what looked like a pasta strainer on the tip in order to pas tec. with that and no power, 108db.

[incorrigible]

Hey what are you guys using for cf epoxy?
I've been looking for hi-temp epoxy but have only been able to find some that is rated to 572 degrees F. We see temps around 700 at the muffler inlet and when we tested cf last year it didn't last.

[Chris Allbee]

Incorrigible,

If the guys you are referring to are myself and Wes, then I have to tell you that our little carbonfiber muffler experiment ended with a melted muffler and a whole lot of stink.

Without getting into too much of the nitty-gritty, we ended up using a Ti Akrapovic muffler. It required a little retuning of the engine map and some small tweaks to the header inlet geometry to pass sound, but it ended up being a better solution.

[jeff-NIUMS]

Last year, in search of cutting pounds I tore apart an old carbon fiber vance&hines muffler we had laying around. I took the shell, found a roll of aluminum mesh, and got some fiberglass packing. Then we just made some stainless endplates that riveted on and it worked great. Right at 110dB while only being 2lbs.

[incorrigible]

Thanks Chris, those were the same results we had with our muffler last year. We've had no luck trying to talk to muffler companies about what they use for epoxy for cf shells.

[Tech Guy]

"Right at 110 dB"!!!

A word to the wise. Having worked in vehicle noise control for one of the OEM's a number of years ago, I would strongly suggest that a wise team will aim to have about a 3 dB margin and not try to get super close to the mandated limit. The recorded level varies with so many factors, including ambient conditions, and there are no correction factors. The number IS the number! And when was the last time you had your meter calibrated?

The potential performance gains for getting right up to the limit are very small, if any. And if you are over at the competition, you are in for a mad scramble to fix the problem, which will put you behind your optimum schedule. It could even mean you do not compete. Give yourself a little margin!

[James Morris]

Has anybody used or had any luck using a Helmholtz resonator just on its own for a silencer?
I was just thinking that a Helmholtz resonator could end up being lighter than a silencer and possibly flow better???