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slomove
June 28th, 2004, 10:08 PM
I picked up a sound level meter at Radio Shack. Not a certified precision instrument but probably reasonably accurate.

Results are somewhat disconcerting (literally)

1. California noise limit (20" distance, 45 degrees from the exhaust in idle at 3/4 of full power revs should be less than 95dBA). Well, I got about 109 dBA :shock: Maybe I did something wrong with the measurement?

2. Drive-By at 50 feet and 50 mph: I measured about 89-93 dBA (compared to 70-75 dBA for the typical tintops)

3. Most troublesome: in the cockpit at full freeway speeds I had more than 112 dbA. That is BAD :oops: I am using earplugs most of the time and anyway on longer blats but I will be using them more diligently now. I got already a hearing loss and Tinnitus and don't need to make it worse.

Gert

P.S.: I can set off car alarms by driving by 8)

Slartybartfast
October 13th, 2004, 03:36 PM
Ummm - you did actually fit the silencer, didn't you ? :wink:

I have the same RadioShack meter - I'll have to compare those figures to my car.

I too used to drive without earplugs until my first couple of drives on a freeway. When I noticed my hearing felt "muffled" after a drive, that's when I decided I needed some protection.

slomove
October 13th, 2004, 05:37 PM
Ummm - you did actually fit the silencer, didn't you ?

Darn, I knew I forgot something..... :)

No, honestly there is a 32" x 4" dia Magnaflow bullet muffler installed plus a tiny tip muffler. But while nicely free-flowing the noise reduction isn't really that much. Oh well, at least the sound is very satisfying.

If you can do some measurements I would be interested to compare results and what your muffler setup is.

Gert

Michael Murphy
October 13th, 2004, 09:56 PM
Gert,

This is most disconcerting. I thought your car was very civilized compared to mine.

I use ear plugs but they don't stop my teeth from hurting.

I guess I should not even bother showing up at Infineon...

slomove
October 13th, 2004, 10:27 PM
Nah, probably not that bad at Infineon. Rich H. wrote they measure 50ft away on the right hand side away from the exhaust. With 103 dBA I should be safe (I hope). But maybe I take some exhaust choke device like a tin can with me, for good measure.

Gert

Anonymous
October 9th, 2005, 04:26 PM
As a Seven admirer for a couple decades who was soon to be a Seven purchaser, when I saw this thread about half-a-year ago, I've kept it in my mind and started collecting info to contribute.

Yesterday and today I saw a news segment on ch 4 in the San Francisco Bay Area about the California Hearing Society giving out earplugs to people at the Marina Green who are watching the Blue Angels this weekend. A Society rep said 30 min or more at 90 decibels causes irreparable (i.e., permanent) hearing loss.

Back on Sept 22, 2005, the SF Chronicle had an article ("Play It Loud and You May Pay for It. A Warning to All About Those Earbuds," Sec. E, p. 1), about the hearing damage many are incuring because of iPod use. Dr. Robert Sweetow, director of audiology at UCSF said, "Hearing loss is one of those things that is insidious. It comes on very slowly. If you're going to experience hearing loss from music, it always starts in the high frequencies, which are above the pitch of most conversations. Everybody knows when they've experienced a sudden hearing loss. You many not notice a gradual loss until it is too late." East Bay audiologist Dr. Mont Stong said, "Hearing doesn't have any pain receptors. By the time you reach the pain threshold, the damage has already been done."

I wanted more details so I went to web and found a Newsweek cover story about hearing loss dated June 6, 2005:
http://www.msnbc.msn.com/id/8017906/site/newsweek/

(open quote)
Various levels of noise affect hair cells in various ways. If a rocket-propelled grenade goes off right next to you, you can experience "acoustic trauma" that kills hair cells and causes the instant loss of a great deal of hearing. (Hearing loss is the third most commonly diagnosed service-related ailment, according to the Department of Veterans Affairs.) Hanging out directly in front of the speakers at a Green Day concert could result in a less serious "temporary threshold shift," in which the hair cells are stressed but not permanently damaged. Such stress is often accompanied by ringing in the ears that can last for hours or even days. (Derebery notes that repeated threshold shifts can lead to permanent hearing loss.) And then there's what might be called noisy-world syndrome. While an individual's noise exposure may not reach the official danger zone, the worry is that the chronic din of daily life could lead to deterioration over time. "There's not a lot of data about it," says Rabinowitz, "but our concern is that there is less and less time for the ears to rest, and so the hair cells are going to be prematurely exhausted."
(close quote)

Be sure to look at the Dangerous Decibels chart (http://www.dangerousdecibels.org/hearingloss.cfm ), which uses more "liberal" cutoffs than the TV news item above.

Gert, at 112 dB, your hearing starts getting damaged in *less than 1 minute of exposure.* :shock:

The next series of quotes comes from a Field & Stream article ("Listen Up (If You Can)" at:
http://www.fieldandstream.com/fieldstream/outdoorskills/article/0,13199,1040284-1,00.html

(open quote)
“I went to a doctor in 1970,” he recalls, “and told him a lot of people seemed to be mumbling. He told me I’d already damaged my hearing and what I’d lost wouldn’t be coming back.” The doctor also diagnosed Petzal with early-stage tinnitus, a persistent ringing that’s been known to drive some victims to distraction. Even more bothersome for Petzal was a third symptom known as recruitment, a phenomenon in which the brain attempts to compensate for growing deafness by amplifying external sounds. “If a normal person hears a fire engine go by on the street, it doesn’t bother him much. But it drives me to my knees. When you get something loud, it’s unbearable.”

***

The physiological cause for conditions such as tinnitus and recruitment are not as well understood, but both are frequently devastating phenomena. Though most tinnitus sufferers, for example, eventually come to accept their condition, Tweed says he has had patients for whom it is “just so unremittingly bothersome they can’t stand it.” In rare cases, some have even elected to have their inner ears surgically destroyed to stop the buzzing.

***

The good news is that you don’t have to eliminate the sounds of gunshots—you just need to reduce them to safe levels (approximately 80 decibels). A good way to do that is to use custom-fitted earplugs, which can cut the sound of virtually any gun to manageable levels. (Consult an audiologist, who will take an impression of your ear canals to create plugs tailor-made for your anatomy.) Earmuffs work better than plugs because they provide significantly more physical mass to attenuate the sound. If you’re shooting a particularly high-powered firearm or find yourself on a range surrounded by other target shooters, experts recommend doubling up for the best protection.
(close quote)

Racers should be concerned not only with the noise level of their own exhaust but also of the other cars they'll be racing against.

Interesting quote at the end of the Dangerous Decibels webpage (NIHL stands for "noise induced hearing loss"):

(open quote)
NIHL is of particular concern to veterans. Because NIHL is not immediately apparent (having a gradual onset), many veterans leaving the service are unaware of the full extent of hearing damage. Although governments are now realizing the link between military service and NIHL, it took a long time and many lawsuits before any compensation was given to the affected veterans. In 1999 the USA alone distributed $291.6 million in compensation for NIHL to some 56,792 veterans. The annual cost of compensation to veterans in France is estimated to be $60 million. In Belgium two thirds of all payments made to veterans with disabilities correspond to NIHL.
(close quote)

I hope it doesn't take someone suing Caterham into oblivion (a class action lawsuit?) to get them to redesign their exhaust system and stop making cars inherently unsafe to their owners and passengers. I hope Caterham offers a Seven that is safe enough for taking a four or five hour drive without the riders having to resort to the unsafe (and illegal?) practice of wearing earplugs and/or muffs.

Perhaps any of you with connections to Caterham USA or the factory could pass this on to them and/or post this on Blatchat.

JohnCh
October 9th, 2005, 06:11 PM
I hope it doesn't take someone suing Caterham into oblivion (a class action lawsuit?) to get them to redesign their exhaust system and stop making cars inherently unsafe to their owners and passengers. I hope Caterham offers a Seven that is safe enough for taking a four or five hour drive without the riders having to resort to the unsafe (and illegal?) practice of wearing earplugs and/or muffs.

I just returned from a 4100 mile trip in my Westfield and I can confirm that even a quiet exhaust won't solve the hearing damage problem. I have a Raceco silencer which is very quiet, so the majority of our db originated at the induction end (the air filter exits through the bonnet) and from wind noise. The latter is an issue at high speeds and although side screens help, you really need ear protection on any kind of long journey. That's just the nature of the beast.

I'm sure Caterham, Westfield, Birkin, and others could do a redesign to minimize the problem, but then they would no longer be se7ens. After travelling through 8 states over the 2 last weeks -- the best 2 weeks of my life BTW -- I can honestly say that would be a terrible shame. The world needs cars like this. Warts and all.

-John

slomove
October 9th, 2005, 06:28 PM
Yep, concur with John.

With good, well-fitting earplugs the noise (exhaust, induction or wind) does not really bother me. Without it is just unreasonable and with expectable health consequences. After the USA2005 trip (I made 3,600 miles) I guess my exhaust is getting even louder, probably the packing is beginning to blow out.

So, one of the winter upgrades (after the home remodeling.....) is to get a Raceco can. Also some new shocks which is a totally different story :)

Anyway, I got the Tinnitus ringing in my right ear years before I bought the Seven (also not a hunter, soldier or rock concert freak). Kind of annoying but it could be worse. And it just started out of the blue.

Gert

Anonymous
October 10th, 2005, 08:58 AM
Gert, let me know when you are going to order the Raceco muffler, as maybe we can do a group buy or at least split the shipping costs?

I made it home from Infineon yesterday, 400 miles of freeway driving, yuck!

Stan

soareyes
October 10th, 2005, 09:01 AM
Oops, forgot to sign in, that was my post above!
Stan

slomove
October 10th, 2005, 10:35 AM
Hmm, that's an idea... I am not in a hurry (remember the remodeling job) but maybe we can get a few together and a better price.

Anybody else interested?

I was planning to go for the 6.5" can. The 7.5" is just too fat.

Gert

Slartybartfast
October 10th, 2005, 10:49 PM
Thanks for all the information 7'Dreamin', but I feel I must clear up a couple of points.

In my car, it's not the exhaust that contributes the most noise - it's other cars. Not their exhaust, but their tyres. Tyre noise on a freeway when the wheels of the other vehicle are only a few feet away from your ears is VERY loud. Sidescreens help, but are no substitute for good quality ear-plugs. I made the mistake of forgetting mine once when I went out for a blat. I was fine while I was having fun on the open road, but the jouney back was on the freeway, and I've regretted it ever since. I am sure I suffered hearing loss as a result. Nothing drastic - but noticeable. Moral of the story - if you forget your earplugs, stuff *something* in them, or find a diferent way home. risking your hearing is not worth the few minutes you might save on your journey.

My second point is about legality. When I got my earplugs, I did some research - primarily because I've *never* been able to get away with anything that remotely breaks the rules in my entire life, so didn't fancy having some nice police officer giving me a hard time. Here's section 27400 of the California Vehicle Code:

"A person operating a motor vehicle or bicycle may not wear a headset covering, or earplugs in, both ears. This prohibition does not apply to any of the following:

(a) A person operating authorized emergency vehicles, as defined in Section 165.

(b) A person engaged in the operation of either special construction equipment or equipment for use in the maintenance of any highway.

(c) A person engaged in the operation of refuse collection equipment who is wearing a safety headset or safety earplugs.

(d) A person wearing personal hearing protectors in the form of earplugs or molds that are specifically designed to attenuate injurious noise levels. The plugs or molds shall be designed in a manner so as to not inhibit the wearer's ability to hear a siren or horn from an emergency vehicle or a horn from another motor vehicle"

So sub-paragraph (d) is a get-out clause. I think freeway-speed noise levels constitute "injurious noise levels" !!

DON'T FORGET YOUR EARPLUGS !!

Ooops - sorry, didn't mean to shout ;)

Wayne

imported_venom7
October 11th, 2005, 01:36 PM
I have a quiet underbody exhaust in storage, I'm going up there tomorrow. It has 10,000 miles on it and probably needs the proper header fabricated as it is for a Vauxhall. Couple of dents in the silencer part. In honesty I can't imagine why anyone would want to own a 7 with an underbody. It is too quiet, too low and too strangulating. I went to the 4-1 Vauxhall race and have never looked back. I wear earplugs usually except for the odd spin around the block in the past. I find the wind noise is the worse culprit to fatigue and hearing.

Roll a 7
October 11th, 2005, 05:41 PM
I am also interested in the Raceco item and am planning to give AMMO a call in the next week or two. After my recent exhaust difficulties @ WSR and finally seeing a real one on John C's Westy it's time to head for the side exit. I'll inquire about the possibility of a group buy.

Can anyone give me an idea how the change will affect my ECU map? Since I am changing to a less restrictive exhaust without a catalytic converter what will be the effect: leaner, richer or no effect?

Best of all, the car should reduce its' overall weight by 1%. Take off the heater and another 1% disappears; before long it starts to add up....

And the driver doesn't have to go on a diet!! 8)

magnusfeuer
October 11th, 2005, 06:24 PM
Brad.

If you order one, can you pick one up for me to? I'll split freight costs with you.

Your engine will lean out somewhat and should be remapped. I'd be happy to help you with this, if you want to.

/Magnus F.

Roll a 7
October 11th, 2005, 06:41 PM
Magnus, What is happening that will cause the motor to lean out, rather than richen? (I have no idea why it would go either way!!)

I will definitely take you up on the remap offer. Our last mapping session made a great difference in the mileage and operation of the snarling bumblebee 7.

Do you know which size silencer you would prefer? Also, the best length?

I suspect that we might be better off to have them shipped individually because we each get a an exemption from import duty of around $600, which likely makes up for the freight cost; but I will ask AMMO.

magnusfeuer
October 11th, 2005, 07:40 PM
I would go for the 7.25" version for no other reason than that it should breathe a bit better.

I also need a suitable collector to hook it up to the header flange. Do you think Ammo can provide that? The collector would determine if the silcenser has a 2 or 2.5" intake. Basically I'd take what Ammo would recommend for my setup.

In my opinion (which may be wrong, I shall check), the engine will lean out since it breathes easier. During the exhaust cycle, the engine will be able to eject more exhaust gasses into the exhaust system since there is less restriction there. I believe this is especially important during the intake/exhaust valve overlap phase when all four valves are partially open.

If we can air out more exhausts during this cycle, there will be more room for fresh air (hence oxygen) during the subsequent intake cycle. The injectors, though, still fire the same amount of fuel as earlier.

The end result is that there is fuel to air ratio is smaller than earlier.

That's my theory anyway. Please correct me if I am wrong.

slomove
October 11th, 2005, 08:04 PM
Well, dunno about theory......I suppose it may be true if you have a *real* restrictive exhaust to start with. :? Otherwise any effect may be too small to notice.

About diameter: I am not sure if the can diameter makes a difference in flow resistance. I suspect the internal perforated tube is the same for both cans. The bigger outer diameter will give you surely more noise attenuation due to more volume for packing. But I have seen the big can mounted and it is HUGE. Kind of ugly, actually.

I will keep my collector and whack off the header tubes to fit the length (I have a slip joint, no flange). AFAIK it is impossible to weld the titanium tube to the collector i.e. must be clamped on.

Brad, I would appreciate if you inquire about a group buy.

Gert

P.S.: About mileage....the tour gave me an opportunity to test the injection map over a long run. With a good mix of fast cruising and spirited driving I got 27.8 mpg. Not bad for throttle bodies and medium hot cams.

magnusfeuer
October 11th, 2005, 08:38 PM
About restrictive exhaust systems:

Catalytic converter.

Enough said.

/Magnus F.

Roll a 7
October 11th, 2005, 08:43 PM
I believe that the reason for the larger can is that it's better for noise reduction rather than anything related to engine breathing. Many of the UK tracks have very strict noise regulations and the bigger can is said to be quieter with additional sound deadening material inside. I'll ask AMMO what the rationale is for different internal diameters. It is also available in an "offset" thru pipe construction to keep the side of the can away from the car. I figure to Email digital photos with the critical measurements when I'm ready to go.

Burns Stainless in Orange County has an array of tubes that you can easily have adapted to fit onto your exhaust and the can. In fact, you would be prudent to have them do the installation. A quick google will turn them up.

There is also a place in the Bay area that can provide similar peices---but their name escapes me in my dottering old age.

I have a Caterham flange if you would like to use it as a template.

After some months of searching the internet for an off the shelf usable/comparable item I have concluded that AMMO has the best true lightweight can around. Anything done here would almost certainly have to be fabricated and would then cost even more $$$.

magnusfeuer
October 11th, 2005, 09:56 PM
Burns is in Costa Mesa, 10 minutes from where I live. I've already talked to them about a complete exhaust system setup, but I can have them just do the collector.

Anyone else interested in this?

/Magnus F.

slomove
October 11th, 2005, 09:59 PM
About restrictive exhaust systems:

Catalytic converter.

Enough said.

/Magnus F.

Oh, you still have that thing on :roll: ?




After some months of searching the internet for an off the shelf usable/comparable item I have concluded that AMMO has the best true lightweight can around. Anything done here would almost certainly have to be fabricated and would then cost even more $$$.

Agree. My Magnaflow muffler was cheap, small, has no flow restriction and looks pretty good. But it is noisy, heavy and not repackable. After a few trackdays and maybe 8000 miles it is shot. At the end you get what you pay for.....

Gert

soareyes
October 12th, 2005, 10:52 AM
Burns is in Costa Mesa, 10 minutes from where I live. I've already talked to them about a complete exhaust system setup, but I can have them just do the collector.

Anyone else interested in this?

/Magnus F.

Magnus, I just looked at the Burns web site and downloaded their catalog. It looks like they produce quality products. I'm curious as to why you are considering the Raceco muffler vs. letting them do the whole system? Do you have a ballpark cost figure for their system, and did they give you an idea how loud it would be compared to your stock exhaust? I know I want to convert to side exhaust but I'm still trying to figure this all out!

Stan

magnusfeuer
October 12th, 2005, 10:12 PM
I got a ballpark figure, if I remember correctly, of USD600 for a complete system, including collector.

The reason for going with Ammo is that it is a tried setup for the Caterham. I always try to go for a proven solution, even if my supercharger proves otherwise.

/Magnus F.

moosetestbestanden
October 12th, 2005, 11:10 PM
If it ain't Ti, it ain't s***. Remember, Ti doesn't corrode and it doesn't fatigue. And his exhaust is sorted in Caterham applications. And, it's English. Lastly, he's a Guzzi man.

Put me down for a bulk buy from AMMO if anyone else still wants to go that way.

Edited to add that I've emailed AMMO in inquiry as to particulars. I'll post later when I've heard back.

Matt S
October 13th, 2005, 04:43 PM
Check out these guys

http://www.etymotic.com

They make custom fitted high fidelity earplugs so that things sound the same with them in, just quieter. I have a pair of their ER-20s that are not custom and cost $20 that I try to wear every time I drive in the car. I notice that I hear thing better with them than with the foam plugs and the noise level is fine. I plan on getting some custom fitted plugs Real Soon Now.

I occasionally take the seven into work which involves about 15 miles on I-15. It does not feel loud like a rock concert, but I did notice that things sounded muffled afterwards without earplugs. So now I make it a point to use them.

I take this stuff seriously. I even wear earplugs at nightclubs and concerts. That may not be surprising coming from someone in their 30s, but I did it when I was 18 too.

-Matt

Elv15
October 25th, 2005, 02:26 PM
One of the side benefits is that the Ammo silencers do not get as hot on the outside and therefore are a "safety" device (ie: so you or your passenger don't burn their ankle!

This can be a _real_ problem...I know of three folks who burned their leg's on the USA2005 tour.

JohnCh
October 25th, 2005, 03:28 PM
Tom brings up a good point. Even when I had my car on the dyno, the Raceco silencer never became too hot to touch. The secondaries, however, were a different story ;-)

-John