KR500 to silence it, at any price. How? (photo and video now added)

[anthony1956]

IT has a Raceco exhaust so repacking it may be step one.

Step two. Use the stack to limit rêve to say 5000

Three, restrict size of exhaust pipe.. how? Have to ask suggested that.

 

And what else?

 

This is to be achieved at any price, though an elegant solution preferred. Are there any tuning mods that help?

 

The test to be passed is:

In 2nd gear, max acceleration over about the distance of a traffic light junction, microphones. Both sides of the road, half way across, must not exceed 73db

 

edit: it now seems this may be not to exceed or look likely to exceed 110db, the max Swiss noise limit for all things. Whereas 73 (maybe 74) db is for cars and I have a permit not to comply with that.

 

 

 

Edited by - anthonym on 23 Jan 2011 17:11:09

[Z3MCJez]

73Db is very quiet. At what distance is that?

 

I'd have thought to get to anywhere near that, and I'm still not sure it would be possible, that you'd be wanting more than one silencer. Either a double-stack, or having a second one under the number plate with a rear exhaust. Exhaust should clearly point backwards and downwards (I.e. Not towards the microphones). I suspect you're going to have to deal with inlet noise with some damping too.

 

Have you got a current reading?

 

Jez

[skydragon]

In 2nd gear, max acceleration over about the distance of a traffic light junction, microphones. Both sides of the road, half way across, must not exceed 73db

---

 

I'd say you stand two chances of achieving that... none and never...

 

73dB is very quiet. As a comparison my 1.6 K series, modded to 182bhp, at 5000rpm is about 94dBu.

 

As well as exhuast you have induction noise.

 

Can you confirm 73dB is the correct figure ?

 

...and some hint as to what the 'test' is for? If it's a police or local authority noise test I'd say your chances of passing it are nil at 73dBu

 

( to be specific, dB is a relative unit rather than a measure of audible noise - you need to stateis that dB SPL, dBu weighted or unweighted?)

[Grubbster]

No chance of 73db IMO, but for exhaust you can fit a 2 silencer system (from powerspeed) which takes it down a lot. Induction can be a real problem - need a decent airbox, with extended intake and then sound deadening foam under bonnet and around the box. But 73 db???

 

Solent Se7ens Web!

[anthony1956]

I reckon the distance to the mics is three metres each side. I have a photo and some video of the test site when I had a peek today

All local sevens have exhausts as described above, boxes under tank etc, suddenly wondering if things are falling into place.

 

RJ are you here?

 

No readings yet.

The preliminary test was with a meter near exhaust at 6500 RPM

WE were all deafened.

 

I find the 73db hard to accept and will be checking it. edit: now seems to be 110db max noise in country as opposed to 73 or 4 for cars.

This is for import to Switzerland.

 

 

Edited by - anthonym on 23 Jan 2011 17:12:29

[Andrew G]

Nothing to do with me, but any chance this could help here???

 

Andrew

 

R300 XX

[k.russell]

rear exhaust and airbox only got my mildly tuned VX down to around 89 db at 5000 rpm. a vertical or horizontal plate in the exhaust tubes for part length of the silencer will make it quieter but not that quiet. can remember someone telling me that just a moving seven without the engine switched on will make more than that in tranmision and tyre noise.

 

Kevin R

 

black(but sometimes orange)-ali HPC

here

[Scalper]

does maximum acceleration mean that the throttles must be fully open, or could there be a misplaced bolt limiting the travel of the accelerator pedal?

I don't recall your car as being particularly loud, but 73db is awfully low even for a tintop

 

Enrico

My Caterham Seven's photo gallery

[Chris Cardwell]

If the exhaust pipe was 20 feet long and vertically orientated would that be acceptable (for the test)?

[Bricol]

20ft long and stretchy? So the open end remains at one side of the site, away from the mics?

 

Sorry - not exactly constructive.

Bri

[CageyH]

You get a slightly higher allowance for a sports car.

You will need an airbox, sound proofing, under tray, throttle pedal stop and a following wind.

 

PM me if it's the same country as I am in.

 

Only dead fish go with the flow....!

[Mr Locust]

A bit of light reading here.

 

References similar test conditions and also references test criteria where tyre noise is recorded at around 75dB(A).

 

By the time you take into account induction, engine, exhaust, cooling fan, drivetrain and tyres; bicycle wheels and pedals might be the only hope you have.

 

Ian

 

Green and Silver Roadsport 😬

My Flickr Photos

Blatchatters Flickr Pool

[anthony1956]

the mics are on both sides of the "road".

 

some amusing ideas :-)

 

here's another piece of the jigsaw, I have a customs document that classifies the car as "household goods". This means that all requirements are cancelled except a cert from the manufacture of 3 things : max speed, weight, tyre type. That's it. Also: both noise and emissions requirements are waived.

 

So I was quietly hopeful.

She passed almost everything, just a couple of minor things to fix, then the noise and emissions issues arose. I remain perplexed how these have become relevant when the docs I have, suggest they are not required to be tested at all.

 

I am trying to find the authority for these regulations so I can read the actual text, but thus far have not found it. edit: it seems there is a general noise limit I have to meet, and the car limit is waived.

 

The "emissions issue" is they want an EU03 number certified and they assured me no car can be legally registered anywhere in Europe without the same.

 

CC Have provided confirmation (in French!) there is no EU number - though I gather EU0 is a code meaning there is no code. Cars from the USA are also imported on occasion so there is a way to go yet, but it is very time consuming and requires endless patience, as well as days of time over and over again. I have been putting this together for over a year now.

 

I have found that sometimes county authorities know county law very well, but are not so familiar with federal law - and here I have county saying they want noise and emissions data whereas I have docs that suggest otherwise. The nuance seems to be that the emissions is a request for "the" EU03 code (for a 2001 car) and the noise test is against the max noise permitted in the country and now, having typed those words what else could it be against.

 

Something just doesn't feel quite right, but then I am a foreigner.

Bit easier to type now, my above posts were from my phone.

 

 

 

 

 

 

 

 

Anthony

 

 

Edited by - anthonym on 23 Jan 2011 17:15:13

[anthony1956]

to skydragon

 

I found this link:

 

Only the type are listed which give results 3 dB or more below 74dB(A): the requirement set by 92/97/EC. Sorted by noise level

 

http://www.xs4all.nl/~rigolett/ENGELS/typetest/carfr.htm

 

which uses figures at the level I have quoted, but decribed as

 

(to Z3MCJez ) Sound level in dB(A) at 7.5 m

 

I am hoping you can convert these in some way to some idea of the db I am accustomed to, which is that 105db measured at 4000 rpm (or maybe 4500 rpm) at my exhaust's exit gets me refused entry to the ring. Or maybe explain the difference between db and db(A) ? Or any other means of giving me some hope.

 

I am thinking that the figure I have quoted may be correct but not correct (or fully accurate) as to units involved.

 

So maybe the 73db I quoted in my op means something very different to waht I was thinking. I sincerely hope.

 

Anthony

 

 

Edited by - anthonym on 19 Jan 2011 23:54:47

[anthony1956]

photo of suspected test site is here

 

and a video, apologies it is sideways

 

here

 

Anthony

 

[tbird]

Anthony Hi, nice to see you back these are some comparisons I found that may help you get some idea of comparative sound levels

 

 

 

Here are interior sound level figures reported by Car & Driver for the Insight, along with some other cars that we selected for comparison purposes.

 

Idle Full-throttle acceleration Cruising at 70mph (117 km/h)

Honda Insight 44 dBA 75 dBA 75 dBA

Honda Civic Si 39 dBA 84 dBA 74 dBA

Honda Odyssey 39 dBA 72 dBA 68 dBA

Honda CRV 44 dBA 81 dBA 73 dBA

Neon LX 46 dBA 81 dBA 73 dBA

Chrysler LHS 40 dBA 72 dBA 68 dBA

Lincoln LS V-6 49 dBA 75 dBA 72 dBA

Audi TT 51 dBA 80 dBA 73 dBA

Porche Boxster S 49 dBA 88 dBA 75 dBA

 

Bearing in mind these are interior sound levels I think you will have fun trying to get any Caterham below 73 even limited to 5k revs, but more importantly every other car in this list would also fail, so maybe you have been given some duff gen.

 

Tim

[tbird]

Hm just noticed you link to similar figures although for your link I can see no reference to the conditions of the test, eg Tick over or 5000 revs or cruising speed etc.

and to answer your other question dB is an absolute measurement of "noise" dBA is a filtered measurement which tries to approximate what the human ear hears IIRC (I realise thats not scientificaly correct but its close enough to get the different meanings over)

 

Tim

 

Edited by - tbird on 20 Jan 2011 00:33:19

 

Edited by - tbird on 20 Jan 2011 00:46:57

[tbird]

Anthony there is a Calculator here which can give you a quick guide to attenuation over distance

 

might help

 

Tim

[Jason Plato]

maybe speak to freddie kumshrick the Swiss Caterham dealer - his cars have the silencers under the tank

 

here is my Duratec R .... C7 TOP

Taffia joint AO with Al

 

[anthony1956]

thanks tim :-)

 

yes, there must be something odd if that list would fail.

 

Dave; yes, last resort because of expected cost, I'll be asking for a quote today. He's a lovely and very helpful chap, but his prices are usually prohibitive; may be the exchange rate or margin matters, don't know.

 

 

 

Anthony

 

 

Edited by - anthonym on 23 Jan 2011 17:16:27

[CageyH]

Or speak to someone like Marcussus sport or SV autos in France about the R500 rear exit system.

 

Only dead fish go with the flow....!

[Rattie]

tbird's link to the dB calc is rather useful.

 

73dB at 7.5m translates to 97dB at 0.5m

 

e.g. Bedford autodrome standard trackday limits are 101dB@0.5m at 2/3 revs in neutral, 87.5dB@?m drive-by. I'd say the drive-by mics are probably in the order of 7.5m from the racing line and KR500s are prone to set them off if their packing is tired. Losing 14.5 dB is going to be very tricky. Probably a combination of airbox and undertank secondary silencer.

 

Good luck Ant

 

Martyn

^_R300GRR

[anthony1956]

some brilliant news just in.. working on it just now (not this noise issue - another one)

 

that rear exit pipe on piston heads kindly linked above, I have contact the man, thing is whether I not all rear exists are the same - for example I recall seing a flat type of box under the tank as well as a rear silencer as well, have request more pics.

 

He says he has an S3 and it just bolts on - will that work with my 4 - 1 exhaust?

 

My deepest fear is getting into a circle of costs and new parts noise text , fit parts, noise test, emissions test, change just fitted parts (e.f. exhaust) all with non trivial costs - the noise test is 300 francs (say £200 quid) -

 

I am not clear whether they will actually test the emissions because of the release owing to the type of import as household goods, but so far that doesn't seem to have achieved anything and they are testing regardless - they do tend to be highly focussed and miss things when outside their usual routine.

 

 

Anthony

 

[anthony1956]

thank Martyn..

 

tim (tbird) that calculator is great in offering a bit of hope.

 

if I enter .5 (6 inches) 100 dbspl and 12 ft distance I get 72.4

 

.6 under the apparent max.

 

of course I am using figures to suit me, but they are remotely related to the sound test at the 'ring

 

I am hoping to get to see a test in action beforehand.

 

 

Anthony

 

 

Edited by - anthonym on 20 Jan 2011 14:31:20

[anthony1956]

ok, depression, that brillant thing didn't happen. may be for the best though. working on an alternative.

 

Anthony