Author Topic: Decibels  (Read 6112 times)

Vince Caldicott

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Decibels
« on: January 21, 2017, 21:10:47 »
Last year I purchased COX5012  and changed the 428 FE for a 427 side oiler. I did attend the ACOC sprint in November but sadly was unable to participate due to the 105db limit imposed. The car I own has side pipes. My question is this, is there any way to reduce the noise emitted from my side pipes to a level which would comply? Somebody did suggest to me that I should do away with the side pipes and replace with a conventional exhaust with silencer but it is not an option that I like. Is there any exhaust specialist  out there that has solution?

minimans

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« Reply #1 on: January 21, 2017, 21:35:07 »
There's plenty of them here in the USA. Just google "Cobra side pipe silencer"
   http://www.carchemistry.com/cc-inserts-silencer-sound-comparison-cobra-side-pipe-application/
   You could also try angling the outlet down toward the ground?

Vince Caldicott

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« Reply #2 on: January 22, 2017, 12:58:14 »
Thanks for your input, has anyone tried these and what was the end result?

TLegate

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« Reply #3 on: January 22, 2017, 13:00:54 »
As I was riding shotgun in said vehicle on the journey to & from the circuit, I can testify that the 427 side-oiler is LOUD. (I look forward to my hearing returning to normal...) I hope your neighbours have finally forgiven you re the car alarms :)
   
   I think nothing short of a mattress up each pipe will solve the problem. Otherwise, buy up all the houses that back onto the circuit.

Robin A Woolmer

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« Reply #4 on: January 22, 2017, 14:58:20 »
Not Legal on the Road either!!

Vince Caldicott

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« Reply #5 on: January 22, 2017, 18:44:27 »
No one seems to know what the legal limit is, from what I read, you are not allowed to put a louder exhaust on the car than the original manufacturer had fitted. Therefore, I guess, there must be a measurement detail somewhere that gives the exhaust decibel level of a 427 Cobra. That would be the legal limit today.

nikbj68

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« Reply #6 on: January 23, 2017, 01:12:17 »
From the MOT  Instruction Manual, Section 7.1:
   "During all parts of the emissions test for the vehicle, assess subjectively the effectiveness of the silencer in reducing exhaust noise.
   
   Reason for Failure [of test]
   
   A silencer in such condition, or of such a type, that the noise emitted from the vehicle is clearly unreasonably above the level expected from a similar vehicle with a standard silencer in average condition."
   
   So. Technically, if there is NO silencer fitted, it can't be failed... Only a silencer that isn't fit for purpose is a fail!

Robin A Woolmer

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« Reply #7 on: January 23, 2017, 09:24:16 »
Noise Regulations started in 1929,cars made in 1978 should meet 82dbA & those after 1996 should meet 74dbA as I understand it , so when was the car made?
   
   Robin

nikbj68

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« Reply #8 on: January 23, 2017, 16:32:02 »
OH dear.

Rob.Hendriks

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« Reply #9 on: January 23, 2017, 18:39:28 »
Personal option would be to have two sets of pipes, one track compliant and the other the current set, for road use. Changing them is about 5-6 bolts and about 30-40mins work per side and would be part of your normal track day preparation

AC Ace Bristol

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« Reply #10 on: January 23, 2017, 18:44:45 »
.
   
   BUGGER
   
   74 Decibels
   
   That means majority of Ace & Aceca Bristol's  and all Cobras would never pass the noise test..[:0]
   
   Someones reading the Old Testiment,  I think we have moved onto the New.
   
   Keith'

Vince Caldicott

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« Reply #11 on: January 23, 2017, 20:04:55 »
Interestingly, when I went for my mot, there was no sound test, no emissions test or brake test and the car  passed with no issues.

Vince Caldicott

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« Reply #12 on: January 23, 2017, 20:06:23 »
Rob,I like your suggestion. Do you know anybody who can do this work for me?

nikbj68

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« Reply #13 on: January 24, 2017, 03:44:27 »
Another option would be to have 'cutouts' fitted so you could bypass the silencers from the comfort of the drivers' seat, which is something I'm considering.
   Not exactly local to you( but closer than Rob's locale in New Zealand!), from the 289Register:
   
quote:
originally posted by "PeterA", on the 289Register Forum:.
   ..Having recently gone through a similar exercise for my FIA Cobra I can offer two suggestions, both very capable but with very different business models. This area is rich in motor racing fabrication shops but prices can vary dramatically.
   
   BTB exhausts Ltd
   Units 3 - 5 The Beaver Centre, Woodford Halse, Daventry, NN11 3DP
   Tel 01327 261797
   sales@btbexhausts.co.uk.
   A larger business with several employees and several fabrication bays. Very experienced and complete with all the usual 3D CAD facilities and test shops. Very motor sport orientated, good stocks, wide experience, a very professional outfit and friendly to deal with. When I attended to discuss my need there was a Daytona in one of the bays being fitted so they have details already. They estimated a stainless system for the Cobra at £1300+ vat using underfloor silencer boxes, these would provide good performance and meet Goodwood noise limits.
   
   Exhaust by Design
   Unit 2 Westwell Farm
   Barton Road
   Tingewick
   Bucks MK18 4BD
   01280 0847756
   exhaustbydesign@yahoo.co.uk
   A one man band business but well equipped with the necessary tube manipulation and swaging equipment. Graham Frankland is very experienced and very capable but can be difficult to contact as he is literally alone and answers phones etc whem not fabricating. He has limited stocks and tends to buy in what is needed for a project. That said I found him easy to talk to, he listens, adds his experience arrives at a design to suit your expectations and then builds it. I opted for Graham who built a stainless steel repackable side pipe system and installed it for £630 all in. The system is everything I hoped for, very neat, unobtrusive and sounds perfect.
   
   Good luck, all the best
   Peter

Rob.Hendriks

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« Reply #14 on: January 24, 2017, 04:49:52 »
Think Nik has answered the question of who can carry out the work
   
   The permanent option (should you so choose) could easily be installed using a bypass and control valve, similar to that below, with the muffled pipe running inside and parallel to your existing side pipe, then rejoining so it comes into the side of the turn-out. The major disadvantage I see with this system is that you're permanently lugging about an extra 30kgs of plumbing under the car for 360 days of the year and when you're going racing, kgs = seconds, so you wouldn't even want it there !!
   
   The removable system gives the added advantage of while the car is up (prior to race day), the camber/castor can be set for the track, tyres changed, brakes checked, components inspected and greased, etc., all the things that you do not want to be doing on race day or have a scrutineer pick up