Absolute Pace

Go Back   Club Cobra > Club Forums > Australian Cobra Club

Welcome to Club Cobra!  The World's largest non biased Shelby Cobra related site!

  •  » Representation from nearly all Cobra/Daytona/GT40 manufacturers
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and nearly 1 million posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

MMG Superformance
Nevada Classics
Main Menu
Nevada Classics
Nevada Classics
MMG Superformance
Advertise at CC
Banner Ad Rates
MMG Superformance
Keith Craft Racing
Keith Craft Racing
March 2024
S M T W T F S
          1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31            
  #1 (permalink)  
Old 10-21-2007, 02:22 AM
stephen low's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Aug 2001
Location: Melbourne, Australia, Vic
Cobra Make, Engine: G-Force Mk I, 5L Windsor, TKO 600, enhanced Jag / Koni suspension & LSD Diff.
Posts: 2,298
Not Ranked     
Cool how low??....small do you have to go?

Have taken several noise measurements of the exhaust in advance of meeting the engineer.

Car generally has a two inch system with AU cats and 14 sports mufflers only, and is hitting around 93.5 dBA at rpms required. Tried first inserting steel restrictors at the flanges at the back of the cats with a 40mm hole and then again with a 28mm hole.

Second effort has gotten noise to 92.5 dBA.

What do I have to do to get under 90 dB?

Am thinking I return to exhaust shop for a pair of flanged hot dogs plus a pair of straight flanged pipes, the hot dogs for engineering and the straights for after.

Is there likely to be a cheaper way for me to meet the limit?

Cheers
__________________
slowy
Reply With Quote
  #2 (permalink)  
Old 10-21-2007, 04:42 AM
BMK's Avatar
BMK BMK is offline
CC Member
Visit my Photo Gallery

 
Join Date: Jun 2003
Location: Australia, Zzz
Cobra Make, Engine: Shelby alum 468 block
Posts: 14,974
Not Ranked     
Default

stephen low

slowy,

Send Aussie Mike a PM. He has experimented a lot.
__________________
Bernie Knight
KMS 427 #662 Shelby 468 CSX 1026
Reply With Quote
  #3 (permalink)  
Old 10-22-2007, 01:00 AM
CC Member
Visit my Photo Gallery

 
Join Date: Oct 2007
Location: Darwin, NT
Cobra Make, Engine: Classic Revival Kobra,LS7 427
Posts: 380
Not Ranked     
Default

try a resonater at the rear. if all else fails use a factory set up to get rego
Reply With Quote
  #4 (permalink)  
Old 10-22-2007, 02:48 AM
Jac Mac's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Feb 2006
Location: Gore. New Zealand., SI
Cobra Make, Engine: DIY Coupe, F/T ,MkIV.
Posts: 808
Not Ranked     
Smile

On TVR ( SBF ) that is raced only- non roadgoing- we have been checked @ 87db with one large 'Flowmaster' type low profile ,dual 3" inlets- one 3.5" outlet into 'ovalised' 4" tailpipe 30" long. Test taken trackside at full throttle in third gear @ around 6500rpm.

Jac Mac
Reply With Quote
  #5 (permalink)  
Old 10-22-2007, 03:52 AM
Aussie Mike's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Jan 2001
Location: Sunbury, VIC
Cobra Make, Engine: Rat Rod Racer, LS1 & T56
Posts: 5,391
Not Ranked     
Default

This test is at about 1 meter from the exhaust tip at 4K RPM.

Cheers
__________________
Mike Murphy
Melbourne Australia

Reply With Quote
  #6 (permalink)  
Old 10-24-2007, 02:51 AM
letsboogie351's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Aug 2007
Location: Melbourne, vic
Cobra Make, Engine: Kenmer with Ford Quad Cam Boss 260
Posts: 979
Not Ranked     
Default

Slowy
how well do you know your exhaust man? I know of a couple of fellows who received a canary for noise. Their local exhaust man loaned them a couple of mufflers to pass the test. Then refitted the originals for them for a reasonable fee. I am told that this has been done a number of times. Alas the shop is not here in Melbourrne.
Food for thought?

Doug
Reply With Quote
  #7 (permalink)  
Old 10-24-2007, 03:29 AM
stephen low's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Aug 2001
Location: Melbourne, Australia, Vic
Cobra Make, Engine: G-Force Mk I, 5L Windsor, TKO 600, enhanced Jag / Koni suspension & LSD Diff.
Posts: 2,298
Not Ranked     
Default

Doug

Did this for a road bike once, only a ZX6, and the smart exhausty said bring it back with the real exhaust pipe on it for me to check!??!!

The noise maker was in fast, just, legal.

But you did really need ear plugs. It was the best quasi horn I've ever had, a 10,000rpm twist of the wrist, and every driver looked in their rv mirror. Made it hard to miss me in traffic too for those dopy tin lidders out there.

However, am now planning to present on Friday and see what happens. Plan is to revisit exhaust shop, if needed, and get an additional pair of flanged mufflers into the car, to pass, but also have made up flanged straight sections to go in post engineering. At 93 dB I'm very happy with how is sounds and that ain't deafening for normal use.

Cheers
__________________
slowy
Reply With Quote
  #8 (permalink)  
Old 10-26-2007, 04:22 AM
CC Member
Visit my Photo Gallery

 
Join Date: Jun 2006
Location: Newcastle, Warners Bay, NSW
Cobra Make, Engine: RMC . 393 Dart alloy block Stroked 351 alloy heads ..all the goodies plus a pre oiler. al
Posts: 1,495
Not Ranked     
Default

Slowy, I had some "fun" getting my 351 C passed. It started out as a stationary test on a "temporary" system to pass rego...just kept adding mufflers. In the end it passed the stationary test. Then I was required to pass a "drive by" test. It kept failing because it "whistled" too much. It was quiet to the point that standard cars were noiser. The muffler man was stumped but I tried a larger diameter pipe and the whistle dropped in decibels.
After creative mathematics the official report met and exceeded the required decibel level. I had a good argument point after the noise test man admitted that he used to pass harley choppers for rego. Ha ha ha..good luck
Reply With Quote
  #9 (permalink)  
Old 10-26-2007, 03:28 PM
stephen low's Avatar
CC Member
Visit my Photo Gallery

 
Join Date: Aug 2001
Location: Melbourne, Australia, Vic
Cobra Make, Engine: G-Force Mk I, 5L Windsor, TKO 600, enhanced Jag / Koni suspension & LSD Diff.
Posts: 2,298
Not Ranked     
Default

I was a bit lucky at the test as I've measured mine at 93 at the right test revs 3950rpm but my man came out initially saying ok now you rev to 4500rpm,

I challenged his mathematics, ie 3/4 of max power rpm and he re-thought through and said your right rev to about 3,500 - 3600 and bingo - 89.3 dB.

Even he acknowledged these cars need a bit of burble.

So no exhaust work needed for the moment.

Cheers
__________________
slowy
Reply With Quote
Reply


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -7. The time now is 11:08 AM.


Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
The representations expressed are the representations and opinions of the clubcobra.com forum members and do not necessarily reflect the opinions and viewpoints of the site owners, moderators, Shelby American, any other replica manufacturer, Ford Motor Company. This website has been planned and developed by clubcobra.com and its forum members and should not be construed as being endorsed by Ford Motor Company, or Shelby American or any other manufacturer unless expressly noted by that entity. "Cobra" and the Cobra logo are registered trademarks for Ford Motor Co., Inc. clubcobra.com forum members agree not to post any copyrighted material unless the copyrighted material is owned by you. Although we do not and cannot review the messages posted and are not responsible for the content of any of these messages, we reserve the right to delete any message for any reason whatsoever. You remain solely responsible for the content of your messages, and you agree to indemnify and hold us harmless with respect to any claim based upon transmission of your message(s). Thank you for visiting clubcobra.com. For full policy documentation refer to the following link: CC Policy