Exhaust pipes silencers; is a protruding baffle tube needed?

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sportston
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Exhaust pipes silencers; is a protruding baffle tube needed?

Post by sportston »

On my old set of racing pipes the baffles protrude into the expansion chambers.
Is this necessary?
Would it upset the performance if I cut the old silencer/baffle section off and welded on flanges for bolt on silencers that don't have a baffle pipe intruding into the expansion chamber?
This is on my 1975 GT380
Zunspec4
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by Zunspec4 »

Hello sportston,

From a performance point of view the baffles protruding into the divergent cone are likely to degrade the effect of the pipes. I would imagine it was done for noise reduction purposes only. Replacing what you have with bolt on silencers is unlikely to affect their performance, in fact it might slightly improve them. Ensure that the diameter of the central part of the silencer is the same as you currently have and is more or less the same length (include the final end pipe in that length).

Cheers Geoff
sportston
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by sportston »

Thanks for the advice Geoff. That is very useful to know. I am curious; Why must they be the same length?
Zunspec4
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by Zunspec4 »

Hi sportston,

The various lengths & diameters of a set of expansion chambers are still something of a black art, despite the sophisticated (and expensive) software/simulation programs that are available. This includes the diameter and length of the final tailpipe (or stinger). A top notch computer program will give you a lovely set of shapes to manufacture, BUT, then have to be adapted to the actual shape of your engine/chassis. By the time you fitted it to miss the chain/wheel/stands/ground clearance etc you have compromised your perfect solution. If the original fabricator decided on a final length/Dia of the tail pipe (and got it right) it would be best to try and match his solution if you can. I can see no reason why you cannot replace the existing tail pipe, eliminate the protrusion into main body of the pipe, fit a bolt-on type end can etc.

The set of pipes I have on my T500 race engine were made by Tony Green Racing. Tony has been making/fitting 2-st pipes for decades. He does not use any software programs but has several massive binders full of designs/data of what works for particular engines. He them applies his experience to adapt a particular set of dimensions to your bike. You have to leave the bike with him while does this.

Here's a photo of the pipes he made for my T500 engine.

Image

Cheers Geoff (hope I didn't add too much to the confusion :lol: )
sportston
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by sportston »

ah right ok. I never knew that. Very interesting. Thank you
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tz375
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by tz375 »

sportston wrote:On my old set of racing pipes the baffles protrude into the expansion chambers.
Is this necessary?
Would it upset the performance if I cut the old silencer/baffle section off and welded on flanges for bolt on silencers that don't have a baffle pipe intruding into the expansion chamber?
This is on my 1975 GT380
If the baffle is a simple perforated tube, it will not hurt performance. It may be an attempt to run an internal stinger to reduce noise and to use the same tube as teh baffle core to save on fabrication. Do you have any pictures?

Internal baffles reduce noise considerably.
sportston
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by sportston »

will see if I can dig it out tomorrow and take a few pics.
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Re: Exhaust pipes silencers; is a protruding baffle tube nee

Post by Craig380 »

There's an old Gordon Jennings article on chamber design which covers this. Basically, having the 'stinger' tailpipe protruding into the actual chamber itself is simply a way of shortening the overall length of the pipe (think of the Allspeed shorty chamber design).

The Jennings article says that, providing the stinger is inserted into the chamber all the way so that the 'mouth' of the stinger is at least level with the start of the final, convergent cone section of the chamber, it will not affect power at all, and will be a lot quieter.

Here's the article: http://www.bridgestonemotorcycle.com/do ... eally6.pdf" onclick="window.open(this.href);return false;
1976 GT380 - wounded by me, and sold on
2006 SV650S - killed by a patch of diesel and a kerb in Feb 2019
2017 SV650 AL7 - naked and unashamed
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