Hole size

V

Vince

Hero member
Continuing from another thread, just for my inquiring mind I would be interested in any variation in the exit hole diameter of mufflers in use. My stainless mufflers bought in Oz from Eades measure at 30mm dia ID. The seamed mufflers it came with when I bought the bike measure at 25mm ID. I am thinking proper Jota mufflers are bigger than 30mm? Even 3 into 1s size would be good to know. Add if your bike runs the 4 small extra holes as well.
 
Stainless (and most steel I'd say) is limited in sizes available to imperial I think. My custom SFQ sys uses imperial tubes, cut longditudinally to create taper.

SFC factory 2/1 exit from reverse cone is 50mm, mega widest end is 80mm - now that is why they're LOUD!! My baffles are open right through, and about 1m long, 44mm in 54mm out. Sorry - no triple or Jota info in my shed!!
 
Europe does use metric tube sizes.  Caused a major headache for me a while back when I constructed a vacuum system for a project at work from components sourced from Germany rather than the more typical US-of-apple-pie-A.  While the flanges still complied with the Conflat geometry (ie taking the standard sized copper gasket and having the imperial bolt circle diameter), the typical US version would be something like 68.9mm OD mounted to 1.5"x16g (38.1 x 1.6mm) or sometimes 1-5/8"x16g (41.3x1.6mm) tubing.  The German flanges were 70.0mm OD and mounted to 40 x 1.5 stainless tubing, which I'd never seen before.  So yeah, metric tubing is a thing.  You sometimes see exhaust tubing in metric if it's been made in Europe.  I've never been able to source other than imperial sized tubing in Austraila, but it must be common enough in places like Germany and Italy.

Reminds me that various steels and aluminium round and flat bar stock which always used to be imperial in the good old U-S-of-Australia, is now sometimes metric sized.  Perhaps this is more the case with aluminium, can't remember, but I've come across metric sized stock more in recent years.  Probably because it's all made in Taiwan, Korea or wherever these days.


 
Pretty sure the SFC headers at least are metric. If you get someone here in Oz to make a copy of your headers, you'll either get slightly under or lightly over the original tube dia. Frustrating.

I've also noticed that alu comes in metrics now, Steve.
 
breganzane said:
Europe does use metric tube sizes.  Caused a major headache for me a while back when I constructed a vacuum system for a project at work from components sourced from Germany rather than the more typical US-of-apple-pie-A.  While the flanges still complied with the Conflat geometry (ie taking the standard sized copper gasket and having the imperial bolt circle diameter), the typical US version would be something like 68.9mm OD mounted to 1.5"x16g (38.1 x 1.6mm) or sometimes 1-5/8"x16g (41.3x1.6mm) tubing.  The German flanges were 70.0mm OD and mounted to 40 x 1.5 stainless tubing, which I'd never seen before.  So yeah, metric tubing is a thing.  You sometimes see exhaust tubing in metric if it's been made in Europe.  I've never been able to source other than imperial sized tubing in Austraila, but it must be common enough in places like Germany and Italy.

Reminds me that various steels and aluminium round and flat bar stock which always used to be imperial in the good old U-S-of-Australia, is now sometimes metric sized.  Perhaps this is more the case with aluminium, can't remember, but I've come across metric sized stock more in recent years.  Probably because it's all made in Taiwan, Korea or wherever these days.
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You're not wrong...Most steel tube made on rolling machinery is imperial. Until the machinery wears out and is replaced with metric equipment that's going to stay the majority. Extruded or DOM tube is now frequently metric as it's comparitively easy to change a die. Hydraulic tube for instance is now almost all metric sizes.
Sheet and plate has gone over almost exclusively to metric. Plate rolls can be adjusted to whatever thickness is wanted. But there's little demand now for imperial thicknesses. Tried to buy 1/4inch thick MS plate lately ?  5mm 6mm 8mm are the common thicknesses now.
Here in NZ I haven't seen imperial aluminium plate for years. Sheet, yes, still available in imperial gauges as is stainless.
 
192 views from registered members and who knows how many visitors and nobody has a genuine Jota or SFC  muffler they can measure.
 
Vince said:
192 views from registered members and who knows how many visitors and nobody has a genuine Jota or SFC  muffler they can measure.
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I still have my original pipes ('81 Jota) lying around in the shed, so went and measured.
Exit holes measure 31.5mm give or take with a bit of carbon.
Edit:- Should have said, bike is Australian delivered with a Low Volume approval plate affixed by Stanco as per Maurice's comments.
 
Thanks for taking the time to do it, but I do have a memory that Jota muffler holes were considerably bigger, maybe 38mm?
 
Vince said:
Thanks for taking the time to do it, but I do have a memory that Jota muffler holes were considerably bigger, maybe 38mm?
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Perhaps so for the earlier ones?
These are just a steel shell, nothing in the them and sounded great.
My current system has a larger outlet (larger diam headers etc) and is not as loud!
 
Vince said:
Thanks for taking the time to do it, but I do have a memory that Jota muffler holes were considerably bigger, maybe 38mm?
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I measured 31.5 on my original Jota pipes too vince, just cause you asked twice :-*
 
Agree, it's slowly heading in the wrong direction. New years Eve and things like the Cricket won't help at all.
 
TC said:
I measured 31.5 on my original Jota pipes too vince, just cause you asked twice :-*
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Well, I'm glad someone with a bit more cred than me replied, I better stick to the Joke of the week thread.
Speaking of which, posted a new one which many will find corny, but I had a good laugh ??? :D
 
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