silencer inner tube diameter affect on noise
Discussion
What effect would the diameter of the inner perforated tube wrapped in (second part of the question..) glass fibre or steel wool, have on the exhaust? Specifically, volume.
I can come up with two theories;
A - a smaller tube has less surface area for muffling to work on, gases will flow faster and carry more energy And therefore noise.
B - a larger tube is less of a restriction, gas flows through at a lower pressure, less pulses are absorbed by the muffling, therefore more noise.
C - I'm a spanner.
Clearly only two of these can be correct. The pipe is 500mm long, and 2.25 OR 2.5 inches wide.
I can come up with two theories;
A - a smaller tube has less surface area for muffling to work on, gases will flow faster and carry more energy And therefore noise.
B - a larger tube is less of a restriction, gas flows through at a lower pressure, less pulses are absorbed by the muffling, therefore more noise.
C - I'm a spanner.
Clearly only two of these can be correct. The pipe is 500mm long, and 2.25 OR 2.5 inches wide.
Some years ago I had a Rover SD1 Vitesse. I had an exhaust system made and boy was it noisy, especially as it was in stainless which seems to have a sound of its own! One of my customers who supplied OE ex systems to Rover told me the OE way of getting rid of lots of noise was to make the exit pipe smaller than the inlet pipe to the last silencer/box in the system.
Peter
Peter
PeterBurgess said:
Some years ago I had a Rover SD1 Vitesse. I had an exhaust system made and boy was it noisy, especially as it was in stainless which seems to have a sound of its own!
Apparently it's due to the SS being of a thinner gauge, Ferrous is thicker so it takes longer to rust through.Answer of, it's not quite how things appear.
You'll get more absorption from a bigger or longer cannister around the pipe than worrying about 2.0 vs 2.25" inner (there'll be a very marginal diff between the two). It's an acoustic impedance- matching problem; if you want quiet, fit the biggest volume - largest diameter - of canister you can manage, around the pipe diameter you want for other reasons. And site it as close to the end of the exhaust run as you can.
You'll get more absorption from a bigger or longer cannister around the pipe than worrying about 2.0 vs 2.25" inner (there'll be a very marginal diff between the two). It's an acoustic impedance- matching problem; if you want quiet, fit the biggest volume - largest diameter - of canister you can manage, around the pipe diameter you want for other reasons. And site it as close to the end of the exhaust run as you can.
PeterBurgess said:
Interesting observation Mr ShiningWit, that would explain why my mates Sherpa V8 exhaust was whisper quiet and was oem stainless...must have been thicker gauge.
Peter
It's very good of you to say so Mr Burgess Sir, I never knew such an Automobile existed until I enlisted the services of Google, Crivens! What an unwieldy beast it must have been.Peter
I do hope you have a good weekend Sir, will you be sharing afternoon tea and cake with comedy genius Michael of One eye? I do know he anticipates your little soirées with much optimism.
The Sherpa v8 was supersmooth and very torquey. John, the guy who owned it, had walked away from high stress professional job and gone for a life of driving through Europe dropping off and picking up parcels here and there. He fitted a pair of our Econotune heads and got more bhp when required and more economy if driven in a reasonable manner.
One eyed Mick is fighting fit and seems happy enough. He popped in the other day whilst passing the area to see how we are getting on with buying our Superflow 901 engine dyno. The 901 has had very little use, we understand it was only used to develop a 600 bhp V12 race engine and a little other light work. The answer was nice and steady and maybe up and running in three or four months. My friends Martin Faulks of PRV and Fiat fame, Dave Gollan who co-authors our books and is currently well into tuning Harley's and I have clubbed together to invest in the 901 dyno, we are looking forwards to doing some engine dynoing in the near future. Steady work as we have to put mezzanine floors in our second unit before we can get it all into the dyno cell we purpose built in 2001! Leaves us with the brand new 250 bhp Clayton electronic engine dyno still unused and gathering dust since I bought it in 2003
Peter
One eyed Mick is fighting fit and seems happy enough. He popped in the other day whilst passing the area to see how we are getting on with buying our Superflow 901 engine dyno. The 901 has had very little use, we understand it was only used to develop a 600 bhp V12 race engine and a little other light work. The answer was nice and steady and maybe up and running in three or four months. My friends Martin Faulks of PRV and Fiat fame, Dave Gollan who co-authors our books and is currently well into tuning Harley's and I have clubbed together to invest in the 901 dyno, we are looking forwards to doing some engine dynoing in the near future. Steady work as we have to put mezzanine floors in our second unit before we can get it all into the dyno cell we purpose built in 2001! Leaves us with the brand new 250 bhp Clayton electronic engine dyno still unused and gathering dust since I bought it in 2003
Peter
Hi Peter , really enjoyed the visit a few days ago any more to add about the new / different dyno would be interested to see the new install another visit later in the year ? .A bit off thread but never mind the works leyland rally team buit a few v8 sherpas as fast service barges when they were running the 6r4 ,managed to have a peek at one a a local service halt on theRAC many years ago the guy driving it said it was good for 125 with atrailer and 6r4 hooked on the back but the brakes were marginal ?. I have had a complete s/s exhaust fitted on the new toy [ mazda mx5 ] head face to tail pipe bigger bore than std lovely cruising but a real bark at 6500 + , keep well and don't behave it's no fun mick
Hi Mick
A quick update. The dyno and ancillaries have been uplifted and safe and sound with us. A little more history and specs for you. The dyno was bought new by Lister Storm racing to develop the Storm V12 race engine and has had very little use since. Whoever bought it picked the top of the range SF901 pro which, as well as suited to basic work, is designed for endurance testing of engines. The buyer must have gone through the accessories catalogue and bought one of everything The dyno ancillaries have also been added to by Lister Storm. the tricky bit will be getting it all installed and running, which is a jigsaw but it was a complete test cell with cooling towers, stainless steel exhausts, extraction fans etc etc.
I attach a pic of console with dyno in background...LeMans stickers on window to cell!
Peter
A quick update. The dyno and ancillaries have been uplifted and safe and sound with us. A little more history and specs for you. The dyno was bought new by Lister Storm racing to develop the Storm V12 race engine and has had very little use since. Whoever bought it picked the top of the range SF901 pro which, as well as suited to basic work, is designed for endurance testing of engines. The buyer must have gone through the accessories catalogue and bought one of everything
The dyno ancillaries have also been added to by Lister Storm. the tricky bit will be getting it all installed and running, which is a jigsaw but it was a complete test cell with cooling towers, stainless steel exhausts, extraction fans etc etc.I attach a pic of console with dyno in background...LeMans stickers on window to cell!
Peter
Hi Peter that looks a serious piece of kit ,the Lemans sticker on the door is 2 years before my first visit [aseries ofaround 12 trips ] I well remember a Storm in Newcastle colours banging round on 1 bank for the last hour or so to qualify as finisher don't recall what year though [ its my age you know ] mick remember don't behave it's no fun
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