Royal Enfield user
take the energy out , look at motogp exhaust , yamaha, a couple of inches at the end , lets the volume flow through , ( little bit of turbulance ) BUT the engergy of the wave is ( a little ) absorbedOriginally Posted by koba
Stephen
ps from top of head just before bed ,,, so someone else can cross the t's
"Look, Madame, where we live, look how we live ... look at the life we have...The Republic has forgotten us."
Ta
You mean, someone else can make a point. Have you heard a motoGP bike in the flesh? The muffler on them does little or nothing to silence them!
From 200 meters you still need ear protection.
Low personal B.M.E.P.
MotoGP and F1 cars, as I understand it have no noise restrictions at all...
Brian is onto it - you've got to take the energy out of the wave before it hits the atmosphere.
The problem here in NZ is unusual in a world wide sense in that we don't have a defined sound test.
The Euro/Brit test where the piston speed is the defining point for measurement is actually easier to meet as it is quite possible to tune a silencer for that specific frequency...and bugger any other frequency, I've passed the test...
Unfortunately, most of the pubished info - at least recent stuff - is about meeting specific frequency related regs.
Basically, you can't go wrong with plenty of silencer volume.
Long Haired Yobbo
From my muddlings and observations of other peoples, I'd come to suspect that was the case. It's great to hear it from someone like yourself.
Heinz Varieties
Armature speller
Meh. The same could be said for a stinger on a Kwakka classic mx 2 stroke...
The cops could use that for crowd control.
Ta
Ok, well that is all cometsly useless because Glen intends to build a light, functioning race bike. Heaps of volume flies in the face of that, so we're back to square one, and looking for efficient.
No8 Wire Extraordinaire
Well the baffling material is light & ally tube is too.
Don't you look at my accountant.
He's the only one I've got.
Low personal B.M.E.P.
To turn one of your arguments back on you...if it doesn't meet the noise regs it can't be used anyway...
When anyone builds a bike now, meeting the noise regs is just one of the factors which have to be balanced.
The muffler I recommended and i think Sketchy has, I'd estimate is less than 1KG...
In this particular case, it's not like silencing an unsupercharged single - you couldn't care less about exhaust tuning, megaphone or length.
All you are worried about is getting the gas out with as little restriction as possible so as to keep the exhaust valve temp down.
For this application a large volume, straight through type will work well.
OK, so who's next?
? A supercharged engine responds to exhaust tuning just like a na engine does. Well...maybe not exactly the same....
Drew for Prime Minister!
www.oldskoolperformance.com
www.prospeedmc.com for parts ex U.S.A ( He's a Kiwi! )
Ta
Are you talking about those shite Chinese ones? Because everyone I've heard talk about them, says they do little to quiet down a bike.
Can a pipe be made of perf pipe, then second skinned the whole length with sloid pipe and a quantity of soft stuff between?
That way it only needs to be inch and a half pipe like a tiny motor needs (I don't care if it's supercharged, the gas output won't match that of a 250cc MX motor). This way length and tuning is still possible.
No8 Wire Extraordinaire
That sounds like my std Tiger pipe, except there are baffles leading back & forth inbetween, but there is a large volume with not that much inside it.
Don't you look at my accountant.
He's the only one I've got.
111000101000100010011110
I think you can get perf pipe where the holes are more directional, like a cheese grater, this may make for better air flow. Add a layer of steel wool right on the perf, then muffler pack for the rest, should contain the fury. Flatten the outside a bit, so it is slightly eliptical, makes for better sound reduction.
"A shark on whiskey is mighty risky, but a shark on beer is a beer engineer" - Tad Ghostal
Royal Enfield user
I think I have had a little experience with moto gp.... only a touch mind
Stephen
"Look, Madame, where we live, look how we live ... look at the life we have...The Republic has forgotten us."
Low personal B.M.E.P.
Well the one I've been using is very acceptable build quality and works very well indeed. IMO they're not suitable for NA singles though which is probably where people are having problems
The gas output won't match a 250 MX motor - close though - 100cc at 1 bar boost equals 200cc unblown so not a lot more boost needed to exceed the 250 output.
Exhaust tuning, again, is not needed or necessary or desirable on a blown motor...aside from the difficulty of geting a reverse wave at atmospheric pressure to pass into a combustion chamber which is above atmospheric pressure most of the time - certainly when any reverse wave arrives...the last thing you need is charge contamination with hot gasses at a critical point in the cycle. Carburation is easier to set too as there is no reverse flow whatsoever.
Ta
Where I'm really struggling though, is why a supercharged engine is not making as much noise as an N.A motor. I know why a turbo motor is quieter, at least I thought I did, and it had nothing to do with the forced induction.
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