Four-stroke muffler thoughts?

[jellywrestler]

whacking together a muffler, exhaust hole
cross section 645 square/mm about a square inch and what i will have is the tailpipe blanked off at the other end so my question is what's the best set up for holes in that part for muffling as well as free flowing gases.

muffling insert approx 250mm long and wont be removeable to repack etc

how many holes, what size, what format ie holes or slits with indents etc etc
it's a 250cc single

[Motu]

I just covered all bases as far as hole size goes....they work pretty well, it's a gutted system, collector and mufflers and does 94db.

[F5 Dave]

It's four 250 singles? Volume is key, that might be an issue. Reversals are useful to take sound energy out. That might be an exercise in miniaturisation.

[Drew]

I think the bucket guys should be able to give good advice, (not that their bikes are anything close to quiet. Grumph is real clued up on that shit too.

I fluked it on my bucket with muffler that shouldn't quieten down the thing at all. But the pipe is long and muffler underseat.

Depends on what performance you're after, have you considered a chambered muffler? Not that a quick scan of my weak mind can think of an easy way to do that, but it's certainly how bike and car manufacturers get around the issue.

[Drew]

Just realised, so the muffler is gonna be 450mm-500mm long in total? 1" perforated pipe straight through a piece of 3" would keep it pretty quiet wouldn't it?

[jellywrestler]

It's four 250 singles? Volume is key, that might be an issue. Reversals are useful to take sound energy out. That might be an exercise in miniaturisation.

i'll be duplicating it four times so what i essentially have is a 250 single with one square inch of outlet area.
i don't understand your word reversal though Dave

[jellywrestler]

Depends on what performance you're after, have you considered a chambered muffler? Not that a quick scan of my weak mind can think of an easy way to do that, but it's certainly how bike and car manufacturers get around the issue.

it's not about performance as much is trying to quiten an open pipe (warlord as i picked up the steel yesterday) although I dont want to choke it either

Just realised, so the muffler is gonna be 450mm-500mm long in total? 1" perforated pipe straight through a piece of 3" would keep it pretty quiet wouldn't it?

external is 1451mmsq internal 650mm/sq 1/12inch and 1 inch extrnal is the whole length of the pipe but this will only complicate it all to others out ther methinks

[Drew]

it's not about performance as much is trying to quiten an open pipe (warlord as i picked up the steel yesterday) although I dont want to choke it either


external is 1451mmsq internal 650mm/sq 1/12inch and 1 inch extrnal is the whole length of the pipe but this will only complicate it all to others out ther methinks

Oh right. Now I get it.

No balance pipes I take it?

Buggered if I know how you'd go about it in that instance. I imagine that the insert being as long as possible with the inside end blocked, and baffle packing from half way down it would suffice.

Picture should explain what I sorta see working.

[jellywrestler]

Oh right. Now I get it.

No balance pipes I take it?

Buggered if I know how you'd go about it in that instance. I imagine that the insert being as long as possible with the inside end blocked, and baffle packing from half way down it would suffice.

Picture should explain what I sorta see working.

packings not an option really as it's going to be one peice and nee chrome plating...

[Drew]

packings not an option really as it's going to be one peice and nee chrome plating...

That just makes it difficult, can't be impossible though.

Would it matter if the packing got wet while it was in the chroming tank? Long as it's clean it shouldn't contaminate the....broth. (Fucked if I know what the water mix in the tank is called).

At the halfway point of the perf in my picture, is a plate. It could be sealed up with a bit of silicon. Wrap the perf in tape. That'd keep the juices out.

Or seal the ends. Wouldn't they need to do that anyway, or do they let the inside get chromed at the same time?

[jellywrestler]

That just makes it difficult, can't be impossible though.

Would it matter if the packing got wet while it was in the chroming tank? Long as it's clean it shouldn't contaminate the....broth. (Fucked if I know what the water mix in the tank is called).

At the halfway point of the perf in my picture, is a plate. It could be sealed up with a bit of silicon. Wrap the perf in tape. That'd keep the juices out.

Or seal the ends. Wouldn't they need to do that anyway, or do they let the inside get chromed at the same time?

it's more about it getting it in there, chrome by nature wont go up the guts of the pipe, if anything i'd be packing wire netting down there on assembly, at the end of the day whatever i do will be a vast improvement on what's there now...

[Drew]

it's more about it getting it in there,

Assemble my baffle design, with the reducer from the big pipe to the little pipe on it. And the plate for in the middle.

Wrap the packing around it and tape it tight as a mother fucker. Slide that in, and weld it up. Send it for chrome. Boom, shiny quiet pipes

[Grumph]

whacking together a muffler, exhaust hole
cross section 645 square/mm about a square inch and what i will have is the tailpipe blanked off at the other end so my question is what's the best set up for holes in that part for muffling as well as free flowing gases.

muffling insert approx 250mm long and wont be removeable to repack etc

how many holes, what size, what format ie holes or slits with indents etc etc
it's a 250cc single

Put a bulkhead at the front end of your piece of tube. The tube should be the smallest perf available - from memory, I think 3/4in od is available. The bulkhead has the front end of the tube welded into it, at least 3 tags bent back on the OD so it can be slipped into the can.Drill holes in the can to match the tag position, rosett weld, grind clean pre chrome.
The bulkhead can have a ring of holes 5, 6 8 mm whatever fits in which in themselves are a silencing element.
Weld it all up, clean up and chrome. Forget....

[Drew]

Put a bulkhead at the front end of your piece of tube. The tube should be the smallest perf available - from memory, I think 3/4in od is available. The bulkhead has the front end of the tube welded into it, at least 3 tags bent back on the OD so it can be slipped into the can.Drill holes in the can to match the tag position, rosett weld, grind clean pre chrome.
The bulkhead can have a ring of holes 5, 6 8 mm whatever fits in which in themselves are a silencing element.
Weld it all up, clean up and chrome. Forget....

Open "paint", and draw us a picture would ya?

[F5 Dave]

By reversals I mean changes of direction. Just went back to thread for another look at old pipes. Are there going to be any changes? Maybe some wedge type arrangement, or slip in caps?