Measurements for side-bleed expansion chamber?

[John Orchard]

Hey Guy's,

I'm interested in experimenting with a side-bleed outlet on one of my 2-strokes.  Does anyone know any measurements when converting from tail-bleed?

eg; placement of outlet, diameter of outlet, length of stinger?

Thanks  :-)

[pancho]

  Side bleed???

[skypig]

I'm no expert, but I understand nothing changes.
That is, you could cut the current stinger off and attach it anywhere on the chamber without affecting the "formula". Another option is insert some of the tuned length stinger inside the chamber.

[Lozza]

As above nothing changes except noise is less.

[80-85 husky]

just continue the tail pipe to and end point and put the muffler pipe into the fattest part of the chamber. principle is simple....send a complete sound wave back to the exhaust port while drawing the "noise " off where the sound wave is the widest

[bigk]

I just put a Husky one which had been converted to side bleed, back to tail bleed only because it looked pox. It was quieter though.
K

[80-85 husky]

they only look good on a go kart as it looks like a lifting handle....unless you can hide the extra long tail pipe behind the main chamber, it will look messy but if looks are irrelevant and noise / performance the key driver, its a good mod. I don't know who here remembers Terry schulze, used to write for adb in the late 80's. he had a dx 200 with a bleed pipe on it and it went well. he was a "don't care what it looks like" guy and never even washed his bike, rekons it damaged seals and reduced grease effectiveness etc. but he had lots of neat tricks and gadgets.

[John Orchard]

Personally I think it looks cool because it is different, in these modern times of needing quiet bikes, I think they all should be side-bleed then.  But then, how many 2-stroke road or trail bikes are left.

[Tahitian_Red]

Hey John,

Ch Industries sold an "Afterburner" pipe, in the 70's.  I always thought these were cool, but wondered how well they worked?

I can not seem to attach a pic today. ?  Ok, here it is. 

[80-85 husky]

another spot to get a good burn with that one!

[John Orchard]

Hey John,

Ch Industries sold an "Afterburner" pipe, in the 70's.  I always thought these were cool, but wondered how well they worked?

I can not seem to attach a pic today. ?  Ok, here it is. 

That's what I remember the 'afterburner' ...... funny that it takes me 40 years to actually take it serious and want to do something with it ........ well you can't rush these things  ;-)

[vmxrider]

I think Miller Mano designed and built those 70's pipes, "Everything's Sano at Miller Mano"

[skypig]

I can't see the Web adress for CH Performance Products 
"Graphics by WEST" - LOL

I love these old ads, I can remember drooling over many of them as a kid.
Thanks for posting.

[James P]

I would like to resurrect this topic in the hope of getting some advice. For the purpose of the exercise, I would like to differentiate between two different arrangements which effectively achieve the same objective (i.e. noise reduction):

1. The "side bleed" arrangement, where the stinger emerges at an approximate right angle from the parallel-wall belly section of the expansion chamber

2. The "internal stinger" arrangement where the expansion chamber resembles the traditional type, but the stinger starts in the parallel-wall belly section and continues through the reverse cone before emerging in the usual position at the end


I have had some experience with Arrangement No.1, mainly because it suited that particular bike to have the silencer mounted below the reverse cone portion of the expansion chamber - I had to keep the chamber as short as reasonably possible. This arrangement was a success in that it kept noise at a reasonable level. The pipe was built from scratch (using a pair of pressings for the diffuser, belly and reverse cone sections), so I can't make a direct comparison with an otherwise identical pipe having a traditional "rear exit" stinger (i.e. no before & after results). However, I am satisfied with performance, so have left it there.

Moving on to my present project; I want to quieten the exhaust on my PE250B (see here for some background info: http://forum.ozvmx.com/index.php?topic=42480.0). Using Arrangement No.1 (the "side bleed" set-up) would be difficult, as there isn't much space to accommodate the existing FMF silencer (which I want to keep) in any position other than at the end of the stinger in the traditional position. The existing stinger is reasonably long (about 380mm from end of reverse cone to start of silencer), although it could be shortened slightly (perhaps 30mm) without the silencer fouling the left-hand side cover.

Gordon Jennings recommended that for the "internal stinger" arrangement (No.2 listed above), the stinger entry should be located "an inch or so" before the start of the reverse cone for optimum results (i.e. noise reduction with no performance loss). This would add about 250mm to the length of the existing stinger.

Since I have some other specialist jobs waiting to be done (including magnesium welding and removing dents from existing chambers), I approached a well-known service provider (and member of this forum) who carries out such work and also builds expansion chambers. He is willing to either modify my existing chamber with an internal stinger or to build a new chamber from scratch incorporating the same feature. I initially intended to have the existing chamber modified, but due to certain difficulties I am now leaning towards having an entirely new pipe made. However, he has never made an "internal stinger" chamber before and would like me to specify some particular requirements for the proposed pipe.

With that in mind, there are a few questions I have for those who can offer the benefit of their experience:

a) Using the dimensions of the existing chamber as an example; If the existing 25mm ID stinger is already 380mm long (with allowance to shorten by 20-30mm), would an increase in diameter be required (to prevent undue heat accumulation in the cylinder) if another 250mm length is added?

b) For structural integrity over a long period of time, should the internal end of the stinger be welded to the wall of the parallel-wall belly section and/or the reverse cone section? If so, is this accomplished simply by drilling a hole (or holes) and welding through it/them as part of the assembly process?

c) Although Gordon Jennings didn't mention it, is it advisable to alter any other aspect of the design of the chamber to allow for the internal stinger?


As an alternative, there may be enough space on the bike to allow for a "side bleed" stinger, turning a right angle, then meeting up with the "existing" stinger in the normal position (meaning that the reverse cone would have a closed end), but this would add even more length, which may be undesirable from a heat retention point of view.

I'd be glad of any advice or useful opinions .


Thanks & regards,
James

 

[80-85 husky]

i dont know if you have access to the adb magazines in which you can see the terry schultz job. his stinger exited the right angle bend of the chamber underneath where it turned over the motor (kdx 200) and then the stinger / tailpipe ran just under the chamber before popping up and straightening to arrive at the muffler at the right spot. i think he had a piece of perforated steel as a guard over the lot.

cant place in my mind the PE pipe (i had an x from new) but i think it would be possible. ( note schultz's dx had no side covers or very small ones from memory)