Tuned Pipe For Husqvana 346xp HELP!

[MarshallArb]

Trying to work out the dimensions of a two stage tuned expansion pipe for my husqvana 346xp

none of the two stroke pipe design software ive looked at is suitable for smaller engines.

not a clue where to start from to do it manualy my maths and physics is no where near good enough.

any pointers gratefully recieved

anyone allready made one that works well that would be willing to share how they worked out for a correct back preasure optimum for power of saw.

 

[chainsman1]

begin with a simple formula to find your reflection point


Lt is the distance from the edge of the piston to a point half way down the baffle cone


Lt = Eo x Vs / N

Lt in inches (tuned length)
Eo is exhaust open duration in degrees
Vs = speed of sound in fps (1700 fps as an average)
N = engine speed in RPM

i hope it will give you a point to start

 

[MarshallArb]

done that cheeers that formula led on from what id got

also managed to find some more info from a few other threads and the net

it all made sense with some explanation

have a rudimentary design of a 2 stage diffuser drawn it out to scale

wow its bigger than i thaught

 

[MarshallArb]

going to make a card model for the templates for the cone parts.

anyone know any one in the North yorks/North east that could weld up or bend pipe obviously pay them.

my mig welding aint up to gas proof standard

dont think local agricultural fabricators i know would be able to do it. they are great for mending forwarders and tractors but not delicate stuff.

 

[timberwolf]

Look at the two stroke wizzard software, for a low cost download it is a lot better than any of the "free" stuff on the web. It will print templates out and save a whole pile of work, paying for it's self easy on the first pipe.

My advice for a first pipe keep it simple, there is little to be gained with a multistage diffuser. If you have a gas mig, set it up with .023 wire and 22 ga autobody sheet steel and no reason you should not be able to stick one together. Does not need to be gas proof. Build in a slippy overlap section in the middle to fine tune it.

 

[troutfisher]

What the 'ell are you doing with a chainsaw in Brooklyn??:yourock: You're gonna get yourself in trouble !!

I would start with a lefty pipe at first, lots easier to build a header for a leftly pipe vs a righty.

 

[MarshallArb]

Look at the two stroke wizzard software, for a low cost download it is a lot better than any of the "free" stuff on the web. It will print templates out and save a whole pile of work, paying for it's self easy on the first pipe.

My advice for a first pipe keep it simple, there is little to be gained with a multistage diffuser. If you have a gas mig, set it up with .023 wire and 22 ga autobody sheet steel and no reason you should not be able to stick one together. Does not need to be gas proof. Build in a slippy overlap section in the middle to fine tune it.

cheers timberwolf

came accross that software might get it if i build another pipe. cos as of now ive done all the hard math and constructed one out of card therefore having done all the hard cone nets.

great idea about sliding section! will definatly do that.

have got a gas mig will give it a go have a feelin that my welding might let me down. more used to welding car sils etc.

 

[trappermike]

I have a design for smaller cc saws that is really hot! Some experimenting was involved,this design has won many races in Canada/U.S.A. Send me your exhaust port timing,desired power peak,and type of power band and I'll send you a set of templates which is the cheapest and best way to go.
Your fuel delivery system and carb are important as this pipes craves massive quantities of fuel.