Husqvarna 44 Muffler mod?

[Gareth83]

I have a Husqvarna 44

What can I do to the muffler on this one?

By my 'brief' calculations, the exhaust port at piston is ~230mm^2 (hard to calculate accurately)

So the ideal exit area would be between 184mm^2 and 196mm^2 (80 and 85%)

the existing exhaust port is 113mm^2 so I'd need to drill an additional hole that would yield an area of ~70-80mm^2

Do I just therefore drill an additional hole of between 9 and 10mm in diameter?? If so where?

Or must I port out the existing exhaust to 15mm diameter?

There isn't a spark guard at present as my guess is due to the baffled design this takes care of its self internally

Finally, is it essential to have a tube fitted or would a hole just suffice?

 

[Gareth83]

anyone care to help out?

 

[scottr]

Search Forum

Hey Gareth, member TopJimmy posted a picture of his 44 muffler mod. Search '44 muffler mod' and author TopJimmy.

 

[Gareth83]

Thanks to this thread here:
http://www.arboristsite.com/showthread.php?t=81297&highlight=44muffler+mod

I am a bit more enlightened.

Although my muffler has an exit pipe as opposed to a louvre vent. Can anyone suggest where I can just drill into or cut on the below?

 

[scottr]

What do you mean by 'cut on the below' ?

 

[Gareth83]

What do you mean by 'cut on the below' ?

on the pics below where I said it, not sure whether I can do the same or whether it is a different design muffler to the ones previously modded

(thanks for hooking me up with the links by the way)

 

[scottr]

Does the outlet pipe on your muffler connect to a baffle plate or a diffuser box ?

 

[Gareth83]

not sure what you're asking? The muffler is exactly as is in the pictures I posted. Nothing else attaches to it

 

[scottr]

Look in the outlet pipe of your muffler, then look in the exhaust inlet of your muffler and tell us in your own words what you see.

 

[Gareth83]

Look in the outlet pipe of your muffler, then look in the exhaust inlet of your muffler and tell us in your own words what you see.

Looking through the exhaust inlet there appears to be a 'tube' the same shape as the port itself and runs straight through and is blocked off at the end. On the side of this 'tube' are several small holes

Looking through the outlet port is pretty tricky but it seems to run straight down at the same angle as it sticks out, aside from that I cannot really see much to be honest

 

[scottr]

Would you say that the total area of the holes in the side of the exhaust inlet tube( diffuser) is greater than the area of the outlet pipe?

 

[Gareth83]

Would you say that the total area of the holes in the side of the exhaust inlet tube( diffuser) is greater than the area of the outlet pipe?

No, they are small holes and not that many to be honest

Sounds like it needs ripping out then?

 

[scottr]

That inlet tube or diffuser probably helps support the front of the muffler to prevent it from crushing when the mounting bolts are tightened. Measure the holes and do some math. You can probably add a hole above the existing outlet pipe to get closer to the 80% -85% exhaust area at the cylinder wall.

 

[Gareth83]

That inlet tube or diffuser probably helps support the front of the muffler to prevent it from crushing when the mounting bolts are tightened. Measure the holes and do some math. You can probably add a hole above the existing outlet pipe to get closer to the 80% -85% exhaust area at the cylinder wall.

why not just put a hole right in the front that is directly opposite the inlet port? That way it would be like a straight through sytem?

or when you say above the existing outlet would I need to go through the 'tube' that seems to run deep into the muffler at an angle?

 

[scottr]

Some guys drill a hole in the front of the muffler with a straight shot to the exhaust port some know better. That muffler would look good as a over/ under double barrel. It would look like a hack with a hole in the front. You gonna do the math or you gonna be a hack?

 

[Gareth83]

Okay, so can I just drill a hole with a 9mm diameter on the flat section above the existing outlet?

Must I drill through the tube that runs to/from the existing outlet?

Is it essential to weld a pipe on it or would just drilling suffice?

Just to double check would a 9mm hole be about right based on my math in my first post?

 

[scottr]

If your math supports the fact that the diffuser has more outlet than the current outlet pipe then drill in the same axis that the outlet pipe is running. I don't have the engine in front of me to calculate the exhaust at the cylinder wall. You have to make the effort.

 

[Gareth83]

Sorry for the numerous questions, but I'm not sure what you mean when you speak of a diffuser?

If you are referring to the perforations within the 'tube' direct from the inlet side of the muffler being larger than the existing exit pipe then as stated this is not true.

So I'm going to drill vertically straight down and into the existing exit pipe? Or vertically stright down into the inlet tube of the muffler? So rather than having a front exit pipe which you said is the hack way I would just have a top exit.

Is it then essential to have a pipe welded on or would a hole suffice?

 

[scottr]

The tube that runs from the back of the muffler to the front of the muffler that has hole in the side of it is a diffuser. Don't drill straight down. You want to drill as if you were drilling another hole the same as the hole that the outlet pipe is in but above it so it will have a over/under shotgun look. So the hole will be on the rounded corner. It is not absolutely necessary to have a pipe welded in the hole but it would be more durable if had a pipe.

 

[Gareth83]

I get you now! So basically run another hole parallel to the existing one, but seen as I wont fit a pipe (just yet anyway) just drill

But you mention that the diffuser should have a larger area than the existing outlet? This doesn't appear to be so

Many thanks

I'll post up a vid next weekend of before and after.

Just to confirm, it is only the high screw I will need to adjust as a result, and to start with a quarter turn anticlockwise and go from there?