Muffler mod adds how much?

[livemusic]

Stihl ms290... specs say 3.8HP. If I were to do a muffler mod and the requisite carb adjustment, what could I expect? How much more horsepower or other value could it increase? Do you find it appreciable, but also do you have any idea of a specific number of some sort? Or WAG, lol.

My used saw came with new 20" bar, appropriate sprocket and a full chisel chain. Still considering 'waking it up' as I have read, lol.

 

[Ironworker]

I had a 390 I did a mm on and was pleased with the results

 

[Macman125]

I have several saws. All of them have benefited from opening the mufflers up and retuning. Do it, you will be happy you did.

 

[Canadian farm boy]

Almost every saw will benefit from opening up the muffler. The ms290 and ms390 both respond very well to a muffler mod. Exact gains will vary depending on the muffler mod. I would think a 5%-10% gain can be had on a ms290 or ms390. Make sure you retune the carb( both the low and high sides) You'll also likely see better throttle response, higher WOT rpms and it will also run a little cooler. Win win if you ask me

 

[Chainsaw Jim]

Here are the results of a muffler mod I did on my 290. Actually these are the first couple cuts after complete rebuild and new top end, so it isn't as strong as it should be.

 

[MnSam]

Some saws have extremely restrictive mufflers. You would definitely notice a change on your 290. I don't know about adding value and probably wouldn't do it if you are going to sell it. The majority of people in my area wouldn't understand the modification and would probably look at it as a negative thing to do.

 

[Chainsaw Jim]

I believe the muffler mod is necessary for the 290 type models. I find many of these models have been claimed by overheating and carbon problems. Increasing the flow through the muffler prevents this problem....which isn't a problem chainsaw were originally built with. The epa dicks restrict muffler flow in order to high five each other, while you get stuck using a saw that will no longer have a reputation for longevity.

I view chainsaw emission just like I view a fart. Whether it's a big boomer or a tiny little squeaker....IT STILL F'IN STINKS!!!

 

[longbowch]

Don't forget the cool factor from the sound!


Sent from my iPhone using Tapatalk

 

[Jeff Lary]

I have done some of my mufflers as well but just be honest with yourself you will not gain a 1/2 hp or something. I think it may help a little but you also have to ask yourself how many men do you know that don't love the loud muffler? be it on a 425 cat Charger Hemi or a saw sound can add to the belief that " Now I got a bad ass saw !"

 

[Homelite410]

The 390 290 saws are like a different saw after muffler and a Lil timing bump. Also, more flow=less retained heat. Please correct me if I am wrong here.

 

[CR888]

l always wonder how an operater can validate a 5% power increase in their hands. I am not saying a MM won't increase power on saws but us humans are pretty poor at quantifying the result. The louder noise makes the perception of more power, l know this from bikes when guys would put a new pipe on that is louder and truly believe they were riding faster with more power, sometimes they were sometimes not. The stopwatch usually does not lie and tell porkies.

 

[Chainsaw Jim]

We're talking way more than 5% FFS!!! 20% increase in performance isn't unheard of with a few models. And I'd say the 290 is minimum 15% increase from the right muffler mod.
You can get 5% from a better spark plug!

 

[Terry Syd]

That series of saws has an ignition timing tolerance of between 23.5 degrees and 28.5 degrees because of manufacturing tolerances. That is a 5 degree spread!

Some guys have saws that are at the low end of that range and have added as much as 8 degrees more advance to get the saw working the way they wanted. You may want to try tweaking your timing and see what you can get.

 

[066blaster]

When I first got my 290 I was disappointed. The chain stopped easily and it just wasn't that powerfull . I read about the muff mod on here and decided to give it a try. It's not that difficult to do..
I'd say 15 to 25% gain if I had to put a number on it. Well worth it. You will be glad you did it. Mine was probably just a mild mod but It made a big difference. Just drill all the holes bigger and grind the deflecter open. Take the limiter caps off and richen it up a little. Make sure you Blow the muffler out with your air compressor after drilling. I got rid of the screen too. Some people get all technical about it,but your just making the exit holes in the muffler bigger so the exhaust can get out easier. I've seen some people put holes in the front of the deflecter, I wouldn't do that, you will get exhaust bouncing of logs and blowing in your face and it can start a fire.
Ive had a few logs catch fire with a smaller saw with a bad muffler , it does happen

 

[fearofpavement]

How much a saw benefits from a muffler mod depends on how restrictive the muffler is. Some older saws are already very "open" and will have little or no power increase from additional flow. Others are choked down a lot and can really be improved with some simple ventilation.
The 1127 series saws are quite restricted and probably benefit from a muffler mod as much or more than any saw out there. It's not just "more noise" but an actual increase in power that will be immediately apparent by comparison.
I mod a lot of these mufflers. Some for my own saws and others to go on eBay.

NOTE: It is very important to remove all the shavings and metal pieces after doing muffler work.

 

[Deleted member 83629]

90% mind
10% performance

 

[Macman125]

As stated previously, it depends a lot on how restrictive the muffler already is from the git go. I know it will on a 290, I opened one up on my friend's 290 and re tuned it. It made a considerable difference in the cut. Not just "more noise".

 

[CR888]

I don't think any of the portwork l have had done has increased hp by 25%.......lifting the powerband can improve cutting speed by 25% but nett HP....I dunno. I think cutting speed and HP is easily confused. Big numbers get thrown around AS with little quantative proof. Perception IS reality I suppose. Guy's work pretty hard in the racing world to get 1-5% gains in areas and pay good money for it. I am not saying for one second a muffler modd will not improve performance and allow a saw to breathe and run cooler but 25% gains from stabbing your muffler can with a scrench certainly is cheap HP.

 

[Terry Syd]

Different saws, different times as the industry moved through the EPA hoops. A number of saws over the years came out with very restrictive mufflers, but then they also had 25 degrees of blowdown to compensate. If you did a muffler mod, suddenly you had a ported saw that would turn a higher RPM. The muffler technology has gotten better and the blowdown figures have decreased, so those newer saws don't see the big gains from a muffler mod that some of the earlier saws did.

 

[drf255]

It all works together in concert. The porting of the saw has a relation to how much back pressure it will run ultimately at.

The 029/039 mufflers are a joke though. Take off the front cover and have a gander. Same muff on a 55 and 65cc saw.

It's trying to exhale through a coffee stirrer, not even a straw.

I'd say an easy 15% gain on this saw.

If we ever get our chainsaw Dyno off the ground, I will be able to answer this question factually.