Dolmar PS5100 Muffler Mods Underway

[davefr]

I have a new Dolmar PS5100 and am starting a muffler modification. I could have simply drilled a hole in the front of the stock muffler but decided to uncrimp it and take a look inside.

Image 1 is the stock muffler removed from the saw and uncrimped. This thing is pretty stout so uncrimping it was difficult. The screwdriver trick won't work. I made a starting slit with a Dremel at the bottom edge and used a set of dikes to gradually pull up the crimp and peel it open.

Image 2 is the two halves seperated. Left side is cylinder side and right side is front piece. Those two pipes are simply recessed channels for the attachment screws. (not some fancy tuned exhaust port!!)

Image 3 is a closer view of the cylinder side. There's a swiss cheese rectangular channel that doesn't look too bad but then there's a 90 degree deflector on the end of it. My plan is to keep the channel for noise reduction but cut off the deflector since it seems like it would impede the exhaust flow. However removing this entire unit would be very easy since it's just tack welded on.

Image 4 is the top front half of the muffler. The outlet hole is .375" in diameter. I plan to enlarge it to about .675" but retain the round shape.

Image 6 is the top outlet deflector. It's measures about 1.25 X .25. I will probably try and bend it upwards so it's convex and cut out some of the middle plate that sandwitches the spark arrestor screen.

The exhaust port of the saw is approx. .5 sq in at the muffler interface but I'd estimate about .4 sq in at the cylinder wall.

With the exit hole enlarged to .675" diameter that's an area of about .35 sq in. (up from .11 sq in). That'll make the ratio of muffler exit port to exhaust port about 87% (up from about 27.5%) .

If anyone has any feedback or suggestions on this plan I'd sure appreciate it.

 

[stump doctor]

Wow sounds like you have given this some thought. The pics are great and really give a good idea of what you want to do. I miss the days of the two piece muffler design. Guess we have the EPA to thanks for these new crimp type mufflers. I did not see a screen in your pics. Do you not plan on using one?

 

[davefr]

Wow sounds like you have given this some thought. The pics are great and really give a good idea of what you want to do. I miss the days of the two piece muffler design. Guess we have the EPA to thanks for these new crimp type mufflers. I did not see a screen in your pics. Do you not plan on using one?

Yea, I have the screen and plan on re-attaching it when all is said and done.

 

[davefr]

P.S. Does anyone know the purpose of the 90 degree deflector at the end of the baffle chamber in image #3.

My first guess was it's there to deflect exhaust flow upward towards the exit hole but wouldn't expanding hot gasses tend to rise anyway?

Another guess was it's there to help bust up sound waves?

Or is it there to provide some backpressure?

The last possibility I thought about was it's there as an internal heat shield to prevent a hot spot on the front case of the muffler?

All in all the baffle doesn't seem overly restrictive. I can't decide whether to leave it stock, remove it totally, remove the deflector, or just widen the holes and deflector slot.

 

[ehp]

Dave I have played with a few 5100's now, I leave the deflector stock cause I seen no gain by removing it , putting holes in it nothing . I will take a picture of the muffler mod on RBtree's 5100. this work real well

 

[Toneman]

Does the inside of the PS 6400 and PS 7900 look similar to the PS 5100 shown?

 

[rahtreelimbs]

Does the inside of the PS 6400 and PS 7900 look similar to the PS 5100 shown?

Pretty Much!!!

 

[davefr]

Here are images of the modified muffler:

Image 1: I decided not to remove the baffle however I did grind off about 3/16 " off the tip of the deflector and enlarged the baffles holes two drill sizes larger. On the mufflers inside exit hole, I enlarged it to about 3/4". (was about 3/8")

Image 2: I was able to increase the deflector outlet just by bending it so the top is crowned. It also clears the chain brake handle. It's area is larger then the exhaust port.

I'm really happy with the end result. This Dolmar is a wonderful little saw. Now I just need to replace the crappy chain that came with the saw.

P.S. I had to remove one of the wings from the high speed idle limiter cap to richen the mixture about 1/8" turn past the limit. That gives me a slight blubber at full throttle.

 

[Toneman]

Nice work Dave!
I am impressed with your re crimping, it looks good.

 

[artwood]

I enlarged the original outlet whole on mine last week to 1/2"
Then added an additional 1/2" hole on the side. I really noticed a difference in power. I'd like to add a small pipe to direct the exhaust away. Any suggestions as to what material is good for this? I was going to some 3/4" electrical conduit. Too thin?

 

[SawTroll]

Artwood,
I noticed from your picture that you seem to have a narrow kerf Husky bar and 95VP chain on your 5100.
Have you compared it to other setups on that saw?

 

[artwood]

Sawtroll, I took the stock bar from my 346xp ( I've been running 3/8 LP 14" on it) and Carlton .325 N1 says on the DL. Haven't used the stock Dolmar chain yet, grinding off the bumper links & planning to use it on my 357xp with 18" bar. The way the 5100 is running though, It might give the 357 a run for the money. There might be a video in the making!

 

[GlennG]

Eric

I just ground all the bumps off my stock 5100 chain, just like whats depicted in your last photo. I have no timed measurments but I noticed the chips changed to "curly fries" and the saw pulled itself into the cut with more force. Seems to cut like a real chain. I`ll leave it on for now...its good enough, not great, but good enough to not throw in the trash. The saw is great, might sell my 026 and pick up another 5100.

Glenn

 

[PA Dan]

@davefr any chance you still have pics of the mods you did to the 5100 muffler? Great thread but the pics would explain a lot more. If you have them could you repost them?

Thanks,
Dan

 

[davefr]

That's an old thread but here are the images that I still have.