Part Six: The Exhaust System

[Johnmn]

Will they be at your gtg?

 

[tree monkey]

Will they be at your gtg?

if you bring them

 

[srcarr52]

Since I made that post, I have had to tighten and keep an eye on screws. I've since gone so welding the deflectors

That is why I weld in press-fit nuts. You get to weld them from the outside and they stay put.

 

[MustangMike]

I have a 660 BB that that is obnoxiously loud due to a very large opening in the side of the muffler, but it seems to need it to run right. Large openings produce loud noise.

 

[Lightning Performance]

Was using self tap torx from the outside to hold a SS deflector. May switch to welded Reds.
The tall one please

 

[MG porting]

Nice!

 

[~WBF]

Since I made that post, I have had to tighten and keep an eye on screws. I've since gone so welding the deflectors

OK. I was meaning to ask you that about 10 months ago on a different site.. Since WCB upped the standards over 20 yrs ago then all 3 series Husqavna have been done with 266 deflectors. They look the most natural with a triple port and work good. Some industries like G&O, you are not allowed and go through equipment audits so you have to fake them out. My builder used these little black screws with a nut head and painted the muffler. Supper clean work but they fell out right away. Unfortunately when it happens on the brake side then you melt the brake off pretty fast or you are blowing it in up in your face. Sinking brass and redrilling a tight hole worked good but wasn't 100℅ for pro use. I believe walker's welds three sides and peens down the back so they/you can change the screen.
I have just tried a few ported 357 with the 266 deflector behind the baffle. It seemed like it was plenty for that saw? Just a quick trial though. 288 ears are good. Pretty Barky. I have used them with triples on 372 and 2186 and 390. QUOTE

 

[~WBF]

That is why I weld in press-fit nuts. You get to weld them from the outside and they stay put.

View attachment 186928

I was assuming it must be getting done something to that effect as it simply doesn't work otherwise. Apparently you are the undisputed real deal with this method. *Tips hat* impressive! Good Job!

I think you just separated the Pro's from 'Joe's.

 

[Basher]

Weld is the word if the saws actually get run for work.

 

[Lightning Performance]

Never lost a self tapping screw. Heat and counter sink the two holes, cool it and drill a 1/16 pilot hole in each location for the screw. Then cut out the exhaust hole. So easy to add a screen under the deflector or not

 

[Jedd]

Fell down the rabbit hole thinking to improve my bodged mufflers and read 113 pages of the show us your muffler mods thread before I came back here to necro this thread with some queries. This is the link as it covers a lot that could be put in this thread: https://opeforum.com/threads/show-off-your-muffler-mods.6898/

When doing a pipe outlet does having the pipe extend into the can rather than cutting and mounting it flush like a deflector make a difference?

80% of exhaust - 125% of exhaust port at the exit of the cylinder for exit seemed to be mentioned as a safe bet - would that be as measured around the circumference on the skirt of piston / cylinder wall or flat as seen peeking down the port?

When doing deflectors does placement - ie top / side / more towards front or rear make a difference?

Is there a tangible difference between pipe and deflector apart from looks or possibly pipes having better directional control of exhaust flow?

 

[Dieselshawn]

I use a dyno to find the right exhaust outlet size for a saw.

So far I’ve only worked on the 661 exhaust at the moment.

Looking for the least amount of noise for most power.

I’m in the process of doing 660’s but waiting on parts for the stock one I have to get it running.

I recently gutted the 660 can thinking they are restrictive like the 661 but several guys here said that’s not the best thing to do to a stock saw. Good thing I have another can with a baffle still intact to try drilling the holes in instead to see what works best first.

I have a Mastermind 660 with a gutted can and large side opening. Works really well and not obnoxiously loud.

On Thursday, my buddy is bringing his Mastermind 660 and stock 661 over for dyno runs and to find improvements.

Right now the most powerful saw that ran my dyno is a 661 with a banana stuffed cylinder and triple port muffler with no baffle.

My 660 doesn’t make the torque this beast makes.

 

[Ketchup]

Fell down the rabbit hole thinking to improve my bodged mufflers and read 113 pages of the show us your muffler mods thread before I came back here to necro this thread with some queries. This is the link as it covers a lot that could be put in this thread: https://opeforum.com/threads/show-off-your-muffler-mods.6898/

When doing a pipe outlet does having the pipe extend into the can rather than cutting and mounting it flush like a deflector make a difference?

80% of exhaust - 125% of exhaust port at the exit of the cylinder for exit seemed to be mentioned as a safe bet - would that be as measured around the circumference on the skirt of piston / cylinder wall or flat as seen peeking down the port?

When doing deflectors does placement - ie top / side / more towards front or rear make a difference?

Is there a tangible difference between pipe and deflector apart from looks or possibly pipes having better directional control of exhaust flow?

Extending the pipe 1/2” or a little more seems to create better flow and is a little quieter.

I think technically it’s a percentage of port area, so the curve of the cylinder wall would be accounted for but I doubt you’ll go horribly wrong with an approximation. Remember that lots of pistons don’t travel all the way to the exhaust port floor (so the effective port area is smaller). I have seen very few saws that benefit from 125% muffler exit but plenty that perform just fine (and are loud).

Front Muffler exits are louder and transfer more heat to the wood (greater fire risk). Side exits flow less at the same size, but are quieter.

I feel pipes and front exits move exhaust more quickly and help keep heat down. Opinions may vary.

 

[Moparmyway]

Front Muffler exits are louder and transfer more heat to the wood (greater fire risk). Side exits flow less at the same size, but are quieter.

I feel pipes and front exits move exhaust more quickly and help keep heat down. Opinions may vary.

GREAT post !!!
I'm not sure that I agree with the flow portion of your first sentence. (What goezinta, goesoutta). Side exits CAN move exhaust quickly, but is too quickly a good thing ?

It helps keep heat out, except if we're getting the heat out effectively by other means. .........................
MY observations:
1. front exits are monumentally louder, and provide little to no benefit, unless all out racing is involved
2. Pipes need to be better defined ........ tuned pipe, megaphone, or piped exit ???
3. Size of the pipe, or the restriction it imposes greatly affects its performance
4. Where does the pipe direct the exhaust ? Towards the "wall" of the wood in front of it ? or towards the atmosphere, away from the air intake and/or the operator ?

 

[MustangMike]

Just my opinion...

An engine is not a constant flow, but a series of pulses. A properly tuned pipe can demonstrate the dramatic effect the exhaust can have.

You can not duplicate a tuned pipe with just a muffler, but IMO, venting on the sides instead of in the front, helps to establish a "pulse" instead of just a release. If you are lucky enough to get the pulse in sync with your engine, you will be rewarded.

A little back pressure followed by a release can provide more benefit than just a continuous release, which is why most saws will lose some power if the muffler is simply removed. How the cylinder is ported, and the timing advance, will have a big influence on what works.

My thought process is similar to why they put collectors on headers on cars. If they are tuned properly, they also make a big difference, providing both more power and efficiency.

 

[Dieselshawn]

MustangMike; makes sense why I see some power loss with a open port through the front cover of a 661 vs a closed cover with more ports around the sides.

Same saw with no can installed just cackles blue flames but makes the same power as the open port through the cover.

Put the can back on, cover on, the power band rises a bit.

 

[stihlman441]

interesting

 

[Dieselshawn]

The mufflers I’ve been experimenting with on the dyno....

Left row down is dual port 066/660 mufflers

Middle row down is the tree slapped 661 can and cover. The black looking open can and the abused cover is the best for power at the moment.

Below is the stock 661 can with baffle.

Right row is the logger hacked baffle and enormous hole in cover with deflector.

 

[Dieselshawn]

This is my Ms260 with the 044/046 carb.

I shipped my cylinder and muffler to randy years ago for some work over.

I like the side port with deflector that he put on. It really blends in and looks factory to me.

The one hole cover was not the original to this 260 but I didn’t know that at the time when I purchased a replacement. It took me only one start up after putting the muffler cover on that the saw was so quiet and felt turdy.

I looked online and sure enough, this 260 originally had the 4 hole cover.

After some molesting with a die grinder, I made it a slot instead. Much better.



I’ve used this saw with 32:1 oil and the Mastermind worked over exhaust port is still purty

 

[Ketchup]

I don’t totally understand back pressure in a can muffler. It doesn’t seem like a can is able to back-stuff the cylinder like a pipe.

My crude thinking is that a saw that blasts all the exhaust out should run the same, no matter how much raw charge makes it out after the exhaust. Have you guys tried tuning a saw with no can? I’m tempted to think it will make the same power if properly tuned.

I guess too little back pressure could inhibit scavenging. Especially if the transfers weren’t aimed well.

@Dieselshawn , have you put the 661 on the dyno after a carb reset with no muffler?