Echo CS-590 Timberwolf Muffler Mod - Flow bench Measurements

[Team FAST]

I recently acquired an Echo CS-590 Timberwolf Chainsaw. As promised, I intend to measure the muffler on my flowbench and then measure the incremental improvements as a result of the common "muffler mod" alterations.


Here's my saw. I purchased it last week at Home Depot. It was a "return" basically brand new. I purchased it for $275 Piston skirt looks factory fresh. Probably hasn't had a tank thru it yet.

 

[Team FAST]

I had to machine an adaptor plate to install the muffler onto my Superflow SF-110 flowbench,

The plate allows me to install the muffler directly onto the flowbench.

 

[Team FAST]

Here's the muffler installed on the flow bench.

I'll post flow results later on today. I burnt a lot of midnight oil getting everything installed and tested.

Test plan so far is:

1. Stock
2. No screen
3. No screen, no deflector
4. Modified Deflector and screen
5. Modified deflector, no screen

This will show the incremental changes and effects on exhaust flow from altering the muffler.

I may also drill holes, but that depends on the results....

 

[7sleeper]

VERY NICE!!! Exited about the results.

7

 

[GrassGuerilla]

 

[James Miller]

Will be watching this one as I just pulled the 90 out of the deflector on mine the other week but left screen in.

 

[Team FAST]

Here are the initial muffler flow results.

I went as far as modifying the deflector. I haven't drilled any internal holes into the muffler yet.

For those that care, here's the atmospheric data during the test session (which was about one hour).



Here's the Flow results. I am reporting Raw (uncorrected) airflow numbers. Since the test conditions are more or less constant over the hour of testing, these flow values can be directly compared with each other.

 

[GrassGuerilla]

Interesting... The screen makes less difference than I would have guessed.

 

[Team FAST]

Here's how I modified my deflector. I machined the inside baffle away on the mill. I removed as much material as I could. I also completely deburred the part. In original factory condition, there are quite a few burrs and raised edges everywhere on that part. I don't like burrs and edges, so I deburred it (the machinist in me).








And here it is installed on the muffler:

 

[cedarshark]

I did the exact same thing w/ a foredom grinder and although a retune made the saw much better, I had no idea how much better the muffler flowed. Thanks for the flowtest and the effort involved.

 

[hi-fi]

Very interesting. Thanks for the effort.

Subscribed.

 

[Team FAST]

Thanks.

There is another piece to this puzzle which I wanted to consider when making changes to the exhaust: The carb and air filter.

I already had a carb adaptor plate machined, so I went ahead and flowed the carb as well. Two stroke engine tuning is really best accomplished with a "total system" approach. I wanted to see if the intake limits the available airflow. Common sense thinking says that if the muffler flows more than the intake, there probably isn't any benefit or further gains to be had. We all understand that a certain amount of exhaust backpressure is required to prevent short circuiting of the incoming fresh fuel mixture. Exactly how much is highly dependent on several factors.

The throttle butterfly was held in the wide open (WOT) position for these measurements. I did test the air filter with and without lithium grease applied around the seal surface to the orange air filter base (the area suspected of leakage of dust by members on this forum). Not surprising to me, it did not reveal any changes to the airflow numbers. However it still may be a sealing issue for dust. The air filter restriction will only grow (get worse) as the saw is operated and debris is trapped in the filter media. Carb tuning will definitely be affected by the presence of the air filter

I didn't install the outer cover, due to clearance issues to the bench.



With air filter installed:




Here's the flow data for the carb and air filter assembly:

 

[009L]

TF,

This is a very freaking cool thread!!! I can't believe one of you chainsaw hicabilly's actually rolls with a Flowbench...Lmao! Have you done this with other mufflers/carb's? (390xp, 261, 550, etc.) It really takes all the guess work out of the equation.

Thanks,

Pat

 

[Big Block]

this looks to be an awesome thread !

 

[Chris-PA]

Interesting tests! A couple of random thoughts:

19.5 CFM is 552,179 cc/min. A 60cc engine at 10,000rpm is only 60,000 cc/min even at 100% volumetric efficiency, which is 10X less.

On the other hand the intake and exhaust ports are only open for about 1/3 of a cycle.

On the other, other hand the flow is not constant, and the peaks may suffer more significantly from restriction.

 

[GrassGuerilla]

Thanks.

There is another piece to this puzzle which I wanted to consider when making changes to the exhaust: The carb and air filter.

I already had a carb adaptor plate machined, so I went ahead and flowed the carb as well. Two stroke engine tuning is really best accomplished with a "total system" approach. I wanted to see if the intake limits the available airflow. Common sense thinking says that if the muffler flows more than the intake, there probably isn't any benefit or further gains to be had. We all understand that a certain amount of exhaust backpressure is required to prevent short circuiting of the incoming fresh fuel mixture. Exactly how much is highly dependent on several factors.

The throttle butterfly was held in the wide open (WOT) position for these measurements. I did test the air filter with and without lithium grease applied around the seal surface to the orange air filter base (the area suspected of leakage of dust by members on this forum). Not surprising to me, it did not reveal any changes to the airflow numbers. However it still may be a sealing issue for dust. The air filter restriction will only grow (get worse) as the saw is operated and debris is trapped in the filter media. Carb tuning will definitely be affected by the presence of the air filter

I didn't install the outer cover, due to clearance issues to the bench.View attachment 520211



With air filter installed:

View attachment 520212


Here's the flow data for the carb and air filter assembly:

View attachment 520210

So... Can we assume you'll be further modifying the muffler looking for a few more CFL of flow? And did you by chance do any test cuts befor the mods or are we sticking with follow bench numbers?

And thanks for a great thread by the way. Love to see more flow numbers on different mufflers. Those as how are obviously pretty stuffed up from the factory. How's about say Husky 346xp, 545, 555, 550, 562 mufflers? Love to see those quantified.

 

[James Miller]

So with just the deflector opened up the spark screen isn't a big restriction? Nice to know as mine stay in to keep the stink bugs out of the muff.

 

[Rio95]

19.5 CFM is 552,179 cc/min. A 60cc engine at 10,000rpm is only 60,000 cc/min even at 100% volumetric efficiency, which is 10X less.

Isn't 60cc x 10,000rpm = 600,000cc? Not 60,000. Or am i missing something?

Seems like the carb has been matched fairly well if this is the case, maybe just a slight restriction.

 

[Chris-PA]

Isn't 60cc x 10,000rpm = 600,000cc? Not 60,000. Or am i missing something?

Seems like the carb has been matched fairly well if this is the case, maybe just a slight restriction.

Lol, you are of course completely correct. I apologize in general - that's what I get for throwing something out in a spare moment at work. Naturally it makes much more sense too.

If we take 600,000 and multiply by about 2/5 that the port is open we get 240,000 cc/min, which is still much less than 552,000 but by a more reasonable factor than 10:1.

 

[Rio95]

If we take 600,000 and multiply by about 1/3 that the port is open we get 200,000 cc/min, which is still much less than 552,000 but by a more reasonable factor than 10:1.

If the ports aren't open, the carb wouldn't be flowing either, as the carb only flows when a vacuum is created in the crankcase. Therefore matching the flow of carb to the displacement as closely as possible is desireable. We must remember that the flow measurements are done at and arbitrary pressure, which may be different to the pressures/vacuums that the engine draws through the carb.