MS661C Muffler Mod Testing

[blsnelling]

Then how do you know you found more rpm?

My internal frequency monitoring device told me

 

[SquareFile]

My internal frequency monitoring device told me

I prefer just winging it.

 

[Chris-PA]

Thanks Chris!

It looks like you did 4 cuts each video, pushing harder each time? For consistency which cut do you want the rpm on?

 

[blsnelling]

It looks like you did 4 cuts each video, pushing harder each time? For consistency which cut do you want the rpm on?

Highest and lowest RPMs.

 

[Chris-PA]

OK, here's what I did: I watched each video to try to find cuts that sounded consistent and steady. Then I picked a light and a high load section from each video to plot. I noticed when listening that the high load cuts varied a lot more, and this showed in the plots where the width of the spike was much wider than for the light load. And I had to pick a section carefully to get a clean a plot as I did. But then this is not a surprise with a powerful saw pushed through...what the hell was that anyway?

I had to put the cursor somewhere on the high load plots so I mostly picked the middle. Given that, the results were remarkably consistent. Here are the plots (you can see the name at the top) - the area that is shaded on the time plot is the area that is plotted in the frequency analysis, with the heavier loading being later in time:









Here are the numbers I came up with (wish this thing did tables, and it removes extra spaces ):

Config--- Load--Freq---RPM
BISI-------Light---167----10020
BISI-------High---141-----8460
BOSI------Light---172----10320
BOSI------High---141-----8460
BOSO-----Light---166-----9960
BOSO-----High---140----8400
BOSODP--Light---167----10020
BOSODP--High---144-----8640

Of course this is just rpm, and you have to combine it with times to have it mean much.

 

[blsnelling]

Thanks Chris. Very cool. Thanks for the effort.

 

[blsnelling]

I forgot I hadn't uploaded this one. What's it making at 0:16, and 0:39?

 

[MustangMike]

Its kinda like runnin any big strong powerhead with a smaller bar.

Actually, a lot of big saws don't show their power unless they are running longer bars. In 20" wood, I'll put my stock 044 up against a stock 660 any time, although the 660 would win in bigger wood.

The 661 and ported big saws are different, they generally cut very fast with smaller bars.

 

[Deets066]

Actually, a lot of big saws don't show their power unless they are running longer bars. In 20" wood, I'll put my stock 044 up against a stock 660 any time, although the 660 would win in bigger wood.

The 661 and ported big saws are different, they generally cut very fast with smaller bars.

 

[Moparmyway]

Discussions ended by single picture posts without words deserve more than 1 "like" !!

 

[Chris-PA]

I forgot I hadn't uploaded this one. What's it making at 0:16, and 0:39?

Well, it's screaming at 16s - 12,000rpm:

Around 39s it's varying a bit, from 7,440 to 11,100rpm. The center is around 9,000rpm:

 

[blsnelling]

7,400-12,000. I'll take that!

 

[SAWMIKAZE]

View attachment 429357

Bingo...you beat me to it..thanks dawg

 

[SAWMIKAZE]

Actually, a lot of big saws don't show their power unless they are running longer bars. In 20" wood, I'll put my stock 044 up against a stock 660 any time, although the 660 would win in bigger wood.

The 661 and ported big saws are different, they generally cut very fast with smaller bars.

Mike , if you gear a 90cc saw properly its gonna pound a 70 cc saw in 20" wood.

And i hope a 660 beats a 044 in bigger wood...its 20cc bigger..it better beat it...i know what all these saws do mike , you really dont have to point out the obvious to me..but thank you for the contribution.

 

[blsnelling]

This is my personal saw. I'd love to test in larger wood, but this is the largest I have. So, I installed an 8-pin rim and a 20" bar. It's a hand filed Stihl RS chain. The saw was re-calibrated after each mod and a couple cuts made before the video was shot. I'm running E-Free 91 octane gas with 800 2T Off Road @ 32:1. I made two moderate load cuts and then two heavy load cuts. The 661 makes it's fastest cut times with a heavy load.

I started with a muffler that already had the factory port opened as much as the deflector will cover...left to right and front to back. The screen is intact to start with. I would never mod one with any less than this.


Here I have removed the internal baffle but left the screen installed.


Here I have removed the screen.


Here I have added a second port, actually a series of louvers, right in the center of the muffler cover.


With every change, I progressive made the muffler freer flowing. As expected, performance improved with every change. The MS661C loves to breathe, as do all chainsaws. With that said, I will be purchasing a new muffler cover as this one is too loud for normal use. The saw does just fine with the factory port opened up and the baffle removed.

Baffle In / Screen in - 4.99 average
Baffle Out / Screen In - 4.81
Baffle Out / Screen Out - 4.76
Baffle Out / Dual Port - 4.44

The fastest combination is no baffle and as much exit area as your ears can tolerate.

 

[MustangMike]

Brad, is that on ported saws, or all saws? I think in some of his previous tests, the baffle helped the stock saw, but not the ported one.

 

[blsnelling]

Brad, is that on ported saws, or all saws? I think in some of his previous tests, the baffle helped the stock saw, but not the ported one.

I don't test stock saws to that level, but would be very surprised to see it any different.

 

[Trx250r180]

I don't test stock saws to that level, but would be very surprised to see it any different.

My ms460 seemed to like the baffle when it was stock vs gutted ,stock baffle ,rh opening enlarged ,and dual cover it was happy on my particular saw ,once ported ran better gutted .

 

[Andyshine77]

I don't test stock saws to that level, but would be very surprised to see it any different.

Go big or go home!![emoji6]

 

[Squad_Boss]

What purpose does a 20 inch bar serve on a 90cc class saw? Just curious.

I recently picked up a 661 and it doesn't cut any faster than my 362 until it's buried in bigger wood.

661 36 inch bar
362 28 inch bar