I call B.S. on Stihl. My dyno doesn't lie. MS 461 is king over MS 660

[MustangMike]

I ran two ported Smittybuilt 660s at the Upstate NY GTG (one was also over bore). They were throwing chips 25' and going through Black Locust like it was cotton candy.

And those guys are Western Tier NY, they could drop right down into PA!

 

[chadihman]

Sorry no more testing this week. 19 hr day yesterday and I 'm taking a break and going camping with the Family. Got Randy's 261 cm yesterday so I'll have some results next week.

 

[DMZ]

Any chance you could test 1 ring vs 2 rings on the piston?

 

[chadihman]

Any chance you could test 1 ring vs 2 rings on the piston?

Might be able to get that.

 

[MustangMike]

Chad, Thanks for all of the wonderful information, and enjoy your break.

Next Step: My 2 Cents

The 660 obviously benefited enormously from your dual port muffler mod, with power increases across the usable range. However, peak Hp is still at a rather anemic 9,000 RPM. Based on this information, I believe an increase in timing would be the best "next step". It only makes sense to increase timing after you increase the flow of air/fuel. As I recall, we always used to advance the timing a good bit when we opened the headers on our cars (22 of us did it on the Bicentennial 4th of July, and yea, we got law enforcement awards!). The WW II Marine who lived across the street said we sounded like a Battleship coming down the road! He heard us before he could see us and could not figure out what it was.

Also, just for my information, is that 660 running a HD-2 filter?

Thanks again.

 

[blsnelling]

Isn't 9,000 RPMs where the factory rates max HP? Pretty cool matchup there.

 

[MustangMike]

I'm not sure Brad, i can't seem to find that info, but I do think a timing advance would help, just makes sense to me. If you can move peak HP up and increase it, cut speed will increase. Obviously, the saw can breath much better now and should benefit from an increase in timing.

 

[blsnelling]

Timing advance WILL help on that model.

 

[MustangMike]

Just removed the baffle from my 046, and if it ever stops raining I may even see how it runs.

 

[blsnelling]

You should advance the ignition on your 046 as well.

 

[MustangMike]

How much would you recommend on a stock saw with HD-2 filter and dual port (& baffle removed)? Would removing the base gasket also be a good idea? I was thinking of doing that to the 044, but it does not have C/R and I did not want to make it any harder to start when hot on hot days (the cord just pulls through my hands).

 

[blsnelling]

Go 6°. That's probably close to 1/3 the width of the key.

 

[MustangMike]

Thanks.

 

[CTYank]

Not meaning to cast any dispersions or anything, but it seems that a reasonable prerequisite for this course would be Physics 101. Seriously, a common understanding of the rotarional stuff could really simplify discussions.
Stuff like torque, angle, rotational speed, work, power, force, energy. "Horsepower" is just another unit. Calculus later.
With the basics in place, we could readily digest the importance of the curves, where & how the "rubber meets the road"; and how peak readings can be totally misleading.
Thanks, Chad, for all the discovery and demystification you've done and will do. Marketeers must hate you.
With your texts open, discuss.

 

[Dieselshawn]

How about opening the single port 660 muffler to a 1" square hole? Mine has one and it's quieter than the dual port while making same power.

 

[Hedgerow]

How about opening the single port 660 muffler to a 1" square hole? Mine has one and it's quieter than the dual port while making same power.

That works fine too...
The muffler mod is an expression of individuality...
Just open that dude up...

 

[Haywire Haywood]

Might just direct the sound differently so it appears to be quieter to the operator.

 

[chadihman]

I still have to test a variable opening muffler.

 

[MustangMike]

And Timing, only makes sense to increase timing after you increase the flow.

Back in the day, we would not think of opening the headers w/o increasing the timing. I had the distributor positions memorized, I did'n bother using a light.

 

[wyk]

A bud of mine in the UK hasn't muff modded his 550xp. I wonder how well that responds to the MM, and if timing advance helps any.