No. It's just like a 460. I port them exactly the same.
Ms461 saw design
- Thread starter KG441c
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KG441c
Keith
The transfer design is totally unlike the 460. As mentioned previously, the 460 transfers are fed from the side of the cylinder and only had two ports. I've never bothered with the piece under the piston.
KG441c
Keith
Appreciate the explanations Brad
Mastermind
Work Saw Specialist
The 461 is not a stratified engine.
It does have a different design in many ways from the 460.......but it isn't stratified.
I don't port the 460 and the 461 the same......at all.
It does have a different design in many ways from the 460.......but it isn't stratified.
I don't port the 460 and the 461 the same......at all.
KG441c
Keith
I agree its not stratified in the usual way on the intake but on the Stihl tech sheet pg 3 and 4 they refer to it as stratified exhaust? Whats ur take on that term Randy and does the saw Peform better with the large baffle removed from the muffler? I have the unlimited coil on there now and tuned to about 14000rpm
Mastermind
Work Saw Specialist
I think they perform better with the muffler completely gutted.......they are loud though. Also I like a dual port cover on them. The AM ones that weedeaterman sells are fine.
The biggest difference between this saw and the 460 is the length of the transfer passages. They are also tight and fast flowing compared to the 460. If you raise the transfers and lower the intake too much on this unit, you just built a turd.
I compared a 461 that I built to one that was ported in the manner I just described.......ours was over 7 seconds faster in one cut. The other saw just didn't have any guts. Plenty of RPM......but gutless.
The biggest difference between this saw and the 460 is the length of the transfer passages. They are also tight and fast flowing compared to the 460. If you raise the transfers and lower the intake too much on this unit, you just built a turd.
I compared a 461 that I built to one that was ported in the manner I just described.......ours was over 7 seconds faster in one cut. The other saw just didn't have any guts. Plenty of RPM......but gutless.
KG441c
Keith
Wow!! Thanks Randy! I sure like hearing from u guys that have dug into these motors and put the hours in and get sound advice on the subject! Appreciate u fellows
RPMs and torque here.
1. There are two main sources of unburned fuel out the exhaust in a traditional chainsaw: First is scavenging losses due to the exhaust port being open as the cylinder fills. Second is the poor mixture control of the carbs where even a small increase in air velocity makes them so rich the engine misfires. Strato deals quite well with the first, and feedback carbs deal with the second, but it appears you don't need to do both to pass emissions. On top of that there are provisions for emissions credits, and I don't know the details but it looks like they don't have to make every model pass. So it should not be assumed that every new model has strato. With M-tronic and carefully designed transfers and timing they may be close enough on this saw.
2. Without strato some portion of the fresh fuel charge will go out the open port, but it seems that some air gets pulled back into the cylinder towards BTDC. If the engine has a wide open exhaust port then the fuel that does get pushed out is lost to the atmosphere, and what gets pulled back in will be mostly air. On the other hand, if there is a fairly enclosed can on the exhaust, then this volume will have old exhaust and some of the fuel still in it, and that will be what gets pulled back in. So it would make sense that the muffler restriction, as well as port timing, is part of the emissions control strategy.
You can see where strato, which delays the arrival of fuel to the cylinder so less can go out the port, would allow less compromises on porting and muffler restriction.
2. Without strato some portion of the fresh fuel charge will go out the open port, but it seems that some air gets pulled back into the cylinder towards BTDC. If the engine has a wide open exhaust port then the fuel that does get pushed out is lost to the atmosphere, and what gets pulled back in will be mostly air. On the other hand, if there is a fairly enclosed can on the exhaust, then this volume will have old exhaust and some of the fuel still in it, and that will be what gets pulled back in. So it would make sense that the muffler restriction, as well as port timing, is part of the emissions control strategy.
You can see where strato, which delays the arrival of fuel to the cylinder so less can go out the port, would allow less compromises on porting and muffler restriction.
KG441c
Keith
Chris that makes sense to me. So far Ive gutted the muffler, enlarged exisiting hole behind deflector amd reinstalled screen, and added a dp cover. Added a 660 unlimited coil and adjusted to 140000 rpm and also took .020 off the keystock and advanved timing. Runs really good! I guess now all thats left is to send it to somebody and let them stick that silver dremel tool in the cylinder and make it go woot woot!!! Lol!
nmurph
ArboristSite.com Sponsor
What am I supposed to see on the IPL??
KG441c
Keith
explanation of stratified delayed scavening on exhaust
nmurph
ArboristSite.com Sponsor
I only see a parts list when I click on the link.
KG441c
Keith
i may have downloaded the wrong one
Trx250r180
Saw polisher
I tried a couple different muffler setups on my 461 to try to quiet it down ,full baffle ,partial baffle ,the gutted one ran the best ,that saw must pump a lot of air .......
Mastermind
Work Saw Specialist
Ron660
Addicted to ArboristSite
Reading all of this info makes me think of one thing.....what's faster? A ported 046, 460, or 461?
Mastermind
Work Saw Specialist
The saw I tested against ours still had the baffle...... flanges not ported matched.......even after we fixed that it was still way behind ours.
Mastermind
Work Saw Specialist
Faster or stronger?
