Ms461 saw design

[KG441c]

If the 461 has "Delayed Stratified Scavenging Technlogy", then so does the MS260, MS361, MS440, MS460, MS660, and MS880. You can throw a bunch more Stihl, Husky, Dolmar, and many other saws in there as well. Like we're trying to tell you, the port timing and flow of fuel charge and ehaust are no different in the 461 than any other typical 2-stroke saw. Stihl is #1 in OPE for a reason. One of the biggest reasons if marketing, and you guys are buying it without logic to back it up.

Actually thats why I started the thread was I havent heard of it before and wanted to know more about it. I surely dont claim to know anything more than what Ive read from AS and asking guys a few questions and thats pretty much why Ive ask you and Randy everything about every saw ive had and appreciate all the advice you guys have given me and taken ur word for the decisions Ive made in purchasing these saws. Sometimes I post and ask questions and start threads because I dont wannabug the **** out of you and Randy but make no mistake when either of the 2 of you have given me advice, ive taken it to heart

 

[Ron660]

Actually thats why I started the thread was I havent heard of it before and wanted to know more about it. I surely dont claim to know anything more than what Ive read from AS and asking guys a few questions and thats pretty much why Ive ask you and Randy everything about every saw ive had and appreciate all the advice you guys have given me and taken ur word for the decisions Ive made in purchasing these saws. Sometimes I post and ask questions and start threads because I dont wannabug the **** out of you and Randy but make no mistake when either of the 2 of you have given me advice, ive taken it to heart

Just think, all this advice is FREE! I started with a stock 660 and now it's getting ported. I changed from 50:1 to 32:1, stihl ultra HP to Motul 800, bought a tach, and learned how to adjust my carb. All from reading and posting threads on AS. You're right, the individuals that port saws and experienced members on this site are some of the most helpful people I've talked to on a social media site. My wife told me the other night I'm more addicted to AS than my daughter is to facebook! I told her at least AS is educational, facebook isn't.

 

[albert]

If the 461 has "Delayed Stratified Scavenging Technlogy", then so does the MS260, MS361, MS440, MS460, MS660, and MS880. You can throw a bunch more Stihl, Husky, Dolmar, and many other saws in there as well. Like we're trying to tell you, the port timing and flow of fuel charge and exhaust are no different in the 461 than any other typical 2-stroke saw. Stihl is #1 in OPE for a reason. One of the biggest reasons if marketing, and you guys are buying it without logic to back it up.[/QUOTE

If the 461 has "Delayed Stratified Scavenging Technlogy", then so does the MS260, MS361, MS440, MS460, MS660, and MS880. You can throw a bunch more Stihl, Husky, Dolmar, and many other saws in there as well. Like we're trying to tell you, the port timing and flow of fuel charge and exhaust are no different in the 461 than any other typical 2-stroke saw. Stihl is #1 in OPE for a reason. One of the biggest reasons if marketing, and you guys are buying it without logic to back it up.

What is the reason for the 461 being more fuel efficient than the 460?

 

[windthrown]

I get what you are saying......but the port timing numbers tell a different story.

So you refute the tech bulletin that Stihl has on the 461? Amusing. Brad thinks it is a bunch of marketing hype. Well, I do not make any money selling saw modder t-shirts or grinding saws, so I have no horse in this race. What bothers me is that people take you two as "qualified experts" and worship the ground that y'all walk on, but you both seem to be completely blind-sided by this tech bulletin and how this saw (and the 661) actually work. Me, I believe the tech bulletin for what it says. I am a multiple degreed engineer, and it makes sense to me. Exhaust scavenging in the 461 has been touted for some time now and has been posted on this site by the likes of Tommy Hall and others. Yet people seem to have the erroneous idea that the 461 works the same as the 460, or that this idea is new. It does not.

Now on to the saw: Splitcase has the right idea above. Its about crankcase-combustion chamber pressure differential. The way that this design works is that the ports flood with exhaust gasses for a brief duration when the transfers open when the pressure in the crankcase is lower. Then they are forced back up by the piston downforce with a fresh charge of fuel behind it. The xfer port timing being later/lower is likely due to needing the combustion chamber pressure to be lower when the ports open. Like most things in a 2-stroke engine, it is an ingenious way to add a stratified layer (it is in fact a stratified layer) of exhaust gases before the fuel charge to keep unburned fuel from leaking out the muffler like the pre-EPA saws did. However, the downside of this design is that the piston tends to overheat, and so they had to add the piston pusher/cooler to the design to make it work.

One thing I learned as an engineer when I was up for design review was to invite my worst enemies to those meetings. That way I had people intent to destroy my ideas, and I got the bugs out of my designs pretty fast. I retired in my 40s because of my success as an engineer, not because I failed.

 

[Mastermind]

Crankcase pressure ,positive and negative are the keys here

You might be on the something........the placement of the transfer inlet could be a factor here. I just don't see it though.

What is the reason for the 461 being more fuel efficient than the 460?

It has a much smaller main jet in the carb for one thing.

 

[Mastermind]

So you refute the tech bulletin that Stihl has on the 461? Amusing. Brad thinks it is a bunch of marketing hype. Well, I do not make any money selling saw modder t-shirts or grinding saws, so I have no horse in this race. What bothers me is that people take you two as "qualified experts" and worship the ground that y'all walk on, but you both seem to be completely blind-sided by this tech bulletin and how this saw (and the 661) actually work. Me, I believe the tech bulletin for what it says. I am a multiple degreed engineer, and it makes sense to me. Exhaust scavenging in the 461 has been touted for some time now and has been posted on this site by the likes of Tommy Hall and others. Yet people seem to have the erroneous idea that the 461 works the same as the 460, or that this idea is new. It does not.

Now on to the saw: Splitcase has the right idea above. Its about crankcase-combustion chamber pressure differential. The way that this design works is that the ports flood with exhaust gasses for a brief duration when the transfers open when the pressure in the crankcase is lower. Then they are forced back up by the piston downforce with a fresh charge of fuel behind it. The xfer port timing being later/lower is likely due to needing the combustion chamber pressure to be lower when the ports open. Like most things in a 2-stroke engine, it is an ingenious way to add a stratified layer (it is in fact a stratified layer) of exhaust gases before the fuel charge to keep unburned fuel from leaking out the muffler like the pre-EPA saws did. However, the downside of this design is that the piston tends to overheat, and so they had to add the piston pusher/cooler to the design to make it work.

One thing I learned as an engineer when I was up for design review was to invite my worst enemies to those meetings. That way I had people intent to destroy my ideas, and I got the bugs out of my designs pretty fast. I retired in my 40s because of my success as an engineer, not because I failed.

You win.

I'm not as smart as you.

 

[albert]

You might be on the something........the placement of the transfer inlet could be a factor here. I just don't see it though.



It has a much smaller main jet in the carb for one thing.

Yep, but it doesn't run too lean with that jet and it still makes great power. The 460 would not survive nor make power that lean. So step back and think about the porting and exhaust stratification again.

 

[Mastermind]

I can't see it. Not knowing what the port timing is.

As far as jetting goes......the main jet is small......but the high speed needle is out 2 turns. That sorta cancels all that out.

 

[Chris-PA]

Now on to the saw: Splitcase has the right idea above. Its about crankcase-combustion chamber pressure differential. The way that this design works is that the ports flood with exhaust gasses for a brief duration when the transfers open when the pressure in the crankcase is lower. Then they are forced back up by the piston downforce with a fresh charge of fuel behind it. The xfer port timing being later/lower is likely due to needing the combustion chamber pressure to be lower when the ports open. Like most things in a 2-stroke engine, it is an ingenious way to add a stratified layer (it is in fact a stratified layer) of exhaust gases before the fuel charge to keep unburned fuel from leaking out the muffler like the pre-EPA saws did. However, the downside of this design is that the piston tends to overheat, and so they had to add the piston pusher/cooler to the design to make it work.

Yes, which is pretty much what I posted above. To my engineering mind, this looks like a poor alternative to a piston ported strato, and I am skeptical how well it really works. Here is the text that accompanies the images in that document:

The piston moves downward. This first opens the exhaust port and then the transfer ports. On opening the transfer ports, the pressure in the combustion chamber is initially higher than the pressure in the transfer port and in the crankcase - exhaust is pushed into the transfer ports. Exhaust is stratified above the fresh gas in the the transfer ports.

After reaching bottom dead center (BDC) the piston again moves upwards. After the exhaust is almost completely pushed out from the combustion chamber, fresh fuel flows through the transfer ports. The piston closes the exhaust port before the fresh fuel reaches it.​

This is mostly just an explanation of a 2-stroke with a long transfer duration where the transfers open while the cylinder pressure is still high, but how does that last part work? The transfers have clearly closed before the exhaust port does, so how does the fresh fuel get there after the exhaust port closes? Were I in the design review, I'd be asking about that bit.

These things may be getting by on credits from all the other piston ported strato saws they sell. For perspective, Echo is getting away with selling saws that have no strato, no feedback carb and (apparently) no cat, at least on some saws. The 461 at least has a feedback carb. Husky is selling the 543 with strato and no feedback carb. Why do some need all the bells and whistles while others not? I suspect it is about averaging over the product line and total sales. I think the proof of this delayed scavenging technology is that they don't use it on their high volume saws.

 

[albert]

I can't see it. Not knowing what the port timing is.

As far as jetting goes......the main jet is small......but the high speed needle is out 2 turns. That sorta cancels all that out.

How? Put that size jet in a 460 and you can open the H needle 5 turns out and it will still be lean. You still haven't answered how can the 461 run with a 460 on less fuel. The same power on less fuel isn't a carburetion only factor. Some other design area is the reason for it.

 

[Mastermind]

How? Put that size jet in a 460 and you can open the H needle 5 turns out and it will still be lean. You still haven't answered how can the 461 run with a 460 on less fuel. The same power on less fuel isn't a carburetion only factor. Some other design area is the reason for it.

Not true at all.....have you never dissected one of those carbs?

 

[albert]

Not true at all.....have you never dissected one of those carbs?

What makes the 461 to have the same power as the 460 on less fuel?????

 

[Mastermind]

What makes the 461 to have the same power as the 460 on less fuel?????

Oh good lord.

 

[albert]

Oh good lord.

Likewise

 

[splitpost]

You might be on the something........the placement of the transfer inlet could be a factor here. I just don't see it though.



It has a much smaller main jet in the carb for one thing.

wouldn't matter where they were as long as they are long enough to allow for efficient scavenge,the front was probly the best option on a saw to save room ,it probly could have been achieved with the old design but the cylinder would have to be a lot longer in order to get the runners long enough, that would be a tall bodied saw for sure

 

[Mastermind]

I really don't care if the damn thing is a strato saw or not......why in the hell am I even here?

Carry on.

 

[splitpost]

I really don't care if the damn thing is a strato saw or not......why in the hell am I even here?

Carry on.

??????

 

[windthrown]

You win.

I'm not as smart as you.

Ah, you're no fun!

I really don't care if the damn thing is a strato saw or not......why in the hell am I even here?

Carry on.

You port saws and you do not care how they are designed? Sad... and worrisome.

 

[windthrown]

These things may be getting by on credits from all the other piston ported strato saws they sell. For perspective, Echo is getting away with selling saws that have no strato, no feedback carb and (apparently) no cat, at least on some saws. The 461 at least has a feedback carb. Husky is selling the 543 with strato and no feedback carb. Why do some need all the bells and whistles while others not? I suspect it is about averaging over the product line and total sales. I think the proof of this delayed scavenging technology is that they don't use it on their high volume saws.

Well, as for what saws have to meet what EPA emissions levels, that depends on the size of the engine and the number of units sold by a company. The 461 passes the more stringent CARB requirements and is sold in California. EPA/CARB numbers are likely met along with lower fuel use by not pushing raw fuel out the exhaust (like the earlier strato saws). That is their claim anyway.

My read on delayed/exhaust scavenging is that this is Stihls latest/new direction in technology along with Mtronic. The last two saws to be released have it. It is likely cheaper to produce than earlier strato designs, it is less complex, and seemingly has similar results on fuel saving and lower emissions. This and direct injection on their cut-off saws are the latest and greatest stuff from Stihl. I mean, its all just marketing hype, right?

Marketing.. two drink minimum!

 

[splitpost]

Well, as for what saws have to meet what EPA emissions levels, that depends on the size of the engine and the number of units sold by a company. The 461 passes the more stringent CARB requirements and is sold in California. EPA/CARB numbers are likely met along with lower fuel use by not pushing raw fuel out the exhaust (like the earlier strato saws). That is their claim anyway.

My read on delayed/exhaust scavenging is that this is Stihls latest/new direction in technology along with Mtronic. The last two saws to be released have it. It is likely cheaper to produce than earlier strato designs, it is less complex, and seemingly has similar results on fuel saving and lower emissions. This and direct injection on their cut-off saws are the latest and greatest stuff from Stihl. I mean, its all just marketing hype, right?

Marketing.. two drink minimum!

The stupid thing about it is its old tech ,nothing new about delayed scavenging,its definatley marketing,bloody clever is what it is selling old school tech to the tree huggers hahahaha EPA wankers