# what is "strato charged"



## kurtty (Apr 4, 2008)

i keep on hearing about strato charged engines like in the 441. what defines a strato charged engine?


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## PES+ (Apr 4, 2008)

They have 2 sets of ports and a second butterfly that opens progressively from the main carburetor butterfly.

The transfers open after the main transfer ports and allow more complete combustion of the charge after the initial burn event.

Kind of like an air injection pump on a car engine.....adding oxygen after the initial power burn to oxidize/burn off the leftovers. 

A very simplified definition because it is more involved than that


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## icelation8 (Apr 4, 2008)

In a 2 srtoke motor your in coming air/fuel mix pushes out the exhaust from the combustion chamber and you always loose some air/fuel mix out the exhaust. A stratified charge engine allows a charge of air into the combustion area in front of your air/fuel mix to push out the exhaust and to greatly reduce the amount of unburned fuel that is released through the exhaust. It boils done to emmisions is why this technology is becoming popular.


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## PES+ (Apr 4, 2008)

Are you confusing the compression wave with strato charged?

The Strato works a little different in theory and both designs currently do not deal with air density reduction at altitude well.


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## icelation8 (Apr 4, 2008)

Stratified charge introduces air in the cylinder to push the exhaust out. Thats the reason for 2 throttle valves in the carb on the 441 one is for air only the other is for fuel/air mix. There is a cutout in the piston that allows air to enter into the transfer points at the same time air/fuel is entering into the crankcase and the air enters the combustion chamber first to push the exhaust out. The result is less fuel exiting the exhaust which equals less hydrocarbons which equals less emmisions.


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## Lakeside53 (Apr 5, 2008)

I see nothing wrong with ices explanation of the 441...


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## kevlar (Apr 5, 2008)

icelation8 said:


> In a 2 srtoke motor your in coming air/fuel mix pushes out the exhaust from the combustion chamber and you always loose some air/fuel mix out the exhaust. A stratified charge engine allows a charge of air into the combustion area in front of your air/fuel mix to push out the exhaust and to greatly reduce the amount of unburned fuel that is released through the exhaust. It boils done to emmisions is why this technology is becoming popular.



Yep!


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## Lakeside53 (Apr 5, 2008)

No, I didn't write this (Stihl did), but..... it will help quell arguments that will undoubtedly arise.. I'm sure I posted an extract from a tech note a year or two back that detailed the sequence of operation.


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## Lakeside53 (Apr 5, 2008)

Here's the old discussion, See post 13 for tech details..


http://www.arboristsite.com/showthread.php?t=38362


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## PES+ (Apr 5, 2008)

That Stihl description (text) is describing the compression wave theory not strato charge theory.

The strato in strato charging means stratified....describing what happens within the combustion chamber. The layering of the gas mixtures to obtain a more complete combustion of the "wasted" extra incomplete burned charge inherent in a performance 2 stroke engine

The compression wave does as Stihl states and only arrives at a "cleaner" burn by changing in main port timing which render the engine it uses quite lackluster in performance

It doesn't help that Zenoah described their original design and patent in this way though that was filtered though the marketing department and lost something in translation from Japanese to English
(englisch for you Stihl guys)


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## Haywire Haywood (Apr 5, 2008)

I always assumed that they called it stratified because of the layer of air in front of the layer of fuel air.

Ian


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## Griffbm3 (Apr 5, 2008)

I just thought they were talking about guitars and stuff... But thanks for the explanation Ice/Pes+/Lake...

Jason


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## Zodiac45 (Apr 5, 2008)

Griffbm3 said:


> I just thought they were talking about guitars and stuff... But thanks for the explanation Ice/Pes+/Lake...
> 
> Jason



You thought they were "casting" strato charges!


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## PES+ (Apr 5, 2008)

The semantics are sticky at best........no question


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## PES+ (Apr 5, 2008)

Cool..I am going to call my clean 2 stroke "Telecast charged"


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## icelation8 (Apr 5, 2008)

compression wave theory do you mean back pressure from the muffler???
Straified means layer in the dictionary. A layer of air in the combustion chamber. It has nothing to do with a compression wave of any kind. 

I really don't think we are talking the same thing here.


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## PES+ (Apr 5, 2008)

*It is hard to find now but*

I will search for the patent and white papers on the John Deere compression wave 2 stroke.

Like I said.....semantics and from the porting layouts I have seen with strato charged motors they do not simply use air at atmospheric pressure to close the exhaust.....it is a bit more involved.........however they may have gone back to that point in search of power which would explain a need for a cat with a strato charged design.

The odd part is, if that is what they have done, there are far simpler methods to achieve the same result.

I have not seen a 441 cylinder yet so I do not know how Stihl has laid it out


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## PES+ (Apr 5, 2008)

I will see if I can lay my hands on a 441 cylinder and a Husky 575........if that is what they are doing muffler modding will be a big no no as that will throw the whole design out the window


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## icelation8 (Apr 5, 2008)

This was posted by lake in a previous thread this is the new technology that STIHL is using and I have just seen material for i think it was echo having a similar design



Lakeside53 said:


> Here's how the 441 version works...


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## icelation8 (Apr 5, 2008)

PES+ said:


> I will search for the patent and white papers on the John Deere compression wave 2 stroke.
> 
> Like I said.....semantics and from the porting layouts I have seen with strato charged motors they do not simply use air at atmospheric pressure to close the exhaust.....it is a bit more involved.........however they may have gone back to that point in search of power which would explain a need for a cat with a strato charged design.
> 
> ...





The piston still closses the exhaust port its just the volume of air fuel mix that usually goes out the exhaust is replaced by a pure air charge before the air fuel enters the combustion chamber.


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## Freakingstang (Apr 5, 2008)

does this mean jonsereds version will be called turbo charged?


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## PES+ (Apr 5, 2008)

They already used Turbo and Turbo clean......Clean turbo maybe?


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## PES+ (Apr 5, 2008)

icelation8 said:


> This was posted by lake in a previous thread this is the new technology that STIHL is using and I have just seen material for i think it was echo having a similar design



Can you point out to me the stratification in that explanation? The "layer"?


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## Freakingstang (Apr 5, 2008)

PES+ said:


> They already used Turbo and Turbo clean......Clean turbo maybe?



no....turbo charged sounds like a better marketing ploy.....


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## PES+ (Apr 5, 2008)

*They already clamed that*

The first Jonsered "Turbo" models claimed they were running 2 to 3 pounds of boost into the sealed air filter chamber


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## Toyjunkie (Apr 5, 2008)

They are also claiming better fuel economy with it. So you can cut more for less  

So cleaner running for less!! Now you can hug that tree while you are cutting it down! :greenchainsaw:


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## icelation8 (Apr 5, 2008)

If you look up Stratified on Dictionary.com it explains to place in layers. I just said that to try and make it easier to understand.


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## PES+ (Apr 5, 2008)

Show me any layering going on in that Stihl white page......

What they are doing is more like the compression wave not strato charging

I don't care really......they can call it whatever they want but it is calling an apple an orange


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## icelation8 (Apr 5, 2008)

It doesn't say layer in the text but if you look at the picture it shows that fresh air enters through the cut outs in the piston into the trasnfer ports on top of the air fuel mix in the bottom of the crankcase creating a "layer" and because the air is on top (lol on top) it enters the combustion chamber before the air fuel and pushes out the exhaust and then you are left with very little fuel exiting the exhaust as the piston comes up and closes the exhaust port.

But because the text doesn't say layer I guess i am wrong on this one. 
Thats to bad.


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## Lakeside53 (Apr 5, 2008)

Haywire Haywood said:


> I always assumed that they called it stratified because of the layer of air in front of the layer of fuel air.
> 
> Ian



your assumption is correct.


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## Lakeside53 (Apr 5, 2008)

PES+ said:


> Can you point out to me the stratification in that explanation? The "layer"?



I'll try to get someone to post the color infrared photos of the inside of a 441 cylinder during actual operation.. I have them, but they are not mine to publish (what is..?)..


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## Simonizer (Apr 5, 2008)

kurtty said:


> i keep on hearing about strato charged engines like in the 441. what defines a strato charged engine?


It means it's a 2-stroke being forced to eat something it doesn't want to, in the name of the environment. A glass of water with every bite of your cheeseburger anyone?


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## PES+ (Apr 5, 2008)

Where is the "layer" Andy?


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## Tzed250 (Apr 5, 2008)

Here is a video of the concept:

http://www.stihl.de/knowhow/produkttechnik/technik_im_detail/triebwerk/popup_2_mix_isdn.htm


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## PES+ (Apr 5, 2008)

Maybe you can point out the "layer" in that animation? I am not seeing it


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## PES+ (Apr 5, 2008)

OK...A much simpler question......do the air transfer ports open before the fuel air mix tranfers? That is indeed the way that Stihls explanation reads


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## icelation8 (Apr 5, 2008)

Well if you look Blue( the color of the sky) is air and green(the color of grass) is your air/ fuel mix. Now you have to look really close (Zoom in) at the animation but the air enters the same transfer ports that the air/fuel mix does the difference is the clean air (blue like the sky) stacks up or layers on top of the green (like grass) air/fuel mix. Thus instead of using your air/fuel mix (Green like the grass) to scavange off the exhaust instead you use the fuel free air (Blue like the sky) to push it out the exhaust.

I don't think it can be explained any clearer.


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## PES+ (Apr 5, 2008)

So you are saying that there are only the 4 transfer ports,one intake and one exhaust in the cylinder.

IE there are no separate air only ports
.

Or am I still misunderstanding?


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## PES+ (Apr 5, 2008)

Like I said before....I have now read Stihl's description up, down, sideways, backwards and in three different languages and there is NO mention of stratification in the process......on the contrary they mention mixing of the remaining fresh air charge with the incoming fuel/air mix from the transfers


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## PES+ (Apr 5, 2008)

*I'll but this one*

It's just like strato charged....only different......but we'll call it that

strat·i·fy (strt-f)
v. strat·i·fied, strat·i·fy·ing, strat·i·fies
v.tr.
1. To form, arrange, or deposit in layers.
2. To preserve (seeds) by placing them between layers of moist sand or similar material.
3.
a. To arrange or separate into castes, classes, or social levels.
b. To separate into a sequence of graded status levels.
v.intr.
1. To become layered; form strata.
2. To develop different levels of caste, class, privilege, or status.


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## windthrown (Apr 5, 2008)

Tzed250 said:


> Here is a video of the concept:
> 
> http://www.stihl.de/knowhow/produkttechnik/technik_im_detail/triebwerk/popup_2_mix_isdn.htm



"Der Zweitaktmotor mit 2-MIX setzt neue Maßstäbe. Abgas wird vom Frischgas getrennt wird und verhindert weitestgehend, dass unverbranntes Kraftstoff-Luftgemisch mit dem Abgas in die Umwelt entweicht."

Yah, der words are klear as der mudd... The wording may as well be an order for a cheeseburger with fries for all I know. But the graphics seem to be simple enough. 

As for strato vs back pressure wave design in the graphics, I do not see any muffler or exhaust port back pressure wave tuning here. I see air injection from separate ports. One set of ports delivers gas mix earlier in the cycle, and another set delivers air later in the cycle. It seems that they create an upper shell or volume of air-gas mix, and a lower volume of air-only mix. This then creates a scheme where air just above the piston leaks out the exhaust during early compression of the piston, rather than air-fuel mix, which is typical of 2-strokes. In back-pressure wave tuned exhausts (like the ones I had on my dirt bikes) the expansion pressure wave from the exhaust in the expansion chamber forces the leaking gas-fuel mix back into the exhaust port and into the combustion chamber just before the piston closes the exhaust port. Different beast than this one. 

To me it seems that in the 441, they are injecting a small volume of fresh unmixed air over the piston and under the fuel-air mix volume from separate ports, and that air is what 'leaks out' the piston before the piston closes the exhaust port. This reduces the amount of unburned gas-air mix that typically escapes from typical design 2-stroke engines. That in turn would increase inefficiency as well as reduce the amount of unburned gas released and considered smog emissions. I would also presume and/or assume that the added air injected into the exhaust at this point would also help burn off any remaining unburned fuel in the exhaust. Air-injected scavanging, or secondary burning of left over fuel. But that is just a guess... 

So, I would say that this is a strato-air layered design, and not a back pressure wave design.


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## THALL10326 (Apr 5, 2008)

PES+ said:


> Like I said before....I have now read Stihl's description up, down, sideways, backwards and in three different languages and there is NO mention of stratification in the process......on the contrary they mention mixing of the remaining fresh air charge with the incoming fuel/air mix from the transfers



We were taught exactly the oppisite of that Pest. From what I understood the air/fuel mix is ignited. As the piston goes down a rush of fresh air delivered from the air intake ports. This rush of air is layered over the combustion itself forcing the air/fuel mix to stay in the combustion chamber longer and burn more completely. The result is a engine that runs 40% cleaner. Makes sense to me. As to how it actually works is beyond me but they do have proof from their own emmision labs along with EPA tests that the engine does indeed run 40% cleaner that its older counterpart without the air induced combustion, or layered air or as they call it, stratified.


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## PES+ (Apr 5, 2008)

*Did you read the white pages?*

It describes it very different in cycle than what you just described and hence my confusion.

I do not see that air is running under the charge trapped in the upper portion of the cylinder as I don't see how that would be possible.


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## PES+ (Apr 5, 2008)

THALL10326 said:


> We were taught exactly the oppisite of that Pest. From what I understood the air/fuel mix is ignited. As the piston goes down a rush of fresh air delivered from the air intake ports. This rush of air is layered over the combustion itself forcing the air/fuel mix to stay in the combustion chamber longer and burn more completely. The result is a engine that runs 40% cleaner. Makes sense to me. As to how it actually works is beyond me but they do have proof from their own emmision labs along with EPA tests that the engine does indeed run 40% cleaner that its older counterpart without the air induced combustion, or layered air or as they call it, stratified.



What you just stated is very much like what I said....oxidation of the charge after the power event but neither the description nor the animation show anything like that Thall


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## THALL10326 (Apr 5, 2008)

PES+ said:


> It describes it very different in cycle than what you just described and hence my confusion.
> 
> I do not see that air is running under the charge trapped in the upper portion of the cylinder as I don't see how that would be possible.




Well don't feel bad, I don't understand how it works either. I just described what I understood from what they told us. I may be completely wrong but something is causing that engine to burn 40% cleaner and the only differance is its getting a charge of fresh air. Somehow something in that cylinder is making it burn the fuel mix up more completely and it has to be that rush of air. How it works is beyond me..


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## windthrown (Apr 5, 2008)

PES+ said:


> It describes it very different in cycle than what you just described and hence my confusion.
> 
> I do not see that air is running under the charge trapped in the upper portion of the cylinder as I don't see how that would be possible.



Why not? One set of ports feeds the air-fuel mix first, and then another feeds in the air only mix toward the end of the down-stroke. The air-fuel ports are located above the air only ports, and they open earlier. That would create a layer of air-mix on top of air on top of the piston. An open faced strato sandwhich.


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## windthrown (Apr 5, 2008)

PES+ said:


> What you just stated is very much like what I said....oxidation of the charge after the power event but neither the description nor the animation show anything like that Thall



No. That would be what I call scavaging; more air injected would burn off unburned gasses after ignition. And yes, they do not describe it, but it seems obvious to me that that would happen in the process (just my engineering education getting in the way).


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## PES+ (Apr 5, 2008)

It appears the air only ports do not feed directly into the cylinder 

The air only ports are fed into the case through windows in the piston.


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## THALL10326 (Apr 5, 2008)

windthrown said:


> Why not? One set of ports feeds the air-fuel mix first, and then another feeds in the air only mix toward the end of the down-stroke. The air-fuel ports are located above the air only ports, and they open earlier. That would create a layer of air-mix on top of air on top of the piston. An open faced strato sandwhich.




Thats pretty much how I understood the workings of it. My reps's boss explained that yes a 441 will run stronger than a older 440 and its doing so by burning up more of the fuel mix in the cylinder. In other words if both were fed the exact same amount of mix and the 441 burned up 40% more of that exact mix it would produce more power from it. 

When I see Stihl #1 in here I will get him to explain it in more detail.


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## PES+ (Apr 5, 2008)

*I see what is going on now*

The animation shows it quite clearly.....the only thing I can't picture is the fresh air tract to get to the transfers.

The animation shows fresh air either first or last depending on which position of the piton you wish to consider the start point.

OK....I still say not stratified and I will wait for an explanation on why they chose this name but that is strictly a matter of semantics.

If you have a true stratified charge the layers stay separate until some point as all ICE do stratify during the combustion process within the combustion chamber.

I see what Stihl has done and it is interesting and it does seem to run a lot better than the 575 but there are many things that contribute to the 575 being a pain in my opinion......the worst of which is the intake runners and flange.


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## THALL10326 (Apr 5, 2008)

PES+ said:


> The animation shows it quite clearly.....the only thing I can't picture is the fresh air tract to get to the transfers.
> 
> The animation shows fresh air either first or last depending on which position of the piton you wish to consider the start point.
> 
> ...





Well don't hold me to anything I've said about it, I'm only going by what I understood from what they explained to us. I'm quite positive there was alot I didn't understand,LOL


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## windthrown (Apr 5, 2008)

Here is a simplified strato-scavanged engine design of another manufacturer, to show what is happening in a typical strato-scavenged 2-stroke engine. I believe that Stihl has dual porting through the piston skirts for the air injection, and as Pes+ says, they are not so clear in the white papers or online diagrams as to how and when that is delivered to the combustion chamber. 

However, this shows a simpleton concept of how scavanging works by injecting air so that it burns post-ignition gasses more completely on their way out the exhaust port, and how the air-head layering can keep air-fuel mix from leaking out the exhaust port during the early compression cycle before the piston closes the port off. Oh, and note the air layering effect. 

I had to create this jpeg file from a PDF file, so it is large in size... (maybe I will fiddle with it more to get it right).


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## Lakeside53 (Apr 5, 2008)

PES+ said:


> It appears the air only ports do not feed directly into the cylinder
> 
> The air only ports are fed into the case through windows in the piston.



Finally, he gets it!


Now.. how about the other "stihl" way - the TS700 and 800 - reed vaves for the "strato" ports...


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## PES+ (Apr 5, 2008)

I have seen that one and that one is very much like the picture windthrown put up with different points of plumbing ......and that diagram is also not technically strato or what the original strato was...I'll find that box of three ring binders with all that techno junk yet.


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## Lakeside53 (Apr 5, 2008)

So.. was the FS8? made by ?????? licensed by  Stihl in the mid 90's for California sale technically "stratocharged"? :monkey:


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## PES+ (Apr 5, 2008)

Not familiar with any FS8

Can you throw up some links? or pics?

Wait a minute......the pics windthrown put up are the basic diagram aren't they


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## Lakeside53 (Apr 5, 2008)

TS700/800..

note... "layer".....


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## Lakeside53 (Apr 5, 2008)

PES+ said:


> Not familiar with any FS8
> 
> Can you throw up some links? or pics?
> 
> Wait a minute......the pics windthrown put up are the basic diagram aren't they




No.. not FS8.... FS8? 

just making you do some leg work... :greenchainsaw:


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## PES+ (Apr 5, 2008)

Lakeside53 said:


> No.. not FS8.... FS8?
> 
> just makeing you do some leg work... :greenchainsaw:



HAAAAAAAhahaaaaaa I appreciate it and deserved it

 

Now...on to the diagram.....where would this "layer" that they mention be oriented?


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## PES+ (Apr 5, 2008)

No kickin in the Shinds now


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## PES+ (Apr 5, 2008)

*I got it now......*

 

I see now what happened.....Komatsu stated the name from the original concept and the name stuck and has become completely generic.

I did stumble over a very simplified version of how we got where we are today in my travels.

Read this and think next time you wear that Deere John hat

http://money.cnn.com/magazines/fortune/fortune_archive/2002/05/13/322885/index.htm

"The $13-billion-a-year farm machinery giant had come up with a low-emission technology for its Homelite line of two-stroke consumer handheld products, which it had purchased only a few years before. The design, called compression wave, is similar to RedMax's stratified design. What was not similar was the full-court press that Deere's lobbyists put on the EPA to persuade the agency to stick with the more stringent Phase II standards, despite the howling protests of PPEMA. Deere's efforts paid off, as the EPA adopted the tougher standards in July 1999.

But what happened next was bizarre. Although Deere licensed the technology to Stihl, not a single product embodying it has ever reached the market. Last November, moreover, Deere sold the Homelite division to TechTronics Industries (TTI) of Hong Kong. Under a squeeze from big-box retailers, Homelite had lost $100 million in 21 months. Deere has few friends in the handheld industry today. "What's fascinating is that Deere persuaded the EPA, and then the industry gets screwed," says an industry source closely involved with the EPA. Deere won't comment, but in fairness it must be said that its intense lobbying efforts may have incited fresh waves of innovation among the handheld manufacturers. "

Nothing runs like a Deere............


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## PES+ (Apr 5, 2008)

*Now......*

If the Stihl strato does not oxidize the fuel charge at all to complete burning as I mentioned......how did they increase the burn efficiency to such a degree that the layers of air simply force out the completely or nearly completely burned exhaust gases? 

Enquiring minds and all that


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## Stihl #1 (Apr 5, 2008)

You guys are killing me!!!
First go back and re-read this post, page 2:
http://www.arboristsite.com/showthread.php?p=945266#post945266
Pay attention to the explanation about grams per kilowatt hour (g/kWh) measurement of emissions.

OK, are you back now? But first some history and definitions.

Red Max was the first to offer a Strato-Charged engine as they called it back in 97 or 98, and still do sell their design, which uses reeds in the top of the trasfer ports to let air stack up in the transfer port. On low RPM applications like trimmers and cutoff machines reeds are effective at controlling scavenge loss by putting a little puff of clean filtered air between the air-fuel mix coming in from the crankcase and the burnt exhaust gases that need to be pushed out.
SCAVENGE LOSS: unburned fuel coming in from the crankcase, through the transfer ports, leaking out the open exhaust port before the piston has time to close the port.







See how the red shows the air fuel mix coming in and sweeping back and across to push the exhaust gases (purple) out? That is called loop scavenging. Old two-stroke designs had the transfer ports across from the ex ports, called cross scavenging, and had to have a big tall ridge across the top of the piston to keep all the fuel from going straight out, when the transfer ports were open. It was a straight shot across the top of the piston. Here is a cross scavenge Jacobsen engine, reed induction, about a 3k RPM motor.






This design will not work at high RPM.
Here is a pic of loop scavenging.






See how much fuel is leaking out of a 2 port cylinder? This is called short circuiting and in older engine designs amounted to as much as 1/4 of each tank of fuel leaking out the exhaust port into the air as scavenge loss, or emissions. And this is what the EPA said must be reduced. 
Here is a MS 360 cylinder, compared to a MS 361. The MS 361, has four closed ports, compared to the MS 360 it replaces. When measuring the emissions on these two saws, a MS 360 is rated at 121g/kWh, and the completely new design MS 361 is rated at 82 g/kWh. Four port design, along with other design changes, makes a positive impact on lowering emissions, as well as increasing performance and fuel economy.











The MS 361 is still a conventional two-stroke, it is just more efficient at transfer and loop scavenging that it's predecessor. Four ports are better than two to create the loop needed to scavenge out the exhaust gases and not lose as much unburned fuel in the process. Also notice that the transfer ports are longer on the MS 361. That is important in stratified scavenge design.

More to come on the MS 441 stratified scavenge process. And it is stratified and that does mean LAYER!

And maybe later I will do a thread on the compression wave injection design, which is altogether different.


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## icelation8 (Apr 5, 2008)

Thats exactly what i was saying you just had access to all those fancy graphics not fair.
lol


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## PES+ (Apr 5, 2008)

I'm waiting for the second set of drawings with the layering

And the now defunct OMC would beg to differ about not being able to use deflectors at high RPMs but I digress.......


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## Stihl #1 (Apr 5, 2008)

STIHL marketed the FS 83 with a RedMax engine, mainly in CA until the FS 110 was introduced. I think 1999, 2000 was all.

So the EPA said clean up the exhaust. The easiest way is to put a CAT in the muffler, which is just an afterburner and does nothing for power, fuel economy, etc. and just adds weight and cost. But it does do a good job of lowering emissions.
Stratified scavenging addresses the problem in the combustion chamber and results in less scavenge loss of unburned fuel. So the end result is not necessarily a lot more power, but for sure better use of the fuel, so better fuel economy. Put a measured amount of fuel in a MS 440 and a MS 441 and with the same chain, wood and operator the MS 441 will cut longer, maybe even 10 to 20 % longer. At $3.30 a gallon for fuel (here) that is a good reason to buy a MS 411. And let's face it, when was the last time anyone went to a dealer and said they want a new saw that has low emissions? But if it is less thirsty for fuel, then that is a plus.
So the MS 441 has 6 ports in the cylinder. 4 come from the crankcase in the usual manner, they are closed, but they are very long. 2 ports come from the clean air bypass butterfly, and open at the rear of the cylinder just under the rear set of transfer ports. This pic has red for for transfer ports and blue for air intake ports.






Now look at the pockets in the side of the piston.






When the piston is at TDC the pocket opens the 2 fresh air ports up to feed air into the top of all 4 transfer ports to fill them with air. The air is drawn in because as the piston went up it created low pressure in the crankcase, which is also drawing air-fuel mix from the carb through the intake port in the usual manner of a two-stroke. This pic has the piston next to the cylinder in the proper position.






As with any piston ported two-stroke engine the piston is the valve, and in this case it just continues to act as a valve to let air into the transfer ports from the top down. That air stacks up in the long port but never makes it into the crankcase or mixes with the fuel laden air in the crankcase. As soon as the piston starts back down it closes the fresh air ports and the transfer ports and the intake port and starts building pressure in the crankcase. The air is trapped in the transfer ports. Then when the piston goes down far enough on the power stroke to open the exhaust port the exhaust starts flowing out, then the transfer ports open a fraction of a second later and the first thing in is LAYER of clean filtered air that begins the loop scavenge process and pushes out the exhaust gas, and then the fuel air mix comes in just a tiny little bit later. But by then the piston has started back up in the bore and closes the ex port before much of the fuel has escaped.






See how there is a layer of air (blue) between the exhaust (purple) and the fuel air mix (red).
This is stratified scavenging, and expect to see it on just about any new two-stroke engine.
The new 575 Husky and a new RedMax saw that I can't remember the model of is more or less identical in this way. It is not just STIHL doing this.


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## Stihl #1 (Apr 5, 2008)

Yes Ice you had it, but pics help. At least it does for this old Aggie!


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## PES+ (Apr 5, 2008)

I see a slug of air.....no layering but my mind is usually mush.....

So this theory is simply using the air to clear the spent gases and to hold back the crankcase mixture and has no other effect?


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## Just Mow (Apr 5, 2008)

Stihl #1 said:


> Yes Ice you had it, but pics help. At least it does for this old Aggie!



HOOK'EM


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## Stihl #1 (Apr 5, 2008)

PES+ said:


> I see a slug of air.....no layering but my mind is usually mush.....
> 
> So this theory is simply using the air to clear the spent gases and to hold back the crankcase mixture and has no other effect?



Yes it has a major effect, less scavenge loss of unburned fuel. So lower g/kWh emissions. And better fuel economy. More wood cut on less gas. Money in your pocket. And I would guess that as time goes by and more is understood and new young engineers come along and add their ideas to what has been done allready, it will only get better. How much better is a MS 440 than the saw it replaced?


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## Stihl #1 (Apr 6, 2008)

Just Mow said:


> HOOK'EM



no comment


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## Lakeside53 (Apr 6, 2008)

I knew it was only matter of time... big thanks to


*Stihl#1*


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## Just Mow (Apr 6, 2008)

Stihl #1 said:


> no comment


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## Just Mow (Apr 6, 2008)

Lakeside53 said:


> I knew it was only matter of time... big thanks to
> 
> 
> *Stihl#1*


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## Lakeside53 (Apr 6, 2008)

Stihl #1 said:


> . And I would guess that as time goes by and more is understood and new young engineers come along and add their ideas to what has been done allready, it will only get better. How much better is a MS 440 than the saw it replaced?



wait.. you're saying old engineers have no new ideas?????  


oh.. I get it... we're required to filter the fountain of youthful ideas.. kind of like boat anchors... :greenchainsaw: :greenchainsaw:


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## PES+ (Apr 6, 2008)

Could you share the drawings showing the differences to the percussion wave set up?


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## Stihl #1 (Apr 6, 2008)

Lakeside53 said:


> wait.. you're saying old engineers have no new ideas?????
> 
> 
> oh.. I get it... we're required to filter the fountain of youthful ideas.. kind of like boat anchors... :greenchainsaw: :greenchainsaw:



Don't start putting words in my mouth, Lake! LOL
But you will agree that sometimes you have given a problem all you have got, and then someone else, maybe younger, maybe not, comes along, and says "try this" and off you go. 
I think it will continue to get better as new ideas are tried. I am excited about what is goinf on with these little motors. Like the other thread on "Fascination" it really is fascinating to see what new technology and design will be next.


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## Stihl #1 (Apr 6, 2008)

PES+ said:


> Could you share the drawings showing the differences to the percussion wave set up?



Tomorrow, I am done for the evening. Good night.


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## PES+ (Apr 6, 2008)

*Thank You in advance*



Stihl #1 said:


> Tomorrow, I am done for the evening. Good night.



Great info


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## redprospector (Apr 6, 2008)

I'm convinced that the "stratocharged" engine will be the saw of the future, just to comply with the EPA. I'll just be glad when tech's understand them so they will run well at altitude. Not trying to be a stick in the mud, but the stratocharged saw's are real dog's at 9000'.

Andy


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## romeo (Apr 6, 2008)

redprospector said:


> I'm convinced that the "stratocharged" engine will be the saw of the future, just to comply with the EPA. I'll just be glad when tech's understand them so they will run well at altitude. Not trying to be a stick in the mud, but the stratocharged saw's are real dog's at 9000'.
> 
> Andy



Completely worthless at altitude. Unfortunately, I think that all of them well be in a few years.

But technecally, if it puts out a third less emissions but has to run twice as long (yes, they are that slow at high altitude), isn't it causing MORE polution. Kind of like a water saver toilet you have to flush 4 times to get the turd down.


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## windthrown (Apr 6, 2008)

I think that this technology will only be around for a short while, and then it will all go to 4 strokes. From what I have heard, the main small engine companies all have designs developed for the 4 strokers. CA CARB regulations and EPA requirements loom ahead. 2010 is a cut-off date for small hand held engine manufacturers to meet the emissions requirements for EPA. Many saws today already cannot be sold in CA. There are also European emissions standards, and there will no doubt be more regulations put into effect after 2010 by the EPA, CARB, and Europe.


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## 1rockinacman (Apr 6, 2008)

romeo said:


> Completely worthless at altitude. Unfortunately, I think that all of them well be in a few years.
> 
> But technecally, if it puts out a third less emissions but has to run twice as long (yes, they are that slow at high altitude), isn't it causing MORE polution. Kind of like a water saver toilet you have to flush 4 times to get the turd down.



Romeo that last line got me laughing so hard I almost hacked up a lung. It got me thinking though.......... I must have a water saver toilet.


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## Haywire Haywood (Apr 6, 2008)

No, you just have giant turds. Hang a butter knife on a string by the toilet and slice that italian sausage up into chunks before you flush... :greenchainsaw: 

Ian


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## wanab (Apr 6, 2008)

thanks for setting the book strait on the 441, #1.


strato, then 4stroke, :censored: .


i have been told there are some other developements coming to saws that will offset the engine setbacks.


 



so the answer is yes they will have a better mousetrap but how long before they get it right?


:jawdrop:


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## Lakeside53 (Apr 6, 2008)

windthrown said:


> I think that this technology will only be around for a short while, and then it will all go to 4 strokes. From what I have heard, the main small engine companies all have designs developed for the 4 strokers. CA CARB regulations and EPA requirements loom ahead. 2010 is a cut-off date for small hand held engine manufacturers to meet the emissions requirements for EPA. Many saws today already cannot be sold in CA. There are also European emissions standards, and there will no doubt be more regulations put into effect after 2010 by the EPA, CARB, and Europe.



I'm betting 10 year or more for "basic strato" .. maybe that's short.. but.. and it may well evolve with electronic carb/injection contols way beyond that.. Of course.. strato with cat! Very likely for the small machines...

The European regs are bascially a mirror of the EPA regs, but with no credits.


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## martinjs (Apr 6, 2008)

Stihl #1 - Fantastic posts. It is so helpful to have a process explained in terms that we can understand. Thanks for sharing your knowledge.


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## Stihl #1 (Apr 6, 2008)

PES+ said:


> "The $13-billion-a-year farm machinery giant had come up with a low-emission technology for its Homelite line of two-stroke consumer handheld products, which it had purchased only a few years before. The design, called compression wave, is similar to RedMax's stratified design. What was not similar was the full-court press that Deere's lobbyists put on the EPA to persuade the agency to stick with the more stringent Phase II standards, despite the howling protests of PPEMA. Deere's efforts paid off, as the EPA adopted the tougher standards in July 1999.
> 
> But what happened next was bizarre. Although Deere licensed the technology to Stihl, not a single product embodying it has ever reached the market. Last November, moreover, Deere sold the Homelite division to TechTronics Industries (TTI) of Hong Kong. Under a squeeze from big-box retailers, Homelite had lost $100 million in 21 months. Deere has few friends in the handheld industry today. "What's fascinating is that Deere persuaded the EPA, and then the industry gets screwed," says an industry source closely involved with the EPA. Deere won't comment, but in fairness it must be said that its intense lobbying efforts may have incited fresh waves of innovation among the handheld manufacturers. "
> 
> Nothing runs like a Deere............



This is interesting, Pest, as back in 95 or whenever the meeting was with the EPA most manufacturers were telling the EPA we can't hit the numbers you are asking us to lower emissions to, and then JD showed up with a prototype engine and said "sure, no problem, we have a technology right here that can do it". So the EPA said if they can do it everybody can do it. Now this is just heresay but the story I heard was that some dude came up with the idea, built a modified Homey trimmer engine that used compression wave injection to dramatically lower scavenge loss, in his garage, and managed to sell it to JD. And they went to this EPA meeting and shot from the hip with no real testing or R&D on the design, just a dyno run that showed low HC exhaust.
And as the article said, supposedly Stihl tried it and decided not to market an engine with this technology. Something about cold weather running not being consistent, but I am not sure about that.
So I agree with the article in that JD probably does not have any friends left in the hand held business, but their actions did cause the industry to come up with some ideas that we are now seeing on the new models of saws. And more new stuff will no doubt come. Whether we like it or not. But the end result will be lower emissions which is a good thing, and better fuel economy, which is also a good thing, and the end of the conventional piston ported two-stroke, which is a sad thing. I used to teach auto tech at the high school level. I told the kids about my 65 big block vette roadster. 25 hp, 8mpg, raw low-tech, no replacement for displacement HP. Then the 70s and 80s with smogged up slug engines in everything. Jump to now. I showed them a video of the Venom Viper. I forget the details but basically a 500 to 600 hp v10, fuel injection, 200mph, 1/4 mile in 10 seconds, and can be driven daily and get 18 mpg. That is high-tech HP. And what has happened to the auto industry is trickling down the the power equipment industry. Ignition modules with automatic timing adjustment. Electronic carbs. Cat mufflers. I suspect some form of fuel injection for hand held stuff. Who knows what is next. So stock up your collection of saws trimmers and whatever else you like with recent models and examples, then sit back and lets enjoy the ride!


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## Stihl #1 (Apr 6, 2008)

martinjs said:


> Stihl #1 - Fantastic posts. It is so helpful to have a process explained in terms that we can understand. Thanks for sharing your knowledge.



Thanks Steve, my pleasure. 

The rep bar just keeps getting longer!!! LOL


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## PES+ (Apr 6, 2008)

Deere wishes they bought it cheap.....it was an adaptation from their failed diesel technology of the same name


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## THALL10326 (Apr 6, 2008)

*Eddie*

Great info my friend, nice posts indeed. You still have more saws than me so I refuse to rep you,LOLOLOLOL, just kidding.

Now tell us if this is true. A little birdie told me, well one about 6'3 235 lbs named Kevin, that fuel injection is on the way. He esitmated within 10 years but it is being put on the drawing board now and is being considered and he felt it would be on small power equipment when all is said and done. That should really clean up the emmisions just like it did auto's. Have you heard anything about that???


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## Stihl #1 (Apr 6, 2008)

*Compression Wave Injection*

So here is CWI (compression wave injection)







The carb looks similar on the outside but is totally different in what it does. The low pressure is created in the crankcase by the piston moving up. Some air and fuel-oil mix go into the crankcase in the usual manner, about 15%, to provide lubrication to the bottom end. And this is supposed to be enough. So why are we at 50:1? Anyway, the rest of the fuel the engine needs is routed to the compression wave tube. The tube is long and wraps around the intake flange.






So when the piston is at TDC the fuel is being drawn further around the tube but never makes it to the crankcase. Notice that the top of the tube is closed by the piston skirt.






Now the piston is moving down building positive pressure in the crankcase which is pushing back on the fuel in the tube. The pic doesn't show it but there is a check valve that keeps the fuel from being pushed back into the carb. And again, notice that the top of the tube is still closed by the piston skirt.






So now the piston has come down far enough to open the exhaust port so ex gases are flowing out. And the transfer port is open, so the extremely lean air-fuel mix comes in and loop scavenges the ex gas out, but also notice that the top of the compression wave tube is also open, exposed to the hot, high pressure combustion gas. That little squirt of gas pushes on the fuel and adds pressure in the tube, pushing the fuel towards the crankcase, but now the bottom of the piston skirt has closed the tube so the fuel is being compressed in the tube.






So now the ex gas pressure has bled down through the open ex port, and the piston has started back up to close the ex port, and the pressure behind the fuel in the tube is higher than the pressure in the combustion chamber, so fuel now is injected into the air that came in from the crankcase, mixing with it to Lambda = 1 or so, and the delayed injection of this fuel gives the piston time to close the ex port, so scavenge loss is less. Emissions are lower, and fuel economy goes up. All well and good in theory, but it is my understanding that with the liquid fuel sloshing around in the tube, the engine would run erractically and that it was sensitive to tuning and temperature.
So for what it is worth that is how CWI works. Next post is a pic of the parts.


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## Stihl #1 (Apr 6, 2008)

Here is a pic of the JD motor.






The clear tube is the compression wave tube, and there are extra holes in the cylinder wall and flange that correspond to the openings depicted in the drawings. This is the only pic I have, so the drawings in the previous post explain it better.


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## PES+ (Apr 6, 2008)

Do you have a pic of the Stihl saw that they converted?


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## Stihl #1 (Apr 6, 2008)

THALL10326 said:


> Great info my friend, nice posts indeed. You still have more saws than me so I refuse to rep you,LOLOLOLOL, just kidding.
> 
> Now tell us if this is true. A little birdie told me, well one about 6'3 235 lbs named Kevin, that fuel injection is on the way. He esitmated within 10 years but it is being put on the drawing board now and is being considered and he felt it would be on small power equipment when all is said and done. That should really clean up the emmisions just like it did auto's. Have you heard anything about that???



You heard what? From who? Man you better check your sources. A company like Stihl, thinking about something as modern and as high tech as fuel injection on a chain saw!!! I can't imagine!!! LOL

And I will always have more saws that you. He who dies with the most stuff wins, right?

Actually I plan on going to heaven when I die, and I bet there is a cool saw collection in God's house!
You want me to leave my saws to you? You are so ornery I bet you out live us all!


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## Stihl #1 (Apr 6, 2008)

PES+ said:


> Do you have a pic of the Stihl saw that they converted?



My understanding is that it was a small hedge trimmer motor that it was tried on, not a saw.
I think JD did market a saw with this induction on it, but I don't know what model.


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## PES+ (Apr 6, 2008)

I am pretty sure it was an 044 but it may have been a 036......that was a long time ago.....and so much of that stuff has vanished like it never happened

I hate cloak and dagger carp

They tried to corner the market of all 2 stroke engines by leveraging something they didn't have yet.....


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## PES+ (Apr 6, 2008)

I never saw it run but I remember that was why the larger hand held engine emissions reductions were set where they were


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## Stihl #1 (Apr 6, 2008)

Pest, you are right that there was a direct fuel injection 044 (I think) built as a R&D project back in the early 90s or late 80s. I have seen a pic of it, not the actual saw. To my knowledge it was never marketed, it was just an engineering exercise.


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## THALL10326 (Apr 6, 2008)

Stihl #1 said:


> You heard what? From who? Man you better check your sources. A company like Stihl, thinking about something as modern and as high tech as fuel injection on a chain saw!!! I can't imagine!!! LOL
> 
> And I will always have more saws that you. He who dies with the most stuff wins, right?
> 
> ...



You are planning are ya, thats good, me I'm orenry, not really, when ya going,LOLOLOLOLOL

OKOKOKOKOK, I see somethings aren't supposed to be mentioned. You answered my question. I can't wait to see how they run,


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## PES+ (Apr 7, 2008)

Ypsilanti is hot in the summer man.......


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## drkptt (Apr 8, 2008)

*CWI chainsaws have been on the market for almost 3 years*

Emak has been manufacturing compression-wave injected chainsaws since the 2005 model year badged as John Deere CS36LE and CS40LE. They also sell them under their own label (Efco MT3700 and MT4000).

German forestry institute award:
http://www.emak.us/Sezione.jsp?idSezione=591&idSezioneRif=623


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## 1Alpha1 (Apr 3, 2015)

So.....are more Stihl engines Strato Charged than not? 

Or.....does it take a certain # of cc's for it to be effective? Or......does the engine size even matter?


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## stihlaficionado (Apr 3, 2015)

2123 said:


> So.....are more Stihl engines Strato Charged than not?
> 
> Or.....does it take a certain # of cc's for it to be effective? Or......does the engine size even matter?


I do believe the 193 top handle is a strato


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## 1Alpha1 (Apr 4, 2015)

A dealer told me that _strato-charging_ is more or less, an EPA thing more than anything else. He implied that it's a bit more fuel effective, and of course, reduces emissions to some degree. 

I was just curious if* ALL* Stihl saws are strato charged? If I'm not getting all this right, or misinterpreting it, I'd appreciate it if someone would school me a bit on it. And......just to muddy the waters a bit more, are string trimmers, pole saws, blowers, etc. strato-charged?


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## theoldwizard1 (Sep 19, 2015)

THALL10326 said:


> Now tell us if this is true. A little birdie told me, well one about 6'3 235 lbs named Kevin, that fuel injection is on the way. He esitmated within 10 years but it is being put on the drawing board now and is being considered and he felt it would be on small power equipment when all is said and done.


Well it is not quite 10 years so I guess they have a few more years to get that FI _(or should I say Direct Fuel Injection)_ on "small" single cylinder 2 stroke engine !

First, The "strato" term is obviously a "marketing name". Any two gaseous volumes not separated by some physical barrier will not stay "stratified" very long, less if pressures above atmospheric are involved. That is just the physical properties of gases. The key to the technology is get "fresh" air into the cylinder BEFORE the air/fuel mixture to push the exhaust out. There is some "stratification" of the air and air/fuel mixture in the transfer port but calling it "stratified" is kind of an exaggeration. _(Look up Honda CVCC technology or Ford PROCO and EcoBoost)_

Second, the current "leader" in DFI for 2 stroke is BRC/Evinrude with their ETEC technology. Back in the 90s, OMc worked with a German (Austrian?) company name Ficht to develop a direct injector for 2 stroke applications knowing that if only air came through the transfer port there would be less unburned fuel _(lower emissions and better fuel economy)_ going out the exhaust. OMC bought the patents from Ficht. OMC was bought by Bombardier _(now BRC)_. The first generation Ficht engine had more than their share of problems. BRC made many improvements to the injector design and the electronic controls and rename it ETEC. All 2 stroke Evinrude engines now have been using the ETEC DFI system for over 10 years now.

Now this where it get interesting. BRC wanted 100% of the Evinrude lineup to use ETEC, but it was just not cost effective ! First, their DFI injector is quite large compared to a typical gasoline injector. Being large, it is hard to package on a small 1 or 2 cylinder engine. Then of course there is the electronics and sensors. Consequently all "small" Evinrude engines are 4 stroke _(actually Tahatsu with white paint)._

So if "strato-charged" works why would you want EFI/DFI with all the extra weight and cost ? Both technologies use the same "technology" _(clear the cylinder with "fresh" air not air/fuel)_, they just do it differently _(as did Mercury's now discontinued OptiMax.) _ Glad to see small 2 stroke engine are "not dead yet !"


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## bwalker (Sep 19, 2015)

This is a good thread.

I believe the Strato charged tech is in its infancy and will be around for some time.


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## Rx7man (Sep 19, 2015)

It will get MORE popular, though the flavors of it may change a little as technology progresses.. EPA will force it to happen.


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