what is "strato charged"

[windthrown]

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.

 

[THALL10326]

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.

 

[PES+]

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.

 

[PES+]

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

 

[THALL10326]

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..

 

[windthrown]

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.

 

[windthrown]

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).

 

[PES+]

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.

 

[THALL10326]

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.

 

[PES+]

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.

 

[THALL10326]

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.

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

 

[windthrown]

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).

 

[Lakeside53]

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...

 

[PES+]

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.

 

[Lakeside53]

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

 

[PES+]

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

 

[Lakeside53]

TS700/800..

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

 

[Lakeside53]

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:

 

[PES+]

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?

 

[PES+]

No kickin in the Shinds now