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Reed Valves-the modern ticket to 2-stroke power

sean donato

sean donato

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True the Math & theories around this stuff has been around a long time. I would say his solutions are unique to maximize the implementation of those numbers, therefore innovative. I'm sure there others but I would be interested for you to show me another more innovative than his motor or even a channel that has taken the math and put it into practice at the level he has out side the well funded factory operations as Yamaha was and KTM, Husqvarna, and Stihl. That is what "pushing the boundaries" means :) And he shares with humility. There is this guy who's putting forced induction ideas on rc motors.... After spending my first career in "bleeding" edge technology, was always interested in the personal dynamics of the true innovators. The "ridged" this is the way it is types rarely innovated anything always going back to the established for security. Often that "front" is as much about convincing themselves of their theory & knowledge base as anything. The more secure and not concerned about the reaction from others types usually were "free" to explore concepts or push boundaries considered. This dude is entertaining as he has that spirit. We have a few here as well. Four come to mind that frequent here, two are "established" builders... ( and in my most humble opinion one is a true innovator, although he might not see it that way, my opinion )

And I think it's cool to GET the discussion going relative to things like reed and rotary valves, thanks to the OP. Internal combustion engines did go through huge changes during the 1930-1950. The history of the "Miller" race engines and some of the early two strokes is really interesting. Loved learning about the "sleeve valve" aircraft engine. By the 1970's the issue changed from how to get power to how to get rid of heat on the dirt bikes so MORE of that power could be had reliably. And to me that is the 800lb gorilla in the "saw" world because of space and weight constraints. Why the new designs from Husqvarna and Stihl are..... innovative in using that heat in a useful way. Kind of hard to blend the Yamaha road racing 125 cylinder , water cooling, and pipe to a saw that has to be carried around. Maybe some of the more knowledgeable folks might want to go into why those transfers are routed as they are on the new saws.

( My opinion on reed valves is they are a great way to build a motor with a larger range of useful RPM's with good peak power vs. being all about "peak" power. Outboards come to mind as they are essentially "one gear" machines, so have to both get out of the "hole" to pit a boat on plane, but then have the power to get to higher RPM's for speed. Don't know of many piston port outboards when two strokes were the rule vs. four strokes, had reed valves in the 1940's and 1950's on outboards. )
If your referring to the rb innovations supercharger, they simply dont work. Well I guess that's a misnomer, they work at WOT at peak rpm, but not well, and fuel consumption is through the roof. Most of the extra fuel air mix is lost from poor timing numbers, not designed for a forced induction engine, as with most 2 strokes to get full benefits of forced induction some sort if exhaust valving should be implemented, and or direct injection technology to mitigate fuel leaving the cylinder with the bypassed air. Ski doo has just released an engine that is turbocharged, but I dont know how one would make the tech used small enough, and light enough for saw use.
Another point, although I find his process fascinating, he is working around his own paycheck and unregulated by any governmental entity. These are important factors in the implementation, and advancement of any engine.
The secondary issue as I see it, using the loop scavenging method, weather piston ported or reed valve, you still only get a narrow window of peak efficiency in a 2 stroke. This has always been a constant, even with reed valves it's not much better over piston port or rotary port engines. This can be seen in many examples from small nitro rc engines, to larger reed case engine. So really we should be looking to achieve a few different things, a wider useful power range, and higher efficiency at a wider rpm range.
 
weimedog

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If your referring to the rb innovations supercharger, they simply dont work. Well I guess that's a misnomer, they work at WOT at peak rpm, but not well, and fuel consumption is through the roof. Most of the extra fuel air mix is lost from poor timing numbers, not designed for a forced induction engine, as with most 2 strokes to get full benefits of forced induction some sort if exhaust valving should be implemented, and or direct injection technology to mitigate fuel leaving the cylinder with the bypassed air. Ski doo has just released an engine that is turbocharged, but I dont know how one would make the tech used small enough, and light enough for saw use.
Another point, although I find his process fascinating, he is working around his own paycheck and unregulated by any governmental entity. These are important factors in the implementation, and advancement of any engine.
The secondary issue as I see it, using the loop scavenging method, weather piston ported or reed valve, you still only get a narrow window of peak efficiency in a 2 stroke. This has always been a constant, even with reed valves it's not much better over piston port or rotary port engines. This can be seen in many examples from small nitro rc engines, to larger reed case engine. So really we should be looking to achieve a few different things, a wider useful power range, and higher efficiency at a wider rpm range.
I have no idea what your reference is on supercharging, that's all u not me, my reference was a some dude wants to play that game on YouTube for those interested in a freak show. Have no opinion one way or the other except I would never assume a thing, part of the creative & innovative lesson learned over the years. And as far as two strokes are concerned, they have been both supercharged and turbo charged for decades...... Detroit Diesels and the EMD variants used in Tug Boats and Locomotives have since the beginning. The forced induction is analogues to primary compression. I'm sure a lot here have experienced them and had to use those little Tee shaped "picks" to set the injectors. As far as for small single cylinder engines where the "primary" compression is about the crank case and downward movement of the piston, from my perspective not practical for a lot of reasons more related to the applications than anything else. A LOT of this BS online is answering questions no one asked.

I do agree on my favorite innovator. Although while his "innovation" isn't in changing the math, its in building clever devices to maximize power based on that math.

Certainly agree with your analysis on loop scavenging , It is the age old discussion for as long as I can remember, These things use a piston that cycles as a pump to move compressible fluids or gasses through passages. They are gas "springs" with complex harmonics, And the timing has everything to do with using the changing pressures at the right time to move enough mass to matter. Nothing about a two stroke is "steady state" therefor the concept of "tuning" actually means something. Reed valves have been around since the beginning on these little two strokes. Piston ports by their very nature will work over a relatively narrow RPM range, but when everything is in tune will make a lot of power. Pretty much common sense and my bet is everyone who would engage with a discussion like this here understands that.

So once we get past the standard stuff... WHO is going to take on the new cylinder designs? I'm curious on the thoughts, tried to drop a hint to kick it off as to why they do that. What is the physics behind that design? And does it work is my question. They sure run strong!
 
sean donato

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I'll assume by your post were not talking about the same company on the rc forced induction and leave it at that.
I was a heavy duty diesel mechanic for years. I am very familiar with detroit and EMD, they use the uniflow principal for scavenging, have valves, and a wet sump. Neither will even start without the blowers. Totally different theory of operation from what 2 strokes were discussing.

Being into 1/5 scale rc, there has always been the premise that a reed case engine will have a broader power curve, this isnt necessarily true. First if were talking about taking the same top end and essentially swapping cases out then they will run pretty close to the same. They key in the reed case is the extra porting allowed and the chance for a more complete fill of the crankcase. Expansion chamber design also plays a big role in the powerband of both reed and piston port engines, actually I think you can include rotary valve induction as well, although it has it's short comings, like the piston port engine.
If were keeping the topic of conversation strictly to small power equipment, specifically saws, then a decently designed reed cage would eat up considerable real estate in the frame of the saw. Even on our small 32/34 cc rc engines that have purpose built reed cases, moves the carburetor out approximately an inch to an inch and a half, and makes the case a good bit bulkier on the carb side of the engine.

At any rate, with all engines were looking to do something, have a certain amount of power, in a certain sized package. So to converse properly I think we need some basic standards by which to discuss. If were talking theory I dont really have much interest as we have the technology to make a very powerful 2 stroke currently.
 
bwalker

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If your referring to the rb innovations supercharger, they simply dont work. Well I guess that's a misnomer, they work at WOT at peak rpm, but not well, and fuel consumption is through the roof. Most of the extra fuel air mix is lost from poor timing numbers, not designed for a forced induction engine, as with most 2 strokes to get full benefits of forced induction some sort if exhaust valving should be implemented, and or direct injection technology to mitigate fuel leaving the cylinder with the bypassed air. Ski doo has just released an engine that is turbocharged, but I dont know how one would make the tech used small enough, and light enough for saw use.
Another point, although I find his process fascinating, he is working around his own paycheck and unregulated by any governmental entity. These are important factors in the implementation, and advancement of any engine.
The secondary issue as I see it, using the loop scavenging method, weather piston ported or reed valve, you still only get a narrow window of peak efficiency in a 2 stroke. This has always been a constant, even with reed valves it's not much better over piston port or rotary port engines. This can be seen in many examples from small nitro rc engines, to larger reed case engine. So really we should be looking to achieve a few different things, a wider useful power range, and higher efficiency at a wider rpm range.
Actually modern two strokes with things like power valves, 3D ignitions and DI have pretty broad power curves.
An old cylinder Reed, iron sleeved, exhaust valves'less cr500 has a pretty broad power band as well.
 
sean donato

sean donato

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Actually modern two strokes with things like power valves, 3D ignitions and DI have pretty broad power curves.
An old cylinder Reed, iron sleeved, exhaust valves'less cr500 has a pretty broad power band as well.
Is that the topic then? Like I said it's a moot conversation if we can throw current tech at it to make it work better. Variable exhaust ports, and direct injection allowed all that. Carbed not so much, at least not without the sacrifice of something. Usually fuel economy, which was always unacceptable. Also owning a 96 cr500. Its power band was hugely dependent on what pipe you ran. A pipe that gave the best all around powered suffered down low and up high. Depending on where we were riding we'd swap pipes out to get the power curve where we thought we needed it. Now thays not saying it dodnt have a good power curve, but it's still peaky compared to a 4 stroke engine.
 
bwalker

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Is that the topic then? Like I said it's a moot conversation if we can throw current tech at it to make it work better. Variable exhaust ports, and direct injection allowed all that. Carbed not so much, at least not without the sacrifice of something. Usually fuel economy, which was always unacceptable. Also owning a 96 cr500. Its power band was hugely dependent on what pipe you ran. A pipe that gave the best all around powered suffered down low and up high. Depending on where we were riding we'd swap pipes out to get the power curve where we thought we needed it. Now thays not saying it dodnt have a good power curve, but it's still peaky compared to a 4 stroke engine.
A FMF is the best all around pipe I've tested.
 
bwalker

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In regards to 4 strokes. A 450 will never have the snot of a well setup 500. On top of that they are very expensive to keep running.
 
weimedog

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Actually modern two strokes with things like power valves, 3D ignitions and DI have pretty broad power curves.
An old cylinder Reed, iron sleeved, exhaust valves'less cr500 has a pretty broad power band as well.
I raced those old monsters from 1985 until 1990. The 86 was a beast, and they started "softening" them up after to have a nicer to ride power band. SO much displacement, a lot of power to play with. Problem was I would have slower lap times on the open bikes than the 250's, and even the 125's at times. Another discussion :)
 
weimedog

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An English version of our "in house" diesel mechanic, love the comments on this one as well. And to those interested in details, the SECOND picture in his "book" is Detroit, The Third? I'll let u guess.

 
weimedog

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AND for a little "two stroke" history....Fairbank Morse was a pioneer in opposed piston two strokes....and they were turbocharged or supercharged. Many a submarine were pushed around with 8 or 10 cylinder FM's. Some Locomotives too back in the late 1940's into the early 60's. Point is like Detroit using external pressure vs. crank case pressure is common place with two stroke design. External Pressurizing with turbo's and superchargers the little ones where the crank case is the primary compression or pump isn't wide spread as of NOW :) How does all this relate to the original OP and reed valves? My point early on is never say "never" to concepts. I would speculate that in the spirit of the OP, Rather than be a wet blanket I would ask, is it possible a clever use of reed valves allows concepts out side the rigid box of convention? I have no Idea, but rather than "assume" I have that answer based on "convention", I'll assume over time clever folks will answer that question...and with an open mind allow pushing all boundaries. And also like I said , " from my perspective not practical for a lot of reasons more related to the applications than anything else. A LOT of this BS online is answering questions no one asked." kind of still is my mind set on the concept as we get enough power for spinning chains right now.
 
sean donato

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For the love of christ. Your talking about 2 different designs, and I already sited ski doo as having a turboed two stroke. If you actually look into the tech behind a properly turbo charged loop scavenged 2 stroke you will see there a lot more going on then just a reed valve. As a matter of fact there are at least 4 valve devises being used by ski doo that they have showed thus far. Not to mention 2 different fuel injection systems, and the bearings are direct lube like a 4 stroke. Now what's the conversation about? A loop scavenged engine or uniflow engine? How much tech can we throw at it? ( I believe I also stated that we had the tech to do it). You seem to want to keep the simplicity of an ancient design and not understand its limitations. People have been trying to effectively use forced induction for years and have typically failed miserably, and at best case scenario have had a very picky engine that was always on the verge of a meltdown, as can be seen on older snowmobiles and peoples attempts to turbo them. No it's not a new concept you just dont seem to understand the different operating principles of 2 cycle engines. The funny part is you remind me of someone I just recently had this exact discussion with, he used the same videos you did. And once pinpointed out the same flawed logic of the challenges of forced induction on a loop scavenged engine, and his primary examples of the detroit and EMD were uniflow scavenging. He left the other forum. Theres a reason the world went 4 stroke mate. Once you gussy a 2 stroke up enough to handle an actual turbo system, be reliable and not hog fuel, you have all the major components of a 4 stroke and non of the advantages of one.
 
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