The Scotch Yoke Engine is Alive! 8 Pistons, 4 Rods
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Published 2023-05-28
Last week I made a video explaining scotch yoke engines and I did a bit of an update on Alfadan, the company that is planning to release a scotch yoke inline four engine in the future.
But after making the video I was still thinking a bit about the scotch yoke design and it’s related balance so I decided to do some research. Now on the Wikipedia page for scotch yoke I found this interesting chunk of text that mentions the Bourke engine as well hot air and steam engines, that’s all pretty well known stuff. But what I never heard about before is this, something called the sytech engine. And as you can see this is not hyperlinked…there’s no wiki page on sytech engine.
So I google sytech engine and eventually ended up on this page right here, and boy was I surprised. Look! This is not a 3d render. This is a photo of an actual engine. This thing is real. And it’s incredibly interesting. Now before we go any further, I just want to say that this is not in any way a sponsored video. I have not even gotten in touch with this company. I’m not promoting anything. This is just me exploring and sharing something really really interesting that I found purely by chance. And as you will see I didn't need to get in touch with these guys because all the information you could possibly want, they have already published it, they have done all the testing, this is pretty much a production ready engine. Honestly this whole page really made my day as it’s been a long time that I stumbled onto something this new and this interesting. Look, they even made a flat 8-cylinder non-boxer scotch yoke engine
And as you can see the engine in this video is a scotch yoke flat four non-boxer opposed piston engine, which interestingly enough is a completely different approach to Alfadan which aims to make a inline four scotch yoke engine.
Now this is extremely interesting because a flat four non-boxer engine is a stupid idea from the perspective of engine balance. Now as you have seen from my previous video the scotch yoke design completely eliminates secondary balance issues which means that a four cylinder now becomes the lowest number of cylinder needed to achieve perfect balance without balance shafts, whereas with a conventional crank and rod the lowest number of cylinders needed to achieve this is 6.
A scotch yoke inline four has perfect primary and secondary balance. But a flat four non-boxer does not, regardless if it’s scotch yoke or not.
The four cylinder scotch yoke engine is supposed to be a range extender and when you take this into account the flat four non-boxer configuration really starts making sense because this is overall the most compact possible four cylinder engine configuration.
And if we scroll down to the bottom of the website we can find three very interesting PDFs. If we open the first one we will find an incredible wealth of data among which is also this page. And here you can see that a very compact flat four engine enables placement almost anywhere in the car or in the words of sytech “the engine can be placed in areas of the vehicle that other engines cannot”.
As you can see a flat four scotch yoke beats other four cylinders in terms of size. In the boxer each rod gets its own crankpin but in the flat engine we put two rods on one crank pin. This is why a flat non-boxer engine is noticeably shorter than a flat boxer engine. But the scotch yoke design takes this a step further. In conventional flat non boxer we have to stack the rods side by side but in a scotch yoke the engine is constructed in such a way that the pistons are perfectly opposed which means that a scotch yoke flat four can be shorter than any conventional four cylinder engine configuration.
Another interesting thing to observe Is that this is a modular engine. According to this Sytech is planning to offer a 2 a 4 and an 8 cylinder version. Modularity means high parts commonality and this means reduced costs and increased market coverage. The 2 cylinder version can for example be used for home generators, the four cylinder is a great range extender whereas the 8 cylinder is likely intended for performance oriented combustion only or hybrid vehicles. I have to say that the 8 cylinder is extremely interesting as this is a true engine-head configuration. I’m pretty sure they went for 8 cylinders because this configuration enables perfect balance out of the box without balancing shafts. Judging from the engine codes the 8 cylinder is a 3.0 liter engine and in turbocharged form it churns out 335 horsepower which isn’t especially impressive by modern standards but it’s still definitely respectable.
A special thank you to my patrons:
Daniel
Pepe
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Peter Della Flora
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#d4a #scotchyoke
All Comments (21)
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Some times people need to relax their expectation of every idea needing to become a commercial success to be considered anything but a failure or scam. Whether it becomes a relavant piece of technology going forward we should all just enjoy this process or seeing and working through this engineering challenges
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This guy has unlocked the ability to love engines more than most guys love women.
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Huge props to the company for posting their data.
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I've studied engine balance for over a decade. You consistently break it down in a way I've never been able to translate to others.
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Thank you. As someone who had to leave behind mechanical engineering to pursue IT, your amazing channel helps me stay up to date with the field I truly love.
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At ALFADAN we looked at this same design given that the owner personally owned the only Bourke 400 ever built. The Bourke 400 was this same flat 4 design but in a two stroke, 400 cubic inch version. The ALFADAN outboard project required a 7.5 Liter displacement and the i4 was the best platform that gave us the smallest engine possible. Although our design ideas originated from the Scotch Yoke we had to take a completely different design approach due the weak lower end of the rod as described in this video. In summary, the ALFADAN design achieves large displacement in a small engine package operating under perfect primary and secondary balance without the added friction and complexity of balance shafts. Great video D4A!
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Dude your videos are LITERALLY the most detailed and informative videos on YouTube!! And you’re the only one who can keep me completely attentive even with A.D.D. 🤣😂
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I am a private pilot that owns a single opposing piston engine airplane in a land configuration, My airplane is a 1949 North American, Ryan Navion which is powered by a Teledyne Continental E-225-4 over head valve opposing 6 cylinder engine with a 5in bore and a 4in stroke, which means that this engine is not a boxer. This engine has 470 cubic in displacement and gives 225 HP at 2,600 RPM. The engine in my airplane works well and is proven dependable after decades or application. The continental engine company has the only engine that has a 8 cylinder version of this design, which supply's an impressive 400 HP and to my knowledge is only in one airplane and that is a Piper Comanche 400. All that being said, this Scotch Yoke engine would be a great engine for the aviation industry. I would love to see this happen. So thank you for your video and update on a modern tech improvement in my opinion.
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Looks like it could drop into a Subaru :D
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I just love your expressions. you actually really glow up/ geek out over it. it's fascinating
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Been watching this channel for some time now, going from strength to strength, focusing on FACTS, rather than hype. There's an engineer in there somewhere, directing the excelelnce of the information and the video quality....Congratulations, keep this up! A credit to YT.
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Seeing your happiness and enthusiasm is what makes the heart of this channel beat. We feel just as enthusiastic as you about seeing new engine technology become available and the exciting possibilities of adding more power! Your smile at the end of the video really summed up why I started watching this channel.
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The grin on your face shows how excited your are and is so fun to watch. The ICE is not dead, and your enthusiasm for it brings a smile to my face too. I bet when you discovered this, it even exceeded the joy of your first motorcycle ride.
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I love how excited you were scrolling through all the data on the website, great video!
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I think you might have missed an aspect of the cylinder wall forces @12:30. In the boxer configuration, the piston leaning force during the compression stroke is shared with the non-combustion cylinder through the single connecting rod. This should roughly half the twisting load between the cylinders and spread the wear from this friction to both sides of the cylinder. This could reduce overall wear due to these forces. Great video!
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I love this guy's zeal and understanding of engines and engineering. He singlehandedly has caused me to look forward to new technology in the world of engines. The way he breaks down the science and evolution is incredible. Thank you so much for sharing your knowledge, I am in your debt. Another great video.
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The flat non-boxer addresses basically all of the flaws mentioned in the first video. Bravo to the Sytech engineers. Let's hope Porsche and Subaru can adopt this configuration ASAP.
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The bearing surface is probably made of a relatively soft metal, since it appears to be made for "easy" replacement
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Your honesty and interest always shine through, thank you.
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Also YOU! YOU ARE THE BEST GUY ON THE INTERNET! I have learned more from your videos then any other source or any kinda experience! Keep doing your thing!
