A video that can help you better understand engine balance and the difference between flat boxer and flat nonboxer engines:    • Deep Dive: Inline 4 vs. V4 vs. Boxer ...  

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 8cylinder nonboxer scotch yoke engine

And as you can see the engine in this video is a scotch yoke flat four nonboxer 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 nonboxer 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 nonboxer 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 nonboxer 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 nonboxer 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 enginehead 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.


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