The Engine of Our Dreams Exists. It's a Clean, Powerful, Supercharged and Rotary Valved Two Stroke

The Engine of Our Dreams Exists. It's a Clean, Powerful, Supercharged and Rotary Valved Two Stroke

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How do you know an invention is genius? For me  it's that moment when I see it for the first time and I immediately think "hey why didn't  I think of this?" A genius invention seems very obvious and simple once you see it. And once  you see it you can't unsee it ever again And you also somehow can't figure out why it was ever  elusive, why didn't somebody just do it before? Today we're going to talk about just one such  Invention the RevForce engine from Alpha Otto Technologies Which is an ultra powerful, clean and  efficient two-stroke engine. And to understand how it works we first of course must understand  what makes a conventional two-stroke engine great and also what makes it not so great. You  see, a two-stroke engine is THE BEST ENGINE EVER!!! Okay, I'm going to have to stop this childish  display of whatever, because yes, two strokes are fun No doubt about that. But they also have to  burn oil by design and that means that they're

bad both for the environment as well as the people  that breathe in this KAPOW! There's no way that something that smells this good is bad for the environment Okay, that's enough of that Two-stroke D4A is a bit crazy so don't take him too seriously. That being said  he does have a point, and two-stroke engines are indeed very fun. They're very fun because they're  extremely power dense and they're capable of this very impressive power density because they use  both the area above and below the piston In a reciprocating piston engine one stroke equals 180°  of crankshaft rotation. And a four stroke requires four strokes to complete one full combustion  cycle. Going from top dead center to bottom dead center

we have our first stroke which is intake,  during which air and fuel enter the cylinder The piston then goes back up and compresses the air  fuel mixture which is our second stroke The air-fuel mixture is then combusted and pushes the  piston back down to bottom dead center which is our third stroke. And finally the piston goes  back up and pushes the exhaust gases out from the engine which is our final, fourth stroke.  But a two-stroke engine does all of this: intake compression combustion exhaust in half  the time of a four-stroke. And that's because it can do two things at once. As the two-stroke  piston moves up it creates a vacuum below it And so the air and fuel mixture enters through  the crankase and accumulates below the piston At the same time as the piston goes up it is also  compressing the air and fuel mixture already above it So it's actually doing intake and compression  at the same time. When the piston reaches top dead

center the air and fuel mixture gets ignited  and combustion pushes the piston down As the piston moves further down it uncovers the exhaust port and exhaust gases vacate the cylinder But at the same time as the piston moves further down it  pushes the air and fuel mixture already below it into the transfer port which it also uncovers as  it moves even further down. The fresh air and fuel enters above the piston ready to be compressed and  ignited again. In other words, everything happened within 360° of engine rotation. And every time the  piston is at top dead center combustion will occur In a four stroke, combustion only occurs every  other time the piston is at top dead center Twice the combustion events or power pulses  within the same period of time theoretically means twice the power. On top of this a two-stroke  doesn't need valves and valve springs and lifters

and rockers and cams and cam chains. It's far more  simple and lightweight than a four-stroke which is why it easily beats the four- stroke in terms  of power per kilogram or pound of engine mass Okay, if two strokes are more power dense then why  are four strokes the dominant mainstream engine powering the world? Well, the reason is that  a two-stroke engine as we just described it has three big disadvantages. Fuel inefficiency,  emissions unfriendliness and poor longevity If we have air and fuel both above and below the  piston, then that means that we cannot have a large quantity of engine oil lubricating the crankshaft  and connecting rod and cylinder and piston skirt If we did all that oil would be pushed through  the transfer port and it would end up above the piston where it would immediately kill any hopes  of combustion occurring. This is why a two-stroke is lubricated using only a minimal amount of oil  that is mixed with the fuel. Usually the ratio of

fuel to lubricating oil is around 50:1 in  a modern two-stroke. This reduced lubrication means that engine components simply can't last as  long. The fact that we have oil in the fuel means that oil will get inevitably burned together with  the fuel which of course leads to poor emissions The other reason we have poor emissions is that  the exhaust port of a two-stroke is always open So when the air and fuel mixture comes out of  the transfer port and goes above the piston and the piston continues moving up there  exists a period of time during which the air and fuel mixture is free to escape out the  exhaust port. And that's exactly what happens Some fresh unburned fuel always goes right out  the exhaust port before the piston moves further up and closes off this exit pathway. What we can do  is make funky exhaust chambers that push some of that air and fuel mixture back into the cylinder  using the power of sound, but even these are far from completely efficient, and some unburned  fuel will always escape. Of course spitting unburned fuel right out the exhaust leads to poor  fuel efficiency and a further worsening of the emissions So the two-stroke has a few problems.  Okay but we still want that power density!

Well, let's try to do something right here, right now.  Let's try to fix the problems of the two-stroke while keeping the power density. First up, let's get  rid of the transport completely. We want longevity And if we want longevity then we must have better  lubrication. If we get rid of the transfer port we can have oil below the piston lubricating  everything, and we won't need to mix oil into the fuel which means we are also improving emissions  because we won't be burning oil anymore Now, if we  remove the transfer port that also means that  we must not let air and fuel come through the crankase anymore, otherwise it will again end  up below the piston. So now the intake port

must also be relocated from the crankcase to the  cylinder. The final problem we need to fix is fresh fuel escaping out the exhaust port and ruining our  efficiency. So let's turn that into an exhaust port with an exhaust valve on top of the cylinder head,  just like on a four-stroke. So let's see how this engine would work. Let's imagine combustion just  occurred and the piston is going down Of course during combustion we keep the exhaust valve  closed and as the piston goes down torque is generated and the air and fuel mixture burns and  turns into exhaust gas. We open the exhaust valve and of course some of that pressurized exhaust gas  escapes until pressure in the chamber equalizes with outside atmospheric pressure. When pressure  equalizes we will still have a significant amount

of exhaust gas inside the cylinder. As the piston  keeps going down it uncovers the intake port and... a major problem in our design. Remember, the exhaust  gas still left in the cylinder is at atmospheric pressure The air and fuel that's supposed to  come into the cylinder is also at atmospheric pressure And that means that the air and fuel is  NOT coming into the cylinder. There's no vacuum

inside the cylinder nor is there anything to push  the air and fuel mixture into it which means that we are stuck. There's only one way to fix this.  Forced induction. We add a supercharger which pressurizes the intake air. As that air is now at a  pressure higher than atmospheric it will push the remaining exhaust gas out of the cylinder and fill  it with a fresh air and fuel charge. And what we have just done is create an existing engine design.  Engines with an anatomy very similar to this are known as two-stroke diesels, marine two-stroke  diesels. That's what's powering the tankers and

the container ships full of junk from Temu. It's  not a bad design, it definitely has its purpose but for us it's a mission failed because remember  at the beginning of this video we wanted to fix the problems of the two-stroke. Emissions, longevity  fuel inefficiency, while retaining power density This anatomy fixes the problems but it loses  the power density because now we have poppet valves poppet exhaust valves. And if we have that  we have cams and valve springs and rocker arms and cam gears and cam chains and weight weight weight. Which means power density goes out the window But even even if we somehow magically retain the  power density we lost something else that's very very important with this anatomy, and it is  the capacity to rev higher. Marine two-stroke

diesels they run at... wait for it... 60 to 120 RPM. That  makes your washing machine look like a Honda F20C They run at this very low RPM because number one  they're giant engines with very heavy pistons and rods and accelerating these components to high  RPM is simply impossible. But even if we had very small pistons and rods this engine could still  not rev high and it could not rev high because it cannot breathe fast enough. The higher the RPM  the smaller the time window to complete intake

exhaust and the other strokes. And in this  two-stroke anatomy, this distance from here to here The height of the intake port, that's all the  time we have in relation to the total stroke of the piston to get air in and exhaust out. Compare  it to a four stroke which has the entire stroke of the piston, the entire height of the cylinder, you  realize just how little time that is. And as RPM increases the time frame becomes even smaller.  So the only way for this engine to rev higher would be to somehow be capable of breathing  very very well, and a traditional poppet valve is simply unable to breathe that well because  by its design it's an obstruction to air flow The only way to get this engine to rev higher and  to breathe well enough is to use something like a rotary valve which has great airflow capacity.  So why don't we do that? Why don't we replace

the poppet exhaust valve with a rotary valve? And  what we have just done is created the RevForce engine Seems so obvious now right? That's what the  REV in RevForce actually stands for Rotary Exhaust Valve. Now, I have talked about rotary  valves on this channel before and as we know they are amazing at flowing massive amounts of air  very quickly. They also have a low number of moving parts They're simple but they have problems with  sealing combustion pressures. But here is where

the genius of the RevForce engine comes in. It  makes these sealing inefficiencies of rotary valves irrelevant while at the same time reaping  the benefits of the massive airflow capacity Now let's start from the moment when combustion  occurs and the piston starts descending from top dead center. Combustion pressure builds  drives the piston down and creates torque. When the piston reaches this point it uncovers the exhaust  port and as you can see by that time the rotary exhaust valve has also rotated into its fully open  position. The maximized opening means that a large amount of pressurized exhaust gas can freely and  quickly exit the cylinder. As the exit path is now much less obstructive it allows the pressure in  the cylinder to reach atmospheric faster than with a traditional poppet valve, leaving less gas in the  cylinder. As the piston continues down it uncovers

the intake port where we have supercharged  air which now starts entering the cylinder As you can see the rotary valve is still open and  so it allows the pressurized air to quickly push out the remaining exhaust gas out of the cylinder.  By the time the piston reaches bottom dead center and starts going upward the rotary valve is fully  closed. This is the point when we can inject our fuel using our injector in the intake port. As  the rotary valve is now fully closed it means that no fuel will be escaping out the exhaust  leading to greatly improved fuel efficiency As the piston continues going up it closes off  the intake port and starts compressing the air and fuel mixture during the entire remainder  of the stroke. Near TDC we fire our spark plug and combustion happens again restarting the entire  process. And here comes the genius part, as you can

see the rotary valve is never in direct contact  with combustion, and that means that it does not have the task of sealing off the extremely  high pressures of combustion. That is done entirely and effectively of course by the piston  rings. The only thing that a rotary exhaust valve seals off is air and fuel, the pressure of which  is much much lower than that of combustion which means that even a loose- fitting rotary exhaust  valve will be perfectly capable of preventing a measurable amount of fuel from going past it. So we  have zero issues with rotary valve sealing while at the same time allowing massive airflow capacity  for quick exhaust gas evacuation. Ultimately what we have here is a valved supercharged two-stroke  capable of high RPM operation. It's clean because it doesn't burn oil. It's efficient because it  doesn't spit unburned fuel out the exhaust

and it has good longevity because the entire rotating  assembly is conventionally lubricated by engine oil as in any four-stroke engine. Something else  that's interesting, is that as you can see we have an upper and a lower ring pack. The upper one  controls combustion and the lower one controls the oil And as you can see the lower ring pack never  goes above the intake and exhaust ports The ports  never see the oil. And that means that we have the  same oil consumption as in a four- stroke What's interesting is that despite this the crank case of  the RevForce is still equipped with reed valves As the piston goes up it creates a vacuum under  the ring pack which helps improve the sealing of the rings. And as the piston goes down it  pushes a certain amount of oil out the crank case through the reeds and into the engine's  semi dry sump system, which further reduces any possibility of oil getting into the combustion  chamber. So the RevForce engine is clean, efficient

and capable of high RPM operation but it's also  still power dense. Every stroke is still a power stroke and the engine is still lightweight and  simple like a two-stroke should be. But here's the best part, It's not just a bunch of theory  and CAD. It's already a living, breathing engine

Now before you type in "swap it into a Miata" let  me stop you right there because no, you cannot go out and buy a RevForce engine. It is not a  production engine just yet. It is at this stage what I would call a mature prototype. But as I said  many times on this channel it's precisely this stage from prototype to production that requires  the greatest investment of all kinds of resources But because we have a living, breathing prototype  we can talk something very important: Numbers Currently the RevForce engine is an inline  two-cylinder liquid-cooled two-stroke It has a displacement of 578cc and it weighs just a  hair under 50 kg so you can lift it up with your own two hands, but it makes 220 horsepower.  It has a peak torque output of 176.26 Nm

It has a brake mean effective pressure of  25 bar. It is very compact as you can see from the dimensions. It has a static  compression ratio of 10:1 It has an expected redline of 8,000 RPM, currently tested and validated up to 7,000 RPM and it has a brake specific fuel consumption  at peak power of 221 gram per kilowatt hour I believe that is everything. Did I miss something?  It is oversquare by design at this stage and yeah, that's everything. So as you can see, some  very very impressive numbers at this prototype stage But numbers are still not the end of the  story. Not the only trick up the sleeve of this

amazing engine. Because the rotary exhaust valve  is electronically controlled, so you can change the timing of this valve on the fly, and we have  a supercharger, we can manipulate the pressure of that as well, and that means that we have full  control of the dynamic compression ratio of this engine on the fly. And this means that the engine  is multi-fuel capable. It can run on gasoline It can run on heavy fuels, it can run on CNG, it can  run on hydrogen, you name it. But it cannot just run all of these different fuels, it can switch  from one fuel to the other on the fly. Have a listen Okay, so it's too good to be true? Drawbacks?  There's got to be some sort of fatal flaw right? Well, to be honest right now from the information  that I have I cannot find a serious fault on this engine It has two ring packs so a bit more  friction there but the rotary valve makes up for it because it is very low friction and it has less  friction than a conventional poppet valvetrain We also have the benefit of not needing  complicated exhaust shapes like conventional two-strokes because we have a rotary exhaust valve.  You could say that, okay, it needs a supercharger to run but naturally aspirated engines are kind  of dead, so whatever you compare it to nowadays if it's relevant and modern it probably has  forced induction. Pretty much everything has

a turbo nowadays. So even if it has a supercharger,  not really a, you know, some sort of major flaw So it is still much more power dense than  your typical four- stroke. It is more lightweight and it's not dirty. So yeah, I've been reviewing  novel engine designs on this channel for a pretty

long time and to be honest this is one of my  absolute favorites so far because it sort of tries to give the two-stroke engine a future. And  as you've probably noticed I'm kind of partial to two-strokes. I love them, because the first time I  experienced the power delivery of a two-stroke I was hooked. It's something you really can't put  into words. You got to experience it yourself to see what I'm talking about. Anyone who has knows  what I'm talking about and I think the anatomy of

a two-stroke engine is genius, and I think that it  deserves a future and should not be discarded And that's what the Rev Force engine does and what  I like about it is that it does it in a not pipedreamy way It uses conventional components,  stuff that can be easily replicated and made It doesn't need some sort of weird novel cutting-edge  anatomy that would require millions upon millions upon millions just to create a, I don't know,  a proof of concept, which is why I really hope that this engine does get to see production. Now  the project has been currently up to this stage financed exclusively by a small research grant  and out of pocket by the inventors of the engine John Krzeminski and David Dusseau. But bringing it to  the final stage, to mass production is of course impossible without a further much much larger  investment. So in case you're somebody who's

a bit of a petrolhead, maybe even a two stroke enthusiast  and you're at the same time sitting at the helm of a, I don't know, a giant hedge fund or  obscene personal wealth or something along those lines then I suggest you go down to the  video description or the pinned comment you check out Alpha Otto Technologies, get in touch  with them and you strike some sort of mutually beneficial deal and we all get access to this fun  fun engine. Yeah I really hope that happens. I hope you enjoyed this one, that's pretty much it for today,  it was a very fun one for me. Yeah, as always thanks a lot for watching and I'll be seeing you  soon with more fun and useful stuff on the D4A channel

2025-06-01 10:00

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