60 years ago I worked on the Foden 6 cylinder 2 stroke marine diesel engine. It was very similar to this concept, using a supercharger and exhaust valve. No reed valve needed. The exhaust valve operated on the kadenacy system which allowed the valve to stay fully open longer for better scavenging. The high profile cam gave the valve a snap shut operation. It was the smoothest running engine I ever experienced.

I like that Mazda is willing to walk a different path to other companies.

Love how Mazda is involved in so many diverse technologies and are trying to reinvent the 2 stroke!

It's amazing that Mazda created a backwards spinning supercharger!

At 7:30 time mark the video states that in a normal 4 stroke engine the camshaft rotates 360 degrees for every 1/2 rotation of the crankshaft. This is exactly the opposite of what happens. The camshaft in a traditional 4 stroke rotates at 50 percent of crankshaft speed. Using the same poorly described action as the video, the correct description would be, the crankshaft rotates 360 degrees for every 1/2 rotation of the camshaft.

The longest production engine ever was a two stroke diesel with a crankcase and an oil pan(crazy, right?) It is the 71 series detroit, made between 1932 and 1994. Because a blower was mandatory for the engine to run, the standard engine-with-blower configuration was considered naturally aspirated, with forced-induction classification only given to engines equipped with the blower AND 1 or 2 turbos. The series classification indicates the displacement of each cylinder in cubic inches(ei 53 series, 71 series, 95 series, etc) meaning that to find the displacement you multiply the number of cylinders by the series classification (8v71 -> 8*71=568in^3) truly the greatest engine of its time, it’s fully mechanical, and can be gravity fed if necessary, with no true requirement for pumps(high or low pressure). They didn’t make very much power, they weren’t very fuel-efficient, they leaked plenty of oil, and they were extremely loud earning them the nickname “screamin jimmy”, but dammit they were probably the most reliable engine of the century, alongside the 6BT.

An interesting phenomena to observe, the way gas engines keep edging ever closer to basically being diesel engines but with a different refinement of crude.

I had that idea over 3 decades ago. but at that time no one was even remotely intersted in two stroke technology. I SERIOUSLY hope that Mazda, and then who knows who else will bring back the two stroke. can you tell that I am a two stroke enthusiast!?

Truly amazing how well these new engines work in CAD.

Nothing new here, it’s been know for a century that adding a supercharger means crankcase scavenging isn’t required, while poppet valves have also been used on certain 2 strokes for a century too. Look at 2 stroke aero engines for some examples

I've known how a 2 stroke engine works for 30+ years without actually knowing how it works. That is the best description I've ever seen/heard. Thanks.

A company called Orbital from Australia spent over a decade trying to make direct-injection 2-stroke engines work in outboards and cars. The final nail in the coffin was that they couldn't meet the emission standards after 100K miles.

Despite popular belief two strokes don't rev high, for any given engine size they often rev lower that four strokes. They just sound like it because they fire twice as often as a four stroke.

1n 1978 me and some friends put a Shorrock blower on a Kawasaki KZ900 engine. it had too high of a compression ratio to really use much boost effectively. So we changed sprockets and made it's dual overhead cams turn 1-1 with the crankshaft. Started right up using a Weber carb in draw-through mode. Didn't like to idle down or run slow. Made great drag strip power but longer runs made it overheat. Fuel consumption was ridiculous but we didn't try to measure it.

This sounds really practical. What's lost in horsepower due to lower RPMs should be easily made up in the torque produced with power on every stroke. That should be very noticeable at low RPMs. One of the features of electric motors is the immediate torque when you step on the accelerator pedal. Having a 15:1 compression ratio that can be maintained at low RPMs should deliver that same kind of oomph.

the simplicity of a 2-stroke engine and the fact that you can rebuild a top end sub 1 hour is what makes them incredible, not sure how I feel about complicating the design further.

Both 2 stroke blown motor animations are running in reverse 😂😂😂

10:53 : "given that springs ideally work in revolutions below 8000" Honda: *Nervous laughter*

Somewhat simple, yet totally brilliant design. I love engineers that come up with great stuff like this, and love the companies that support them.

I'd like to see their CFD around their valves and in the cylinders. I would think the cylinders would foul much quicker than current solutions. It would be complicated but it'd almost make more sense to have the intake and exhaust valves be concentric rings with the intake being near the cylinder wall and exhaust being somewhat central. Make them flextures to maintain strength.

I love V6 and V8 two stroke sound. Evinrude handed me my first opportunity to hear a two stroke V8 in 1985. Very fast on the back of a boat.

Nice! You should have also mentioned mixture loss during scavenging at 2-stroke engine. Overheating issue can be significant. 4-stroke is good, because oil temperature on the cylinder wall does not exceed 120°C not to burn oil.

Great video thank you. Around the 7 minute mark you state that in a 4 stroke engine the camshaft rotates 360 degrees for every half a rotation of the crankshaft. It's the other way around.

Supercharged 2 stroke diesel. I designed one as part of my dissertation in 2003. However, I withdrew it because I didn't want the university to own the idea. I then spent 20 years bankrupt and floundering whilst I try to develop the idea on my own. Now optimise the torque curve to a hyper efficient narrow band, and use it to charge full electric transmission. Similar to an old Kawasaki train, except with battery storage.

The start of an exhaust sound in any internal combustion engine starts at the exhaust valve or port. The quick opening square edge exhaust port, in a two stroke, gives them their distinct sound venue, add the expansion chamber with its reverse cone and stinger which add to the high RPM Shriek. A poppet valve, Otis cycle or Miller cycle engine has a slower opening round exhaust area that is shrouded by the center valve. These motors there, pop, pop, pop, noise. Just a few small things that influence exhaust noise.

This idea was proposed a long time ago. An article showed a conventional DOHC engine with different camshaft gearing 1:1. Complained that at 4,000 rpm the valves were operating at the frequency of 8,000, if it were a 4-storke. I immediately thought that if the cam lobes on each cyl were offset 180 degrees, and only 2 valves opened on each stroke, that would solve the problem. Now the flow would be halved, but there is a blower to scavenge.

I came up with this idea in 1976 as a teenager and drew it on a piece of notebook paper. I eventually sent a copy of this idea to a company for evaluation.

Having intake valves too is pretty novel. I worked on 2 stroke diesels for a long time which had supercharger and turbo, with exhaust valves. But intake too, and with petrol? Very intrigued.

great video with excellent animations. Electric motors are 90% efficient. Overall system efficiency including battery charge/ discharge and control electronics is 80%. Achieving 50% thermal efficiency in ICE is tremendous. Standard passenger cars are in the 20% range to keep emissions in check. These new 2 stroke engines would best be for a charging system in a hybrid BEV. By adding additional cylinders (total of 3) would theoretically balance out the vibration along with some fine balance tuning.

At the 7:20 mark you state that in a 4 stroke engine the camshaft rotates 360 degrees in half a crankshaft rotation. That's backwards, that would have the camshaft running twice the crankshaft speed and in fact the camshaft rotates at half the crankshaft speed.

Superb video! The graphics have really helped me understand these types of engines a lot better, great commentary too. I have aphantasia (no mental imagery) so the clear graphics were immensely useful. New sub here!

I designed a 2 stroke gas engine years ago. We use the 360 degrees of crank rotation differently and avoid contamination of un-scavenged exhaust left in cylinder. We used a belt driven compressor setup to suck, not blow. The negative pressure in exhaust manifold pulled out exhaust gasses very quickly. We used a compound forced induction with twin turbos feed into the supercharger. Also, we used short stroke and 6,000 RPM was achievable. On paper that is same as 4 stroke running 12,000 RPM. But 2 stroke is slightly less efficient than 4 stroke due to less time for almost overlapping intake and exhaust cycles. Un-scavenged exhaust led to over heating and less combustion flame propagation. In it's final configuration, we ended up with a radical 12 cylinder flat engine (similar to 2 flat six cylinder engines for perfect primary and secondary balance) with 2 crankshafts on end and opposing pistons sharing 1 common head / combustion chamber in middle, with variable chamber volume. We could increase combustion chamber 1X - 5X.This allowed for high CR (1X) under low / no boost, then low CR (5X) under high boost. We were making 2,500 HP - 5,000 HP. The magic is in the special head and crankshaft. Heads have 4 valves for intake and 4 valves for exhaust. Intake ports are on top of head and exhaust on bottom perpendicular to piston. Crankshafts can more up and down to increase or decrease compression ratios.

Nice animation, but you have the blower turning in the opposite direction. Air moves around the outside of the lobes, not thru the middle. The Detroit diesel mentioned below was considered naturally aspirated because the exhaust valves opening overlapped with the intake ports briefly for air flow thru the cylinder. They had to have blowers to start, but once running, turbos would relieve the power draw of the blower (about 25% of engine horse power) giving the engine more power and better fuel economy.

Amazing video. I'm a mechanical engineer and I wish they had your video 15 years ago to lecture about engine specs when teaching thermodynamics cycles theory

Remember reading about this concept in a Hotrod magazine in the 70s sometime being researched in Australia by Ford I believe. Always assumed that is how they came up with direct injection used on ecoboost motors.

With DI and integrated EGR, it'll be interesting to see how long the valves and seats last before they need decoking. We already see that in contemporary four strokes, and those of us who know about old two strokes know how bad they were for fouling plugs, never mind coking up everything around the combustion chamber. I kinda hope Mazda can pull it off: for one, an unconventional Mazda engine that *doesn't* burn oil; and for another, many companies (Lotus and Ricardo Engineering spring to mind) have failed to get it right. It was assumed then (in the 1990s) that better injection control would be the answer. Maybe this is it...?

Sounds promising, but we will see if there will be any issues with the engine and if there will be enough momentum to push another ICE revolution. I am all for keeping alive the spirit of ICE and pure mechanical/analog feel of the cars.

There is also a small amount of power loss, while the exhaust ports are opening before the detonation can fully push down the piston. Of course this and the overlap between the valve openings are needed for this concept to work. I'm really looking forward to see this in action!

Just found this channel. Excellent graphics and explanation!

@FT - Leave it to Mazda to ride the cutting edges. This is incredible technology. And this would seem to require technicians learn an entire new regime. K, redit - I had to return - (1) Is that a fuel return line? It looks like there's a heat exchanger to keep gas tank temps low(?) (2) With no port injection (and burning diesel?) it's going to be susceptible to carbon buildup on the valves, which would be critical as valve seat design is integral to the flow of intake and exhaust with both valves open. And low RPM, but heavy? Well, trucks and ships would be a good fit, no? As I said, it's interesting technology, and life is about learning; bring it on.

Sound wise, with more pulses per rpm, I would expect a more rotary/smoother sound. Additionally the sound may be deeper than similarly sized conventional engines

Thanks for sharing this information in away that non-engine techies can understand it. I think it's exciting news if we're going to continue to have gasoline engines while others - electric, hydrogen, water (?) are trying to expand their brands to become a viable replacement for the typical 4 stroke gasoline engines.

I'm excited to hear a stroker 2T gasoline engine large enough to power an automobile. Even as an I4 engine, it would sound more like a high-revving, flat-plane I8. I also wish that Freevalve would have received more interest and refinement from major brands, which would have pair perfectly with a product like this. One that could benefit from complex valve timing algorithms.

in the late 1980s, every car manufacturer from fiancé, general motors, Ford, all the way down to Daihatsu had running prototype two stroke cars ready to go into production.. The Toyota design had a wet, crank case, you checked the oil with a dipstick, just like a four stroke. The advantage was, all of the metal needed to create an engine, the weight of which produced twice the horsepower of a four stroke engine of the same weight.. or The two-stroke engine would produce the same amount of horsepower as the four stroke engine with an Engine weighing, only half as much as the four stroke.. All the car companies were just about ready to give this 2 stroke plan the go ahead. All it needed was government approval from the environmental protection agency, EPA.. but The results of long-term testing shot that down. Because….. not one of the companies prototype engines could pass the EPA air quality tests after the engines had the equivalent of 100,000 miles of driving on them.. SAAB had two stroke cars running around in the 60s, there have even been large, two-stroke, dump trucks, trucks for pulling tractor trailers that were two stroke. But the air quality issues/requirements of the future ended the two stroke car before it even got started by all of the car manufacturers in the late 1980s.. I have been a motorcycle mechanic and a motorcycle enthusiast since the 1960s. I am currently on my 107th and 108th motorcycle so far. I roadraced motorcycles, winning six championships, two time national champion, I rode off road, two stroke dirtbike‘s for more than 30 years, motocross, bikes, trials, bikes, I rode two stroke, singles, twins, and triples on the street… I have always done all my own maintenance even on my road racing machines. And there is one thing I do notice about two strokes. they don’t last very long. My road racing machine, factory recommendations, new pistons, every 600 miles, rebuilt, crankshaft or new crankshaft every 1200 miles… The engine trouble I’ve had racing or dirtbike, riding or trials, bike riding, or even street bike riding, have pretty much all been the two strokes, piston seizures, that was the biggest fastest wearing parts, the pistons, rings, cylinders.. on street bikes, like my Yamaha RD 350s, 250s, Kawasaki S2 350 2strokes.. my dirt bikes, KDX 175s and 200s with hard plating in the cylinders, pistons were the weak part. And that is due to marginal lubrication of two strokes. They lubricate the engines with already diluted oil, that has been diluted by gasoline, which is a solvent… A film of oil is only so thick, and a diluted film of oil is only marginally sheer resistant.. there is a lot of engineering and tuning and tweaking of fuel injection systems that will have to be sorted to make any two-stroke engine. Be both EPA responsible, and, be reliable at the same time… no engine suffers more from altitude change than a two stroke. They lose 15% of their power just going from sea level up to a city as high as Denver, which is a mile above sea level.. Super chargers and turbo chargers can reduce that power loss somewhat, with a lot of extra systems to compensate.. cooling the engine will be an ordeal itself. Not to mention how do you cool the piston. They are prone to burning holes in 2 stroke pistons because they fire on every stroke. They don’t get that intake stroke to cool down that a four stroke gets… three of my biggest injuries at roadrace tracks have been from two-stroke engine seizures. My last one was my last race, I woke up two days later in plaster in the hospital after that 140 mph seizure on a Yamaha TZ 250 Factory Rd. race machine… of course, that happened during the days when you had to jet your motorcycle according to elevation, barometric pressure, even taken care to consideration the humidity and temperature into your carburetor jetting. I got it wrong that day… but my point is, in my experience, the Pistons of two-stroke engines are the weakest link. I wonder if Mazda can make a two-stroke engine that the piston will still be within spec and pass an EPA sniffer test at the 100,000 mile mark.. I hope they can do it. They are the company that seems to be the ones that are willing to roll the dice, look at the rotary engine that Mazda has been producing. It didn’t pan out when that was first introduced. A friend of mine bought a 1973 Mazda Cosmo rotary engine car right after he got out of the Navy. In 1973 that car was over $7000. he never had a problem with it. Of course he only kept it for about three years… but willingness to take chances the way Mazda does is a risk. Look how long it took mazda to improve the rotary engine seal problem… I really hope that Mazda has some type of a breakthrough with this two-stroke development. Because I have no plans to ever go to an electric vehicle until I absolutely have to. i’ve worked in the electrical generation field for the past 38 years until I retired. And occasionally the subject came up about California’s electric grid, problems, brown outs, rolling, blackouts, and their inability to make a decision about building new power stations. It takes 12 years from idea to going online when it comes to building a power station. and then California would like everyone to drive an EV.. but consider this. If every car in California right now, what is an electric vehicle.. every bit of electrical generation capacity they have whether it is from wind, solar, Hydro, natural gas, coal, nuclear, All of those generation abilities, concentrated on just charging the batteries of EV cars, is not enough, there’s no possible way that California’s electric grid dedicating every volt of generation capacity Simply to charge car batteries could ever meet the demand if every car right now was an EV.. I would like to see more development of the hydrogen engine. I don’t know if the big oil companies and their lobbyists are keeping the government from putting them out of business by going to hydrogen tomorrow, but it seems like that is a more practical solution than electric vehicles. good luck mazda..

Your supercharger is running backwards.

I used to be a guy who could get it done with 3 strokes, yet I'm happy someone can do it with just 2

It's Mazda and every other car maker is eager to find out how new enginws are going to look like. We drove 2 time MX 5 and now for years a CX 5, industrutable and good quality. We'll see this in the future👍

Im my opinion, this needs compressed air at start in some container or maybe electric turbo to get boost rightaway in low revs.

Overheating will probably need to be overcome. Also, twice the power (2 stroke) with half the cylinder rotation is countered by the belt driven air compressor. There is no need to fear EVs taking over. The drawbacks are explosive. 🔥

the sound will be like a banshee's screech. great vid.

Oh Mazda you reinvented the wheels again. Mad respect.

Fajne symulacje. Szkoda tylko, że wirniki sprężarek obracają się w przeciwną stronę niż w rzeczywistości :(

Now, how would Mazda get a patent for what Detroit Diesel did 80 years ago? Only difference an intake val

Curious what cylinder pressure is during low rpm detonation compared to normal power stroke of a diesel,regardless will require extreme bottom end ,I would try on large cid if were able to have variable valve timing

Nice video. I was drawing up some ideas about a 2 stroke engine 30+ years ago, but never made a working proto-type. My idea was exactly like this motor! I used the supercharger to force the air into the cylinder otherwise it could run backward and stall. My idea was to convert existing 4 stroke engines into this type of 2 stroke. My idea still might work like i thought; but I am glad someone can make the engine I designed on paper.

I dont get how they could get a patent on this? Its all stuff thats been thought/designed/used before?

The pump in a two stroke diesel is not a supercharger , it is a scavenge pump . It operates at ambient or close to ambient pressure . No supercharging occurs. If supercharging is desired , then turbo-superchargers running off exhaust gases will be added to the engine

I love Mazda's ingenuity and passion for thinking outside the box

Like any engine, heat mitigation is key. It is used here to benefit the process. I hope they move to an in-line configuration. This has some promise. Lighter weight perhaps.

A small engine like this in a EV to extend it's range sounds good.

Neat idea. Great for economy.. but I like to work on my stuff. Complexity is a deal breaker. I do like the concept of keeping exhaust gas in the cylinder for EGR instead of circulating it through the exhaust, EGR system, and back through the intake. "EGR" would be a misnomer in this case.

That's one sexy ICE. I like the ability to blow the chamber squeaky clean without spitting fuel in to the exhaust system. The injection system is also a good idea. With the right pump it would allow to burn just about whatever in the chamber. You can run LPG, CNG, Diesel, Petrol, Alcohol, synthetic fuels, paint thinner, whatever doesn't dissolve the seals. Now let's see if Mazda can make a promising production model.

Hi Allan. The Z900 is a Beauty mate. Well done. Cheers from New Zealand 🇳🇿

If it is a normal 2-stroke, the stroke until the exhaust port opens is considered for measuring the legal displacement. This type of engine does not have an exhaust port on the side, and the intake and exhaust valves are open for about half of the piston stroke, so I am interested in how the legal displacement will be measured.

What ever it sounds like its still better than any ev.

Awesome! They invented something already invented.

I love that Mazda is still putting R&D to work! Another example is the "Wankel" (rotary) engine in the MX30. Unlike other manufacturers Mazda does not focus on the fully electrical movement.

It will never see mass production 🦕

So is this going to require the making of a gasoline exhaust fluid instead of DEF to keep the NOx down from using the egr which is going to cause lots of extra heat?

Great video - I've wondered how this could be done, for a long time. Diesel/4-stroke/2-stroke. Great! 🤩

As for sound...some big Cummins diesel pickups have a low rumble you feel as well as hear: so that but maybe twice the frequency

Very well made explanations and graphics. 1 thing though. 2 stroke exhaust systems have far greater effects on efficiency and power then with 4 stroke engines. But they only work well in a narrow rpm range.

The basic 2-stroke engine with reed valve crankcase induction is the absolutely simplest engine yet devised, even with spark ignition. Take apart any old chainsaw engine and be amazed; piston, rod, and crankshaft. Holes in the side of the cylinder for exhausting spent gases. Now comes Mazda complicating something already perfect.

The valves would need to very big, esp.exhaust ones, hence even more prone to valve float (as cams would run at 1x crank speed). Therefore, only with a Desmo valvetrain would this engine really work well and at the needed RPM for proper efficiency.

Ive been saying for YEARS, we need a pressurized intake 2 stroke that uses a port timing on the intake and a set of exhaust valves that release pressure at timed intervals for maximized fuel efficiency. Less losses of unburned, more power, better cooling. You could hybrid cool the head using air and water jackets.

With a long stroke, it should provide high torque at relatively low rpm, especially since every stroke is a power stroke. This seems that it could be a good idea especially for a working truck, or bus. These are applications where high torque is paramount to get a heavy load moving. Perhaps they could blend a fuel that is higher in cetane and lower in octane and bump the compression ratio and get more fuel mileage from this vehicle. With elecronic controls on the valve timing, direct fuel injection timing, and spark timing, I could really see the advantages of this engine. I wonder instead of a roots type supercharger if they could incoporate a belt drive into a turbocharger where it is driven by the engine at low rpm and exhaust heat at higher loads. Something to think about.

Each stroke there is a combustion, so more sound for same rpm ( double the frequency of 4 stroke speed ) , power per volume shall be less than 4 stroke ?

Off setting the crankshaft to the compression side of the cylinder is a common way to almost completely remove oval wear pattern on the piston and cylinder. Additionally important to high compression motors.

Great explanation! Can't wait to see it.

Emmission norms? Does this engine comply with euro 6 and us ut viable fir improvemen5.

If I'm not mistaken Foden, Detroit snd EMD and Commer diesels worked like this. There were probably others too.

Absolutely amazing video! Super cool! Unused exhaust reused without turbo genius

Diesels don't have a fixed 15:1 Air Fuel Ratio (8:41). The air fuel ratio varies depending on how much fuel is injected, which is controlled by the rack position. Unlike an Otto cycle gasoline engine, there is no throttle to control intake air flow on a typical diesel. Power output is controlled by varying the amount of diesel injected, resulting in a variable air fuel ratio. This is why diesels had high NOx issues to deal with before the advent of emissions control systems; lot's of nitrogen in the air fuel mixture at high combustion temperatures promotes the production of oxides of nitrogen, which in turn contribute to SMOG when mixing with un-burnt hydrocarbons and reacting with UV from sunlight. This "new" two stroke technology is very similar to the Detroit Diesel Series 71 series engines (6V71, 8V71, etc, 71 cu-in per cylinder), which were first produced in 1938. Production stopped in the mid 1990s because of problems controlling emissions issues with the engines

General Motors in WW2 had a Tank engine that was 2 stroke supercharged. Most people think 2 stroke is just add oil to the fuel and no valves in the head, but as this shows you can have a valved 2 stroke. This would burn very cleanly and produce a lot of power.

A.I. is so pleasant to listen to.

I wonder if non poppet rotary valves were incorporated if further improvements could be made as well? Also use of that new piston design which incorporates a continuous oil seal ring to minimize "seep thru" too?

The only so called problem with modern teal 2 stroke engines like the ones they run in ktms and the ones they run in sleds. Is emissions laws. The power to weight raito and mpg ate very efficient.

all that is, it's a 4cycle I.C. engine with the camshafts timed 1x1 with crhankshaft and a roots blower shoving a charge inside. I've often wondered why no drag racers have tried this with a small block chevy. Would be an easy cheat, other than the engine sounding like it's at 8000 rpms from hitting on every downstroke

Long stroke two stroke is an interesting concept of which I approve.

Stihl has been using a similar tech for years now. But this is genius. The only thing not mentioned was how much crazy heat this engine would surely make.

In regard to the fact that the revs would drop to 4.000rpm I guess the resulting sound would not be that high pitch pleasing sound we're used to hear but - provided it would keep the same exhaust and adjacent pipes and etc - it might keep the same tone, just at a lower level. *I raced a lot in kart competitions using 125 cc 2 stroke motors and the sound were gorgeous. People get thrilled with that sound! 😎

I believe that Toyota took a very similar approach several years ago using the 6 cylinder Supra motor. The rpm issue was there but I don't remember the other hurdles that they felt weren't worth the effort. However, the automotive companies are hooked on electronic fuel injection. The fuel delivery system can be simplified by substituting an fuel vaporizer using a simple FI system downstream from the compressor. Then the system would on pump a homogeneous gas mixture into the engine with a large range for AFR. This eliminates any chance of preignition. My experience on the dyno with a vaporizer system on a NA 4 stroke allowed up to 24:1 AFR without any misfire. This combination would really give this approach some legs and offer greater fuel economy and a simplified FI system with only 1 very large or multiple small injectors at low pressure. This would be similar to Yunick's mixing system but instead of using a turbo to mix and pressurize, the fuel vaporizer would do the mixing and the compressor pushes the mixture into the cylinder. There is very little data on using a homogeneous gas mixtures at elevated AFR's but there are real benefits if the research depts. would just explore the concept.

You say dont expect a high pitch scream because of low rpm, but because its a two stroke it has twice the amount of combustions as a 4 stroke so may actually sound like its at a much higher rpm

Just curious as to what will happen if you add some suction device on the exhaust stroke?

The benefit of the old two stroke was always more power from a limited space for the motor. That space efficiency was due almost entirely to the lack of a valve train, and no need for external compression, but this engine requires both. What removed two strokes from the streets was the combination of lower fuel efficiency, and added (and more visible) pollution from oil premix/injection, but these have both been alleviated by this design. It seems like it might have a fit in some segment, but I'd like to see a torque curve from a prototype before guessing which segment. I can't wait to hear what these will sound like - hopefully better than Mazda's rotary engines. Hopefully this turns out to be a significant advance - we haven't had major advances in ICE since quad valves, fuel injection, and turbos decades ago, and electric with current battery tech required at least 50 more years of mining and infrastructure to be viable.

Detrit diesel has been using this concept for decades! Boats and fire engines use them. Emissions were the only reason they weren't used in road legal vehicles since then.

The catalyst system makes the burning of fuel more efficiently, but that's after ignition. It cleans the exhaust. What mostly aids power is the timing and fuel modifications along with all the electronic sensors contributing to efficient burning of fuel. Catalytic converter actually reduce the mechanical efficiency

Sounds like a mean machine !❤👍😁

engine vibrations are always an issue 2 stroke or 4 stroke, you just have to balance them well, i'd say that number and size of cylinders is more important for vibrations

The sound would still be similar to an engine of the same orientation and number of cylinders that is running at twice the rpm. So if it runs at 4k rpm it could still sound like an engine at 8k rpm if it has the same exhaust system