Overcoming The Rotary Engine’s Biggest Flaw
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- čas přidán 23. 06. 2023
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The inspiration for the Wankel rotary engine is derived from the geometric principle that when a circle is rolled on its own circumference along another circle that has double the radius, a curve known as an Epitrochoid is created. This curve forms the shape of the inner walls of the rotor housing. The rotor housing hosts all stages of the rotary engine’s combustion cycle, much like a cylinder in a conventional engine.
In order to keep compression in the chamber of a Wankel engine, the three tips of the rotor must form gas-tight seals against the inner walls of the rotor housing. This is accomplished by seals at the three apexes of the triangle, known as apex seals. These seals are usually made of metal and are pushed against the wall housing by springs. Since the seals are in contact with the housing’s inner case, in order to reduce friction they’re covered in engine oil. Because the exposure of engine oil to the combustion process, a rotary engine burns oil by design. The amount of oil used is metered by a throttle-controlled metering pump.
The three apexes of the triangular-shaped rotor move uniformly along the inside walls of the rotor housing, dividing the cavity between the rotor and the interior walls of the housing into three continually changing regions of volume. Because of the unique configuration of a rotary engine, they’re classified as variable-volume progressing-cavity systems. Each rotor has three faces and each face has three cavities of volume per housing. In effect, each face of the rotor «sweeps» its own volume as the rotor moves in an eccentric orbit within the housing.
Each side of the rotor is brought closer to and then further away from the wall of the internal housing, compressing and expanding the combustion chamber. A rotor is effectively akin to a piston.
Starting in the early 1960s, Mazda has released a slew of unique, Wankel rotary powered models such the Cosmo, RX-3 and three generations of the Mazda RX-7. The iconic history of Mazda and the evolution of the Wankel rotary engine began with a joint study contract between Mazda and the German car firm NSU. Which came equipped with a water-cooled single-rotor engine and standard front disc brakes, which differentiated it from other similar cars of the period. Early cars required an engine rebuild only after 50,000 kilometers or 31,000 miles. Many of these failures were attributed to poorly designed apex seal tips, a common weak point later realized in rotary engines.
Since the seals are in contact with the housing’s inner case, in order to reduce friction they’re covered in engine oil. Because the exposure of engine oil to the combustion process, a rotary engine burns oil by design. Because of the direct contact of apex seal, the biggest obstacle engineers faced in initial designs were the chatter marks on the rotor housing’s sliding surfaces. To an extent, these carbon seals were self-lubricating, addressing the issues facing the rotor housing wall surface.
They were also used in conjunction with an aluminum rotor housing, in which the walls were chrome-plated for durability. What made this possible was the new porous chrome plating on the interior walls of the rotor housing. Ths surface finish of this plating improved the effectiveness of the lubrication between the apex seal and the rotor.
From 1975 -1980 it was discovered that the current apex seal version was subjected to high thermal and centrifugal loads during high RPM operation and under periods of high engine load. To rectify this issue, Mazda implemented a slight crown of . This additional crowning compensated for the rotor housing’s slight deformation under high loads, ensuring sufficient contact with the rotor housing walls. Mazda also improved the corner pieces by incorporating a spring design to keep the clearance of the rotor groove at a minimum.
By the early 1980s, further refinements by Mazda led to the adoption a top-cut design that extended the main seal. The purpose was to reduce gas leakages at one end of the apex seal, where it would segment into two pieces. From 1985 to 2002, the apex seal had been further reduced in size to 2mm. Additionally, Mazda filled the center cavity of the spring corners with a heat-resistant rubber epoxy, adding additional sealing properties.
This latest iteration of the apex seal design was used in Mazda’s iconic high output, low weight twin turbocharged 13B-REW engine. Made famous by the 3d generation RX-7, it was used until the engine was finally dropped from production and replaced with the Renesis engine which used its own apex seal design. The apex seal in the Renesis engine was now a two-piece design made from cast iron with a low carbon content.
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Absolutely love your work, could you do an evolution of the transmission……..alternator, thermostat, air intake, solenoids would all be awesome topics if you haven’t covered them, are ye going to get back into computers…….missiles, sensors, sonar, radar, EO, jet engines would all be awesome topics……god bless
Can you do Detroit diesels next? :)
except it hasn’t been overcome yet
and unlike the usual youboobers who hopelessly fall for the merchandisers of men at every drop of the video hat I’m not going to fawn over this regurgitation that offers zero rotary engine value because it was only done for one purpose; to promote your advertiser. People are such saps, it really is sad that they can’t even see the obvious when it’s literally punching out their eyeball.
.
@nobodyspecial5026 The Wankel engine was a failed concept and there is no longer any serious, legitimate development of this fundamentally inferior design.
Good video but I think it's missing some of the story though. Apex seals have gotten improved significantly by rotary shops after Mazda abandoned the rotary engine. Some rotary builders don't even consider them the most common source of the major issues with the engine.
100% spot on. Aftermarket support for apex seals are so plentiful and great that it’s now the least of problems, especially when more owners learned to premix their fuel as well. Now the longevity of rotary engines, especially boosted ones, dealt with the immense torque produced with the added boost.
This could be an important topic someday, considering the new 800cc extender in the new SUV was also physically larger than the 13B designs. With Mazda planning something big for their future sports car based on patents I’m very certain Mazda definitely looked more into improving the strength of the rotors and housings under extended load.
@@Nafeelsthe engineering continues but emissions is something the aftermarket doesn't have to worry about.
This is great for prolonging the life of vintage engines, but it doesn't address the fuel economy or emissions problems with new engines.
They are dirty, inefficient, unreliable, and completely outclassed in every measurable metric by both piston and EV cars. It's a neat idea and the FD is one of the most beautiful cars ever produced, but that engine is a piece of dogshit.
They are a product of their time. The new Wankel engines look extremely promising. You cannot simply look at the engine and declare it trash, as you have to weight the advantages and disadvantages for their use case. Also EV is trash, their supposed cleanliness is flawed when it comes down on the environmental damage mining of lithium causes and when you take into consideration that there are big losses from the flawed logistics of making the electricity in a power plant and then transferring it to a battery. A fully EV future is a impossible, there isnt simply enough lithium for all the cars. Hybrids are the future.
I would argue that the apex seal was totally resolved by Mazda and this was clearly not the biggest problem related to this engine. The large combustion chamber surface area with corners that prematurely quenched the combustion flame front resulting in high HC emissions was a far more fundamental problem than simply could not be resolved.
Right?
Didn't watch the video after I found out it wasn't how to fix low MPG or even emissions.
Thats exactly what I was thinking.
40+ years ago, apex seals were most certainly a challenge. Mazda and the aftermarket have made sure they are no longer much of an issue. But the long, thermally inefficient combustion chamber is an issue that cannot be rectified without the rotary becoming something totally new and unrecognizable as Mazda's darling.
This sounds like a more interesting video, honestly.
there's liquid piston design (not a wankel) which resolves that and has ~40% eff
Seems like there are few components with any geometry flexibility in the wankel, so opportunities to fix these issues are... probably not great.
The materials science in the apex seals is incredible
All that work and they're still shit.
Shut up
Freaking love it! Electron beam cooling? Porous chromium? Whatever, no problem.
Also incredible -- Cast Iron competes against the latest and greatest composite apex seal materials. Nicely satisfying and low tech.
@@scottcatesCast iron is an excellent material for engine seals... it's the shape and design of the Wankel engine that is the problem.
As a previous owner of more than one rotary powered vehicle ( A 12a and a Renesis ), I would argue that these days the biggest flaw with Wankel Rotary is that combustion is still occurring during the exhaust cycle. This results in poor fuel economy and really hot exhaust manifolds. If you've ever watched an underhood camera in a race rotary engine, you can see that the exhaust manifold is absolutely white hot.
Edited for spelling
This can be countered by advanced engine control systems... Look into Rob Dahms work
@@mikesledge6187That's just a bandaid though, it doesn't fix the core issue.
@@qwertykeyboard5901 there are core flaws in most designs, the different designs are a symptom of people making different compromises...piston engines have reciprocating mass leading to more more stress on internal component's and wear and tear from vibration... Balancers are only a bandaid fix though...
Might as well buy a Tesla right?
@@mikesledge6187 Except that solves the ROOT of the problem, not the symptoms.
Extra engine cooling doesn't make the combustion stop happening in the exhaust section. The core issue still exists.
@@mikesledge6187You are wrong, the thermal efficiency cannot be countered by engine controls...
The Wankel engine is less efficient because of its design is limited by lower adibatic efficiency, lower combustion efficiency and lower mechanical efficiency.
A small correction: the Apex seal does not move uniformly across the epitrochoid, it instead moves at a variable speed throughout the sweep of the rotor, further complicating the lubrication and sealing issues.
I've always thought that a reliable wankel engine would be a great boon to aviation because of the low weight of these engines. But "reliable wankel engine" is an oxymoron. My beloved RX-8 made it to 70k miles before I needed an engine. These seals are a fascinating engineering problem; thanks for a nice video!
In aviation use it might not even necessarily be an oxymoron. You aren't doing 9krpm pulls in a GA or light sport craft, so *maybe* it's *conceivable* to have a reliable Wankel power plant that's engineered to last forever at 4000rpm. The problem is, as undeniably cool as that would be, would I trust my life and checking account to it, versus a Continental or Lycoming? Fat chance.
my rx8 is at 200,000 and still going, what did you do wrong?
@@davidhusband5022 treated it as a normal engine
@@davidhusband5022bruh don't act like the Renesis going boom is rare
@@papa_pt The Renesis issues were mainly due to being bought by people who didn't drive them hard. This included every single automatic sold which couldn't even run to the engine's redline. The bigger issue with the engine was flooding which made it completely untenable except for a very small enthusiast market.
The biggest flaw is surface to volume ratio of the combustion chamber. This results in excess heat loss of the burning charge compared to a reciprocating piston engine. There is no cure for this basic geometric flaw. That's it, done, over, no recourse for the Wankel. I've followed this design from it's beginnings and also followed the history of NSU. NSU had some if the best engineers in the world and produced some world beating designs. These would include the VW Golf and the beginings of all modern Audis.
Excellent comments
But not original, all of this stuff is known.
@@anvilsvs Indeed, but well said.
Couldn't have said it any better myself.
Your knowledge regarding this topic is excellent... it's refreshing to read among the endless comments posted here by those who have no clue what they are blathering on about.
Great explanation! For years, the extreme challenges facing apex seals have intrigued me.
Thanks!
Yes, it's a fundamental flawed design that is inherently unreliable
NSU Wankel engines were reliable for most of the 10 years they were in production - only the first year of production had problems and it was mostly a reputation problem from then on. Also ignorance was a problem - a lot of engines replaced under warranty were not faulty because mechanics had no idea what they were doing….
NSUs approach to materials was equally interesting. They used cast iron apex seals and developed in partnership with BASF a silicon surface coating for aluminium called Nikasil.
These coating is still commonly used as a bore coating in piston engines. It’s very popular in 2 strokes, as well BMWs for example.
Damn right on ignorance. My grandfather's neighbor (when he was alive) had a 12a with over 300k mi on original build. It blew because he let the oil pan leak until it completely gave out. Neglect.
@@keilmillerjr9701 Dad's Ro80 did 160,000 Miles on its first engine, and was retired on its second one still running perfectly at 230,000 miles. The second engine had to come apart once because of an accident where a thermostat stuck closed and he didnt notice the temp gauge in time - it popped a couple of coolant O rings between a housing and side plate. The engine was otherwise fine, but it was a bit annoying have to dismantle it to get at the O rings!
Ro80s had some trouble with spark plugs in Australia back in the day because of the stupid high lead levels in our poor quality fuel - it would build up on the plugs and literally short circuit them! The introduction of unleaded fuel solved that one.
NSU engines were incredibly unreliable and many Ro80 owners had their engines replaced under warranty as many as 3 times..
Apex seals are inherently unreliable by design and this fact cannot be disputed.
@@keilmillerjr9701You sir are a bald faced liar, please stop posting ignorant lies and misinformation about Wankel engines.
In my state.....elevation and climate were the problem. That and severe flooding from these abortions. Thats not the fault of any mechanic I know. Thats why these engines are all in the junkyard.
Experimental aviation has many companies that take stock RX7 engines, and ceramic coat the inside and convert them to aircraft engines.
They are perfect aircraft engines. Light weight, dual ignition built-in, minimum parts count, runs on regular unleaded gas, can get you home even if you've lost all oil pressure.
This happened to a pilot. After landing they took the engine apart to find ceramic coatings had no wear whatsoever.
Needs a reduction drive. Always causes issues it seems
It's more than just the coating. In stock form, the engine injects motor oil into the housing to lube the apex seals. No oil pressure, no apex lube.
In aviation, they often swap the oil injection to use an external 2 stroke oil reservoir instead. Which means if the main oil pump goes out, the apex seals will still be lubed and be able to maintain compression which much of the rest of the engine fails from oil starvation.
*You sir are a big fat liar.*
There are no Wankel engines reliable enough to pass a FAA or EASA airworthiness certification.
Wankel engines are illegal to install on any type rated passenger aircraft simply because they are too unreliable and unsafe.
The use of Wankel engines in passenger aircraft is the soul domain of crackpots and suicidal lunatics.. No aircraft manufacturers offer a type certified aircraft with a Wankel engine because no Wankel engine has ever been reliable enough to pass the minimum standards to meet FAA certification. Apex seal have a fatal flaw that makes their durability and reliability unpredictable.
Wankel engine offer no advantages over reciprocating or gas turbine engines and are unsafe for passenger aircraft.
@@dirty_haute In aviation, they don't modify engines or deviate from the manufactures specified procedures.
Wankel engines are too unreliable and its illegal to install one in a certified passenger aircraft.
several major aircraft engine manufacturers developed and tested Wankel engines and found that meter oil injection using 4-stroke motor oil offered superior durability and improved reliability but this was not enough to pass airworthiness certification.
even Mazda does not recommend 2-stroke oil or premixing because it reduces engine life and increases engine failure rates.
Wankel engines can only be used in homebuilt and experimental aircraft that are untested and unproven, they do not meet safety standards and all of the risk is beared by the owner/operator... and this has resulted in several fatal accidents in recent years.
The Wankel KKM is an evolutionary dead-end concept, it was a failure because it offers no advantages over reciprocating engines and has poor durability and reliability..
Fantastic video about the apex seals - thank you!
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The mechanic said, “You blew a seal.”.
And the penguin said, “No, that is just ice cream.”…
As told by Emo Phillips in the 1980s 🤣
@@howardosborne8647 - ah, no…
What seals the sides of the rotor and the walls of the housing? Is this area larger than on an equivalent piston engine?
There's 2 rotor covers create a seal with the engine housing (oval metal piece) and the rotor (metal dorito) is sandwiched inside.
Machined flat surfaces and some gaskets also the maintain pressure from combustion
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I expected this would cover some new breakthrough.
Pls review next the liquid piston engine!
Would love a video about the new rotor-charged hybrid. The new engine uses exhaust recirculation and direct injection to increase efficiency by up to 25%, helping the other downside of rotary engines as far as mass consumer use. Pretty interesting, especially if you can get more info from Mazda itd be interesting to see a vid. Now if they develop a better AT, combined with Skyactiv and their other tech, they could have the best MPG and efficient stuff out there without a CVT, let alone their fun higher power Turbo CUVs and hatchbacks (or tiny hatch-cross-things, like the CX-30 lol) edit: go figure you cover the MX-30 at the end a bit lol, would still love a vid on the in depth stuff. They even pass strict emissions standards with the little engine now which probably wouldnt have before.
in addition to the apex seal probs the side seals would stick due to carbon buildup from running at light loads, idling in traffic etc.
this lead to blow by causing loss of compression and oil leakage causing the plugs to oil up, making cold starts sometimes impossible without changing or cleaning the plugs. most rotary mechanics came to realize that a poor running engine just needed a good 10 minute blast down the freeway and it was good as new.
Carbon build-up is caused by low compression and damaged seals.
Carbon buildup is because of using bad fuel and oil. The main problems of rotary are not seals and emissions, the engine is not stiff enough and need 2 kind of oils to lubricate it. There are people that fixed most of the wankel problems but well, its too late.
@@szaka9395Carbon fouling is clearly a symptom of low compression, especially for fuel injection engines.
Show me a Wankel engine that floods or loads up with Carbon, And I will show you a Wankel engine with bad apex seals.
amazing video, great search and care on content, conglatulations
Particularly enjoyed the section on electron beam hardening.
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General Motors Chevrolet used an engine as a generator extend the range of the Chevrolet Volt many years ago and it worked extremely well and met emission standards.
The Chevrolet Volt was a Hybrid vehicle and had a notorious reputation for being unreliable, it was discontinued in 2019.
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Epic failure.
Aw I was really hoping to hear about the new "Inside out" Wankel 2.0 apex seals. The vertexes are now in fixed positions, and I wonder how that effects the means of sealing
Wait a minute. Why didnt they use Cylindrical roller bearings?
Btw the hybrid would be better with a diesel. Two stroke it is for me
Cylindrical roller bearings are designed to support high radial loads and reduce friction between rotating parts, whereas the apex seals in a rotary engine serve a very different purpose.
Apex seals maintain a seal against the housing of the rotary engine, handling high temperatures, pressure, and friction. Using cylindrical roller bearings instead of apex seals would likely lead to problems, as they're not designed to withstand the combustion pressures and heat inside the engine.
A needle roller apex seal is an interesting idea. It would be fitted into a radial semicircular grove in a support housing across the apex width, supported by a spring between the roller seal support housing and the rotor apex seal assembly in the rotor. A rolling needle seal will roll on the interior surface of the rotor housing instead of sliding on the rotor housing. Also, similar to needle roller bearings, a rolling element apex seal would not need as much lubrication as sliding apex seals, reducing lube oil consumption and emissions from burning lube oil.
@@retiredbore378 Particularly at the high RPM and RPM changes a roller would have to turn at.
How would it seal if it has enough clearance to roll freely?
Design Ideas has perfected the apex seal. These seals work at boost pressures not seen since the F1 turbo era of the 80's. They are not cheap, but worth it if you are trying to make real power with a rotary. Reliability is there too. I've heard of Design Ideas seals being so durable that they are not changed when rebuilding the engine-- and that is in drag racing applications!
Rotaries seem to love life best when at full throttle.
@@loganlachance1890 Yeah and you don't really even need seals at high RPM, the gas escaping gets closer and closer to being negligible. Its the slow speeds like idle and startup that you can tell the most difference.
A screaming rotary is a happy rotary, keep rotaries happy and singing!
That is a big lie, no one has ever solved the reliability problems that have always plagued the Wankel engine...if someone tells you otherwise? They are without any doubt trying to sell you overpriced garbage parts.
@@loganlachance1890If that was true? Wankel engines would be ideal for aircraft applications... which they're not.
@@jakegarrett8109 High rpm is when a gas tight seal is most critical, hot gasses passing by the seals overheat them, causing ablation damage that destroy the seals and the engine.
Your video is very good at describing the way of overcoming the biggest practical issue with the rotary engine. However the fatal flaw is a theoretical one: it's afwul at captchuring the energy of the cumbustion. In a piston engine, a good portion of of the flame front directly pushes down on the piston, while in a rotary it always squeezes into a wedge. Even with having to translating the longitudinal motion into a rotating one, piston engines will always be at a significant advantage and the numbers in efficiency and consumption speak for themselves. Even in that latest Mazda you described, those numbers sound awful. 13 gallons for 337 miles? Are you sure those are correct? Cause that doesn't sound like anything I'd be bragging with.
The biggest fatal flaw in the Wankel engine has never been solved, that is its unacceptable reliability issues and overall poor durability.
The Wankel has never been efficient it has inherent limitations in combustion efficiency, thermal efficiency and low mechanical efficiency... it offers no advantages over other engine types and has several major disadvantages.
As I saw it written once; "It (the rotary engine) has the worst combustion chamber shape known to mankind!"
This is absolutely true, the combustion chamber architecture is appallingly bad and cannot be improved as it is dictated by the geometry of the engine.
I think part of the issues with the apex seals was that there wasnt really a "cool" side like a piston ring had.
But the other thing that i have always found a bit odd about the rotor itself was the pockets for combustion. They were symmetrical and i feel like having the back half of the pocket just as deep as the front half worked against the forward movement in the later half of the ignition stage. I would be curious to see what would happen if the leading half of the pocket was deeper and tapered to flush towards the back half of the pocket.
Won't have any effect, you must have been sick the day they taught Pascals Law...
@@sandervanderkammen9230 yes assuming the chamber was stationary but the rotor is moving and has inertia
@@joshuaszeto Unless the chamber is moving fast enough to form a supersonic shock wave? (which it doesn't) *NO,* Pascal's Law does not allow pressure to be "off-set" in the combustion chamber, pressure IS ALWAYS exerted EQUALLY on all sides.
Any questions?
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could you do a vlog regarding the liquid piston engine to see if it has similar seal problem as the mazda latest engine.
BEWARE OF LIQUIDPISTON it is a fraudulent vaporware investment scam
With no data to back it up.. I think a small rotary engine as a generator for a range extended EV is a great idea and one could manage the weaknesses of the engine to make best use of benefits. Low NVH, power dense, simple.
Why would anyone permit themselves an unsupported opinion without data to back it up?
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I had two RX3s back in the seventies no problems with the apex seals it was the coolant finding it's way into the combustion chambers that killed them on both of mine, much later on about ten years ago I restored two Suzuki RE5s rotary engine motorcycles, no problems at all and very reliable, regular oil change and maintenance is key to a long life Suzuki rotary engine.
See my Suzuki RE5M restoration.
Remember the RE5M well … Weird motorcycle!
@@sking2173 It handled surprisingly well for such a heavy motorcycle, it's was cool to be different and ride a motorcycle that almost bankrupt Suzuki.
@@leeandjancruise - I hope you enjoy it … It’s definitely a piece of history.
Apex seals are the primary failure mode of all Wankel engines, they are inherently unreliable.
My RX2 did the same. I think the expansion rates between the aluminum sections and the cast iron sections were the main problems.
Can you also make a video about the liquid piston engine
Have you seen warped perceptions video on them?
@@buiItnotbought yes. But I wanted to see an in-depth engeneering video
Beware of LiquidPiston, it's a fraudulent vaporware investment scam
Liquid piston design is the rotary done right, seals are stationary and both the rotor and housing are oval - no edges. It has pre-chamber and CR of ~18:1
The housing is tri-lobed, but true it has no significant edges. I’d love to see more people covering this design. It’s an awesome and potentially revolutionary design, pun intended.
And they solved many of the Wankel engine's other deficiencies, while retaining all of the benefits. I am hopeful a company will use Liquid Piston technology to make a family of aircraft engines, they would totally dominate the market as they would be better than existing piston engines in every way.
LiquidPiston is not a legitimate company it's a notorious vaporware investment scam
Can you do a video on strain wave gears
I had an RX-4. I once set fire to dead grass in an orange grove because of the exhaust system heat as I was driving away from the grove. Luckily I was able to stomp out the fire. The apex seals wore out around 50K miles. Nice little car while it lasted. Very smooth running
It will work someday. Engineers are nothing but persistent and insistent, and very qualified above that
Just in time for demand to disappear as ICE-driven vehicles are displaced by electrics.
I think it's potentially a great design.
@@campbellpaul It's not, really. The engine works, but it has some significant drawbacks. The wear issue can be engineered out, yes - but the poor efficiency cannot, and nor can the terrible emissions profile. Those are just part of the fundamental design. The biggest upside it has is very high power density, which is why it was a good choice for a hybrid vehicle range extender.
@@retiredbore378 I wonder if you could make an engine that operated as both two and four stroke, using electronically actuated valves? Then you could get the efficiency of four-stroke most of the time, but sacrifice it for the power of two-stroke when acceleration is needed.
All of the manufacturers reached the same opinion about the Wankel... that it was fundamentally inferior to reciprocating engines and it has come to the logical conclusion of its practical development potential
I can't imagine the type of research that was done to provide the details covered in this video. Great job.
and not all of it is correct.
not enough
@@ValentineC137 Is there alot of incorrect information in the video?
@@mikeyp2277 There are some smaller things like talking about the chatter marks as if they were a problem in production engies.
Rather, the chatter marks were an issue on the design given to them from NSU which they resolved with different oiling and apex seal designs before ever construction a production engine for a car
The main problem with the video is the focus on the apex seal being the flaw in the rotary engine, it’s like saying the piston rings or valve seals are a flaw in the piston engine.
As an avid rotary enthusiast I have not heard of the apex seals being an issue in any stock production Mazda rotary from the Cosmo to the RX-8
The only problem they might present is for people modifying their engines as even very minor knock/pre-detonation can cause the apex seal to warp or crack
The real flaw(s) that’d likely be talked about if you asked people familiar with the engines would likely be efficiency and emissions
There are some problems encountered in the RX-8 that were born directly from Mazda’s modifications to improve the emissions when they switched to sideport exhausts, the major one being the shape of the internal port made it so carbon would build up in a sharp corner and, when the buildup got big enough, it would catch a side seal and snap it making you lose compression and require a rebuild.
The other problem is more for tuners because the middle plate has 2 exhaust ports right against eachother, and as the extreme heat of the rotary exhaust is blasting that area, then the dividing wall between the two ports melts and falls out.
Michaelharrison should be near the top comments and makes a good point about the combustion chamber size, I’d like to think that there are more people talking about the misguided focus of the video with equally good points all over these comments.
It could have worked better if New Mind had a title more like “The Rotary’s Most Stressed Component” or if it just talked about the actual flaws of the design.
Currently it just purpetuates the myth of apex seal unreliability
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The biggest flaw in the Wankel has to do with lousy BSFC due to the huge area sucking out heat.
No the biggest flaw is the way they throw still burning fuel out the exhaust as the RPM goes beyond the "Optimum"
Another flaw is the lower combustion temperatures in the corner near the apex seals that will always result in less than optimal combustion throughout the entire chamber. This is easily seen in the experimental transparent combustion chamber tests.
@@mzaite That's not a flaw, its a feature! I like the pops and crackles, sure only getting 16.23 mpg average taking it easy on the highway isn't the greatest (single digit MPG in town but I drive a lot more aggressive normally), but its that belching of flames and pops and the sound of winding those things up past 9,000 rpm that makes them fun.
Its true that sport bike engines are rather close in power to volume (I could make a 1.3 liter V8 out of 2 of my motorcycle engines and it would be 268 HP, about 30 HP more, and probably WAY higher fuel economy), but nothing really sounds like a rotary. Sure an inline 4 at 16,000 rpm sounds GOOD, but its got nothing on the sounds my car makes, just makes me smile. That fuel isn't wasted, its MPG is converted to SPG (Smiles Per Gallon), and nothing compares to the rotary!
@@jakegarrett8109single digit mpg in town. Omg that bad.
@@jakegarrett8109 Sorry, it's just an inexcusable inefficiency.
I was a member of the Rotary Club but we all drove Buicks with conventional V8 engines.
Enough has been said about the rotor's tip seals... But what about top and bottom? Every chamber has 4 sides where gases could escape.
My friend bought an 87 rx-7fc a few months ago, and next week we’re pulling the engine out. An event that’s become affectionately known as “yanking the wankie”
My condolences to your friend, perhaps next time he will chose a better car...
It's a shame that rotary engine is rarely used today...
I'm just glad Mazda is bringing them back!
It really isn't. Great power density. Not-so-great everything else.
@@vylbird8014 the boost in Apex seals out and the spinning dorito memes are pretty good tho
Angry Rob Dahm noises.
@@jayyydizzzle Power density: Great.
Service interval: Crap.
Oil use: Slurp slurp slurp.
Noise: PRRRRRRRRRRRRP
Reliability: Liability.
Emissions: Smogtacular.
Fuel efficiency: Deficiency.
Can apex seals be replaced by inset roller bearings?
No, a roller cannot form a gas tight seal.
The liquid piston engine might actually move progress forward in rotory tech. They swapped the trocoid and triangle so not the rotor is trocoidal and the combustion banks form and triangle. The intake and exhaust flow through the rotor and allows for egr mixing and exhaust cooling. Not sure how the apex seals will hold up but maintaining the engine looks pretty straight forward.. Time will tell
That is a company that has made no money for a decade and is always begging for investors.
BEWARE OF LIQUIDPISTON it is nothing more than a fraudulent vaporware investment scam
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The RX3 had a nice cabin layout and best flow-through ventilation. Too bad about the engine.
Miata BP-ZE 1.8L says Hi.
Well I think it’s track performance to date pretty much puts these “inherent faults” in to perspective. 🇦🇺 Without Aussie tuners pioneering new tech it absolutely wouldn’t be such a powerhouse currently that’s for sure
Wankel engines were ultimately a huge failure in motorsports and Mazda never won a single world class championship title before completely leaving racing.... Mazda no longer has any factory motorsports program.
Australia is a primitive, backwards country that no longer manufacturers automobiles and has never been relevant in automotive technology.
The range extender rotary is not coming to the USA, and probably not going into production.
Mazda president Akira Marumoto's announcement 3 weeks ago confirmed that the MX-30 was cancelled.
Back in the early 70s there was some R&D work done with Beryllium Nickel alloys as a possible solution to the apex seal problem. To the best of my knowledge it was not successful. Part of the joy of materials science is the trial and error aspect of trying something a little different.
The fatal in the Wankel design is not related to materials science... its a flaw inherent to the basic fundamental design of the engine
Instead of an Apex Seal, why not have a wide roller bearing similar to a steam roller at each tip of the rotor?
I was thinking the same thing. I would imagine that no bearing could possibly keep up with the speeds the roller would require, not to mention the need for some type of tension mechanism to ensure contact with the housing, which of course would add extra weight and complexity at the edge of the rotor, which then decreases the usable horsepower... I found a thread on the old RX7 forum discussing exactly this.
HOW WOULD IT FORM A GAS TIGHT SEAL IF IT HAS ENOUGH CLEARANCE TO ROLL FREELY???
It would likely leak some but you'd reduce friction and have more strength... in theory.
@@DoktorBayerischeMotorenWerke
@@ricepony33 But you cant have any hot combustion gasses leaking passed the seal... if there is the hot gasses will quickly destroy the seal.
Can't call the rotor a triangle because it's not made of 3 straight lines. It's actually called a reuleaux.
Can't call it a "Rotor" either, a Rotor is something that spins concentrically on a fixed point... only the DKM54 had a Rotor, the KKM57 has an Orbiting Piston assembly.
It both reciprocates and rotates simultaneously in a planetary orbit around the inside the chamber housing.
Cylinders are better in every single way.
Cyclinders are in efficiency with a lot of moving parts the only advantage they have is that they have been used longer by more companies and only mazda is doing rotary
@@thabanitambanemoto3385 Piston (4-stroke) engines are more thermally efficient. They can extract more force from each combustion event, with less waste heat. than a rotary can using the same amount of fuel. Rotaries only produce more power with less displacement because they have a power stroke every rotation of the E-shaft (for a one rotor) while a piston engine has a power stroke every two rotations.
The combustion chamber geometry on the rotary is terrible so a lot of power is wasted as heat and/or thrown out the exhaust because the fuel couldn't burn efficiently.
Don't get me wrong, the rotary engine is an awesome piece of machinery but there is a reason that it's only use for even Mazda itself is as a range extending generator for a hybrid
I hear about all the problems but when you drive a wankel it’s just magic. They are incredibly smooth, they’ve got a great exhaust note and they love to rev its quite exhilarating driving.
@@ronengel4586 That's that thing. it's not always about "well its way cheaper to make power with an LS" or "a big block is way more reliable over 1000 hp". It's about what you as an individual likes. The same applies for those people who say "Why spend all that money building an engine just to get beat by a tesla plaid to the 60?"
Sure the Tesla is fast but something about a 2 rotor Brapping away at idle and then screaming to 10,000 rpm or a v8 loping along with a nasty cam is way more exhilarating even if its half as fast as the tesla.
A small diesel piston engine is superior as a "generator" for range extension.
More efficient and less fuel to lug around. Diesel will also run hundreds of thousands of miles. Rotary as a generator is rather silly.
How long do the apex seals last as a generator ?
I guess very long because of only 700rpm
@@TheAdatto 4700 is what they state, but that should double its lifetime without hard loads. Just guessing.
Theoretically, it could last up to ten times longer.. It really depends on the reception it gets from the consumer market, though.
Apex seals Don't last, which is why Wankel engines are obsolete technology today.
@@TheAdattoWankel engines have been developed I the past for generator applications and have no advantages over reciprocating and have several crippling disadvantages which is why Wankel generators were never successfully sold commercially.
i love my rotary and will probably have it forever. i dont want some ev charger bs. give me some form of turbo 20b mazda
I always use quality synthetic two stroke oil when I fill my petrol tank to help with seal lubrication, it the same as using upper cylinder lubricant in a piston engine.
You shouldn't use synthetic oil in a rotary engine because it doesn't burn like mineral oil does and it leaves deposits in the engine.
It's all very well using an oil to extend the life of the apex seals, but the issue with that is emissions, a conventional ICE engine doesn't burn any oil (in most cases) whereas an oil injected rotary (or even one running on premix) burns 500ml per 1000 km which in the modern world is unacceptable.
@@onecookieboy I would agree with the slightly increased emissions, but I have increased the life of the combustion chambers and seals. I have been playing with these issues since NSU came out with the Ro80, others were dropping V-4 Ford in them while I kept the engine going.
I have lots of experience with Mazda engines in the MX5 and RX8.
@@chrisbarnes2823 Exhaust emissions are such a huge deal these days that Diesel engined vehicles are becoming impossible to make 'clean' enough and look like they are all but dead in passenger cars, so it's hard to see how any engine which necessitates the burning of oil can meet standards. I don't know how Mazda have overcome this problem with the 'generator rotary engine' except perhaps a combined DPF/catalytic converter type setup. I worked for a Mazda dealership for many years back in the 1980's-early 2000's and while Mazda engines were solid and reasonably trouble free, they were also rather boring and uninspiring. Most of the mechanics I worked with detested the rotaries, I didn't mind them so much, but the life expectancy was pretty dismal and after 50,000km most of the customer related 'not running very well' problems were because they were getting worn out, which is unacceptable.
You have to be monumentally stupid to pour the wrong oil into the wrong filler hole... if you cannot read your owners manual or the label on a bottle of motor oil? You have absolutely no business under the hood of any car.
Every manufacturer that thinks of making rotary engines should be forced to make a prototype *rectangular piston* 2-stroke engine that's also compliant with all modern emissions regulations.
How does the rotor seal at the sides ?.
Why they haven't rounded the corners to eliminate any corners is interesting. Plus fitting a set of reed valves to the intake ports increase the power output of these things
If you were not aware? the corners is what seals the gas pressure.... reed valves only work on 2-stroke engines
Do inverted wankel motor where the seal is fixed by geometry. And why it never saw light of day despite nearing perfection.
Someone is trying to develop them, actually. Look up liquidpiston. But yes, the best part is no part. The inverted topology gets rid of apex seals entirely.
What's the compression ratio, I wonder..
@@campbellpaul near ideal. It would work great with hydrogen as fuel too
@@manipulativer A fuel that burns cooler than gasoline would also be ideal
@@campbellpaul Well if you want the best thing i suggest you to check out Mike McCulloch.
He fixed dark matter and found a propelantless propulsion and gotten better results than NASA with ion drive which uses a propelant.
Mazda is one of the most overlooked engineering manufacturers.....the rotary and the sky active technology is some of the best engineering in the car business
Mazda is the smallest and least successful of all the Japanese automakers... mainly because of its poor quality and mediocre engineering.
Mazda relies heavily on other companies for engineering support.
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There are many small engines that are super efficient and would've been a better choice for the new Mazda Electric Hybrid.
It doesn't make sense to use an engine that has terrible emissions as a back up to the batteries.
At its "Optimum RPM" a Rotor engine is much less terrible. The mistake was using them with cars where the engine is constantly changing RPM. meaning you're basically never at the optimum RPM.
Generators were one of the original design considerations for the design. Back in the NAZI days.
Pound-per-pound it generates more energy than any existing ICE.. Combine that with longevity and it is actually within ESG standards for fuel efficiency.
@@retiredbore378 You probably are correct, however this is a purpose built engine that operates at a set RPM that is lower than any of those engines. Every one of those engines would be better if they were manufactured for the task (minus the cost and fuel efficiency) but would each have more drawbacks than the wankel.
@@retiredbore378 2-stroke engines have worse emissions.. An F-1 engine runs at too high an RPM and (like the 2-stroke) is more difficult to manufacture. Removal and replacement would likely be more difficult as well as an F-1 engine would take up too much space. These engines probably have never been made to go into an electric vehicle, either.
@@retiredbore378 I think diesel cars are outlawed in the US, but a 2-cycle diesel would be bulletproof.
The main issue with the Wankel is that people treat them like normal engines. Rev it when you start, and rev it when you turn off- get that Oil flowing!
The main issue is that Wankel engines are inherently unreliable and fundamentally inferior to reciprocating engines.
No amount of maintenance can make these engines as reliable and durable as reciprocating engines... this is an irrefutable fact that cannot be denied.
They're cute and fine for lightweight disposable missions like drones, but their pollution issues are not resolvable and the Wankel just doesn't accomplish much. It's also impractical to recondition using standard machine tools. They're fine for niche uses which is where they'll remain.
The big Wankel engine problem are emisiones and housing lubrication, not apex seal, they dump the combustión in the exhaust port still burning ! Thats why the big flame in the muffler. I wonder how Mazda is going to resolve that problem. 😂
That is completely false and dishonest.
The biggest problem with the Wankel has always been poor reliability and durability.
The Primary Failure Mode of all Wankel engines is compression loss due the apex seal failure and damage.
This problem is inherent to the design of the Wankel engine and is in no way related to lubrication.
Emissions are not the major cause of Wankel engines becoming obsolete.
The last production Wankel engine was the Mazda Renesis and it met or exceeded the strictest emissions standards in the world right up until production ceased in 2012.
Sale of Mazda RX models was actually worse in countries with absolutely no emissions regulations.
@@sandervanderkammen9230 Nop ! Emission are the problen en todays Wankels. The engine are very reliable in racing today.
@@josecora1917 Wankel engines are no longer made today, series mass production ended over a decade ago.
Absolutely False, the Mazda Renesis engines met or exceeded the strictest emissions standards in the world right up until production ceased when sales dried up completely.
Wankel engines were an epic failure in motorsports competition..
A Wankel engine has never won a single Major world-class professional motorsports series Championship title.
Any questions son?
@@sandervanderkammen9230 metes. Mazda make oem parts, and aftermarket manufacturer make parts far better than oem.
@@josecora191765 million new cars were sold last year, ZERO has a Wankel engine..
The Wankel engine has been obsolete for over a decade.
It is a rounded triangle, that's crazy
Pistons aren't just round...
really cool thumbnail :)
MX-30 only gets 373 miles on 13 gallons? My 2017 Chevy Volt can go an additional 367 miles with an 8.9 gallon tank! (My direct experience is more like 420 additional miles of mixed driving on gas) So yeah, the rotary isn't very fuel efficient. Too bad. And btw I am a total Mazda fan, my and my family have owned a half dozen Mazdas over the years and loved them!
Exactly. This MX-30 will flop badly with that thirsty rotary.
Also, GM was foolish to can the Volt. That was a nice, versatile little car …
Mazda's president Akira Marumoto's announcement in July confirmed that the MX-30 was cancelled.
It's BIGGEST FLAw is that it made it off the drawing board. When theory and reality collide this engine loses 100% of the time.
Nice, but no cigar.
When Felix Wankel (The Creator of the Rotary/Wankel Engine) saw the design of the Rotary Engine that NSU (and Mazda and everyone else) adopted he said -
"You've replaced my thoroughbred with a plow horse."
Felix created the DKM Wankel, everyone else goes with the KKM design.
The DKM can rev beyond 20,000 rpm and it's walls never get scorched.
Learn the difference and you'll understand the real problems.
@@retiredbore378 Thanks for showing us you don't know what you're talking about. From the mid 80's forward the DKM should have been used. Unleaded fuel and electronic ignition eliminated it's biggest problem and you're wrong on thermal inefficiency, DKM vs KKM.
@@retiredbore378
Wikipedia is NOT my source.
Somewhere around 4 to 7 years ago, I went (multiple times) to
The New York City Science and Technology Library to access research books unavailable to the general public on Wankel engines.
It is from these books and from owning a Rotary powered Mazda and years of studying the engine, that I draw my knowledge of the Wankel.
Additionally, the thermal inefficiencies you talk about, which are real, can be turned into an advantage, especially in DKM Wankel engines that operate at constant / consistent rpm’s (20,000 +) in boats, planes & highway driving.
@@retiredbore378
My final response.
First excuse me for not telling you the DKM's biggest flaw and assuming you knew it.
The DKM's biggest flaw was having to tear down the engine every time a tuneup was required in order to change the spark plugs that were housed inside of the rotor, which was housed inside of the combustion chamber!
In a world of leaded gas, weak ignition coils, points, condensers and short life spark plugs, that meant every 5 to 10thousand miles.
That's 10 to 20 engine rebuilds per 100thousand miles, just to change the spark plugs.
By the 1980's those 3 problems had gone away, hence the DKM could thrive in that environment, but Mazda, the only Wankel manufacturer by then, never addressed the DKM.
As for DKM cooling problems, whatever they were or are, the engine ran 100 hours straight, so cooling was not the problem, independent of what is reported to have been Wolf-Dieter Bensinger statement.
An excellent point that everyone overlooks, the Wankel KKM design was not Felix Wankels.
It was designed by Hanns Paschke and Walter Froede.
Wankel hated this clumsy, non-rotory design.
Wankels engine was based on pure concentric rotary motion and was so smooth it did not require any flywheel or external mass dampers.
Whether Wankels engine was practical or efficient is purely speculative and ultimately unknown.
@@retiredbore378 As far as I know, only one example of the DKM exists and it resides in the Bonn museum.
In 1950s terms, even the KKM57 was considered efficient enough to be commercially viable but is certainly not by today's standards.
Advances in ignition technology may have made the DKM practical for the 1960s-70s?
Reliability problems have always plagued the KKM57, one can only imagine how reliable the DKM would be... certainly maintaining the spark plugs would have been a significant disadvantage.
Many questions and few answers.
7:31 you mean PeePaw's hytemp he used to seet rings in place may have come from Mazda's Wankel ?
I never got rotary engines. They’re inefficient compared to inline 4. Can some one explain why this engine got fans? Is it purely due to Rx7?_
Mostly autism. Not kidding, it's common among those who only care that something mechanical is different but not about how it functions IRL. Learn why railfans are referred to as "foamers" for some real insight into unusual ways humans engage with technology.
The Wankel rotary engine can be given perfect mechanical balance without the need for anything rotating in the opposite direction, so it is very smooth-running. Apart from that it is not as good as the reciprocating engine in most ways.
can we used mixed fuel with 2 stroke oil ? so it will lubricate the seal
Only if the manufacturer instructs you to.
I don't see what is the advantage of the rotary engine... the piston engine seems to do everything it does, minus the issues.... the only nice thing about is that you can ignite the exhaust and make some sick flames...
I'm surprised you haven't included the inverted rotary engine
Are you referring to the Adams-Farwell?
....I was always ruminating about finding ideal balance between combustion of propane in wankel engine so as low friction high octane fuel gets the best output out of genuine simplicity of a rotary engine....cracking such rubicone might open another era of alternative high-rew engines...
It was exhaustively developed many years ago and abandoned, the Wankel engine cannot support the higher static compression ratios needed to operate efficiently on high octane, low density gaseous fuels like propane, CNG and hydrogen.
The Wankel operates at maximum efficiency on Gasoline.
@@WilhelmKarsten It runs well on Hydrogen. Google it.
These engines needs to run at high RPM. The Mazda race car that won at Le Mans, had less gasoline consuption comparing to the opponents.
That's funny! I love your sarcasm.
2:07 I was surprised to see this Dutch text in this English-spoken video. Cool though!
The Quasi turbine is a better rotary/ positive displacement engine. Less vibration and the generator can be mounted inside the rotor
How are the flat sides sealed? Never been able to figure that out.
7:11 paused.
You can see the seal in the groove all the way around the rotor. These seals press out on the side housing.
@@Danger_mouse I see
you'll prbly have to watch a rotary rebuild vid to see it, but there are seals on the flat sides near each edge of the triangle.
More companies should be investing in generator system research and production
The fact that it needs oil injection to lubricate the surfaces makes this engine obsolete. It will never be fuel efficient or emission compliant.
Other than it's a oil burning fuel gobbling 2 stroke (spare the 'indignations'.. it is exactly That!)
In which Combustion sealing has proven a perennial failure..
Bin the design as unworkable and Move on as everyone else has done.
I still think that the best way to deal with this type of engine is to bin the whole idea! There is an engine that is massively more efficient and was invented and perfected years ago, it does not need the use of fossil fuels and is called the electric motor.
Yo where my man Rob at?
Crackhead Rob?
DORITO GO BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP BRAP
This is a good application of the technology as a range extender. Keep the RPM at optimum.
No, it isn't.
Wankel engines were exhaustively developed for generator applications decades ago and proved to be fundamentally inferior to reciprocating engines in generator situations.
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Range extenders were a very trendy but short-lived concept 10 years ago... they all failed to make it in the market place for the obvious drawbacks.
Timing Chains/Belts, as well as Waterpumps, have Long required being Changed/Replaced.
Thus it need only Easier to Access and Replace these Tips, perhaps Offer a Replacement 1x or at Service Intervals?
Relatively Easy, especially if the Repair is nothing but Time or Labor, with it taking Less than 1 Day to Replace/Repair....
Especially now that Cars are so Expensive..
Wankel engines are not just less durable than reciprocating engines, their internal components are also much less reliable... this is why Wankel engines cannot be used in type rated passenger aircraft and have become obsolete in the automotive industry since the introduction of comprehensive manufacturers powertrain warranties
I adore my 13b sounds when shifting and holding the clutch down a little longer, just can’t even explain it. The exhaust notes def aren’t bad either!
It is said the less the curve of the rotor, the better. I think this curve can be modified.
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The curve cannot be changed, there is a fixed ratio between the Piston/Rotor diameter and circumference to the chamber circumference.
just noticed one thing. at 2:07 you talk about the German NSU but the text is in dutch, maybe a mistake?
and how is it that the configuration as a range externder is making it more efficient , reliable and less fuel consuming over a piston engine ?
*It doesn't*
@@sandervanderkammen9230 i know... it was more a rethoric qurstion
@@megunded Indeed, it's such a stupid idea it's hard to believe that anyone takes this seriously.
With 13 gallons of gasoline, this shiny new vehicle can extend its range by 'up to 373 miles'. With the same amount of fuel, I could drive my regular old gas powered Mazda 405 miles. So congrats, Mazda - you just created an incredibly complicated and expensive way to get worse fuel economy. Bravo.
Always wondered if a 5 face piston would be better, higher rpm, less vibration, could run it as a 2,3, or 4 stroke.
This is how hard u can push a rotary🔥🔥😱😱m.czcams.com/video/xtVVPioU9p8/video.html
So sad Mazda only put their new one in a lame hybrid crossover, I want a full-gas RX-9!
I wonder if rollers (cogged) were put at seals wud Mazda have tried this ! the wall shud also be cogged too
How would it form a gas tight seal?
I thought I was going to see a solution here. Wouldnt Tungsten be better for the seals. Expensive but how small ammount needed and its high temperature tolerance.
I nearly bought the new Norton F1 in the early nineties but after reading about the new model with better suspension brakes and other improvements, I decided to wait the few months extra. Sadly Norton went bust so never happened. There wasnt much talk about these sealing problems back then.
It's a design problem, not a materials problem... the apex seal is inherently unreliable by design.
Seal problems is exactly why Norton went tits up.
The Wankel KKM is a deeply flawed design and is simply inferior to other engine types.
7:56 what the hell is "cast iron with low carbon content"
Cast iron ranges in carbon content from typical 2% to 4%.
2% carbon would be classed as Low Carbon cast iron
What's the benefit of two piece design?
Maybe the solution was to put a needle roller bearing on the tip of the rotor, or as i've seen invert the engine layout to have a triangular stator and an epitrochoid rotor.
My brain hurts trying to think of the challenges of balancing the mass of an epitrochoid rotor.
@@WBradleyRobbins it has been done... See liquid piston rotary engine
@@tomaspreece3126LiquidPiston is not a legitimate company, it's a notorious vaporware investment scam.
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This is how hard u can push a rotary🔥🔥😱😱m.czcams.com/video/xtVVPioU9p8/video.html
I had a beautiful red RX-7 back in the 1990s and loved the "Wankel" it came with. I babied that machine like my first born. Right up until it blew up on me and left me stranded on the highway. Rotary engines are trash.