How Rotary Engines Work – Mazda RX-7 Wankel – Detailed Explanation


Hello everyone and welcome!
In this video we’re gonna be talking about how rotary engines work and in front of me I have a 13B Wankel engine out of a 1985 Mazda RX-7. So to start things off we’re just gonna be talking about all of the different components in here then we’ll
be talking about how the combustion cycle works and then from there we’ll
talk about some of the different unique features on this engine and then get
into the advantages of this design. So just starting on the right here and then
working our way across this is the front plate, here we have the rotor
housing for the first rotor, we’ve got the centerplate, the second rotor housing
and then the rear plate. Now the 13B is a two rotor design so here we have the
two rotors, these are the rotary equivalent of pistons. And finally we
have what is called the eccentric shaft and this is essentially the crankshaft,
but for a rotary engine and so this is where your two rotors are gonna be
connecting up to and ultimately trying to rotate.
So getting into how combustion works we’re gonna be looking inside of this rotor
housing and what we have here are the intake ports so as the rotor rotates
over this it’s gonna be drawing of vacuum and pulling air out from these ports and
it’s important to realize that there’s ports on both sides so both the back
plate and the centerplate have ports, so air will be drawn in from both sides
into the combustion chamber. Moving right along here you have the two holes for
your spark plugs and there’s gonna be two spark plugs used which will get into it
a bit but basically it’s because the rotors gonna be rotating and the
combustion chambers really long so you’re trying to speed up the process of
combusting that air-fuel mixture and then finally as that rotor rotates it
will press the gas fell through the exhaust port which you can see here.
So now let’s work our way through the four cycles which need to occur for
combustion so first we’re going to be starting with an empty pocket so as you
can see the rotor’s completely up against the rotor housing and there’s nowhere in
there as it begins to rotate however it starts to open up a pocket and this
creates a vacuum and as it continues to rotate that vacuum opens up to the
intake ports allowing you to draw in air and fuel that continues to rotate and
then eventually you start to fill up this entire chamber and then you close
off the intake ports and now you’ve begun compression so now the this chamber is going to start squeezing
down that air until mixture into a smaller chamber until it reaches the
equivalent of top dead center which is about right there and so you so you can
see you’ve got this really small pocket and so now you’re two spark plugs are
going to fire and it’s going to continue to rotate and combustion is going to force
this rotor to rotate in this direction as you can see expanding that pocket and
then finally you will open up to the exhaust port where that exhaust can then
dump out and the rotor continues to rotate forcing out all of that exhaust
and then the cycle repeats itself. So looking on the side of the engine you
can see the intake ports so in the center for the centerplate it’s going to
divide between them so this will go to the rear housing and then this one will
go to the front housing and then you’ve got these two intake ports on either
side which will also feed into these rotor housings now as you continue down
you’ve got the exhaust port so one for each housing now it’s important to
realize that at any moment within this rotor housing you have multiple stages
of combustion occurring so you’ve got the initial cycle right here we’ve got
intake you’ve got compression happening right here and then you’ve got your
exhaust stroke occurring right here and all of these are occurring
simultaneously when the rotor’s in this position. Now if you were to continue to
rotate it here you’re gonna be having your spark they’re going to have the
exhaust and here you’re going to be having your intake stroke as you
continue to rotate that rotor here you can see combustion occuring we have our
exhaust occurring and then we’re starting to exit the intake stroke and
start to get into the compression stroke and when the rotors in this position
here we have our compression occurring here we have our combustion and the
exhaust is finishing up and then the intake is just beginning know it’s also important to realize that
while all this is occurring in one rotor in the other rotor the rotor is exactly
a hundred and eighty degrees offset from this rotor and so the opposite going to
be occurring in here so you’re about to start your combustion with the sparks
firing you’re ending your exhaust stroke over here and you’re starting with your
intake stroke over here. So here we have the eccentric shaft and as you can see these rotors are gonna be placed at
a hundred and eighty degrees apart and that’s done so that it balances on that
axis so as this rotates its going to be well-balanced rather than if it was offset it wouldn’t be balanced. Now you will still have a moment occurring
because you’ve got one rotor going this direction in other going this direction
simultaneously but because all of this is rotational and because it’s balanced
vertically along the axis it’s gonna be a very smooth very low vibration running
engine so let’s see if we can make sense of how this will work out so here we
have a rotor which will be on one end and then are eccentric shaft which will
go inside of that and then our other rotors going to go on to the other lobe
and of course it’s going to be a set of agrees it’s gonna look something like
that and see you can see that the inside of this rotor has this gear and so this
gear is actually gonna mesh up with this stationary gear and so as that rotor
rotates it’s going to force the eccentric shaft to rotate because this
is stationary so that gear’s gonna mesh with this gear and then force that lobe
to turn as you can see demonstrated somewhat there now this stationary
gear’s gonna go on the outside of the front plate and so there it’s going to
be bolt up so it’s not gonna move and then on the other side you can see that
gear will come through and mash up with that internal gear up the rotor ok so
now that we understand how combustion works in a rotary engine lets take a
look at some of the unique features to this engine design so you’ll notice
right here on the intake side of the rotor housing this little hole in this
isn’t actually for fuel in fact it’s for motor oil and the reason this is done is
to inject oil in here in order to help lubricate the seals unlike a piston
cylinder engine you can’t spray oil up on the bottom of the pistons to help
create a seal there and help lubricate things so it’s actually done directly
within the housing and you actually have injectors that also inject in oil with
the air-fuel mixture as well so looking at this on the other side that’s what
I’m showing right here so this is where oil injector and this is the pump which
would be hooking up these oil injectors to these certain locations where they be
injecting oil and this is essentially throttle control so as you press on the
gas it opens up and injects more oil so by design you’re going to be burning oil
so one of the other unique challenges to the Wankel engine is how to seal it and
so you have to keep in mind you want to keep the combustion chamber from
crossing over from one side to another from here to here but you also don’t
want any crossing over this direction outside of its you have to seal it this
way and you have to seal it at all these three edges and so the way they do that
is the use these apex seals and so these apex seals it’s actually a two-piece
design for this 13B engine and so it’ll be something like that and
these will slide in here and they will press up against the housing and so the
way that it continues to be pressed up against that housing is using this
spring so this is essentially like a leaf spring and it goes on like that
there’s a little not true to hold it in and then you can slide that down in
there and that spring will press this apex seal out against the housing so you
maintain a seal as this rotates around and so here’s a little bit of a better
view you can see you’ve got the apex seal it’s got a little notch there at
the bottom and so that spring will line up with that notch and then you’ve got
the top piece of the apex seal and that’ll be right there on the top and it
also has a notch to hold the top of the spring in and so you’ll have your apex
seal there you can slide that spring down and with it and that will help keep
it pressed out then you’ve got the top portion of the apex seal and then you
have this little piece right here which will hold that all together now as I
mentioned you also have to seal off so that nothing comes over this side so you
have these side seals which can get inserted into these little grooves here
and so the way that those are maintained up against the housing is that you have
this spring you can see it’s rounded if you look at it from one side but it’s
actually a spring if you look at it from the side so that we get placed down into
that groove and then your place the side seal over that and that will maintain pressure up
against the housing and then finally you have your face seals which will be
resting in here somewhat similar in idea to piston rings and of course you have
to maintain pressure against the housing as well so you’ve got this spring right
here you can see a perfect circle but if you look at it from the side it’s got
these bins in it so that it creates pressure that will slide in there and
then you put your ring on top of it and it maintains pressure against the
housing. Now one of the things you may have noticed are these drill holes and so after the rotor has been manufactured, you want to make sure it’s balanced and so you’ll put it on a machine, you can spin it and see how it balanced it is – and then you can drill holes accordingly in order to make sure it’s balanced you can see that on both sides being done in order to balance out the rotor. Another interesting thing you’ll notice on the rotors are these con que pockets and so
with these do by removing material from the rotor you increase the displacement
of the engine now I’m going into the various advantages of using a rotary
engine versus using a piston cylinder engine and so were the first things you
probably notice is that there’s very few moving parts 1-2-3 that’s it – three moving
parts it’s an extremely simple design which has its own benefits of being
simple because it’s very simple it can also be made very reliable. Another
advantage is the fact that there’s no reciprocating mass all of this is always
rotating so one of the disadvantages with piston cylinder engines is that
when you have a reciprocating mass such as the valves which are going up and
down you can have valve float and because of the valve float you can’t rev to higher rpms so an
engine like this can rev extremely high because it’s not limited by
reciprocating mess the other thing to know with rotational mass versus having
reciprocating mass is that it’s going to be very low vibrations with a very
smooth running engine one more advantage is that has extremely smooth power
delivery and that has to do with the fact that there’s one powerstroke for
every revolution of this eccentric shaft for each rotor and so let’s kind of look
at a demo how this works now one thing you wanna notice is that
when this rotor the way it’s geared to the eccentric shaft is that for every
full rotation of this rotor it’s going to rotate the eccentric shaft three
times and that’s just simply based on the gearing now the other thing we wanna
understand is that for every time this roto rotates one full
time around you’re going to have combustion occur
three times so let’s take a look at it here you can see we’ve got these two
parts drilled out in here it’s a flat surface certainly paying attention to
this spot and rotating around one full-time and see how many times
combustion occurs so right here we have our two spark plugs so this is going to
be our first combustion which is going to be occurring in here as that rotates
and so there you have that and then you press that out there as you can see is
our second combustion and so that’s continuing on and then we’re going to
get into our third combustion so here we are igniting our third combustion here’s
that F that we were paying attention to
so we’re marking when this gets back to here and so as you can see it finishes up
back on that spot and you’ve had combustion occur three times now this
is different from a piston cylinder design with four strokes because with a
four-stroke engine for every two rotations of the crankshaft you’re only
gonna have one combustion cycle so for this for every rotation of the eccentric
shaft you’re gonna have combustion occur as a result of this power delivery is
going to be much smoother and finally another huge advantage of the Wankel
engine is just how compact it is so as you can see it’s about a foot long it’s
about a foot wide and it’s about a foot tall so all of this occurring within
about one cubic foot a very compact engine and you can fit a lot of power in
a very small life form and that gives you a lot of options for packaging so
it’s great from that sense as far as how small it
is and also want to say thank you to Shawn for letting me borrow his rotary
engine thank you guys for watching if you have any questions or comments feel
free to leave them below

Comments 100

  • I always thought those pockets on the rotors determined compression ratio…..

  • Rube Goldberg and Felix Wankel had to have been brothers😀😀

  • This is the same concept as a 2 stroke engine like on a dirt bike, and it also has similar properties to a 2 stroke, such as bad fuel economy, but a huge amount of power.

  • Bring back the illuminati engine ffs those rotors just looks cool

  • Thanks for the great info!

  • this guy explains better with actual rotary than people explaining with diagrams

  • You’re a smart dude I watch a lot of your videos

  • When did YouTube allow porn on this website again?

  • side note: the renesis in the RX8 has the exhaust ports moved to the plates from the rotor housings

  • Great video explanation of working thanks! Also how does the eccentric shaft transmit the power from the rotors to the transmission??

  • Suck squeez bang and blow

  • what does the 20b or 13b mean? cant find it anywhere!!

  • Great explanation. Well done!

  • wankel design is the best

  • wankel engine is a head time

  • Sorry, I just had to ask, I've been watching SO many of your videos, and they're pheneomenal! But How in the world did you learn all of this stuff!? You know so much about all the small details of the cars. Did you get an engineering degree, then became a mechanic or something??

  • If the lube oil is fixed in his housing system then after power the exhaust gas will mix with the lube oil and lube oil get dirty very fast it mean we have to change lube oil very fast right????

  • Pretty good explanation Jason. You might have added/shown the several ways that the engine can be modified. Bridge Ported or a Peripheral Port where the plates are blocked off and fuel goes through the rotor housings. Also another interesting fact is the cooling system surrounding the engine and that if overheating occurs it warps the housing allowing coolant in the combustion area. Another note what you refer to as the "face" seals we called the oil control rings/seals and those have rubber seals installed both inner and outer rings. The fact of mid 1970's Rotary's came with the 4 bbl carb stock is worth a mention. Like the Pick up with pick up the REPU. (ROTARY ENGINE PICK UP) The 60 cubic inch 10A R100 was a neat little Mazda too. But the absolute best of them all is the MAZDA RX3 SP. The Dream Find of any/every rotary fan. God do I love the little Wankel Engine. ATTN: If anyone has or knows of any early Mazda's available? Please reply and leave me a comment.

  • Always loved these engines. The info from 11-12 minutes made me cum a little bit

  • BEST ENGINE OF THE 21 CENTURY GREAT NEWS

  • somewhat reminds me of an 2-stroke

  • I’m new here but this engine type looks like it requires a lot of maintenance. What is it’s endurance limit?

  • If it better than four stroke then why it is absoluted?

  • One of the best Engines and cars I have ever owned. I was sorry to see them disccontue production. I owned 2.

  • Is it possible to put more rotors on the shaft?

  • For anyone who has an RX7 or RX8, don't even think about fitting aftermarket air induction equipment… you'll lose power! Air has to arrive in a rotary in a very specific way.

  • Is there an oil reservoir that the oil injector draws from?

  • Uhmm.. Mazing!!

  • Excellent Video, great job thank you

  • …Then it goes ROUND, ROUND, ROUND, ROUND, ROUND, ROUND, ROUND,
    PISS SPIN

  • if mazda could make piston engine more efficient, y not on rotary. if mazda could make spark controlled compression ignition on piston engine, y not on rotary. problem solved.

  • I am sure with more thought the Apex seal problem could be eliminated, particulary those seals on the side wall of the engine; for instance using an entire pressure plate instead of individual seals.

  • Wow

  • Back in the day I bought a new one and the salesman told me before I bought it make sure you check the oil every time you get fuel and make sure you change it every 3k . Nowdays no matter what you have to do a salesman will not tell you what the car really needs to keep it running. To bad, I had to sell it when I went in the NAVY and went on submarines and got sent to Holyloch Scotland. Now day I am probably shaving with the steel sent overseas

  • It looks more like a 2-stroke engine then a 4-stroke

  • It looks like the two spark plugs would cause the rotor to move in opposite directions?

  • It's so simplistic compared to inline's/straight's, v's, w's, and boxer's, but on the contrary, it doesn't exactly perform as well as them. (I saw this because of all of the cons present within the engine) Still quite an amazing design.

  • Thank you so much for an excellent explanation of a rotary engine it is a very simple working engine but I never knew anything about them so it always scared me my son and I just picked up a Mint RX7 with a supercharger on it it's a race car that never got finished but now that I understand a little more more willing to tackle.

  • Is there a part 2 where he explains the cons?

  • WTF? sure – DON'T tell us how much horsepower is generated by such a small engine comparatively

  • 2 Rotors = V6

  • AIE UK use ceramic rotor tip seals. No oil needed. Their engine has a sealed oil system

  • interesting design yes, garbage engine yes.

  • I have a question, what does the air fuel mixture compress up against, because if there is nothing for it to compress against the mixture would just continue being pushed around the chamber, unless the rotor rotates around a central shaft like a planetary gear sistom making the rotor crawl around the chamber.

  • Dude you rock this video man i never knew how a rotary engine works and you explain it very well

  • 13b with single turbo can easily getting 500 + hp, able to with stand high turbo boost maybe can count as one of another advantage. since there is very few moving parts , a lot less component will be considered.

  • Great german design, even with flaws.
    Is there any try-outs/ improvement through the years of using this engine, by japanese, or they really abandon this beauty for piston engine? This type of engine would be great for small cars, trikes, or even motorcycles…

  • This is probably the most insight I've gotten about rotaries.Back in highschool we briefly touched the subject and I had a friend that was into rx7s but I haven't personally had to work on one.I work on a quite a bit of stuff on a regular basis but still haven't had to mess with one.Unfortunatly there just isn't too many around.Maybe I'll have to plan a project.

  • Would it be possible to use mini rollers around the apexes instead of apex seals, that way lubrication wouldn't be as crucial, and the apexes wouldn't get damaged as much

  • could it be possible to fix the problems with a rotary engine while maintaining it's benefits?

  • That's an old design so I believe that with modern technology they can rectify those flaws

  • I understand the 2 sparkplugs…. but why is there 2 sets of injectors ?

  • Nice explained buddy

  • Love the videos bud, your explanations very clear and simple. Thanks

  • piston can easy to know how many cc there, how about this rotary engine?

  • Does anybody have the dimensions for the width of the rotor in the wankel engine of the RX-7?

  • Excellent well presented and easy to follow. well done young man

  • Holy dann. A 2 roto engine Is like the equivalent of a 6cylinder.

  • Wait, how does the 20B (triple rotor) work? Like what’s the angle difference of the rotors and is it different in any other way? And if the mesh gear that rotates the “crankshaft” goes in the front plate, why does the other rotor also have gear teeth?

  • The Wankel engine is revolutionary

  • I’m saving up to get an FD and I hope that in 5 years I get one

  • They use a similar principal to a two stroke engine. As the piston moves, it uncovers exhaust and intake ports, so no valve train, no valves, no timing chain. They used to be somewhat polluting but university of idaho solved the problem and now 2 stroke snowmobiles run cleaner and are more fuel efficient that 4 strokes. Plus they weigh alot less. While rotary and two stroke engines make need rebuilds sooner, they are exponentially simpler to break down and rebuild. Doing a new piston and rings on a two stroke is not much more difficult than changing a tire.

  • What is the material used in the rotor, eccentric shaft and edge seals of the rotor

  • What a simple amazing design for a motor that lead the racing game good job on the builders this is amazing craftsman ship

  • Thank goodness that engine died long ago…

  • Great video my new RX-8 got about 18 MPG!

  • Many Thanks for your clear description of wankel engine,perhaps moore concerning subject are reliability for aircraft use, the TBO regarding apex seals and its metallurgy specs alloy,and what configurations are for exhaust( lateral located)?? and intake peripheral or side or lateral too? what is gear ratio,and eccentricity of shaft to rotor center of symmetry?trochoidal equation? Best Regards .Its future in hybrids cars or planes wonderfull,air cooling or liquid cooling,which is best,ethylene glycol probably? Bye, Many Thanks.I read that this concept was utilized on 16 century for water pumping or it is a myth?For pumping wonderfull as hydraulic actuator.

  • Jason the teacher.

  • rotarys are awesome
    but people who think they are a simple engine are mistaken .

  • A truly fascinating engine. So many advantages, so many disadvantages.

    I am happy they never went mainstream. Makes seeing and hearing a rotary a special occasion.

  • i own an rx8, 2004, and its been the MOST reliable car to me, sure it takes some quarts of oil every 5000 miles or so, but thats about the only "high maintenance" aspect i had to deal with, been on top of the routine maintenance such as coils, spark plugs, revving 9000 rpm a day, not starting and stopping when cold, etc.

    But i wonder, can the rotary engine be improved upon where it can get decent MPG while lowering emissions, or the limitations on the design of the wankle engine makes that physically impossible? Is there any way to make a rotary engine reliable and moderately fuel efficient? I'm not saying it needs to be have like 29 mpg, but how about something like 21-24 city mpg? is there any solution to the rotary engine? or the design of the engine itself prevents it?

  • Eh? Why is there a throttle linkage for the oil injection when the oil metering pump has a direct connection to the output of the motor? Wouldn't the injection correlate directly to the current RPM?

  • A turbo-charged engine of that size can have 800 hp, just saying.

  • Wish you would talk about the 20B rotary

  • I liken them to 2 stroke engines, port induction, burns oil….

  • does anyone know which directions of the pressurized force points during the the combustion cycle, doing an analysis for my dynamics class

  • Okay. So know how in piston engines everything balances in 3's and why the inline 6 is such a great engine…. What if there was 6 rotors instead of 3? Not sure how many the RX-8 has.

  • I can buy rotary now, Thanks!

  • Good Morning!
      I gave the patent for a new rotary engine, 4 stroke, few moving parts, better than the Wankel, because there are no leaks; I need a partner / partner to manufacture a prototype and market; Do you know who can help me?

  • Brought back memories! I got an ‘87 in ‘96 and “played” with it like that when I rebuilt it. My grandfather, a GM service manager for decades at the time, especially found it fascinating! It was definitely the easiest rebuild I’ve ever done and the simple changing of all the decade old seal springs made a difference of night and day.

  • Despite a few disadvantages, you gotta be very creative to come up with something like that

  • R those engines reliable ??

  • R those engines reliable ??

  • R those engines reliable ??

  • No torque……no poop

  • Thanks Beto O'Rourke!

  • Excellent video, beautifully presented 👍

  • Do they use gaskets or gasket maker sealant when they bolt the engine together?

  • Wow what a great video!! 👏 No joke. I've Never had any knowledge about rotary engines.👍 This was a very well explained and educational video

  • Is each rotary housing equivalent to a 3 piston engine from what I am seeing described?

  • Its crazy how small it is 😀

  • Coming of age in the 2000s, I always thought the RX-8's Wankel had essentially the performance characteristics of the S2000's F20C (both fantastic engines in their own ways). About the same power, about the same rev range.
    Am I way off? Does anyone know if an in-depth comparison of the two? Like, if you had a stock RX-8 and S2000 and swapped their engines with each other… Aside from (probably) sound, what would be the big difference?

  • In a sense, it can be said 1 rotor is equal to a 3 cylinder piston engine. No wonder the 13b went up against 6 cylinders of the time

  • Higher RPM? We have piston engines that rev to over 14,000 rpm.

  • So then why are rotary engines so rare? What's the major flaws that influenced the complete neglect of this technology from virtually every automotive manufacturer?

  • Such a captivating design and look.
    Inefficient, but wonderful.

  • They have to forget this and make it EV systems car with 1000kmpc range with in 10lakhs Rs price

  • I got a Mazda MX-5 commercial before this I swear

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