Rotary Engine | How It Works

Rotary Engine | How It Works

– We’ve talked about engines before, and I don’t know if I’ll
ever get tired of it. The air gets compressed by the piston, and the spark… What? No, stop it! There’s no piston here! What if I told you we could
skip all of that crap? Not worry about turning downward
force into rotational force and cut the size of the
gall dang engine in half? That’s the Wankel rotary engine! In 1951, Felix Wankel
got this idea in his head that if you put a triangular
rotor in a well-designed circely, oval-ish shape,
you could make an engine that took care of intake,
compression, combustion, and exhaust, just like the
traditional piston-drive Otto Cylce engine. And because it’s a spinning
motion, you wouldn’t need to worry about crankshafts
and valves and timing belts and lifters and all that
crap that other people are goofin’ around with. He had some trouble
getting it right, though. So it was in 1961 that Mazda,
intrigued by this idea, helped him out, and here’s how it works. A curved triangle sits in the engine. It’s what’ll drive the
driveshaft, which is also weird. Instead of a piston, this magic
triangle is called a rotor, because it spins. The rotor sits inside
of a housing and rotates around a fixed gear
attached to the housing. This gear makes sure that the
rotor follows the right path, so it’s not just floating around in there. The rotor then spins an
eccentric output shaft, and this is what’ll give the car moving. You can call it a driveshaft if you want, I’ll know what you’re talking about. But just the names of the
parts should let you know that the Wankel rotary engine
plays by its own rules. Now that we know the parts,
let’s see how they fit together and make the boom. We’ll start with the intake. As the triangle-shaped rotor
draws away from the wall of the housing, it’s creating a vacuum. As it passes the intake hole,
it continues to pull away from the wall, drawing
the air-fuel mixture into the chamber it’s
creating, just like a piston would draw air in on its intake stroke. When the peak of the rotor
passes the intake port, well, now that chamber’s sealed. The rotation of the triangle,
still sealed against the housing, begins to
compress the air-fuel mixture as it continues its rotation. When the air is as compressed
as it can be and the rotor has just a bit more mass on
the other side of the chamber, a spark triggers the combustion. The combustion chamber is long. If there’s only one plug, the
flame would spread too slowly to be effective at producing power. Most rotary engines have two sparkplugs. When the sparkplugs ignite
the air-fuel mixture, kapow! It forces the rotor to move in a direction that allows the combustion
reaction to expand, continuing the rotor’s
journey around the housing. The combustion gasses continue
to expand, moving the rotors and creating power, until
the peak of the rotor passes the exhaust port. Just like the rotor compressed
the air-fuel mixture against the wall with the
sparkplugs, on this side of the housing, the rotor
pushes the exhaust gasses out of the exhaust port. And if you look at the
other point of the triangle, the rotor is beginning to draw
air into the intake chamber just as it’s finishing
with the exhaust down here! So the cycle continues,
over and over and over and over and over and over,
and it continues to go over and over and over. But unlike the jerky up-and-down
motion of the pistons, the rotor moves, just
like my favorite band, in one direction. ♪ You don’t know you’re beautiful ♪ There’s so much rubbing
going on between the rotor and the housing that that
gave Wankel a lot of problems as he was designing. Engineers realized that a
hole to let in the engine oil would reduce wear on
the rotor and housing. Also, to make sure that no
chamber of the combustion cycle loses pressure, apex seals
cap the point of the triangle. These tweaks are what took
Wankel’s early underwhelming experiments from
curiosity to practicality. And look at this triangle! With three sides, as
soon as one side begins, let’s say, combustion,
another side is completing exhaust while the third side
is drawing in air and gas! So, unlike a traditional
piston-driven engine, which would need three
cylinders to do that, like the rare but very real
in-line three, you only need one active component, the
rotor, to have three stages of engine combustion
occurring simultaniously. The way Mazda did it on their engines, like what powered the RX7 and RX8, was to put two rotors that
complimented each-other, so when one rotor was entering combustion, the other was about to enter combustion. You can see how evenly
a Wankel rotary engine can deliver power versus
the herky-jerky up and down of a piston-driven engine. This evenly-driven rotational
force spinning the rotors drives the output shaft. The output shaft has round
lobes mounted eccentrically, meaning they’re offset from
the center line of the shaft. Each rotor fits over one of these lobes. The lobes act sort of like the crankshaft in a piston engine. As the rotor follows its
path around the housing, it pushes on the lobes. Since the lobes are mounted
eccentric to the output shaft, the force that the rotor
applies to the lobes creates torque in the
shaft and makes it spin. This makes the eccentric
shaft move three turns for each turn of the rotor,
and that’s why these engines can create such high rev. (engine revving) And if you check out the
horsepower versus torque video, you’ll know horsepower is how quickly force can be produced. A high-revving engine
doesn’t need as much torque to generate more horsepower, because it’s delivering it so quickly. And, like Mazda did with the
RX7, they can be turboed, just like any other engine. And again, because they’re
revving so high, a turboed Wankel doesn’t have to worry
half as much about lag! Some lag! So, what are some other
benefits of a rotary engine? First, there’s fewer moving parts. No lifters, no push rods, no camshafts. All those little things
that can go wrong in a traditional engine simply
aren’t there in a Wankel, so they can’t break. In a two-rotor Wankel, you
got two rotors and one e-shaft to worry about, that’s it. And that means these
engines can rev higher and not bust any of those intricate parts. And also? You don’t need four, five, six cylinders, you’ve got an engine
delivering consistent power, making awesome noises! (engine revving) And taking up half the
room of other engines! Oh! And sometimes, when it
gets moving really quick, you get this! (backfiring) That is pretty cool! But that’s also a drawback. Wankels use a lot of gas because they have a low compression ratio. When they get moving like
that, they make those sweet-ass flames ’cause they’re
shooting out exhaust gasses with unburnt hydrocarbons. That’s not good for fuel economy, and it’s not good for the air! Also, remember how they’re lubed with oil throughout the housing? That oil burns when it’s hot. That means more burnt
less clean hydrocarbons, which is tough for emissions. You remember how they sealed
up the different chambers created by the rotor. Remember, from before? Uh, yeah. You can blow an apex seal,
and if that happens… (screaming) Those chambers bleed into one another and you lose most of the benefits
that made you fall in love with your screaming rotary
engine in the first place. Between being different and being good, Wankel rotaries are pretty rad. Wankel rotary engines! If you like the way we
show how things work on Science Garage, then you
really need to check out Brilliant is math and
science enrichment learning. It’s engaging, and instead
of just getting talked at about how thing worked,
Brilliant is set up to let you really get in there and apply what you’re learning. The sequences lead you
to thought-provoking, challenging problems, and
that helps you understand concepts at a deeper level. Actively solving problems
becomes an addictive, interactive experience,
and I gotta tell you, it’s pretty cool. How do you think the brain
trust we just talked about created the Wankel rotary engine? They had a deep understanding of physics and practical application
and problem-solving, just like the courses at A great place to start is
with Physics of the Everyday. This course gets into how
things work, things you use every day, just like we
do here on Science Garage! To learn more about Brilliant, go to
and sign up for free! Also, the first 200
people to go to the link will get 20% off their
annual premium subscription! I’ll see you there! Brilliant! And follow me on Instagram, @bidsbarto, and follow Donut, @donutmedia. We got shirts like this, and
we got new designs comin’ soon. Guys, we do this every Wednesday! Make sure you subscribe,
hit the yellow button so you get notifications! Like the RX7, you can learn
about turbochargers here, and you can learn about
the RX7 in this episode of Up to Speed! Don’t tell my wife these
engines can be a hassle, ’cause I’m trying to get one.

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  2. The sad thing is i bet if mazda still was able to keep on working on the thing without having to worry about emissions i think that the rotary would of evolved into something amazing but another motor taken down by emissions standards that is still amazing

  3. You didn't give significant performance advantages of rotary engines, only disadvantages; so why did my brother buy one?

  4. To Wankeln (ger. Verb) is kind of what describes the entire process of the rotary engine. German(-Japanese) Engineering at its deepest level.

  5. un story. my dad had an old book that taught him a lot about engines back in the day. he gave me this to read when i was lik 4th grade back in 98. i was the smartest kid in the school according to my teachers lol. I did so many lectures on the Wankel engine an was way knowledgeable about it before any one even knew what it was(in my age group ya dumb fucks). im still a big fan of it, and wish I had the capital to improve on it. in geometry the hexagon is a pretty good, if not the most common form in nature, and thus I believe to implement this shape into a similar design, would be the most efficient bad ass thing ever invented. either for vehicle propulsion or energy production in general

  6. On small island in the Caribbean where I’m from, there was a guy at the track that had a turbo rotary Toyota Starlet called “Problem Child” and, I’m here to tell you, it was a BEAST.

  7. Hey Donut Media abd Science Garage,
    I'm currently working on getting my Airframe and Powerplant lisence. I've watched a several episodes and it's always a good refresher. I was wondering if you could talk about radial engines? About how they work, pros cons etc in sicence garage style.

  8. They should make a better motor that will fit in the RX8 without having to go out every 80,000 because they made a lot of of them but the motor suck too many design flaws p I have one in the motors almost as much as the car with was when it was brand new

  9. Wankel engine will remain just a technological curiosity… with inherent leaks between the intake, outflow and combustion because of the basic design, fuel efficiency and exhaust emission can never be improved.

  10. Love your videos! Anesthesiologist who loves learning about engineering, history, creativity and cars. Thanks your explanations are great

  11. I am studying mechanical engineering and these videos are much more helpful than most of the books about internal combustion engines.

  12. Rotary engine in the Mazda RX-8. (Image: Mazda)The rotary engine has been around since the early 20th century. But it didn’t come to autos until the second half of the century. The “Wankel” engine was licensed by a long list of OEMs but its deployment is best known in Mazdas, the company that put the rotary engine under the hoods of a variety of vehicles, the last of which was the RX-8. Production ceased in 2012.Simple DesignAlthough the rotary engine is compact and simple—as in no pistons, camshafts, etc.—with a quasi-triangular shape (the lines between the points of the triangle are arcs, not straight lines) moving in an eccentric orbit within a combustion chamber.Vexing ProblemsReasons why Mazda stopped producing the engines include not-stellar fuel efficiency and emissions issues, both largely predicated on compression problems, which lead to incomplete combustion such that there was unburned fuel after the spark.Potential SolutionsFormer Mazda technician and inventor Ernie Brink thinks that he has come up with design modifications that address these drawbacks of the rotary engine and he talks about it on this edition of “Autoline After Hours” with Autoline’s John McElroy, Todd Lassa of Automobile Magazine and me.What’s more, Brink provides demonstrations of the way the Wankel works—even using an air compressor to rotate the rotor.

  13. I loved both the RX-7 FC and FD. I thought they were gorgeous cars especially the FD. Then they released the RX-8 and it looked like trash. How you could go from the FD to that is beyond me. Still want an RX-7 FD to this day.

  14. Is a rotary really that unreliable? People say it’s unreliable but I’ve never seen a single video of one blowing up. They’re making crazy power number usually too.

  15. Fucking loud ass sound effects with the dude yelling, I can't even relax and watch this shit. Dude needs to calm the fuck down.

  16. Idk man my rx8 2008s been running fine since still have to replace the seals for the oil chamber not the seals since theyre aftermarket and last for 120k miles maybe 30k miles linger than oem apex seals and DONT FORGET TO ADD 2 STROKE OIL TO YOUR FUEL AND A HIGH REV A DAY KEEPS THE CARBON AWAY

  17. I dont know exactly why but having this video at 1.25x speed seems normal, almost as if they slowed it down in post processing because of some reason

  18. So does this mean the Rotary Engine is better then an engine with a Piston? Since they can do 3 turns for each turn of the rotor?

  19. Well another part i love about rotarys is the really smooth Power-band and if you'll screw on an Supercharger it compliments its nice power-band even more.

  20. I still can’t believe Mazda actually used this piece of shit engine. The only advantage if you can even call it that is it’s small size. It burns oil and uses a butt ton of gas

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