Rotaries also prefer mineral oil to synthetic, and their design means you must top off the oil periodically because the engine is constantly drinking it. Those apex seals don't tend to last long before they need replacing, either. Rebuilding a Wankel at 80,, miles is typical, and earlier than most piston engine need such exhaustive work.
For the RX-8, Mazda alleviated these problems by placing the exhaust ports on the sides of the combustion chambers. Fuel emissions have gotten stricter over the years, too.
That's part of the reason the RX-8, the last Wankel-powered car, went on sale in and was phased out in Back to Mazda VP Martijn ten Brink's rumor, that Mazda could use some kind of rotary engine as a range extender for an electric car. It'd make sense.
Back in , Mazda leased Demio EV electric cars in Japan, but the car's short mile range was a sore point. So in , Mazda created a prototype that incorporated a rotary range extender to nearly double that range and called it the Mazda2 RE Range Extender Mazda2 is what the Demio is called outside Japan. The prototype's wheels were driven via an electric motor, and a 0. Because the rotary engine couldn't power the wheels, the Mazda2 RE wasn't a hybrid like the Volt or Prius. The Wankel was more of an onboard generator that added to the car's range.
But the range extender concept didn't make it into production, and Mazda didn't hasn't sold any electric vehicles since those Demio EVs. Still, the rotary built its reputation mainly as a sports car motor, not as a generator lugged around by electric motors. As long as rumors of a rotary revival endure, car lovers will dream of this fussy, quirky engine once again powering the wheels of a torquey, rev-happy ride. Type keyword s to search.
Today's Top Stories. Getty Images. 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, causing it to spin. The two-rotor engine we took apart has five main layers that are held together by a ring of long bolts.
Coolant flows through passageways surrounding all of the pieces. The two end layers contain the seals and bearings for the output shaft.
They also seal in the two sections of housing that contain the rotors. The inside surfaces of these pieces are very smooth, which helps the seals on the rotor do their job. An intake port is located on each of these end pieces. The next layer in from the outside is the oval-shaped rotor housing, which contains the exhaust ports.
This is the part of the housing that contains the rotor. The center piece contains two intake ports, one for each rotor. It also separates the two rotors, so its outside surfaces are very smooth. In the center of each rotor is a large internal gear that rides around a smaller gear that is fixed to the housing of the engine. This is what determines the orbit of the rotor. The rotor also rides on the large circular lobe on the output shaft.
But in a rotary engine, this is accomplished in a completely different way. If you watch carefully, you'll see the offset lobe on the output shaft spinning three times for every complete revolution of the rotor. The heart of a rotary engine is the rotor. This is roughly the equivalent of the pistons in a piston engine. The rotor is mounted on a large circular lobe on the output shaft.
This lobe is offset from the centerline of the shaft and acts like the crank handle on a winch, giving the rotor the leverage it needs to turn the output shaft. As the rotor orbits inside the housing, it pushes the lobe around in tight circles, turning three times for every one revolution of the rotor. As the rotor moves through the housing, the three chambers created by the rotor change size. This size change produces a pumping action. Let's go through each of the four strokes of the engine looking at one face of the rotor.
The intake phase of the cycle starts when the tip of the rotor passes the intake port. At the moment when the intake port is exposed to the chamber, the volume of that chamber is close to its minimum. When the peak of the rotor passes the intake port, that chamber is sealed off and compression begins. By the time the face of the rotor has made it around to the spark plugs , the volume of the chamber is again close to its minimum.
This is when combustion starts. Most rotary engines have two spark plugs. The combustion chamber is long, so the flame would spread too slowly if there were only one plug. The pressure of combustion forces the rotor to move in the direction that makes the chamber grow in volume. The combustion gases continue to expand, moving the rotor and creating power, until the peak of the rotor passes the exhaust port.
Once the peak of the rotor passes the exhaust port, the high-pressure combustion gases are free to flow out the exhaust. As the rotor continues to move, the chamber starts to contract, forcing the remaining exhaust out of the port. By the time the volume of the chamber is nearing its minimum, the peak of the rotor passes the intake port and the whole cycle starts again. The neat thing about the rotary engine is that each of the three faces of the rotor is always working on one part of the cycle -- in one complete revolution of the rotor, there will be three combustion strokes.
But remember, the output shaft spins three times for every complete revolution of the rotor, which means that there is one combustion stroke for each revolution of the output shaft.
The rotary engine has far fewer moving parts than a comparable four-stroke piston engine. A two-rotor rotary engine has three main moving parts: the two rotors and the output shaft. Even the simplest four-cylinder piston engine has at least 40 moving parts, including pistons, connecting rods, camshaft , valves, valve springs, rockers, timing belt, timing gears and crankshaft.
Attached to an eccentric shaft, these rotors remain in contact with the housing at all times as it spins. The design of the rotor and housing is such that there is a void created which expands and contracts, based on the position of the rotor. Each of these voids is directed to take care of one aspect of the combustion cycle.
As the rotor turns it compresses the mixture, expands the chamber again as it ignites, then squeezes the exhaust gasses out of the exhaust port. Felix Wankel, the German Engineer, was the mastermind behind the very efficient and power-saving prototype of the rotary engine. The rotary engine gained popularity owing to its lower number of components but with the same process as a conventional engine. The absence of valves, timing gears, con-rods, piston, crankshaft makes things considerably lighter and cheaper.
A general rotary engine comprises an ignition system and a fuel-delivery system, quite similar to that of the piston engines. However, there are a few parts that are so different from the conventional engine that it makes even the most avid car lovers scratch their head in confusion. At the top of each of the convex faces, there is a metal blade designed to fix the rotor to the outside of the combustion chamber. The metal rings on each side of the rotor also assist in sealing the component to the sides of the chamber.
Apart from this, the rotor also comprises a set of internal gear teeth, carved on to the centre of one side. These teeth are used to affix it to the gear found in the housing. It is a crucial matter since this connection decides the route the rotor will take through the housing. After the rotor, comes the housing which makes for an important part of the rotor engine. It features an epitrochoid shape, also known as an oval shape, which is designed such that the tips of the rotor are always in touch with the walls of the chamber.
The housing is extremely crucial as each part of it is employed to complete one part of the combustion process which includes Intake, Compression, Combustion, and Exhaust. The intake and exhaust ports are located in the housing, however, there are no valves in these ports. The exhaust port makes direct contact with the exhaust, and the intake port connects directly to the throttle.
The output shaft contains round lobes which are mounted in an offset manner, that is, slightly off from the centre of the shaft. The rotors are designed to fit over these lobes, similar to that of the crankshaft in the piston engine.
When the rotor moves, it pushes back on the lobes, which creates a torque in the shaft, causing it to rotate. In a conventional engine, there is the concept of the four-stroke piston which is used to power the heart of the machine.
Similarly, the rotary engine makes use of the four-stroke combustion cycle which gets the same work done in a different manner. The rotor, also known as the heart of the engine, is placed on a circular lobe on the output shaft. As we discussed, the lobe is unusually placed shaft, which allows the rotor to rotate the output shaft.
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