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Thread: does the rotary engine require replacements every so often?

  1. #1
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    Default does the rotary engine require replacements every so often?

    excuse my newbie question, but i have no clue about engines, only their names. (or cars for a matter... if a car didnt have an engine, i wouldnt realize it even if i was told )
    but anyways, my friend (hes nto the most realible, tho he is correct sometimes ) tells me that if u ride the rotary engine(rx8,. rx7) a lot u will have to replace it every so often? he says that the triangle inside the engine will become more of a circle? i dunno is he correct or is it complete bs?
    Last edited by KPDrag0n; 08-02-2003 at 08:33 PM.
    i dun know a thing about cars. Someone teach me.

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    little seals on the tips of the triangle break (apex seals)they are pretty much the same as piston rings if you know what thoes are

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    if the motor overheats it can warp the apex seals and obviously the engine wont run as well.

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    www.3rotor.com
    http://www.rx7heaven.com/
    http://www.rx7.com/

    here is the history of the motor
    http://www.monito.com/wankel/

    A rotary engine is an internal combustion engine, like the engine in your car, but it works in a completely different way than the conventional piston engine.



    In a piston engine, the same volume of space (the cylinder) alternately does four different jobs -- intake, compression, combustion and exhaust. A rotary engine does these same four jobs, but each one happens in its own part of the housing. It's kind of like having a dedicated cylinder for each of the four jobs, with the piston moving continually from one to the next.

    The rotary engine (originally conceived and developed by Dr. Felix Wankel) is sometimes called a Wankel engine, or Wankel rotary engine. The Basics
    Like a piston engine, the rotary engine uses the pressure created when a combination of air and fuel is burned. In a piston engine, that pressure is contained in the cylinders and forces pistons to move back and forth. The connecting rods and crankshaft convert the reciprocating motion of the pistons into rotational motion that can be used to power a car.
    In a rotary engine, the pressure of combustion is contained in a chamber formed by part of the housing and sealed in by one face of the triangular rotor, which is what the engine uses instead of pistons. The rotor follows a path that looks like something you'd create with a Spirograph. This path keeps each of the three peaks of the rotor in contact with the housing, creating three separate volumes of gas. As the rotor moves around the chamber, each of the three volumes of gas alternately expands and contracts. It is this expansion and contraction that draws air and fuel into the engine, compresses it and makes useful power as the gases expand, and then expels the exhaust.

    In the next section, we'll take a look inside a rotary engine and check out the parts.
    The Parts
    A rotary engine has an ignition system and a fuel-delivery system that are similar to the ones on piston engines. If you've never seen the inside of a rotary engine, be prepared for a surprise, because you won't recognize much.
    Rotor
    The rotor has three convex faces, each of which acts like a piston. Each face of the rotor has a pocket in it, which increases the displacement of the engine, allowing more space for air/fuel mixture.

    At the apex of each face is a metal blade that forms a seal to the outside of the combustion chamber. There are also metal rings on each side of the rotor that seal to the sides of the combustion chamber.

    The rotor has a set of internal gear teeth cut into the center of one side. These teeth mate with a gear that is fixed to the housing. This gear mating determines the path and direction the rotor takes through the housing.

    Housing
    The housing is roughly oval in shape (it's actually an epitrochoid -- check out this Java demonstration of how the shape is derived). The shape of the combustion chamber is designed so that the three tips of the rotor will always stay in contact with the wall of the chamber, forming three sealed volumes of gas.

    Each part of the housing is dedicated to one part of the combustion process. The four sections are:

    Intake
    Compression
    Combustion
    Exhaust

    The intake and exhaust ports are located in the housing. There are no valves in these ports. The exhaust port connects directly to the exhaust, and the intake port connects directly to the throttle.

    Output Shaft
    The output shaft has round lobes mounted eccentrically, meaning that they are offset from the centerline of the shaft. Each rotor fits over one of these lobes. The lobe acts 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, causing it to spin.

    544 wrhp 555 ft/lbs torque @ 15psi

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    Now let's take a look at how these parts are assembled.
    How It's Put Together
    A rotary engine is assembled in layers. 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 part of the rotor housing that holds the rotors
    (Note the exhaust port location.)
    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.
    Producing Power
    Rotary engines use the four-stroke combustion cycle, which is the same cycle that four-stroke piston engines use. But in a rotary engine, this is accomplished in a completely different way.
    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.

    Key Differences
    There are several defining characteristics that differentiate a rotary engine from a typical piston engine.
    Fewer Moving Parts
    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.

    This minimization of moving parts can translate into better reliability from a rotary engine. This is why some aircraft manufacturers (including the maker of Skycar) prefer rotary engines to piston engines.

    Smoother
    All the parts in a rotary engine spin continuously in one direction, rather than violently changing directions like the pistons in a conventional engine do. Rotary engines are internally balanced with spinning counterweights that are phased to cancel out any vibrations.

    The power delivery in a rotary engine is also smoother. Because each combustion event lasts through 90 degrees of the rotor's rotation, and the output shaft spins three revolutions for each revolution of the rotor, each combustion event lasts through 270 degrees of the output shaft's rotation. This means that a single-rotor engine delivers power for three-quarters of each revolution of the output shaft. Compare this to a single-cylinder piston engine, in which combustion occurs during 180 degrees out of every two revolutions, or only a quarter of each revolution of the crankshaft (the output shaft of a piston engine).

    Slower
    Since the rotors spin at one-third the speed of the output shaft, the main moving parts of the engine move slower than the parts in a piston engine. This also helps with reliability.

    Challenges
    There are some challenges in designing a rotary engine:

    Typically, it is more difficult (but not impossible) to make a rotary engine meet U.S. emissions regulations.

    The manufacturing costs can be higher, mostly because the number of these engines produced is not as high as the number of piston engines.

    They typically consume more fuel than a piston engine because the thermodynamic efficiency of the engine is reduced by the long combustion-chamber shape and low compression ratio.


    And thats all I have to say about that.
    Yes it was a good cut and paste thank you.


    544 wrhp 555 ft/lbs torque @ 15psi

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    wow thanks a lot
    i dun know a thing about cars. Someone teach me.

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    Originally posted by hjr
    if the motor overheats it can warp the apex seals and obviously the engine wont run as well.
    Ah I love common rotary misconception. That comment is WRONG plain and simple. Housings can warp not apex seals but one overheating does not neccesarily mean blown motor.

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    sorry, dude. You are probably right about the seal, but aside from that, I didnt mean a blown motor, but dont kid yourself, rotary's are very very suseptible to damage from overheating. Way more than an average piston set-up. Now im not saying the motors are junk, but they have their problems.

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    And 9 times out 10, the rotaries problem, is the person driving it....Maxt
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  10. #10
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    Originally posted by Maxt
    And 9 times out 10, the rotaries problem, is the person driving it....Maxt
    Ding, ding, ding.

    I was driving my bro's RX-7 when it went kaboom.
    -Rob, Wannabe Director
    1987 Ford Mustang 2.3L Turbo


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    Originally posted by hjr
    sorry, dude. You are probably right about the seal, but aside from that, I didnt mean a blown motor, but dont kid yourself, rotary's are very very suseptible to damage from overheating. Way more than an average piston set-up. Now im not saying the motors are junk, but they have their problems.
    Yes and no.

    Overheating any high performance motor will cause major problems. In a piston motor however these problems may go undetected for a period of time after overheating has occured, but the damage has still occured. Do the motors have their problems? Yes of course, the misconceptions about their problems stem from the fact their not the typical problems you might find ona piston motor. Are there more problems with a rotary than a piston? Not really just different and it really comes down to the owner.

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    thanks
    i dun know a thing about cars. Someone teach me.

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