If I am right, the rotatory engine has existed since the 1930's and nowadays, only Mazda produces cars with this kind of engine (the RX-7 series and now the RX-8), it is a lot smaller, and from what I understand, you need just two of this pseudo-turbines to develop more HP's than what you usually get with a traditional four pistons engine... but, is this engine really better than the traditional one (made in base of pistons)???... if that's so, why is Mazda the only major brand actually producing it???

What do you think people???

I think they where first designed later than the 30's.Anyway one main problem was trying to make them economically. And the second was making them reliable. Now that its prefected - they are more reliable and cheap(ish) to make, and also produce less rattles and shuffles.
They're more reliable as they create circular motion straight away, and therefore no need for crank shafts/cam shafts. - which gives a more simple engine. And also because power delivered in one revoluton 3 times, compared with only twice with a piston. This means the engine can spin slower, again incresing reliablity.


I guess one reason why they arent as popular as you'd think is because of the amount of defelopment and investment in the piston ingine - so why was that on a development that is only marginaly better?
Rotary engines are less fuel efficent resulting in high gas emmssions - which pushs up the price. Also they still are more expensive to make than the piston engine - mostly due to the fact that the whole industry is geared towards pistons.

Whoops... mental fart... You are completely right Mallon... the idea began in 1917, but the first rotary engine ever built was in 1958... I just find the page I red this for the first time...

That thing you mention about the investiments made in the pistons make a lot of sense... and not only refering to engines... In engineering, most specificly automatic control, there are certain controllers called PID... this ones are really old, and there are other controllers that are cheaper and more efficient, but nearly 90% of the controllers used nowadays, all around the world, are PID type... this means that the investment they would have to do to upgrade this controllers would be just too huge... that's why they don't change it...

In fact, the geometry of rotary engine is way more complicated than the traditional one, I had to read a bit about it in mathematics, it was an example in my guide book... once more the idea to break the inertia of the whole industry...

You just answered a question I have had since a long time... fuel... but do you know what makes this engines less fuel efficient????

I sure do...

The rotar part of the engine is ised to 'crush' the gas anad fuel before ignition. But the rotar part can only compress to a point where it can still rotate (ie. stay on course to follow the elliptical path path of a rotar engine). This leads to a lower compression ratio than what you see in a piston engine.
Low compression means not all fuel gets combusted - reducing fuel ecconomy

- terribly explained, but its the best i can do! :D

Not at all... I understand it perfectly, thank you... 8) .... now that I used that smilie, I just realized that up there appears a RX-8) instead of a RX-8 )... sorry about that...

There is just one thing I don't get... I understand why a rotary engine can deliver power three times in one revolution as the rotor is a triangle with convex sides, so, in one single spin, the rotor compresses the fuel three times, delivering power in each ignition, but which are the two times in a piston engine???... I mean, the piston can deliver power only when it goes down and when it goes up, but, as I understand, it is the inertia of the system what makes the piston go up, so the piston is only delivering power once in a single spin, that's why in a four pistons engine, 2 pistons go down at the same time as the other 2 are going up... at least that is what I understand... where went I wrong???

yeah ive just written that worng

There is once every 2 rotations for each cylinder in the engine. (my mistake, i just got muddled up; i write 2 not 1/2)

so the piston is only delivering power once in a single spin

But form your explanation above i think you think that in a car engine it happens once every rotation - but thats ony true for a 2 stroke engine (chainsaw engine) - in cars its 4 stoke so its once every 2 rotations.

The other benefit of Rotary is their ability to rev at such hight RPM's (but unfortunately increase in RPM's slower than piston engines). FOr a small displacement they can create lots of HP. But from what I understand the RX-7 rotary's rarely lasted 100k miles before needing a rebuild. I guess the lobe tips would wear down until compression was totally lost..which you say is already low. Now...I dont know if this is b/c they are overheating or not. I know when overheated they tend to **** the bed. But even when NOT overheated do they still last? I have no personal experience with owning an RX and I hope this problem wont be the case with the RX-8.

The other benefit of Rotary is their ability to rev at such hight RPM's

but they dont have to - they produce the same horse power at slower evs - so increasing the revs to comparable revs to a piston doesnt make a pile of sense.

I think that the rotary engine will catch on eventually. How long did it take the internet to catch on? like, 20 years? Maybe mazda has a patent and nobody else can make it, like the hemi? i'm probaly wrong

Rotary engines produce a much higher amount of horsepower from a smaller displacement, are smaller in size and they have less moving parts, so eventually they are more reliable and (in theory) should last longer than piston engines.

The negative points are that they consume more fuel, have higher gas emissions and they are somewhat expensive to develop.

The first rotary engine prototype was created by Dr. Felix Wankel, therefore the rotary engines are also known as "Wankel" engines. They were used mostly by NSU and later on by Mazda. The new Mazda RX-8 will have a rotary engine with a displacement of 1300cc and an output of 240HP (without any turbo-supercharger)!! The redline will be at 9000 RPM!!!!!!!!! :!: :!:

First off... I am really sorry I didn't reply earlier... I just got out of an exams period that was really really hard... that's why I didn't reply before Mallon...

Back on topic...


But form your explanation above i think you think that in a car engine it happens once every rotation - but thats ony true for a 2 stroke engine (chainsaw engine) - in cars its 4 stoke so its once every 2 rotations.

And to think that I thought I really understood how an engine worked... do you mind explaining me why this does not happens in a 4 stroke engine???

In a 4 stroke engine there are 4 stages. Each stage takes have a rotation. They are:
1. Piston head at top of cyclinder - It moves to the bottom and sucks in Fuel and Air.
2 Piston head is at bottom - It moves to the top compressing the Fuel and Air.
3 Piston Head is at top - Fuel and Air is ignited and piston head moves to the bottom.
4.Piston head is at the bottom - It moves to the top pushing out the exhaust gases.

These four stages take 2 revolutions, and as you can see there is one ignition.

For a 2 stroke engine there are 2 stages. They are:
1. Piston head is at top - Fuel and air mixture is ignited. Piston head moves to bottom.
2. Piston head is at bottom - It moves to the top compressing air and fuel.

These 2 stages take 1 revolution, and as you can see there is one ignition.

So that's why. :D

Mallon why did you censor my above post?? :? :shock:
The name of the guy is Felix W-a-n-k-e-l !!! He was a german engineer!

im aware of who wankel is! - its the forum that censored words like that - So nothing to do with me!

What's wrong with this word? (I honestly don't know, so please help me)

Im not goign to explain the word (w*ank)el - try a search at google LOL

LOL ok.... :roll:

LOL mallon I did a search in yahoo and I found the meaning of the censored word!!
LLLLLLLLLLOOOOOOOOOOOOOOOOOOOOLLLLLLLLLL LLLLLLL!!!!!!!!!!!!!!!!!!!! :lol: :lol: :lol: :lol: :lol:

well the problem with rotary is only really repair. there a bit complicated but not if you know what your doing. i like them cause you get a engine that revs higher then most, is only about 60-80 cubes and last but not least works with turbo and nitro with less worry then cylinders. but ill let you decide what floats your boat or runs your wheels. :twisted:

Hey guys, I heard that rotaries are very hard to control.

I also heard that in World War I or II or both, the props had rotary engines in them, and they were very hard to fly because the engine rotated a lot and acted like a gyroscope during flight.

Is this still true with today's rotaries (and is it what makes rotaries so hard to control) :?:

Nah today's roatries have a counter wieght that cancels out any unwanted moments.

About WWII - I *think* those rotary engines refer to the fact that the pistons are all in a circle - I may be wrong though.

You mean the pistons made the shape of an o (i.e. V6 engines are in the shape of a V) :?: :?: :?:

Well yes and no. yes because the spinning motion is hard to control because the rotors can spin so fast. And no because the modern rotary (when i say modern i mean starting in 1980) is built to only let it rev so high but still higher then other engines. have any of you seen a R-100? Its uses a very rare and very un-reliable 3 rotor engine at like 85 cubes. it kicks ass but i wouldent want it because it wears its self out so quick and has alot of problems. basically theres is a such thing as to many rotations like 10,000 too many!!! so you see the problem with triple thats why mazda sticks with the twin rotors design. :twisted:

Oh...

I see :D :D :D :wink: :wink: :wink: :idea: :idea: :idea:

The rotors in a 13b rotary don't ever spin at 10,000 revs......:-k

Each 'face' of the triangular rotor that fires is one revolution of the output shaft, but there is a 3:1 gear inside each rotor, so at 9,000 revs, the rotors are only turning at 3,000 rpm.

...but both rotors fire each 'rev', so TWO power strokes per output revolution, just like a V8!

S

You mean like a two-stroker, not a V8, but anyway this thread is ancient and is locked.