Why Do Rotaries Suck?

[[200]]

i also had a thought last night.....not about what goes round and round or what goes up and down....but what goes in and out....

How old is she? 16?

f**king rock spider.

[ylwgtr2]

How old is she? 16?

f**king rock spider.

how the f**k do i know?but she has great tits....now....heres a spoon....eat my arse

Edited September 23, 2009 by ylwgtr2

[PM-R33]

+1 on the great tits.

PS: What the hell does calling some one a rock spider mean?

Edited September 23, 2009 by PM-R33

[ylwgtr2]

a rock spider crawls into tight crevace's.....and arse eater....well....im sure the other guy can give us a demo

[Smity42]

just something else to argue about, i could be wrong, but if u measure engine speed from the hardware in direct contact with combustion a piston engine does no rpm as a piston moves in a straight line,also for a piston to stoke 100mm dosent the part of the crank that it is attached to have to move 314mm in a circle kind of like a 3 to 1 ratio.

Thats not a really a 3:1 ratio. Its just a method of turning an up-down motion into a round-and-round motion. You can make the lobes as long or as short as you like (within reason obviously), and the crank is still going to turn 1 time for every 1 up-down motion of the piston, although of course you will be indirectly affecting the maximum speed of the engine due to the physics involved, but this is not the same as directly stepping it up or down with a gear ratio.

I spose you could argue that its a 2:1 ratio if you consider each stroke of the piston seperately) or even 1:2 if you consider the entire 4 stroke cycle, however this blurrs the line in comparison to a rotory even more .

It's all irrellevant really, the only valid point of comparison for RMP is the crank vs the eccentric shaft, so 9000 it is .

This is the point I've been trying to convey. That not only can revolutions per minute NOT be applied to a piece of hardware that actually moves up and down...but the crankshaft in a piston engine has lobes that are its own version of the step up ratio on the rotary's eccentric shaft. These lobes are there not just for the conrods to turn the crank, but to provide the necessary torque/leverage for the conrods to turn the crankshaft. If you want to get technical with it...you can swap a piston engine crankshaft for one that strokes the displacement out...you can't do this with a rotary...so the eccentric shaft is in effect more a permanent part of the rotary engine than the crankshaft is in a piston engine. So with our stroker crankshaft...our displacement, torque and maximum engine speed changes...it's still the exact same engine though right? Right? Oops! Oops.

A valid point... though the "revolutions per minute" is a technicality. I spose we could compare RPM of the engines and say rotorys generally rev a little higher, then compare 'strokes per minute' of the pistons with the rpm of the rotors and say the pistons 'stroke' faster than the rotors rotate. Everyone be happy with that?

My question is: If pistons can go up and down at 6000+ times per minute, involving a complete change of direction twice each time, why can't the actual rotors in a rotory, which just keep spinning the same direction, match or even beat that? Why don't we see wankels with rotors spinning at 6000+ rpm for an engine speed of 18000+ rpm?

PS: +1 to great tits

Edited September 23, 2009 by Smity42

[wolverine]

+1 on the great tits.

PS: What the hell does calling some one a rock spider mean?

spend some time inside and tell them you fiddled a kid and you will find out the hard way what a rock spider is.

[Sydneykid]

OK let's get a few things out of the way first. Guys tend to listen to what I say because in over 11,000 plus posts I tell it how I see it, I don't take the popular line, I don't follow the lemmings, I develop my own opinions, based on my own measurements and observations. In this case I see a 13B as being a 3.9 litre, 2 stroke rotary engine where the combustion media do 3,000 rpm. Pleased don't attribute more to that statement that what it is actually says. Secondly, don't diffuse the discussion by adhering to some narrow minded meaning for the terms used. It is a common tactic used by the blind (to the facts) rotary supporters. Silly stuff like rotors don't revolve they ellipse, give me a break, the earth revolves around the sun and it's in an elliptical motion. So calling rotor turns "revolutions" is well within the common use meaning. Another example, stroke in this reference means the same as cycle. Don't get led astray from seeking the truth just because someone says rotaries don't stroke, give me another break. In this context stroke = cycle. So, don't fall for these common tactics used to divert a rotary discussion from the truth. Next time someone tries to narrowly define what is a common use meaning, treat it for exactly what it is, a desperate attempt to stop you from seeking out the truth. Let's move on.

The manufacturers of 2 stroke engines don't double their actual capacity because it fires every cycle, they simply state what it pumps in one full cycle of the combustion medium. ie; a 0.5 litre 2 stroke pump is stated as a 0.5 litres. It doesn't matter whether is does it in 360 degrees of crankshaft revolution or 720 degrees.

The manufacturers of 4 stroke engines don't halve their actual capacity because it fires every second cycle, they simply state what it pumps in one full cycle of the combustion medium. ie; a 2.0 litre 4 stroke pump is stated as a 2.0 litres. It doesn't matter whether is does it in 720 degrees of crankshaft revolution or 1080 degrees.

But not Mazda, oh no, they have a better idea, let's divide what it actually pumps by 3, even though we all know it pumps 3.9 litres in one full cycle ie; a 3.9 litre pump is stated as 1.3 litres. There is no hiding from that fact, you will hear all sorts of arguments about degrees of crankshaft versus eccentric shaft revolutions, 760 degree versus 1080 degrees. Ignore them, they may be true, but they are truly meaningless in determining the capacity of the engine, what it really pumps. But even then, if we use erroneously introduce eccentric shaft revolution, it's a 2.6 litre. So the 1.3 litre doesn't cut it, even with that attempt at distorting the true capacity of the engine by introducing irrelevant facts. Just because they are facts doesn't make them relevant.

So in regards to engine capacity Mazda has been lying for 40 years. I would argue that they have been calling a 3.9 litre engine a 1.3 litre. The Mazda supporters would argue that it’s really 2.6 litres. The FIA currently says it's 2.3 litres, they used to say it was 2.6 litres. But it doesn’t matter, everyone agrees that Mazda lied, the only real question is by how much.

Why did Mazda lie? Well the commonly accepted reason is marketing, they could sell the David versus Goliath story, 1.3 litre engine rules the world, small engine kicks butt, the little engine that could, etc etc. Look back at the marketing campaigns and it’s blatantly obvious. It wasn’t a conspiracy, it was simply convenient for marketing at the time.

That’s brings us to the next lie, 2 stroke/cycle. Again the Mazda lemmings will put up the argument that a rotary engine doesn’t stroke, oh give me third break. They cycle and in one cycle they inlet, compress, combust and exhaust. What’s a cycle? Well in anyone’s language it’s when one particular point of the rotor completes one complete cycle (revolution). Wait I can hear it, hang on, rotaries don’t revolve. Give me a fourth break, they do revolve, it’s just not in a perfect circle.

The fact is a 2 stroke/cycle engine does all 4 processes in one compete cycle of the combustion medium. Yes, it happens to be a piston, but that’s irrelevant when comparing combustion medium. In comparison a 4 stroke does all 4 processes in two complete cycles of the combustion medium. I really don’t see any room for argument here, other than feeble attempts at muddying the water with narrow minded definitions of common use terminology. The fact remains a rotary engine does all 4 processes in one cycle of it's combustion medium, so it’s a 2 stroke/cycle engine.

Why did Mazda lie this time? Well the commonly accepted reason is again marketing, they knew full well that they couldn’t sell the concept of a 2 stroke engine in a serious car to the general public. They were well aware of the contempt that previous two stroke/cycle cars had generated. So that stigma had to be avoided, hence get the term 2 stroke/cycle right away from rotary engines. It wasn’t a conspiracy, it was simply convenient for marketing at the time.

This brings us to the most contentious point, rpm. I call it a 3,000 rpm engine because the combustion medium does 3,000 cycles per minute. The Mazda followers say it’s a 9,000 rpm engine because the eccentric shaft does 9,000 cycles per minute. Obviously both are correct, the rotors do actually do 3,000 rpm while the eccentric shaft is doing 9,000 rpm. There is no point of disagreement there, what is in dispute is which is more relevant? I support my argument with the fact that the combustion medium is the more important rpm to measure. For me, it the most relevant because that’s what a rotary is, an internal combustion engine. Hence measuring the rpm of the combustion medium is somewhat more relevant that measuring the rpm of something that does nothing for the combustion process.

If nothing else, what I have done with the rpm part of this discussion is provide ammunition to dispute the claim that a rotary engine is high revving. The fact is they aren’t, in every common use meaning of the term, “high revving engine”, because that terminology imparts the belief that the entire engine is high revving. When in fact the all important combustion parts of the engine are in fact low revving.

Lastly let's put this diversion tact to bed, there is no conspiracy, just a bunch of Mazda lies, covering up of the truth, distortion of the facts and narrow use of terminology to prevent any meaningful discussion. Comparison with other combustion engines was avoided, or diffused with the furphy that rotaries are entirely different and no comparison is possible. The difficulty in comparison is a weapon used to cover up the truths. Forget about comparison, just look at the facts on their own. They are inescapable.

BTW, if you want a conspiracy theory I'll give you one, that Alan Moffat conspired with a certain CAMS board member to allow a Sports Car (RX7) to race in a Championship for Touring Cars. Now that was a true conspiracy, but it's not relevant to this discussion. Maybe one for another day.

Cheers

Gary

[Sydneykid]

enough.....lets just wait till i finish my 250-300HP mazda factory PP engine 3924cc 3000rpm 2600cc,1308cc 9000rpm 450kg oscar sk90 racecar is finished and if the little hewland doesnt shit its pants and i dont stack it and if it doesnt blow it up and some spectator doesnt cop a 3000rpm or 9000rpm,654cc or 1962cc rotor in the mushki.....the lap times will tell if it sucks arse or not

So do we laugh when you get your ass handed to you by a 3.9 litre Radical (there isn't any of them yet)? Or should that be a 2.6 litre Radical (there are a few of them around now)? No wait, you'll be saying it should be a 1.3 litre Radical (lots of them). Whatever, your ass will still be handed to you.

What this has got to with an engine discussion I'm not so sure, but it was too good an opportunity let slip by.

Cheers

Gary

[GT-R32]

I'm honestly baffled Gary. You seem to have a basic understand how the engine works, a bit here and a bit there, but fail to see how it all comes together as a power unit for comparisons in relative terms to the reciporacating piston counterpart.

3.9L 6 stroke (Wankel 1080°), 2.6L 4 stroke (720°) and 1.3l 2 stroke (360°) are its piston relatives. I guess the closest when you look at this gif (going on power stroke/crank revolution), is the 2 stroke - the only issue is that it doesn't count all chambers (the things that allow the separate parts of the cycle to occur in different locations - that's all they do!), perhaps why Mazda ran with 654cc x 2 for the 13B

I think you are confused by the fact that each part of the Otto cycle takes place in a different location, which is what makes them suitable to Hydrogen... but I digress. Remember, it is still a 4 cycle engine! Not 2!

[Smity42]

I disagree with you on the stroke = cycle sydneykid

the piston does 2 strokes (up and down) in one 'cycle' as you call it, therefore a 2 stroke piston motor you could call a 1 cycle motor i spose, and a 4 stroke is a 2 cycle. But cycle has a fairly blurred meaning as well. You seem to be refering to the cycle of the crank, or just the complete cycle of the pistons motion. I am not sure.

There is also the combustion cycle/ thermodynamic cycle that the engine runs on, and this is what defines an engine.

A 4 stroke motor is a motor that takes 4 strokes of the piston to complete its combustion cycle. This is a 4 stage cycle (intake, compression, combustion, and exhaust - the otto cycle), which happens to take 4 strokes of the piston, or 2 'cycles' of the piston/crank.

In the case of a 2-stroke, this cycle is a little more blurred, but it is completed in 2 strokes, or 1 'cycle', of the piston.

The rotory does a classic 4 stage otto cycle, and completes it for each face of the rotor in 1 revolution of the rotor. So I guess you could call it a 1-revolution motor, which is similar (but not the same) as a 2 stroke piston motor.

It is similar to a 2 stroke in that it completes its combustion cycle in one 'cycle' of the rotor, and in that it uses ports, and that in a single rotor is performing multiple stages of the combustion cycle at once on it's different faces.

However, it is similar to a 4 stroke in that it does do the classic 4 stage otto combustion cycle on each face of the rotor as it spins. Not thate in a 2 stroke, the 'top' of the piston only performs 1 half of the combustion process and the 'bottom' of the piston performs the other half. In a rotory, each face of the rotor does the entire combustion process (like the 'top' of the piston in a 4 stroke).

So, as has been said before, It is NEITHER a 2 stroke or a 4 stroke, it is a rotory cycle, different from both, and similar to both , in different respects.

EDIT: Good gif above, demonstrating the 4 stage otto cycle in progress as the rotor spins

Edited September 24, 2009 by Smity42

[Sydneykid]

I disagree with you on the stroke = cycle sydneykid

the piston does 2 strokes (up and down) in one 'cycle' as you call it, therefore a 2 stroke piston motor you could call a 1 cycle motor i spose, and a 4 stroke is a 2 cycle. But cycle has a fairly blurred meaning as well. You seem to be refering to the cycle of the crank, or just the complete cycle of the pistons motion. I am not sure. There is also the combustion cycle/ thermodynamic cycle that the engine runs on, and this is what defines an engine.

That's a bit hair splitting isn't it? Common, "cycle" versus "combustion cycle", I don't think the meaning of what I said is lost in the narrow definitions you apply. I try and stick to common use terms and their meaning, it means the non technical readers don't switch off. Plus I type slowly and adding extra, irrelevant, words just slows me down

A 4 stroke motor is a motor that takes 4 strokes of the piston to complete its combustion cycle. This is a 4 stage cycle (intake, compression, combustion, and exhaust - the otto cycle), which happens to take 4 strokes of the piston, or 2 'cycles' of the piston/crank. In the case of a 2-stroke, this cycle is a little more blurred, but it is completed in 2 strokes, or 1 'cycle', of the piston.

I don't see any blurring, it's black and white to me.

The rotory does a classic 4 stage otto cycle, and completes it for each face of the rotor in 1 revolution of the rotor. So I guess you could call it a 1-revolution motor, which is similar (but not the same) as a 2 stroke piston motor. It is similar to a 2 stroke in that it completes its combustion cycle in one 'cycle' of the rotor, and in that it uses ports, and that in a single rotor is performing multiple stages of the combustion cycle at once on it's different faces. However, it is similar to a 4 stroke in that it does do the classic 4 stage otto combustion cycle on each face of the rotor as it spins. Not thate in a 2 stroke, the 'top' of the piston only performs 1 half of the combustion process and the 'bottom' of the piston performs the other half. In a rotory, each face of the rotor does the entire combustion process (like the 'top' of the piston in a 4 stroke).

But a 4 stroke/cycle piston only does one at a time, while the rotor does 3 at a time. A 2 stroke/cycle rotary engine wouldn't function with only side, just like a 2 stroke piston engine without 2 sides. So it's illogical to look at one side of rotor to determin it's cycle. That's the import fact, we have to look at what all 3 sides of the rotor are doing, forget piston comparions, what's the rotor doing? The fact is it's doing multiple combustion processes all at the same time.

So, as has been said before, It is NEITHER a 2 stroke or a 4 stroke, it is a rotory cycle, different from both, and similar to both , in different respects.

My view remains that it's a 2 stroke/cycle rotary engine. You seem to think that I'm saying that's exactly the same as a 2 stroke/cycle piston engine, when in fact I'm not.

EDIT: Good gif above, demonstrating the 4 stage otto cycle in progress as the rotor spins

No it's not, because it only shows what is happening to one third of the rotor. What about the other two thirds? Should we just ignore them?

Cheers

Gary

[GT-R32]

Rotor tip speed/rotor 'revolution' has nothing to do with engine revolutions, it is akin to measuring piston speed. To accurately and fairly compare engine, this must be done on a displacement per shaft revolution basis. This will not result in a 3.9L equivalent capacity on a 2 or 4 stroke reciporacating basis (1.3L and 2.6L respectively).

Some people have somewhat two dimensional minds and find it hard to relate all of this information together at once.

[GT-R32]

Gary, it does the Otto cycle in different chambers, which result in a power stroke per crank revolution (how it the comparison needs to be made) somewhat equivalent to a 2 stroke piston engine. Which means the 1308cc combustion chamber volume needs to be doubled to compare to a 4 stroke. Due to rotary engine inefficiencies, some racing bodies don't do a straight doubling of this. FIA does approximately x1.795 based on these basic engineering FACTS.

The gif above accurately demonstrates what happens in one, to help you understand it:

http://www.animatedengines.com/wankel.shtml

You can then apply it to this:

http://www.animatedengines.com/twostroke.shtml

Then you will see that due to the arrangement of the rotary, it's arguably a 4 stroke (really, it's a Wankel) as the elements of the Otto cycle takes place in separate chambers by design, which results in a power stroke equivalent to a piston engine 2 stroke.

I can see why some racing bodies just ban them altogether. Sometimes people just cannot understand in relative terms.

[Sydneykid]

I'm honestly baffled Gary. You seem to have a basic understand how the engine works, a bit here and a bit there, but fail to see how it all comes together as a power unit for comparisons in relative terms to the reciporacating piston counterpart.

You're baffled, well I can see why. Firstly you seem to think I am comparing a rotary engine to a piston engine when in fact I'm not. What I object to is illogical, unique and unsupportable ascertions about capcity, rpm and stroke/cycle type.

This is where I get baffled.......

3.9L 6 stroke (Wankel 1080°), 2.6L 4 stroke (720°) and 1.3l 2 stroke (360°) are its piston relatives.

What you are saying is we should call a 1.3 litre 2stroke/cycle engine a 2.6 litre. Nobody does that, a 1.3 litre engine is a 1.3 litre engine, it doesn't matter how many strokes/cycles it has. If it pumps 1.3 litres then it's a 1.3 litre engine. Look at it another way, you want to make an exception for a 3.9 litre rotary, an exception that no one else in the entire engine world does for their 2 stroke engines. Why is Mazda so special here? Why should they alone get to use maths to change their engines true pumping capacity but no one else is allowed? No wonder you're baffled. one rule for Mazda, another rule for everyone else.

I guess the closest when you look at this gif (going on power stroke/crank revolution), is the 2 stroke - the only issue is that it doesn't count all chambers (the things that allow the separate parts of the cycle to occur in different locations - that's all they do!), perhaps why Mazda ran with 654cc x 2 for the 13B

You hit the nail right on the head, that's the problem with those sorts of simulations, they only show what supports Mazda’s lies. It’s one of the law's cleverest applications, "tell the truth, the whole truth and nothing but the truth". Right here we have an example of telling the truth (for one side of the rotor) but not telling the whole truth (by leaving out the other 2 sides).

Do some research, you will find that the general consensus in the automotive world was that it was marketing driven.

I think you are confused by the fact that each part of the Otto cycle takes place in a different location, which is what makes them suitable to Hydrogen... but I digress. Remember, it is still a 4 cycle engine! Not 2!

I'm not confused, I know that multiple parts of the Otto cycle are happening simultaneously, most unlike a 4 stroke and most like a 2 stroke.

Cheers

Gary

[GT-R32]

The engine takes 1080 degrees to complete a full Otto cycle, displacing 3.9L. This is not 2 stroke by any stretch, if you believe it so, you must call it 1308cc. You are again, forgetting displacement per (crank/e) shaft revolution.

To accurately and fairly compare engine, this must be done on a displacement per shaft revolution basis. How do you rate it in a comparative sense then, Gary?

For instance, if you raced 2 stroke 250cc bikes again 4 strokes, what would the 4 stroke engine size be?

[Smity42]

That's a bit hair splitting isn't it? Common, "cycle" versus "combustion cycle", I don't think the meaning of what I said is lost in the narrow definitions you apply. I try and stick to common use terms and their meaning, it means the non technical readers don't switch off. Plus I type slowly and adding extra, irrelevant, words just slows me down

I could go on for hours why this is both incorrect and confusing. A 4 stroke engine does a 4 stroke cycle. If you replace 'stroke' with 'cycle' you get a 4 cycle engine doing a 4 cycle cycle.

A 2-stroke engine is DEFINED as an engine requiring 2 strokes of the piston to complete its thermodynamic cycle

A 4-stroke engine is DEFINED as an engine requiring 4 strokes of the piston to complete its thermodynamic cycle

I guess you could class a wankel as a 1-revolution engine as it requires one revolution of the rotor to complete its thermodynamic cycle.

It is in no way a '2-stroke' engine.

But a 4 stroke/cycle piston only does one at a time, while the rotor does 3 at a time. A 2 stroke/cycle rotary engine wouldn't function with only side, just like a 2 stroke piston engine without 2 sides. So it's illogical to look at one side of rotor to determin it's cycle. That's the import fact, we have to look at what all 3 sides of the rotor are doing, forget piston comparions, what's the rotor doing? The fact is it's doing multiple combustion processes all at the same time.

But this is not what DEFINES a 2 stroke engine. It's a characteristic of one sure, but not what defines it. Its a characteristic shared by a rotory, but if you read my post again, you'll see it shares some charactaristics of a 2 stroke and some of a 4 stroke, which is why it can not be classified as either.

It is it's own type of engine (for arguments sake, lets call it a wankel ), that shares charactarestics of both a 2 stroke and a 4 stroke engine, with some of it's own thrown in.

My view remains that it's a 2 stroke/cycle rotary engine. You seem to think that I'm saying that's exactly the same as a 2 stroke/cycle piston engine, when in fact I'm not.

I disagree. You are, as always, entitled to your opinion.

I agree with you on the characteristics it shares with a 2 stroke engine. It also shares some with a 4 stroke engine. However it fits the definition of neither, so it is neither.

No it's not, because it only shows what is happening to one third of the rotor. What about the other two thirds? Should we just ignore them?

I'm sure that was just to simplify the demonstration of the process. I'm also sure it is fairly obvious to most that the process is repeated on each face of the rotor, 120 degrees out of phase. No one in here is trying to ignore the fact that all faces of the rotor are working at once.

[Sydneykid]

Rotor tip speed/rotor 'revolution' has nothing to do with engine revolutions, it is akin to measuring piston speed. To accurately and fairly compare engine, this must be done on a displacement per shaft revolution basis. This will not result in a 3.9L equivalent capacity on a 2 or 4 stroke reciporacating basis (1.3L and 2.6L respectively).

Where did I say anything about rotor tip speed, that's an irrelevant rpm related comparison and abslolutely nothing to do with capacity. Using your logic , when I see Honda quote 400cc for a 2 stroke trail bike, it's really 200cc's. I don't think so. Equivalency is a fallacy, stop trying for some equivalency, just state what it is.

Some people have somewhat two dimensional minds and find it hard to relate all of this information together at once.

I'm a simple guy, I measure an engine's capacity by how much it pumps. Actually I can't be that simple, because every engine manufacturer in the world agrees with me and measure their engines' capacities by how much they pump. Except one, why should we allow an exception for one engine manufacturer? I don't think we should.

Cheers

Gary

[GT-R32]

It appears you can't get past your beef with Mazda quoting the 13B as 1308cc.

I'll repeat once again, in order to accurately compare the Wankel to the 4/2 stroke piston, it has to be done on a displacement per shaft revolution basis.

[Sydneykid]

The engine takes 1080 degrees to complete a full Otto cycle, displacing 3.9L. This is not 2 stroke by any stretch, if you believe it so, you must call it 1308cc. You are again, forgetting displacement per (crank/e) shaft revolution.

I'm not forgetting eccentric shaft revolutions, I'm deliberately ignoring them, because they are irrlevant. What determines a 2 stroke/cycle engine versus a 4 stroke/cycle engine si the actions of its combustion medium. not what something geared up from that does.

To accurately and fairly compare engine, this must be done on a displacement per shaft revolution basis.

I dissagree, it should be done, as it is with every other engine, on how much it pumps for one compete revolution of its combustion medium.

How do you rate it in a comparative sense then, Gary?

I don't.

For instance, if you raced 2 stroke 250cc bikes again 4 strokes, what would the 4 stroke engine size be?

What the hell has that got to do with the capacity of the engine? I don't double the 2 stroke's true capacity and call it a 500 cc engine, it's always 250 cc engine, end of story.

Equivalency is impossible, I think MotoGP proved that, so why are you even trying?

Cheers

Gary

[Birds]

Thats not a really a 3:1 ratio. Its just a method of turning an up-down motion into a round-and-round motion. You can make the lobes as long or as short as you like (within reason obviously), and the crank is still going to turn 1 time for every 1 up-down motion of the piston, although of course you will be indirectly affecting the maximum speed of the engine due to the physics involved, but this is not the same as directly stepping it up or down with a gear ratio.

I spose you could argue that its a 2:1 ratio if you consider each stroke of the piston seperately) or even 1:2 if you consider the entire 4 stroke cycle, however this blurrs the line in comparison to a rotory even more .

It's all irrellevant really, the only valid point of comparison for RMP is the crank vs the eccentric shaft, so 9000 it is .

A valid point... though the "revolutions per minute" is a technicality. I spose we could compare RPM of the engines and say rotorys generally rev a little higher, then compare 'strokes per minute' of the pistons with the rpm of the rotors and say the pistons 'stroke' faster than the rotors rotate. Everyone be happy with that?

My question is: If pistons can go up and down at 6000+ times per minute, involving a complete change of direction twice each time, why can't the actual rotors in a rotory, which just keep spinning the same direction, match or even beat that? Why don't we see wankels with rotors spinning at 6000+ rpm for an engine speed of 18000+ rpm?

PS: +1 to great tits

It's not exactly the same as stepping up a gear ratio but the physics of it are very similar in that you are changing the torque output and maximum speed of the engine by playing around with the torque leverage on the crankshaft. Piston engines are actually more dynamic/flexible in what can be done to them internally than rotaries.

And yes if you want to say pistons "stroke" faster than rotors cycle then I would be happy with that and I would certainly agree with you

The eliptical motion of a rotary isn't as smooth as it sounds. It's not circular, it's eliptical. The motion of a piston is in a way smoother, thanks to a few bearings on key components. The running motion of a human's legs is actually pretty similar to the motion of conrods, and just like the stride we take when our foot touches the ground, the change of direction for a piston is not an immediate one...but largely cushioned/buffered by the motion of the lobe. Also, displacement is very much at hand here...I don't doubt a smaller displacement rotary could produce much faster RPM than a 13B.

Silly stuff like rotors don't revolve they ellipse, give me a break, the earth revolves around the sun and it's in an elliptical motion. So calling rotor turns "revolutions" is well within the common use meaning.

The Earth does not revolve around the sun it orbits around the sun. I challenge you to find an astronomer who uses the former over the latter. You need to learn some basic geometry and motion terms; only objects that spin on their central axis in 360 degrees worth of CIRCLE are considered to revolve. This is why rotors themselves don't move as fast as pistons...they would spin ALOT faster were it the rotary engine's nature for a rotor to actually revolve on it's own axis. The fact is, it doesn't - it orbits around the eccentric shaft in an eliptical motion and the nature of this motion limits how fast the rotor can safely and efficiently do this.