Why Do Rotaries Suck?

[Jez13]

Ahh ffs Birds, true to form another epic about nothing.

Bore or block walls, piston and head do not make up the combustion chamber ? go figure

I meant a piston surface is not a combustion chamber by itself. Now you will reply that during the proccess of intake and compression that they have walls there too - but there is no combustion there so it is not a combustion chamber.

[Sydneykid]

And its not even close to the equivalent of a 3.9L 2 stroke... Thats just wrong

SYDNEYKID, you seem to love calling it a 2 stroke/cycle. IN WHAT WAY DOES 2 CYCLES HAVE ANYTHING TO DO WITH THE ROTORS COMBUSTION PROCESS?

It completes its combustion process in ONE cycle of the rotor, NOT TWO

Same as a 2 stroke piston engine, one cycle of the piston.

A 4 stroke piston engine takes 2 cycles of the piston.

Cheers

Gary

[Jez13]

No it's not, even by your flawed definition it's not.

Just trying to keep it simple, I suppose it depends on which direction you look at it lol.

Cheers

Gary

Just trying to keep it simple, I suppose it depends on which direction you look at it lol. But my point stands, it only combusts in one section of the rotory so only that section can be identified as the combustion chamber. Its not combusting anywhere else at anny other time.

[Smity42]

You can't claim it has only one combustion chamber and at the same time it's not a 2 stroke, it inlets at the same time as it exhausts. Everybody knows that 4 strokes don't do that, only a 2 stroke does.

Please re-read my earlier posts. That is a characteristic of a 2 stroke, not the definition of one.

Please note AGAIN. I am not calling it a 4 stroke. It isn't. Nor is it a 2 stroke. Its a wankel.

If you claim it has 3 combustion chambers to avoid the 2 stroke evidence, then you can't claim it is 1.3 litres

You can't claim it's a 6 stroke and then only count 1/3rd of it's combustion processes to determin capacity.

You are doing the exact opposite. You can't call it a 2 stroke and then count all 3/3rds of the combustion process. If you want to compare it to a 2 stroke, you can only look at that 1/3rd of the combustion chamber that actually combusts, and you have to call it a 1.3L.

In the same way when we measure a 2 strokes capacity, we only look at 1/2 of the combustion chamber. If we looked at the whole lot, we'd have to double 2 stroke capacity

[DRD-00F]

Hey Jez, was it you that was saying that if the eccentric shaft moves 360 degrees then the rotary is in the exact same position? You said it would be EXACTLY the same. Well it's not, it's VERY SIMILAR, but it's not the same rotor side, as was shown in rice racings pictures that had the walls labeled. I honestly don't get how you can truely believe that there is only 1 side on a triangle. This is pretty basic stuff here.

The way I see what you're saying is that if you rotate this gear an amount of P then it will be EXACTLY as it was before, doing a full revolution and coming back to its original state.

yeah no... Just cause the gears teeth are in the same spot, it doesn't mean it's as it was.

Are you actually going to sit there and tell me that one full rotation of the Wheel of Fortune is just from $800 to bankrupt?

To be honest, if we're arguing about things like this, then it's never going to be settled.

[Jez13]

I'd be happy if certain posters recognised that advent and invent of new engine design alters the way in which you can measure total displacement. There's no universal way of doing it...the rotary is NOT a piston engine. Fullstop.

Yes and that is why you are able to see the true displacement of a rotory because you are able to open up your mind outside of how a piston works.

[Sydneykid]

I meant a piston surface is not a combustion chamber by itself.

No, but in a roary engine the majority of the combustion chamber is the rotor.

In a piston engine the minority of the combustion chamber is the piston

Not always the case though, in a diesel engine often they have a flat head with the combusion chamber (bowl) in the piston.

So a rotary is not unique in having a moving combustion chamber.

Now you will reply that during the proccess of intake and compression that they have walls there too - but there is no combustion there so it is not a combustion chamber.

Irrelevant, the piston crown is involved in inlet, compression and exhaust, but we still include it in the term combustion chamber.

Cheers

Gary

[Smity42]

Same as a 2 stroke piston engine, one cycle of the piston.

A 4 stroke piston engine takes 2 cycles of the piston.

Cheers

Gary

But we don't call them a once-cycle, we call them a 2 stroke. And you are not trying to call it a one-cycle, you are trying to call it a 2 stroke/cycle. As I have said before, if you want to call it a 1 cycle, please go right ahead, as this is accurate. But please stop calling it a 2 stroke, as this is not accurate.

[madbung]

Yes and that is why you are able to see the true displacement of a rotory because you are able to open up your mind outside of how a piston works.

Oh lols the true displacement as opposed to? should I meditate to fully embrace the math?

I'd be happy if certain posters recognised that advent and invent of new engine design alters the way in which you can measure total displacement. There's no universal way of doing it...the rotary is NOT a piston engine. Fullstop.

Haha Birds.... all pumps/engines be it piston, rotor or impellor are measured using the same methods without bias... <3 fullstops

I meant a piston surface is not a combustion chamber by itself. Now you will reply that during the proccess of intake and compression that they have walls there too - but there is no combustion there so it is not a combustion chamber.

One can't exist without the other so your point was?

This has become a farce

[Jez13]

No, but in a roary engine the majority of the combustion chamber is the rotor.

In a piston engine the minority of the combustion chamber is the piston

Not always the case though, in a diesel engine often they have a flat head with the combusion chamber (bowl) in the piston.

So a rotary is not unique in having a moving combustion chamber.

Irrelevant, the piston crown is involved in inlet, compression and exhaust, but we still include it in the term combustion chamber.

Cheers

Gary

Its not irrelevant because the combustion appears in the same place for a piston but a rotories combustion appears in a completely different place.

[Sydneykid]

Please re-read my earlier posts. That is a characteristic of a 2 stroke, not the definition of one.

Please note AGAIN. I am not calling it a 4 stroke. It isn't. Nor is it a 2 stroke. Its a wankel.

We have domne this before, how many 2 stroke/cycle charateristics do you want?

Inlets and exhausts at the same time

Fires every rotation/orbit/cycle of each combustion face of the rotor

Inlets every rotation/orbit/cycle of each combustion face of the rotor

Exhaust every rotation/orbit/cycle of each combustion face of the rotor

Has no valves, the rotor opens and closes the inlet and exhaust ports

Oil in the petrol

There isn't one thing that the rotor does that is a unique 4 stroke characteristic.

You are doing the exact opposite. You can't call it a 2 stroke and then count all 3/3rds of the combustion process.

Why not, we do it with a 2 stroke piston engine.

If you want to compare it to a 2 stroke, you can only look at that 1/3rd of the combustion chamber that actually combusts, and you have to call it a 1.3L.

Even that doesn't work, because a rotor has 3 sides and a 2 stroke piston only 2. So we would have to look at 2/3rds.

In the same way when we measure a 2 strokes capacity, we only look at 1/2 of the combustion chamber. If we looked at the whole lot, we'd have to double 2 stroke capacity

Exactly, that's why we don't count crankshaft revoltions in a piston engine, but you want to count eccentric shaft revolutions in a rotary engine.

You see your problem? Every rotary argument you raise has consequences elsewhere in the package of Mazda lies. You can't be correct with 1 without killing the other 2 arguments

Cheers

Gary

[Jez13]

Hey Jez, was it you that was saying that if the eccentric shaft moves 360 degrees then the rotary is in the exact same position? You said it would be EXACTLY the same. Well it's not, it's VERY SIMILAR, but it's not the same rotor side, as was shown in rice racings pictures that had the walls labeled. I honestly don't get how you can truely believe that there is only 1 side on a triangle. This is pretty basic stuff here.

The way I see what you're saying is that if you rotate this gear an amount of P then it will be EXACTLY as it was before, doing a full revolution and coming back to its original state.

yeah no... Just cause the gears teeth are in the same spot, it doesn't mean it's as it was.

Are you actually going to sit there and tell me that one full rotation of the Wheel of Fortune is just from $800 to bankrupt?

To be honest, if we're arguing about things like this, then it's never going to be settled.

lol doof thanks for making my points out to be so trivial. I am just trying to find different ways of explaining my same point so people can understand better for visual purposes on what I am trying to get accross. I was basically trying to say dont compare 1 rotor with 3 pistons, instead compare 1 rotor with 1 piston. If I paint one rotor face green, another yellow and another red. One combustion cycle moves the rotor 120 degrees and so all colours are now in a different place, so no a complete rotation of the rotor has not been made but the rotor itself is in the exsact same postition. All points of the triangle are pointing in the same directions before the combustion and thus completing one cycle.

[Birds]

Haha Birds.... all pumps/engines be it piston, rotor or impellor are measured using the same methods without bias... <3 fullstops

Really...I suppose you were right by Mr. Wankel's side telling him how to measure the displacement of the unique engine he designed? You're just generalising the method of measuring displacement because most common forms of internal combustion engine have an easily measurable displacement, with no room for subjective measure. The rotary does not fit that bill. If you think it is so definitive and objectively easy to measure, please tell me why this thread is so long? Clearly there's an issue with that.

This ain't going to end until we all just get sick of arguing...all that's happening is both sides are recruiting more supporters, no one is actually crossing the floor and agreeing here. Thread of the year...for its in depth analysis and informative content...but a painful thread it is.

[DRD-00F]

Sometimes things have to be advertised as clearly as possible so there can be no mistakes made (and no 36 page threads about it either).

You're only thinking in 2D. Yes the X and Y values will be the same, but the rotation value of Z will be different. And since we're discussing something that both elipses and rotates, you would think that might just be important.

Like I've said before, I understand where you're coming from, but I can't agree that it's the most logical or fair way to judge things. A full rotation is a full rotation, there should be no 'muddy water' there, but alas, there is. This is why I am on the side of a 3.9L pump as it shows how much it pumps in one repeatable cycle.

Imagine you had a chip or a score on one side of the rotor, so that 2 of the sides calculate out 1.3L of air, but the other makes it to 1.4L. What would you say then? Oh, it's a 1.3L engine, 66% of the time, every third time it will be 1.4L.

Wouldn't it be more logical to just say it's a 4.0L engine?

[Sydneykid]

But we don't call them a once-cycle, we call them a 2 stroke.

2 strokes, one up and one down

And you are not trying to call it a one-cycle, you are trying to call it a 2 stroke/cycle.

Think Otto cycle, after all it's a combustion engine. It a 4 part cycle, a 4 stroke/cycle engine does each of the 4 individually. Whereas a 2 stroke/cycle engine doesn't, it combines parts of the cycle, it does them simultaneously. Just like a rotary.

As I have said before, if you want to call it a 1 cycle, please go right ahead, as this is accurate. But please stop calling it a 2 stroke, as this is not accurate.

So is it a one cycle because of one revolution of the rotor? Or because of one cycle of the eccentric shaft? Be careful, if you say it's one cycle of the rotor then you admit the rpm lie and the capacity lie, but support the argument on cycles. If you say it's one cycle of the eccentic shaft then you admit the capacity lie and the 2 stroke/cycle, but support the rpm lie.

Your choice.

Cheers

Gary

[Sydneykid]

Sorry, I apologise in advance for jumping in here;

Really...I suppose you were right by Mr. Wankel's side telling him how to measure the displacement of the unique engine he designed? You're just generalising the method of measuring displacement because most common forms of internal combustion engine have an easily measurable displacement, with no room for subjective measure. The rotary does not fit that bill.

But a rotary oil pump does, and a rotary water pump and a rotary fuel pump and a rotary air compressor and 50 other rotary pumps. They all measure their pumping capacity the same way, by how much they pump in one revolution (orbit if you prefer) of their pumping medium.

The fact is only one rotary pump doesn't measure it's capacity that way, the Mazda one.

If you think it is so definitive and objectively easy to measure, please tell me why this thread is so long? Clearly there's an issue with that.

No not realy, there are simply a few rotary huggers that won't admit to the truth no matter how many times and different ways we explain the logic consistency and factuality of it.

This ain't going to end until we all just get sick of arguing...all that's happening is both sides are recruiting more supporters, no one is actually crossing the floor and agreeing here.

I actualy think quite a few have changed their mind. Maybe not on all points, but on some, most definitely.

Thread of the year...for its in depth analysis and informative content...but a painful thread it is.

Having gone into battle with blind rotary huggers for many years, this is not so painful at all.

Cheers

Gary

[Jez13]

Sometimes things have to be advertised as clearly as possible so there can be no mistakes made (and no 36 page threads about it either).

You're only thinking in 2D. Yes the X and Y values will be the same, but the rotation value of Z will be different. And since we're discussing something that both elipses and rotates, you would think that might just be important.

Like I've said before, I understand where you're coming from, but I can't agree that it's the most logical or fair way to judge things. A full rotation is a full rotation, there should be no 'muddy water' there, but alas, there is. This is why I am on the side of a 3.9L pump as it shows how much it pumps in one repeatable cycle.

Imagine you had a chip or a score on one side of the rotor, so that 2 of the sides calculate out 1.3L of air, but the other makes it to 1.4L. What would you say then? Oh, it's a 1.3L engine, 66% of the time, every third time it will be 1.4L.

Wouldn't it be more logical to just say it's a 4.0L engine?

A full rotation is a full rotation of the rotor, I cannot dispute that. But a full combustion cycle of a rotory I can debate. And then that moves to the whole last three pages of my points on where the combustion chamber is and how it is measured. With a piston its easy to determine because it happens in one spot. Well it should be easy with a rotory too because it also happens in one spot lol. But an alas from me too lol, its muddy there as well.

[madbung]

Really...I suppose you were right by Mr. Wankel's side telling him how to measure the displacement of the unique engine he designed? You're just generalising the method of measuring displacement because most common forms of internal combustion engine have an easily measurable displacement, with no room for subjective measure. The rotary does not fit that bill. If you think it is so definitive and objectively easy to measure, please tell me why this thread is so long? Clearly there's an issue with that.

This ain't going to end until we all just get sick of arguing...all that's happening is both sides are recruiting more supporters, no one is actually crossing the floor and agreeing here. Thread of the year...for its in depth analysis and informative content...but a painful thread it is.

No of course I didn't advise Wankel, but it was more than a bit audacious of him to try and invent his own measuring stick to better place his product was it not?

Industry standard not good enough? how can it not be measure by it's displacement like all other pumps/engine. why is it "special" it serves the same purpose of the other products..

What does it flow? ie: what is it's displacement/swept volume it's output and it's efficiency. what else is there? what else is relative to this wankel engine/pump?

Really what other criteria did you have in mind? what else would a mechanical engineer be interested it?

It's mass and weight, yes for different reasons in the overall package...

For a fresh reference if you cbf going back searching.

* note the elliptical movement of the rotar (via the gearset) creating the 4 chambers

Edited October 2, 2009 by madbung

[Birds]

It wouldn't be logical to say it's a 4 litre engine...you would instead average 1.3, 1.3 and 1.4 (well, this 1.4 is assuming that both rotors developed the exact same chip/score in the same chamber).

I lol'd at the wheel of fortune analogy. Can't we end this thread on a bit of humour like that?

[Sydneykid]

Its not irrelevant because the combustion appears in the same place for a piston but a rotories combustion appears in a completely different place.

Hence why it's a rotating combusion chamber, by George I think he got it.

Cheers

Gary