Why Do Rotaries Suck?

[RotarySnail]

Hahaha if you can check what date i joined this forum, it was a long time ago. I get into all your group buys on tyres and crap like that. I also read many a retarded thread on here, thus the name of children given. I didn't assume the majority in this thread had no idea what they are talking about, read the first 2 pages and you can see it for yourself. Theres a comment there somewhere about a 13b making 1xxxhp, and sydney kid replies saying that's ok but 2xxx is more reasonable for it's "3.9L" capacity? Good laugh.

I find it funny how people who seem to struggle with their own engine/vehicle can go bashing on something many qualified mechanics(understandable, because at trade school we only spent about a day looking at rotaries) don't understand, let alone themselves.

And just to clear things up, i'm not a person who loves nothing but rotors. I work on, drive and play around with various different cars through my work.

Edited September 19, 2009 by RotarySnail

[Sydneykid]

SydneyKid, I have much respect for your membership on this forum so please don't think by what i say on here will mean im having a go at you but rather providing a somewhat educated arguement to this fantastic topic!

No problem, I'm impervious to personal attacks anyway, it just detracts from good quality discussion.

From my understanding from aviation and cars, i understand 4 stoke to be the famous quote of "SUCK SQUEEZE BANG BLOW" - that is intake, compression, combustion, exhaust, all a disclosed operation. Whereas 2 stroke is the sharing of the Cycle 1 Exhaust to Cycle 2 Intake. Therefore at the very simplest level, there is a defined difference between 4 and 2 stroke engines.

When, SydneyKid states that "It the same as the 2 cycle truth, the rotary combusts every cycle, not eveery second cycle which is what defines a 4 cycle engine", I strongly disbelieve that as a defined theory.

OK, you're entitled to your opinion, but let me mount a counter argument. Using your definition of a 2 stroke/cycle engine, it's blatantly obvious that a rotary engine most definitely shares cycles. Whilst one side of the rotor is inletting another side is exhausting, hence its a 2 cycle/stroke engine. Obviously there is a 3rd side of the rotor that is combusting, but in your definition that's irrelevant

I think the problem here is you are still trying to equate a rotary engine with a piston engine and we quite simply can't do that. What you are doing is looking at one chamber at a time, like it was a piston. The problem is in a 2 stroke piston engine there are 2 sides to the piston, the crown that combusts and exhaust and the underside that inlets. In a rotary engine there are 3 sides and we can't look at one side only when determining if it's a 2 cycle engine or not.

Again, we can't relate a piston engine to a rotary engine, even when it comes to somthing as apparently simple as 2 stroke/cycle versus 4 stoke/cycle. The fact is a 13B (for example) is a 2 cycle/stroke rotary engine. That's not the same as saying a 13B (for example) is the same as a 2 cycle/stroke piston engine.

Notice, in the rotary and 4 stroke, the intake and exhaust are both separate and disclosed operations. For the 4 stroke and Rotary, there IS a distinct difference between the way the compression and combustion stages occur due to their geometric design, but ultimately performing the same output of exhaust. I suppose, SydneyKid, there is merit to what you are saying because there is no specific "stroke" between the compression and combustion stages. Therefore to claim a rotary as being a 4 stroke engine is probably just as wrong as calling it a 2 stroke engine.

If we explore just a little more, the only difference I can see between rotary and 4 stroke is the process of compression and combustion. 4 stroke will take a stroke between compression and combustion, whereas the rotary will (by the use of their elliptical movement) will compress and combust in the one movement. This if we all think about it performs the same output and therefore defines the process of a stroke and a turn.

The same problem again, you are attempting to convert elipical motion to up and down motion and that's fraught with danger. If you stop thinking of strokes as up and down motion, perhaps just use the alternative meaning of cycles. You then come to a completely different view of what constitutes a 2 cycle engine, and that a rotary is most defintiely that.

Possibly those in the powers to be could not define the process difference of these two and decided to call a rotary's movement as 4-stroke.

The "powers to be" were Mazda and they had an agenda and a major part of that agenda was to avoid at all costs the linking of rotaries with 2 stroke/cycle lawn mowers. That would have been disasterous when they were launching a new technology engine 40 years ago. It's exactly the same reason for the 1.3 litre lie, they didn't want expectations of 3.9 litre power.

I personally believe the rotary is not a 2-stroke.

But is it not a 2 cycle engine?

Cheers

Gary

[Sydneykid]

YES A ROTOR'S FULL COMBUSTION CYCLE IS COMPLETED AFTER 3 TURNS OF THE ECCENTRIC SHAFT...BUT THAT DOES NOT MAKE IT EQUIVALENT TO A 3.9 LITRE 4 STROKE ENGINE...BECAUSE IF WE ASSUME THE SAME GEARBOX/DIFF/TYRES FOR TWO CARS, ONE ROTARY POWERED AND ONE PISTON POWERED...WITH THESE 3 TURNS OF THE ECCENTRIC SHAFT THE ROTARY POWERED CAR WILL TRAVEL 50% MORE DISTANCE THAN THE PISTON POWERED CAR AFTER ITS 2 CRANKSHAFT TURNS (FULL COMBUSTION CYCLE IN A 4 STROKE). INCIDENTALLY THIS IS THE SAME 50% THAT YOU ENJOY ADDING TO THE PROPER 2.6 LITRE EQUIVALENCE TO GET YOUR SUPPOSED 3.9 LITRE ENGINE. Sorry for the caps and bold but this is the most important point of all. End of story.

Hence why I will respond.

What you are describing is gear ratio, diff ratio and tyre diameter effects. If I want to travel 50% less distance, then I simply lower the gearbox/diff ratio. or fit some smaller diameter tyres What has that got to do with engine capacity? Nothing.

Nobody halves the true capacity of a piston engine just because it combusts every second revolation of the cranshaft. So why should we allow a rotary engine to devide its true capacity by 3 just because the rotors turn at one third eccentric shaft speed. There is no logic there.

Regardless, I'm not falling for the trap of comparison, the fact remains a 13B pumps 3.9 litres for every complete cycle of its rotors. Whether that's the same as a 3.9 litre piston engine is irrelevant.

Just so we keep things clear and not enter a debate over it, I'm fairly indifferent to rotaries...I don't hate them and I don't like them. But can you bugger off back to your spot lodged deep inside RICE RACING's colon? It seems to me you only joined these forums to spark some sort of RB vs rotary debate...god knows where this came from anyway...because this thread has for most part been an informative debate about the workings of a rotary engine and a physics based comparison with the workings of a piston engine...until you came along. Making some poor assumption that everyone here, up until RICE posted, has no idea what they are talking about and googled or wikied their sources of information...just...please die. Also, calling us children? Most people here legally drive and own cars...I therefore challenge you to find someone who is legally considered a child and regularly posts on these forums. Even sydneykid with his ultra deceptive name is far from a child. Who decided to post a link to this thread on a rotary fan forum with some members who clearly have nothing better to do than forum hop and bible bash their support for rotaries? If nothing else we have a nice pictorial diagram of the Wankel cycle, and for that I thank you RICE RACING.

The difficulty the blind rotary supporters have with me is I can point to a number of rotary engined cars and say I built/helped build them. I don't have an anti rotary agenda, my agenda is quite simply to tell the truth, expose the 40 years of Mazda lies and dispell the urban myths surrounding them. The fact remains a 13B is a 3.9 litre 2 cycle rotary engine where the rotors (the all important combustion components of the engine) only rev to 3,000 rpm. Don't confuse that with saying a 13B is the same as a 3.9 litre 2 cycle piston engine where the pistons (the all important combustion components of the engine) only rev to 3,000 rpm. That's not my argument, because that would be attempting the impossible, equivalency is a fallacy.

Cheers

Gary

[Gts-t]

Score

Gary 100 Rest of thread 0

[Sydneykid]

Nice thread

Displacement is here, its written in Layman terms so no one here should have any difficulty

I decided to put this together for the new players who struggle with understanding what a wankel cycle is about and also the true capacity of the engine, a picture tells a thousands words, so I cut up a rotor and a shaft and marked them taking a photo at every 90 degree's of main shaft rotation, following a chamber from firing to firing or one full Wankel Combustion Cycle.

From the above you can see each individual separate chamber (3 per rotor) only fires after 1080 crank shaft degree's has elapsed,, this is why the Wankel is so different to ANY other type of engine, 2 strokes fire each individual chamber once every 360 degree's and 4 strokes fire every individual chamber every 720 degree's.

If you look at a 13B with its 654cc per Individual chamber capacity (thus 1308cc) you can see it aspirates this ONCE every single revolution thus you can compare the 13B to a 2 stroke if you must do so on an equivalence basis (but remember you are not counting the other 2/3rd's of the combustion faces!

Now if you compare it to the much more common 4 stroke engine you can see that 2 faces ONLY are being counted in the engine and thus it has aspirated a total of 2616cc over 720 degree's of crank shaft rotation....... nice little bit of info there but it still misses a whole 1/3rd of the engine!

Finally the ONLY TRUE way to look at a Wankel Rotary is to view it in its own cycle! (and not comparing it to something that it is NOT!) this is only over 1080 degree's of crank shaft rotation, where ALL of the working faces can be accounted for (just as when you do a compression test to see if the poor little donk is healthy or not) For it is only when the entire engine has complete one full cycle of work can it thus be rated, be that as functional or in its true capacity sense. You will then see that the humble 13B is indeed 654cc x 3 working faces x number of rotors ! = 3924cc.

Equivalence capacity to time scale (revolutions) for 13B engine, has one power pulse per 360 degree's per rotor

1308cc 360degree's (2 stroke)

2616cc 720 degree's (4 stroke)

3924cc 1080 degree's (Wankel Rotary)

Clearly someone who understands how a rotary works, but is trapped by the 40 years of Mazda lies. It's not layman's terms, it's Mazda's terms, you are simply regurgitating the Mazda myths. So let's get down to the real facts, why are you using eccentric shaft degrees to determine capacity? No one does it (count crankshaft revolutions) with piston engines, but Mazda does it with rotaries. Try it with a full cycle of rotor motion and you end up and 3.9 litres for a 13B, ie; use the same method as everyone does with a piston engine, a full cycle of piston motion. That's the problem with Mazdas flawed logic, it's a useless attempt at comparing crankshaft revolutions with eccentric shaft revolutions but completely ignoring the facts of engine capacity measurment and then compounding that error by ignoring the simple mathematics. Why? Because it didn't fit with their publicity, it's marketing calculation not an engineering one.

The fact is it's completely irrelevant how many revolutions of the eccentric shaft, that's a gear ratio and, as such, has absolutely nothing to do with an engine's capacity, which is how much it pumps. In the case of a 13B that's 3.9 litres for the completed cycles of its 2 rotors.

Cheers

Gary

[karmine-ent]

This is a thread that will never end. There is not ONE person who knows the 'real' answer to this.

Every engine is different until you put a turbo on it, then they all become quite similar in performance.

13btt rx7 300rwkw vs rb26dett gtr 300rwkw who wins straight line? RX-7 due to its weight, not its real engine rotations!

If you are right about 3.9 litre not 1.3. Take a little time out and look at the rx7 rev limiter. Your technically saying the RX-7 is doing 25,200RPMs coming from 8,400RPMS, times 3. A two stroke motorcycle does around 17,000rpm redline at 2 strokes rather than 3 the tacho doesnt read 8,500.

Did Mazda introduce a new RPM reader? That reads 1/3 of the real RPM whats the diference between Mazdas tacho and that motorcycles tacho?

Dont post a silly answer because no one knows the answer to that, just a little food for thought however. Im not saying im right, because I dont know, but its something you need to look at.

[RICE RACING]

Gary,

When was the last time you have had sex with a female?

[Sydneykid]

Gary,

When was the last time you have had sex with a female?

Ah, the old changing the subject trick. So that means you give up then and agree that I'm right?

Cheers

Gary

[Sydneykid]

This is a thread that will never end. There is not ONE person who knows the 'real' answer to this.

Every engine is different until you put a turbo on it, then they all become quite similar in performance.

Realy, so how does a 13B go when you put a 1.3 litre sized turbo on it? Prettry terrible actually.

But when you put a 3.9 litre sized turbo on it they go OK.

Further proof of 3.9 litres, as if we need it.

13btt rx7 300rwkw vs rb26dett gtr 300rwkw who wins straight line? RX-7 due to its weight, not its real engine rotations!

If you are right about 3.9 litre not 1.3. Take a little time out and look at the rx7 rev limiter. Your technically saying the RX-7 is doing 25,200RPMs coming from 8,400RPMS, times 3. A two stroke motorcycle does around 17,000rpm redline at 2 strokes rather than 3 the tacho doesnt read 8,500.

Did Mazda introduce a new RPM reader? That reads 1/3 of the real RPM whats the diference between Mazdas tacho and that motorcycles tacho?

Dont post a silly answer because no one knows the answer to that, just a little food for thought however. Im not saying im right, because I dont know, but its something you need to look at.

Ah......no...........what I am saying is a rotary tacho is manipulated to show eccentric shaft revolutions of 9,000 rpm when the fact is the rotors are only doing 3,000 rpm.

Cheers

Gary

[RICE RACING]

Score

Gary 100 Rest of thread 0

For post whoring and having no idea about mechanical engineering nor thermodynamics? I would agree 100%

If you want to know about how engines work I will tell you right now this Gaz is an oxygen thief with limited idea and no formal qualifications to comment, nothing more. Listen to him if you are a sad deluded fool, if on the other hand you want to know how ALL engines work you must read and then re read my simple post, look at the pictures............ even a 5th grader could get it

Peace out Skyline people, I hope all of you are not as uneducated as what I have seen from some in this thread

[RICE RACING]

Ah, the old changing the subject trick. So that means you give up then and agree that I'm right?

Cheers

Gary

Far from it, its me knowing you are an idiot for your delusional ranting baseless posts on a topic you obviously know very little about

[Sydneykid]

Far from it, its me knowing you are an idiot for your delusional ranting baseless posts on a topic you obviously know very little about

So now it's personal insult time, if you can't support your argument with facts then insult the opponent. Not a very good tactic.

Cheers

Gary

[RICE RACING]

For the benefit of others, have a look over this it puts my pictures along with the cycle description for a 2 rotor

For anyone that cares to learn more about this topic and even how much it confuses rotary people you can go look over and read the main thread I started on it, this subject creates allot of reaction and confusion mostly amongst people with no formal education in mechanical engineering. The ones who have passed thermodynamics though get it very easily

http://www.ausrotary.com/viewtopic.php?f=3...amp;hilit=3.9lt

Peace out, and remember to check the qualifications of the people you choose to worship on your fav forum before jumping onto the bandwagon

Oh and EVERY operating cycle is described by its direct mechanical linkage to the output shaft! be it Wankel, two stroke or 4 stroke! *direct mechanical linkage* the definition is simple one chamber to repeat its power pulse, this defines ALL engines of internal combustion type. The only thing Gaz is kinda right on is the capacity, the lack of knowledge of the Wankel cycle is the only travesty allowed over so many years.

1080 degrees is it.

So in summary if you want to compare it to the common 4 stroke! (remember its all equivalence based) then you only look at 720 degrees and how much it has aspirated, then you will find the classic 2.6lt comparison *Apples to Apples* in volumetric terms. < But does nothing to describe actually how the Wankel works. You need to look over the info I provide and also maybe take a basic course in operation of engines to fully get it if you are struggling.

Edited September 19, 2009 by RICE RACING

[Sydneykid]

For the benefit of others, have a look over this it puts my pictures along with the cycle description for a 2 rotor

For anyone that cares to learn more about this topic and even how much it confuses rotary people you can go look over and read the main thread I started on it, this subject creates allot of reaction and confusion mostly amongst people with no formal education in mechanical engineering. The ones who have passed thermodynamics though get it very easily

http://www.ausrotary.com/viewtopic.php?f=3...amp;hilit=3.9lt

Peace out, and remember to check the qualifications of the people you choose to worship on your fav forum before jumping onto the bandwagon

Well at least we got back to the facts, please answer 2 questions;

1 why are you using eccentric shaft degrees to measure capacity?

2. if you rotate 1 x 13B rotor 360 degrees how much air does it pump?

Cheers

Gary

BTW, anytime you want to compare CV's, I'm up for it.

[RICE RACING]

Answer 2 questions

1 why are you using eccentric shaft revolutions to measure capacity?

2. if you rotate 1 x 13B rotor 360 degrees how much air does it pump?

Cheers

Gary

Simple.

1. The crank degree's are directly linked to the rotor face position, and thus are linked to the cycle position as shown graphically in photos and also in the above post. ALL ENGINES cycles are defined by the output shaft crank angle and firing events or power pulses.

2. In one rotation of the output shaft, 654cc is displaced per rotor in a 13B engine. <, So 1308cc per 360 degree's and you will find also there are two power pulses or ignition events to match to back this up

[RICE RACING]

What people forget is this basic fact and you only need to look at the spark plug (assuming non wasted spark!) < key here is wasted lol.

now a spark plug only fires when it going to produce a power pulse.

2 stroke this happens at 1 rev (360deg)

4 stroke this happens at 2 rev (720deg)

Wankel this happens at 1rev,2rev,3rev! (360deg, 720deg, 1080deg!) and corresponding displacement values are 1308cc, 2616cc, and 3924cc!)

Now if you are objective you can see that Mazda is right in claiming 1308cc for its 13B, but they would need to call it a two stroke so newbies had some idea of how to compare it in a time scale to displacement as ALL people and regulators want to know WTF they are looking at so they can compare it to other more well known engine principles.

The simple fact is though sure it describes one power pulse but it does not describe how much it aspirates as a comparison to other engine types.

Thus you can call/compare it to the two well known and understood engine combustion cycles as outlined below

13B Wankel is like a:

1308cc two stroke

2616cc four stroke

but it really is a

3924cc Wankel

^ The problem Mazda face is that they and others mind you decided to go away from the basic fact that engine cycles and "total" displacement are tied together, so since technically the lower capacity fits the same definition of one power pulse per event they went for the lower figure and no joe shmo actually understood that it took 1080deg for a Wankel to do what it needs to do! thus other basics cause confusion like why and how rotaries technically don't need as much ignition timing advance for the same revs as a piston motor cause it take 1/3rd longer for things (combustion!) to happen !

Its really all is very straight forward.

Edited September 20, 2009 by RICE RACING

[ylwgtr2]

this has turned into a co(k beating competition....i dont have any qaulifications but i have and can use a cnc mill, motojig motorcycle chassis bench,full paint shop facilities,tig welder for titanium magnesium/alloy,autoclave/vacuum forming for carbon products.....can i whack off too???????Oh no....i dont have a piece of paper telling me i know how to use them....just product.....pfffft

[ylwgtr2]

on the other hand....hands up who likes tits???(providing your hands free at the moment)

[Johnny]

I like this thread but the bloke coming in here personally attacking sydneykid is quite pathetic; we like rotary engines here, this is just an education class on what capacity they actually are and whether they are 2 cycle or 4 cycle ect.

Ive learned heaps! now to summarise so far:

-13b is a 3.9litre engine which is why they can make big power numbers and spool up a large turbine - any dispute there?

-13b, each rotor spins at 3000rpm; spins a 1:3 gear so its 9000rpm, hence the lowered torque levels until u hit higher rpms.

-They are fragile just like our piston engines but make up for it by being light n small; good for drag racing and fits in any small spaceframe like car

is that right?

now can we drop the 13b engine and concentrate on the 12a, as it only has one rotor and is probably easy to compare than 2 rotors.

[Sydneykid]

Simple.

1. The crank degree's are directly linked to the rotor face position

But a rotor has 3 faces, you can't look at one face in isolation. We don't look at one cylinder in a 4 cylinder piston engine in isolation, so why should we ignore the other 2 sides of a rotor?

and thus are linked to the cycle position as shown graphically in photos and also in the above post.

That's cycle position of the eccentric shaft, not the cycle position of the rotor, which is after all the pumping medium.

ALL ENGINES cycles are defined by the output shaft crank angle and firing events or power pulses.

No they're not, you don't doube a 2 stoke engines capacity, or halve a 4 strokes capacity depending on crankhaft degrees of rotation. Their capacity is defined as how much they pump for a complete cycle of their pumping media, ie; their pistons. But when we get to rotaries, Mazda (and it would seem you) expect us to divide the amount they actually pump by 3. I completely fail to see the logic in that.

2. In one rotation of the output shaft, 654cc is displaced per rotor in a 13B engine. <, So 1308cc per 360 degree's and you will find also there are two power pulses or ignition events to match to back this up

This is the basis of our dissagreement, you want to use eccentric shaft revolutions to influence capacity measurement and I see no logic in that. It flies in direct contravention of every other pumping (capacity) measurement of every other type of engine.

That, by the way, isn't the question I asked. I'm guessing that you didn't answer the question because you don't like the answer. In the persuit of truth, let me repeat the question "2. if you rotate 1 x 13B rotor 360 degrees how much air does it pump?"

Cheers

Gary