SPiN Racing

ROFLMAO

Wow... Was trying not to reply to this thread.. But I just cant stop laughing.. It is kinda silly actually..
We have a couple people arguing back and forth on the concept they are having problems understanding..

Evil seems to have tried to hit it a couple times... but people are letting it roll by.

Displacement.. in NON-technical terms.. if measuring a cylinder displacement... as in for the sake of mental-Masturbation a radio controlled ONE cylinder.. be it 4-stroke or two... you can CC the cylinder by FILLING the chamber when at BDC with liquid to get the CC of the chamber.
Now... If using that same method.. you were to Crack a rotary apart.. and lay the front housing down.. and lay on a rotor housing.. and then a rotor... and CC the chamber.. at BDC.. that a SINGLE FACE of the rotor holds.. in CCs.. you will get the CC's of the Cylinder..

NOW.. How many is the question many are arguing.. 6? 9 on a 3-rotor? 2? How many...???

I find it hilarious that people are calling them shared etc... There are very Simply 2.
There are TWO chambers.. TWO places that the Gasses get Compressed and then the Magic spark fires them off. NOT 6.. Not 9... 2. The fact that the rotor SHARES this chamber with two other faces is irrelevant. The displacement is measured from the TWO chambers on the engine.

Sorry... Just thought this may make sense... But the paper is starting with Flawed logic... and then runs with it.. and many of you are arguing along with it.. and ironically.. I am amazed that I posted this.. you prolly would continue to argue even if we got Rick Ingman here to tell you otherwise.. ROFLMFAO

SPiN Racing

Oops Browser lagged and double post.. LOL

PS... Using the CC method... Are you going to CC the chamber.. then rotate the rotor to CC the next face.. and the SAME chamber again?????? /wink Didnt think so. THe chamber number is static... 2.


OK resuming work..

MikeC

Is this kind of insult really necessary?

This is correct, how many is *the* question.

I count 6 chambers, gasses most definately get compressed in 6 different independant chambers.

The logic is correct, you have to think of them as 6 independant chambers. They are just like 3 different pistons.

I've noticed a strong pattern with everyone who disagrees with the article that they *never* comment on the engine comparison. Why is this?

MikeC

No, you CC one chamber and multiply by 6, making the assumption that all 6 of those chambers are equal.

Evil Aviator

You can lead a horse to water, but you can't give it your college degrees.

Exactly.

Yeah, I know what you mean. Notice how most of the more educated people on this forum avoided it, lol. I guess the subject gets old after a while, and it is rather frustrating trying to explain it to the next set of newbies who think they have reinvented the wheel. I still reply to these things sometimes because it helps other people who read the thread, but the thread originators rarely get the message.

Send your paper to SAE, and see if they comment on it. If it is truly ground-breaking, they will publish it, maybe give you an award, and then you can post back here with a nice "see I told you so" message.
http://www.sae.org/servlets/index

DamonB

Best comment I've heard in a long time

KevinK2

Your experiment has noting to do with dislacement, which involves more than volume at BDC. It is the difference in volume from BDC to TDC. mabe if you had cc'd combustion chambers and built race engines (piston), as I have, you'd get it right.

Shared chambers for the rotor makes all the difference .... it means independent chambers of gas are involved, just like independent pistons.

And yes, all 3 chambers should be measured, for consistent compression ratio, because they are like different pistons. Any variation in a rotor face/pocket geometry will mean a variation in CR, among the independent chambers.

you do present a comic combination of being cocky and clueless.

MikeC

If you want to get into college degrees I'm a mech eng. I studies the rotary extensively during my uni degree and have written software to test some of my ideas about the rotary engine. I know what I am talking about.

What I tend to find is the least educated people on the forum fill their posts with insults.

I am looking into that but it seems like a long road. Ultimately this is my goal but I'm working full time and trying to start a business at the same time, so can't devote too much time to this. There was an article that supposedly proved the rotary was eqivelant to a 4 cylinder 4 stroke piston engine so I need to find this and disprove it.

BTW, I'm noticing a real pattern here with the people who knock my article. They *never* comment on the engine comparison. The comparison was pretty damning evidence and I believe the think it is better to ignore it than comment on it because it disagrees with their views too much. If you compare the rotary to any piston engine there are always holes in the comparison, some figures between the 2 engines don't line up. But with the engine comparison in the article *every* figure matched. Most people who were approaching the article with an open mind would at least think, "gee that's interesting".

MikeC

Hang on a sec, this is not the SAME chamber as you put it, it is a different chamber. The original chamber has moved further around the housing.

PaulM

If the question is whats the cubic capacity of a typical engine, then I'm with evil...displacment of the combustion chamber x number of chambers = 2 x 654 = 1308cc's.Period.

If the questionasked by a pistonhead is "why does a 1.3 rotary make more power over it's piston counterpart ?"

the answer is because it's clever and your not, so there's no point in me even starting to explain it to you.

If they're not, then all the dynamics are generally true.

paul M

Jeff20B

iTrader: (13)

Again, 654 is the magic number. It's also easy to type.

MikeC

All the experts cannot agree on the capacity, some say 1.3, some say 2.6 and some say 3.9. Strangely, the only ones who claim it is 1.3 work for the manufacturers. Coincidence?

Have a look at the engine comparison in this doc
http://mikeonline.cable.nu:1863/misc/rotor.doc

Evil Aviator

All of the experts (they are not generally on this forum) agree the capacity is 1.3.

I can't speak for everybody else on this forum, but neither SPiN Racing nor I work for the manufacturers.

Strangely, only those with paranoid delusions of a displacement rating conspiracy say 2.6 or 3.9. Coincidence?

Kenku

Well, I say it's 2.066L if I'm doing high speed autocross (12A and 1.8x displacement factor in the rules) and if I'm not, that it's flowing 150ish HP worth of air (at a rough guess)

How's *that* for universal, inarguable numbers?

SPiN Racing

He he Sorry... Classic...... The Chamber has moved Further Around the housing..

Sooo The chamber has moved? REALLY?? Do you mean the face of the rotor has moved.. and the gases contained by the Side/Corner and apex seals have moved?

He he SOrry guys.. I will leave you all alone... I dont like mental masturbation... Specially when there will be no fruition of it..

PS: Degree in Aviation.. and yes I have been building race engines for many years.... from 2 cycle RC aircraft engines in the early 80s through.. Yes V8.. Yes Rotary.
Sorry to Intrude all Will go back to letting you two try to convince everyone its right... AND BTW>. when SAE says youre right I will Humbly beg forgiveness..

KevinK2

Since the expert Mazda calls it a 1.3L, and accepted an engine design award this year for the 2-3L class, mabe they are part of that paranoid (and confused) group?

1.3L NSU Rating:

The original nsu ratings were NOT based on swept volume of all chambers, which was and is the assumed standard for all piston engines. The practice was to rate each rotor by the displacement of one face only. So for 13B, 2x.65 =1.3L displacement rating. Knowing each housing fires once per rev, 1.3L is also the actual air injested in one rev, but it only represents 2 of the 6 chambers completing their required 4-strokes.

3.9L swept volume method:

simply swept volume of all chambers, with no regard for how many revs needed to fire all chambers. for .65L per chamber or cylinder, this puts four piston 2 and 4 strokes at 2.6L, and the 13B at 3.9L with 3 faces per rotor creating 6 distinct and active chambers. These are pure swept volume ratings. But, per rev, the 13B actually ingests 1.3L, the 2-stroke 2.6L, and the 4-stroke 1.3L (all @ 100% VE).

as mike said, the 2.6L 13B rating comes from the actual air injested in 2 revs, for boingers and 13B.

Bottom line is the 13B is a 1.3L per the old nsu definition, and it is the actual air injested in one rev. just don't try to say that the rating is consistent with the common swept volume method.

MikeC

This is simply not true. The SAE were fighting between 2.6 and 3.9. None of them were fighting for 1.3. Only the manufacturers thought it was 1.3.

I meant the only experts that believe the engine is a 1.3 work for the manufacturers. Well, believe is probably the wrong term, they know the real capacity but just lie about it.

Is this the best arguement you've got?

An equivelant capacity for racing purposed is fine but the engine really is a 3.9, it's just very inefficient because of the large combustion chambers at TDC.

Yes, the chamber has moved, they move around at one third the speed of the crankshaft.

I thought you'd back out when I asked you to comment on the engine comparison in the article...

You are quoting mazda and nsu as experts?? Next you be telling me cigarettes don't cause cancer because the cigarette companies say so. Mazda have a huge amount to gain from the rotary being rated smaller than it really is.

You can't use the output shaft for determining capacity because it can easily be geared, eg taking the output of a piston motor off the camshaft.

That would mean that 4 stroke piston engines should be rated at half of what they currently are, which is probably not unreasonable, but that's a bit academic because it affects both engines in the same way. So the NSU rating really is 2.6 litre then.

MikeC

Kevin,

Ignore my reply to you, I misread your post completely and for some reason thought I was reading evil aviators post.

KevinK2

I'd love to see the SAE standard for displacemt, afaik it does not exist. some have said "1.3 is good nuff for sae, then good nuff for me. SAE has standards for hp and torque that are always cited, but you will never see an SAE displacement rating.

QUOTE]Originally posted by MikeC
An equivelant capacity for racing purposed is fine but the engine really is a 3.9, it's just very inefficient because of the large combustion chambers at TDC.[/QUOTE]

And it only injests 2.6L in 2 revs, vs a boinger 3.9L in 2 revs.


QUOTE]Originally posted by MikeC
You are quoting mazda and nsu as experts?? Next you be telling me cigarettes don't cause cancer because the cigarette companies say so. Mazda have a huge amount to gain from the rotary being rated smaller than it really is.[/QUOTE]

The rotary engineers there are more expert than any in this crowd, and are smart enough to know both their uniquely defined in-house displacement rating, and the comparable 'ingested air' rating of 2.6L to contest 2-3L engines for best design awards.

QUOTE]Originally posted by MikeC
You can't use the output shaft for determining capacity because it can easily be geared, eg taking the output of a piston motor off the camshaft.[/QUOTE]

That is a purely academic argument of no practical significance. Engines are designed for functional simplicity. The tests of common sense and minimum cost would never allow such a foolish move. The FD has gearing that is essential to the engine working.


QUOTE]Originally posted by MikeC
That would mean that 4 stroke piston engines should be rated at half of what they currently are, which is probably not unreasonable, but that's a bit academic because it affects both engines in the same way. So the NSU rating really is 2.6 litre then. [/QUOTE]

The unique 'NSU rating' stays 1.3L, equal to air injested in one rev. to compare with boinger 4-stroke, need to use 2 revs, for 2.6L injested air. I don't deny the bizzare NSU rating method.

KevinK2

too late mike , but you raised legit points.

MikeC

Interesting, I was under the impression they had rated it at 2.6 litres. I have a quote about this but I don't have it on me. There was one article which suposedly proved the rotary was equivelant to a 2.6 litre 4 cylinder engine. I'm trying to chase it up but it is hard to get 30+ year old papers.

But the rotary should be running at 1.5 times the output shaft rpm, all things being equal. So will injest the same as a 3.9 litre 6 per second.

I don't think the fact that it does not exist makes it irrelevant. If it can be imagine then it is just as valid to enter it into a discussion as something that does exist. Scientific types do this sort of thing all the time and no-one batters an eyelid.

For a moment imagine that the rotating radial engine you described does exist in production, would it be rated at 2.6 or 3.9 litres?

Kenku

Got any papers in mind specificially? I can see if the engineering library at my college has some; they have the transactions going back to the 60s or so.

Also, from what I've seen from trying to decipher a couple mathematical models for performance from these suckers, most of the inefficiencies of the combution chamber aren't really because of the *large* surface area (some are, true) but because the trailing apex side of things quenches a good deal of the burning mixture.



All right. I had a thought. I apologize because it ignores some of the interesting points you bring up, but it's a way to settle between the 2.6 and 3.9 liter models.

In order to come up with performance numbers consistent with power outputs of peripheral ported motors, a 2.6L engine has to be hitting greater than 100% volumetric efficiency. Call it 120% for argument's sake. This isn't unheard of; it means that the gas intertia in the intake tract is such that it can force more air into a working chamber than it would naturally take in. If, however, you're looking at it as a 3.9L gear reduced engine, you're achieving 80% volumetric efficiency on the same engine for the same power outputs. With me so far?

How does that help us? Well, the amount of air being taken into a single working chamber can be measured independently of everything else! You could, in theory, create a demonstrator motor and run it, measuring the pressure in the working chamber at, say, BDC on the intake stroke. If it's greater than atmospheric pressure, then it's running at >100% VE, then the 2.6L formula is proven. If it's substantially below atmospheric pressure, then VE's below 100%, and the 3.9L equivalent has more support.

Well, that's simplifying things a bit, and of course I don't know that most of us here have the tools handy to conduct that experiment, but... something to think about.



I swear, we're probably the only group of automotive enthusiasts who sit around and argue how big our engines are.

KevinK2

1) making cycle duration the sole basis of scaling displacement rating seems narrow in scope, given that existing stock boingers can rev to 8k+.

2) that example was 4 pistons, and 3 revs for all to fire. it's displacement, per current swept volume method, would be 4xcylinder displacement (with a 3 rev engine cycle).

Most practial rating for 13B would be to just qualify the current nsu 1.3L displacement rating as occuring in one rev. My example engine, with a 3 rev cycle, could also be rated at 1 rev, or 3 revs. Point is engines that don't have a 2 rev cycle should their displ rating qualified by the cycles assumed .... 13B = 1.3L/rev 2 rotor.

Most know that a 5.0 takes 2 revs, and a 250 ktm takes 1 rev. effective power/capacity adjustments are made by race groups, for rotary, 2v vs 4v boingers, etc.

MikeC

The paper I am after was written by Richard F Ansdale and titled "Rotary Engine Development and its Effect on Transport". If you can get me I copy I'd very much appreciate it.

Makes sense.

You wouldn't need to measure the pressure, you could just measure the rate of air inducted which would be a lot easier to do. The only problem I could see is that other factors might effect the results such as chamber shape.

You need to compare the rotary to piston motors with a displacement of 654ccs. Going from posts here the closest was 620ccs which redlined at 7900. This is taking the highest revving engine from all of the production engines. If every manufacturer produced rotaries maybe the range would be between 8000rpm redline and 12000 rpm, we just don't know whether the mazda rotary would be at the top or bottom of the range of rotaries. My theory is that they actually tuned it to rev lower than it could because of problems at higher speeds.

If you modified the example to be 2 banks of 3 radial pistons then it would be very similar to the rotary but still be a 3.9 litre engine. It would have the 270 degree expansion, fire as often and at the exact same times, induct the same air per rev and have the same theoretical torque fluctuation graph. At every point in time what was happening in each engine would correspond to the other.

MikeC

I know this thread is getting old but ... I'm not suggesting that the displacement be scaled from 2.6 to 3.9 because of the 270 degree expansion, I'm saying that it already has been scaled from 3.9 to 2.6 because of the 1.5 ratio. By *removing* the scaling we get back to the true displacement of 3.9.