rotary engine displacement ??
they are 1.3 liters right ? how are they measured ?
my brother insists that it is 650cc for each combustion chamber (each face of the rotor).. Im not sure so I don't coment. anyone knows for sure? |
It's 1.3L Volume. 650cc per rotor, not per rotor face. If you powered water into the engine it would take up 1.3L.
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thank U sir :bigthumb:
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humm.. still. how do U put 1.3 litters ? in it ? how is that measured ?
what's the max volume of a rotor's face? thx (there is still doubt in the air) |
Originally Posted by Parastie
It's 1.3L Volume. 650cc per rotor, not per rotor face. If you powered water into the engine it would take up 1.3L.
e=offset of the eccentric i=length of rotor face r=width of housing don't quote me on this, though (might also be e+r+b) |
Originally Posted by Falcoms
I do belive you are wrong, sir. That is 650cc per face, not per rotor, being that it is measured by how much displacement occours when the working chamber is used once i.e. one face is measured. Also, the equation for calculating it out is sq. root of 3^3(e+i+r)
e=offset of the eccentric i=length of rotor face r=width of housing don't quote me on this, though (might also be e+r+b) Mazda messured the engine to be 1.3L based on volume displacement. |
What fun it is!
You both are kinda right. Each rotor displaces 654 cc per crank revolution. And as you know, the rotor spins at 1/3 the crank speed. So it is 654 cc per face also. Then you get 1308 cc (1.3 L) for the whole engine.
The problem most people have is when they compare to 4 stroke piston engines. The 4 stroke "wastes" 1/2 of its displacement on two of the strokes. So if you want to compare a rotary to a boinger, consider the rotary as being roughly equivalent to a 2 stroke. Usually in normal cfm or mass flow equations, you will need to multiply the rotary (or two stroke) displacement by 2 to get the numbers to work out right. The "muliply by 2 part" is cause most of the equations are derived for 4-stroke boingers. HTH, Scott |
Originally Posted by Parastie
If you want to get technical about this, but that messurement the engine is 2.6L because it does twice the combustions per rotation has a normal piston engine.
Mazda messured the engine to be 1.3L based on volume displacement. |
2 is better than 4? that could be debated. besides, we're still 4 stroke. just different. :)
1308cc pwns joo. 1962cc pwns 1308cc. |
Originally Posted by casio
2 is better than 4? that could be debated. besides, we're still 4 stroke. just different. :)
1308cc pwns joo. 1962cc pwns 1308cc. |
yea, i've asked about 2-stroke before and was told why they're inferior to 4-strokes, but i have no recollection of the answer. :) i remember emissions output is a bit worse. i wonder what the biggest 2-stroke engine is.
2616cc; now we're just getting greedy. i wonder what the front of an rx7 would look like if it were made to fit a rotary "4-banger." its a big engine. :D |
A rotary's displacement or swept volume is calculated just like a piston engine's, being the difference between maximum chamber volume and minimum chamber volume multiplied by the number of rotors. You don't multiply it by the number of chambers because they only one chamber is fired per engine revolution. This makes a 13B 1308cc.
In the automotive media it became common to multiply this by two because the rotary inhales this volume twice as often as a 4-stroke piston engine. Since the amount of air an engine breathes is almost directly proportial to it's power output, this gives a number that makes rotary-powered cars easier to compare to a piston-engine ones (and comparing cars is what the media does). This makes a 13B 2616cc. In motorsport the rotary's swept capacity is usually multiplied by 1.8 as this gives a more accurate way to evenly class rotary-powered cars against piston-powered ones. This makes a 13B 2354cc. The truth is one can't accurately compare a rotary's swept volume with a piston's. There are too many other differences to use just this one number. In my exerience people who actually argue about whether or not a 13B really is 1.3L usually don't fully understand what they're talking about. |
all these different ways of calculating rotary displacement is just nonsense. when someone asks me the displacement of a rotary, i tell them:
12A>1146cc>1.1L 13B>1308cc>1.3L look at the plates in the engine compartment. |
my definition from rx8club.com:
a motor is defined as having completed an entire combustion cycle when all combustion chambers have had a combustion event (fired their spark plugs). in a 2 stroke motor, that means once up, once down (one rotation of the crank shaft). in a 4 stroke piston motor, that means twice up and twice down (two complete rotations of the crank shaft). in a '4 stroke' (otto cycle) wankel motor, that means 120 degrees of rotation for each rotor (one full rotation of the eccentric shaft). being that each rotor in a 13B mazda wankel engine displaces at theoretical maximum 654cc's per 120 degrees of rotation, and it has 2 rotors, it is a 1.308 L engine. case closed, and one more reason no one should listen to idiots who write in car magazines who think they know what they're talking about (thinking of the SCC article). when it comes to calculating rate of mass flow, you need is a rate (which is, yes dependant on displacement, but not solely), so all this bullshit about the 'real' displacement is pretty pointless, especially since it really is 1.3L. |
and another thread that goes to the favorites !! great explanation there :bigthumb:
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^^^:werd:
I always just tell people that if you are going to compare apples to apple, and measure piston engine displacement the same way you measure rotary displacement then the displacement is 1.3L. But it functions so much differently displacement doesn't matter much. OMG, did I just say it? A replacement for displacement??!!??? bwahahahahahahahahaha |
Originally Posted by wakeech
my definition from rx8club.com:
a motor is defined as having completed an entire combustion cycle when all combustion chambers have had a combustion event (fired their spark plugs). in a 2 stroke motor, that means once up, once down (one rotation of the crank shaft). in a 4 stroke piston motor, that means twice up and twice down (two complete rotations of the crank shaft). in a '4 stroke' (otto cycle) wankel motor, that means 120 degrees of rotation for each rotor (one full rotation of the eccentric shaft). being that each rotor in a 13B mazda wankel engine displaces at theoretical maximum 654cc's per 120 degrees of rotation, and it has 2 rotors, it is a 1.308 L engine. case closed, and one more reason no one should listen to idiots who write in car magazines who think they know what they're talking about (thinking of the SCC article). when it comes to calculating rate of mass flow, you need is a rate (which is, yes dependant on displacement, but not solely), so all this bullshit about the 'real' displacement is pretty pointless, especially since it really is 1.3L. Thats the way I feel too however, when comprared to a 4 stroke piston engine, a 1.3L rotary will breath like 2.6L piston engine due to how much air the rotary will move in 2 rotations of the e-shaft. This is one of the reasons why these rotarys will spool a large single fairly decent. |
To bring this back,
to calculate cfm for a turbo selection we just double the cfm of a 4 stroke like a 2 stroke? |
Originally Posted by Parastie
If you want to get technical about this, but that messurement the engine is 2.6L because it does twice the combustions per rotation has a normal piston engine.
Mazda messured the engine to be 1.3L based on volume displacement. just because it takes in it's full displacement every rotation doesn't mean it now has double the displacement because the max amount of volume stays the same regardless of how many revolutions it takes. another thing if anything though with your though of logic a rotary should be 1.3L while a piston motor would be rated at half :p |
Yes the 13B is 1.3L I also agree. It is the rotary haters who like to argue this. They cannot stand that the rotary seems to out do 99+% of the beloved V8s when it comes to HP per cube. Every official book/manual by Mazda says its a 1.3L so I will listen to them before some idiot running off at the mouth on here. I will agree the power is comparable to a 2.6 or so liter piston motor but I will never agree with those who say it is 2.6L by measure of displacment. You cannot rate dispalcement on output of power and I agree just because the rotary can make full use of its displacment also does not change displacment. So to all you rotary hating traders you can SUCK IT! :)
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I'm not a rotary hater, and I think there are some very good arguments for the 2.6L displacement of the 13B. There are so many long threads about this topic, however, that I will leave you to read them and decide for yourself which displacement rating is appropriate in which contexts.
-Max |
Its a 1.3L but it breaths like a 2.6L. I'm comfortable knowing that.
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It's not hard to figure out how so much power can be produced by so few cubes:
First, the power "event" (not "stroke") lasts a full 270 degrees of e-shaft rotation vs. only 180 degrees of rotation for the boinger's power stroke. (for the sake of simplicity I'm ignoring valve and port timing factors). Second, there is no valve train to drive in the rotary so no hp gets wasted on that particular task. Read it and weep, boinger fans! :bigthumb: Oh, and it's 1308cc, not 2616. |
I heard somewhere that a 13b is only 80 ci is this correct?
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^ Yeah, 1.3L converts to 80.1something CI. Also, aviator, I was talking about the 4 rotor engine, which uses 4 13b housings and rotors, coming out to a grand total of 2616cc. just FYI.
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Originally Posted by Falcoms
^ Yeah, 1.3L converts to 80.1something CI. Also, aviator, I was talking about the 4 rotor engine, which uses 4 13b housings and rotors, coming out to a grand total of 2616cc. just FYI.
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If I had to compare engines with each other, I'd compare airflow. The more air an engine pumps the more power it produces and the 13B engine pumps about the same as a 4 cycle piston engine with 2.6l displacement.
Comparing a NA rotary engine with a NA 4 cycle piston engine regarding their displacement appears relatively simple. There's a reason why engineers placed the engine in the 2.5l to 3.0l category. A gasturbine has no closed chambers and therefore no displacement and therefore compares to a 0.0l piston engine? Well I guess that would beat everything. And btw: The largest 2 stroke engine has 25480l displacement. http://www.bath.ac.uk/~ccsshb/12cyl/ |
Originally Posted by t-von
Its a 1.3L but it breaths like a 2.6L. I'm comfortable knowing that.
if anything I say it breaths like a 1.3L the piston motors on the other hand only breath half so if anything a 5.0 breaths like a 2.5L :-p |
Originally Posted by rxspeed87
if anything I say it breaths like a 1.3L
the piston motors on the other hand only breath half so if anything a 5.0 breaths like a 2.5L :-p Yea only if your using one rotation. A 4 cyl 2.6L 4 stroke piston would need 2 rotations of the crank shaft to fire it's full displacment. A rotary would only need one however, when a rotary rotates it's e-shaft twice, it moves 2.6 liters of air just like the piston but without a waisted power stoke. Thats why people say they breath like a 2.6L. This is also why the small rotary can spool a large turbo fairly quickly. |
think the biggest par t as to why a rotary will spool quick is look at the xhuast. straight through. no valves or anything else to absorb that energy it's just a straight shot
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that diesel turbo 2 stroke is retardedly huge!!!!!!!!
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Originally Posted by wakeech
my definition from rx8club.com:
a motor is defined as having completed an entire combustion cycle when all combustion chambers have had a combustion event (fired their spark plugs). in a 2 stroke motor, that means once up, once down (one rotation of the crank shaft). in a 4 stroke piston motor, that means twice up and twice down (two complete rotations of the crank shaft). in a '4 stroke' (otto cycle) wankel motor, that means 120 degrees of rotation for each rotor (one full rotation of the eccentric shaft). being that each rotor in a 13B mazda wankel engine displaces at theoretical maximum 654cc's per 120 degrees of rotation, and it has 2 rotors, it is a 1.308 L engine. case closed, and one more reason no one should listen to idiots who write in car magazines who think they know what they're talking about (thinking of the SCC article). when it comes to calculating rate of mass flow, you need is a rate (which is, yes dependant on displacement, but not solely), so all this bullshit about the 'real' displacement is pretty pointless, especially since it really is 1.3L. The rotary is like a 6 cylinder piston motor that uses some trickery to share a sparkplug amongst 3 cylinders. If we measured such an engine's displacement by the air inducted in the time both it's spark plugs fired it would give a figure of one third the actual displacement, just like with the rotary. |
Originally Posted by ShIvER[PT]
they are 1.3 liters right ? how are they measured ?
my brother insists that it is 650cc for each combustion chamber (each face of the rotor).. Im not sure so I don't coment. anyone knows for sure? |
Originally Posted by MikeC
A rotary has six chambers
Another example: Given a 5.0L 4-stroke piston engine, the rated displacement is 5.0L. Now make it into a 2-stroke. It still has a rated displacement of 5.0L, even though it now "breathes" twice as much (assuming the same volumetric efficiency). The number of combustion cycles per revolution has nothing to do with rated displacement.
Originally Posted by rxspeed87
if anything I say it breaths like a 1.3L
the piston motors on the other hand only breath half so if anything a 5.0 breaths like a 2.5L :-p I'm not sure how good you are with math, but do you notice anything different between the following formulas? :) Rotary Engine airflow rate cfm = (CID * RPM * VE) / 1728 4-Stroke Piston engine airflow rate cfm = (CID * RPM * VE * 0.5) / 1728 |
Originally Posted by EpitrochoidMan
^^^:werd:
I always just tell people that if you are going to compare apples to apple, and measure piston engine displacement the same way you measure rotary displacement then the displacement is 1.3L. But it functions so much differently displacement doesn't matter much. OMG, did I just say it? A replacement for displacement??!!??? bwahahahahahahahahaha |
Originally Posted by Evil Aviator
A rotary engine only has six chambers if it is a 6-rotor engine. Otherwise, the common 2-rotor engine only has 2 chambers. While each rotor may have 3 faces, it still fires in the SAME chamber each time. This is why the 13B is a 1.3L engine. Engine displacement is based on chambers (or cylinders) and not rotors (or pistons).
Originally Posted by Evil Aviator
Woot, we have a winner!
I'm not sure how good you are with math, but do you notice anything different between the following formulas? :) Rotary Engine airflow rate cfm = (CID * RPM * VE) / 1728 4-Stroke Piston engine airflow rate cfm = (CID * RPM * VE * 0.5) / 1728 |
Originally Posted by MikeC
A rotary with 2 rotors has 6 chambers, 3 around each. *Every* technical document you read from authors suck as Felix Wankel and Yamamoto says 6. They *never* say that a rotary has 2 chambers. Just because only 2 are ever firing means nothing, the others are still in 1 of the 3 other strokes. Same thing with a six cylinder piston engine.
Since you seem to like the big names, I refer you to Kenichi Yamamoto, "Rotary Engine", Table 4.1, Formulas for calculating rotary engine output: Total displacement V(l): V = Z * Vh Where: Z = number of rotors Vh = Volume of a single working chamber (l) Also, Jack Yamaguchi states the same thing in this online SAE article: http://www.sae.org/automag/global_viewpoints/01.htm |
Originally Posted by MikeC
I dunno how you guys work in these units :-) Your formulaes are wrong because you are assuming the wrong value for displacement of the rotary and you can't use your incorrect displacement to prove itself.
1) Mine, Kenichi Yamamoto's, Jack Yamaguchi's, SAE's, and Mazda's 2) or yours? Hint: Your team is looking a bit outnumbered right about now. :) |
Originally Posted by Evil Aviator
You are mis-reading those references a bit. Yes, the rotary engine has three working chambers. However, only one of those working chambers factors into the combustion event. It may help you to visualize this if you think of the combustion chamber always being relative to the housing as opposed to being relative to the rotor. If you look at the cross-section of a rotary engine, you will see that the combustion event always occurs in the same place, and therefore there is only one spark plug location on the engine, and not three. Therefore, displacement is based the maximum volume of ONE working chamber per rotor.
Since you seem to like the big names, I refer you to Kenichi Yamamoto, "Rotary Engine", Table 4.1, Formulas for calculating rotary engine output: Total displacement V(l): V = Z * Vh Where: Z = number of rotors Vh = Volume of a single working chamber (l) Also, Jack Yamaguchi states the same thing in this online SAE article: http://www.sae.org/automag/global_viewpoints/01.htm These big names are basically lying. People like that don't get to where they are without knowing the value of kissing some corporate butt. If the head honcho says the rotary is going to be rated at 1.3L then that's what they say. Everything else they say is pretty much always accurate but this one point is inconsistant with everything else they've published. Yamamoto writes the displacement as 650cc x 2, which is his way of not bending the truth as much as he needs to. I don't have his book on my but I don't recall him ever saying directly that it was 1.3L. |
hahaha aviator you're funny. Anyways hasn't this been discussed MANY MANY times. Mazda engineers rated it at 1.3L for a reason. People saying it is 2.6L are doing so for fairness issues (at sanctioned racing events). And other people saying it's 2.6L based on other grounds are wrong. Though arguements against that fact are resonable, it's still wrong.
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Originally Posted by Evil Aviator
Whose formulas are wrong because they are based on wrong assumptions?
1) Mine, Kenichi Yamamoto's, Jack Yamaguchi's, SAE's, and Mazda's 2) or yours? Hint: Your team is looking a bit outnumbered right about now. :) Actually those that think it is 1.3L is quite outnumbered. Most people think it is 2.6 even though that is wrong also. Taking Mazdas claims as accurate is like believing a cigarette company that cigarettes don't give you cancer. Initally mazda quoted the 10A as being 3 litres but realised they could get away with convincing everyone it was 1 litre. Many countries wanted it rated at 3 litres also but somehow mazda won out. |
Originally Posted by p4nc7
Mazda engineers rated it at 1.3L for a reason.
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Ya its 1.3L I believe the designers of the car, before a bunch of loose cannons who hate on the rotarys HP per liter output.
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wow. this is such a pointless argument.
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Originally Posted by usmcjsy
Ya its 1.3L I believe the designers of the car, before a bunch of loose cannons who hate on the rotarys HP per liter output.
As for hating rotaries the only thing I hate is mis-truths. I currently own a series 6 and have owned many rotaries over the last 15 years. |
Originally Posted by p4nc7
hahaha aviator you're funny. Anyways hasn't this been discussed MANY MANY times. Mazda engineers rated it at 1.3L for a reason. People saying it is 2.6L are doing so for fairness issues (at sanctioned racing events). And other people saying it's 2.6L based on other grounds are wrong. Though arguements against that fact are resonable, it's still wrong.
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Originally Posted by Evil Aviator
I think that a lot of the misconceptions come from psychological disorders more so than plain ignorance. A rational person would at least consider the fact that they may be wrong and the engineering standards are correct. It would be like me trying to argue that a "foot" is really only 10.5 inches because that is my shoe size, or that a "cup" is 32 fluid ounces because I measured my Big Gulp cup to that capacity.
Maybe you should consider that you are wrong, you can hardly keep up with the more technical side of the conversation yet are so certain that you are right. The best argument you've had so far is that Mazda say it's 1.3L so it must be true. The very fact that you believe that and use it as an argument shows your ignorance. I've got a mech eng degree which involved extensive mathematics and study of piston and jet engines. They hardly touched rotaries but I involved the rotary in any project I could and gained a very good understanding of the mathematical side of the engine. I also wrote this software www.mikesdriveway.com/engineapp. It is beyond ridiculous that you should call me ignorant. |
It's interesting this whole name calling thing on this post. Man you guys just like to show off how smart you are. Cracks me up. Who cares what the displacement is I know my little engine in my car makes a shitload of power for it's size. Whether it be 1.3L or 2.6L it is still making alot of power. This argument reminds of of Motocross racers who argue about which is better a 2 stroke bike or a 4 stroke bike. It's the same argument hell they put the 2 stroke 250cc bikes with the 4 stroke 450cc bikes to make it competitive. But is the 2 stroke bike actually 500cc's I don't think so. Everyone has there arguments you have your right to voice it but please PM each other and bitch each other out. Someone lock this damn thread it's the same shit but different thread.
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Originally Posted by 13btnos
It's interesting this whole name calling thing on this post.
Originally Posted by 13btnos
Who cares what the displacement is I know my little engine in my car makes a shitload of power for it's size. Whether it be 1.3L or 2.6L it is still making alot of power.
Originally Posted by 13btnos
This argument reminds of of Motocross racers who argue about which is better a 2 stroke bike or a 4 stroke bike. It's the same argument hell they put the 2 stroke 250cc bikes with the 4 stroke 450cc bikes to make it competitive. But is the 2 stroke bike actually 500cc's I don't think so.
Originally Posted by 13btnos
Everyone has there arguments you have your right to voice it but please PM each other and bitch each other out. Someone lock this damn thread it's the same shit but different thread.
2) There has been huge amounts of information on this topic not discussed, it is no-where near the point that threads on the topic should be locked. Unfortunately a lot of this is beyond those who frequent such threads so it's difficult to take the discussion further. |
I could give a rats ass. Yes you are correct it is 3.9L. What ever. I still know that I can extract a whole lot of horsepower out of these little engines. And I guess when I tell people that it's 3.9L they will be dumbfounded. Have a nice day on your side of the pond MikeC. Man some of you guys are soo uptight.
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