1.3, 2.6, what the hell???
04-09-06, 04:53 AM
#26
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Stroke can be altered to produce less hp and more torque (the typical USA way of engine building) or the other way around (short stroke, fast running engines, the European and Japanese way). Short stroke small capacity engines can produce a fair amount of power but will lack the torque of a big (but not very efficient) V8. The main reason US car makers couldn't sell their cars here in Europe was exactly this: their V8's needed so much fuel (and with our fuel prices being *a bit* higher then yours...) and yet didn't make that much power as their large capacity would promise. Torque they had of course.
With a rotary you can do this too, by altering the exentricity of the E-shaft. This basicly does the same as altering stroke (Mazda had one engine that did this: 13A. The 12A and 13B are "just" lengthed 10A's, but keep the same dimensions otherwise). The problem is that you cannot go as far as with a piston engines stroke. Increasing the exentricity too much makes the apex seal unable to seal the combustion chamber, because the angle gets too big. This is a problem in the design of rotary engines, as it seriously narrows choices. And it's why it's hard to build a real diesel rotary (one that doesn't need a ignition circuit).
On the other hand, some of the advantages of rotary engines shouldn't be forgotten.
Since they do not drive valvetrains, etc, they do not loose as much power to be able to run.
They are also way better suited to run on gas (let it be hydrogen or LPG) due to their cold (intake) and hot (exhaust) zone being seperated. This can be of importance in the future when we will need to explore alternative fuels. I'm not talking about hydrogen here, as this will take a lot of time to be production ready. But many other things are possible. All these "alternative fuels" have the same problems with piston engines: valves cause detonation (which is why lead used to be added to fuel). No rotary engine has any problem with new fuels.
With a rotary you can do this too, by altering the exentricity of the E-shaft. This basicly does the same as altering stroke (Mazda had one engine that did this: 13A. The 12A and 13B are "just" lengthed 10A's, but keep the same dimensions otherwise). The problem is that you cannot go as far as with a piston engines stroke. Increasing the exentricity too much makes the apex seal unable to seal the combustion chamber, because the angle gets too big. This is a problem in the design of rotary engines, as it seriously narrows choices. And it's why it's hard to build a real diesel rotary (one that doesn't need a ignition circuit).
On the other hand, some of the advantages of rotary engines shouldn't be forgotten.
Since they do not drive valvetrains, etc, they do not loose as much power to be able to run.
They are also way better suited to run on gas (let it be hydrogen or LPG) due to their cold (intake) and hot (exhaust) zone being seperated. This can be of importance in the future when we will need to explore alternative fuels. I'm not talking about hydrogen here, as this will take a lot of time to be production ready. But many other things are possible. All these "alternative fuels" have the same problems with piston engines: valves cause detonation (which is why lead used to be added to fuel). No rotary engine has any problem with new fuels.
04-09-06, 09:09 PM
#27
One thing I come to realize is not to worry about the displacement so much anymore. Sure the engine is sized as a 13b 1.3L through measured displacement. The scientific fact remains that a 1.3L rotary will MOVE 2.6 liters of air in 2 rotations of the e-shaft and 3.9L in 3 rotations. This is why the rotary is equivalent and compared to a 2.6 liter 4 stroke piston engine. A 2.6 liter piston engine will have only moved 1.3L of air in one rotation of it's crank shaft because it's only firing half it's displacement. Guess what in one rotation of the e-shaft, the rotary will have only moved 1.3L's. When it comes to rpm's, both engines are measured exactly the same. Some of you guys just need to deal with this regardless of what Mazda rated the engine to be.
04-10-06, 12:09 PM
#28
Originally Posted by rotary emotions
Ford didn't really try a rotary Mustang, Curtis-Wright did 
For those still staying they all failed on reliability: that's BS! ALL rotary projects failed on fuel consumption, only GM's engine failed on GM's stupidity. When the licences were sold by NSU/Wankel, all buyers had to share knowledge. All, except one: GM. They had been able to get a more expensive exlusive license, due to them being the worlds biggest at the time. One of the mistakes they made was that they didn't wan't to share their experiences, but therefor ended up not being able to look at other efforts (Curtis-Wright in the USA) and take advantage of those.
So they build a all-iron engine that was soon very heavy aswell as very bad: housing warped.
All other factories build prototypes, and later rather good engines ( Mercedes-Benz build some really serious stuff) but most were peripheral port. This makes the engines very thirsty, as there is a large overlap between intake and exhaust opening times (as if both valves would be open together in a piston engine). The Renesis is the first to finally go back to original ideas of using side intake and exhaust. In the sixties most rotary builders knew this was the way to go (the design of the renesis is not at all revolutionary) but materials couldn't hold the heat.
So when the fuel crisis came in the seventies, nobody wanted a thirsty engine anymore.
The talkings about unreliable engines are all caused by a myth created around the NSU Ro80, which wasn't a bad engine either, but was too complicated for those days mechanics. Of all engines changed under warranty over 80% was good! Engines were changed for several reasons (mainly carbs or ignition) that didn't have anything to do with the engine itself.
For those still staying they all failed on reliability: that's BS! ALL rotary projects failed on fuel consumption, only GM's engine failed on GM's stupidity. When the licences were sold by NSU/Wankel, all buyers had to share knowledge. All, except one: GM. They had been able to get a more expensive exlusive license, due to them being the worlds biggest at the time. One of the mistakes they made was that they didn't wan't to share their experiences, but therefor ended up not being able to look at other efforts (Curtis-Wright in the USA) and take advantage of those.
So they build a all-iron engine that was soon very heavy aswell as very bad: housing warped.
All other factories build prototypes, and later rather good engines ( Mercedes-Benz build some really serious stuff) but most were peripheral port. This makes the engines very thirsty, as there is a large overlap between intake and exhaust opening times (as if both valves would be open together in a piston engine). The Renesis is the first to finally go back to original ideas of using side intake and exhaust. In the sixties most rotary builders knew this was the way to go (the design of the renesis is not at all revolutionary) but materials couldn't hold the heat.
So when the fuel crisis came in the seventies, nobody wanted a thirsty engine anymore.
The talkings about unreliable engines are all caused by a myth created around the NSU Ro80, which wasn't a bad engine either, but was too complicated for those days mechanics. Of all engines changed under warranty over 80% was good! Engines were changed for several reasons (mainly carbs or ignition) that didn't have anything to do with the engine itself.
04-10-06, 01:57 PM
#30
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Originally Posted by classicauto
doesn't torque output also have alot to do with mass more so than mechanical advantage?
I.E. the piston motor of 1.3L displacement has a heavier rotating mass and therfore the larger mass translates through the driveline as more torque..
the rotary on the other hand would have a lighter mass turning the driveline and thus less torque...
am I way off base because I was under the impression of what I state here more so than these other ideas....I am genuinely asking - not trying to faceslap here
edit: and also wouldn't distance from the center of rotation have alot to do with mechanical advantage more so than simply just design...
something like using a longer handled rachet, the piston motor is "wrenching" on the crankshaft with a longer handle than the rotary....doesn't that play in to the torque factor as well?
I.E. the piston motor of 1.3L displacement has a heavier rotating mass and therfore the larger mass translates through the driveline as more torque..
the rotary on the other hand would have a lighter mass turning the driveline and thus less torque...
am I way off base because I was under the impression of what I state here more so than these other ideas....I am genuinely asking - not trying to faceslap here
edit: and also wouldn't distance from the center of rotation have alot to do with mechanical advantage more so than simply just design...
something like using a longer handled rachet, the piston motor is "wrenching" on the crankshaft with a longer handle than the rotary....doesn't that play in to the torque factor as well?
i think you are thinking of inertial energy, not torque.
04-10-06, 10:32 PM
#32
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Originally Posted by 13b4me
Look ***...
I don't care how you break it down, the ambient displacement of a 13B is 1.3L...
I don't give a **** what the cycle entails, because that's just the advantage we have over everyone else... Sorry their engine design isn't as efficient as ours... 
but they aren't as efficiant because the pistons have to change direction, sorry, but rotors move up and down inside the housing too!
are they more efficient because they have a combustion every 360 degrees? so does a 2 cycle piston engine. so by your reasoning, a 2 cycle piston engine is more efficient than a 4 cycle piston engine, because it bangs more times. even know it burns more fuel/produces more polution than a 4 cycle piston engine making the same power.
your entire argument about efficiency is meaningless. what does it do for the rotary if it isn't allowing it to make more torque per ammount of gas burned. who cares about how fast an engine can free rev, that's meaningless without torque production. torque is what accelerates your driveline, and thus, your car. throw a 4.10 rear end on an ls2 corvette (stock is 3.42 on the m6 cars) and you'd be surprised how fast it would blow through 1st gear.
you know, the same arguments you make can be used by the 2 cycle piston crowd, but they aren't, because measuring each engine on a per crank basis rather than what individual people think is the fairest way sactioning bodies can keep things on an even perspective. and that's really what it's all about.
04-10-06, 11:04 PM
#33
Banned. I got OWNED!!!
Originally Posted by particleeffect
personal insults, typical when someone can't make an actual argument.
a 2.6 liter 4 stroke piston motor pumps 1.3 liters per crank revolution too. there you go, it's a 1.3 suddenly, is the field even now?
but they aren't as efficiant because the pistons have to change direction, sorry, but rotors move up and down inside the housing too!
04-10-06, 11:54 PM
#34
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Displacement of a piston engine is defined as area of the piston head x travel of piston x # of pistons.
However, mazda does it by how much air one face of the rotor can suck in at a time x # of rotors, not all 3 faces of the rotor.
The "2.6 liter" arguement comes from logical deduction based off of the power it makes, the air and fuel it uses, and how fast turbos spool up on it... and that for 4 stroke piston engines (which are by far the most commonly used racing motor, and then some) it takes two revolutions to use all the displacement, and two revolutions of a 13b is 2.6 liters.
Getting hung up on its displacement is stupid. Its an emotional attachment to part of the marketing that attracted some people to the engine in the first place, and how a lot of the fans reaffirm to THEMSELVES how superior it is. Heres a hint: power per liter is utterly irrelevant. Thinking its a 1.3 liter engine is just stubbornness. If you actually comprehend how enignes work and all the math and physics behind it, you quickly discover it simply makes no sense in application... unless its a single rotor motor.
Thinking its a 1.3 liter engine because youre going by one crank revolution is ignorance of the fact that it takes THREE revolutions to use the entire motor.
Saying its 1.3 liters becuase youre "going by the combustion chambers " is equally stupid. That would make a v8 with 64cc chambers a 512cc motor.
The bottom line is per 360° of crank (or e-shaft) revolution each individual rotor will displace .65 liters of air. VE will decide if its more or less. Superchargers or Turbochargers decide how much mass of air is in that volume.
Calling it a 2.6 liter makes sense becuase a 4 stroke (two revolution) engine is the STANDARD by which everything else is compared, for a damn good reason! Two strokes are used for sporting applications, two stroke DIESELS are only used in some specialized industrial applications, and fourstroke diesels and gasoline engines are all over the place becuase they give the best return for investment in terms of performance, reliability, and economy.
The rotary is the exception to the rule, that might be why you like it, but you cant have it both ways. Pedantically speaking, a 13b is a 3-revolution 3.9 liter engine. But becuase you WANT it to be a small displacement engine becuase someone convinced you hp per liter actually matters, you'll come up with hairbrained arguements against it. In the 2-revolution world, which is the one I live in, its a 2.6 liter engine. In a 1-revolution world, its a 1.3 liter.
Get it? Got it? GOOD! Someone should make this a sticky already.
However, mazda does it by how much air one face of the rotor can suck in at a time x # of rotors, not all 3 faces of the rotor.
The "2.6 liter" arguement comes from logical deduction based off of the power it makes, the air and fuel it uses, and how fast turbos spool up on it... and that for 4 stroke piston engines (which are by far the most commonly used racing motor, and then some) it takes two revolutions to use all the displacement, and two revolutions of a 13b is 2.6 liters.
Getting hung up on its displacement is stupid. Its an emotional attachment to part of the marketing that attracted some people to the engine in the first place, and how a lot of the fans reaffirm to THEMSELVES how superior it is. Heres a hint: power per liter is utterly irrelevant. Thinking its a 1.3 liter engine is just stubbornness. If you actually comprehend how enignes work and all the math and physics behind it, you quickly discover it simply makes no sense in application... unless its a single rotor motor.
Thinking its a 1.3 liter engine because youre going by one crank revolution is ignorance of the fact that it takes THREE revolutions to use the entire motor.
Saying its 1.3 liters becuase youre "going by the combustion chambers " is equally stupid. That would make a v8 with 64cc chambers a 512cc motor.
The bottom line is per 360° of crank (or e-shaft) revolution each individual rotor will displace .65 liters of air. VE will decide if its more or less. Superchargers or Turbochargers decide how much mass of air is in that volume.
Calling it a 2.6 liter makes sense becuase a 4 stroke (two revolution) engine is the STANDARD by which everything else is compared, for a damn good reason! Two strokes are used for sporting applications, two stroke DIESELS are only used in some specialized industrial applications, and fourstroke diesels and gasoline engines are all over the place becuase they give the best return for investment in terms of performance, reliability, and economy.
The rotary is the exception to the rule, that might be why you like it, but you cant have it both ways. Pedantically speaking, a 13b is a 3-revolution 3.9 liter engine. But becuase you WANT it to be a small displacement engine becuase someone convinced you hp per liter actually matters, you'll come up with hairbrained arguements against it. In the 2-revolution world, which is the one I live in, its a 2.6 liter engine. In a 1-revolution world, its a 1.3 liter.
Get it? Got it? GOOD! Someone should make this a sticky already.
04-11-06, 12:35 AM
#35
Originally Posted by 13b4me
So by your reasoning, why not call it a 1.3 then, since that's how much air it moves! You just blew your own arguement out of the water chap... But a 2.6l 4 stroke engine is STILL considered a 2.6 right? Because that's how much *static* displacement it has right? Yea that's what I thought...
The point of his examples is both engines will move the same amounts of air in one rotation of their respective crank/e-chafts regardless of what their measured displacement is. This is the thing some of you guys don't want to realize. The piston engines displacement is measured through all it's individual chambers. The rotary is not. Technically the rotary could measured as a 3.9 liter if you factor in all 3 rotor faces and 3 rotation of the e-shaft.
04-11-06, 10:56 AM
#36
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First rule in my tech class. Every piston motor is trying to tear itself apart.
Rule two if you dont know what the hell you are talking about keep your mouth shut.
Rule three rotaries confuse almost every average mechanic.
Rule four if you cant win with more pistons ban anything that can win that either operates on less or no pistons.
Rule five the 7 cant lose.
Rule two if you dont know what the hell you are talking about keep your mouth shut.
Rule three rotaries confuse almost every average mechanic.
Rule four if you cant win with more pistons ban anything that can win that either operates on less or no pistons.
Rule five the 7 cant lose.
Last edited by fcdrifter13; 04-11-06 at 10:58 AM.
04-11-06, 12:48 PM
#37
Banned. I got OWNED!!!
Originally Posted by fcdrifter13
First rule in my tech class. Every piston motor is trying to tear itself apart.
Rule two if you dont know what the hell you are talking about keep your mouth shut.
Rule three rotaries confuse almost every average mechanic.
Rule four if you cant win with more pistons ban anything that can win that either operates on less or no pistons.
Rule five the 7 cant lose.
Rule two if you dont know what the hell you are talking about keep your mouth shut.
Rule three rotaries confuse almost every average mechanic.
Rule four if you cant win with more pistons ban anything that can win that either operates on less or no pistons.
Rule five the 7 cant lose.
lol
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