RX7Club.com - Mazda RX7 Forum

RX7Club.com - Mazda RX7 Forum (https://www.rx7club.com/)
-   2nd Generation Specific (1986-1992) (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/)
-   -   GT inspired Exaust tone. (https://www.rx7club.com/2nd-generation-specific-1986-1992-17/gt-inspired-exaust-tone-937866/)

R.O.D 01-19-11 03:39 AM

Well thanks for the videos,
they prove my point all the more.

u DO know a rotary doesnt fire on just one face per rotor right???????

in that last video, it shows 1ONE face on a rotor doing what 1ONE piston does, right?
and a rotor has 3THREE faces that will all do: intake, compression, power, and exhaust in one FULL rotation. so now we have 3THREE piston equivalences. but there are two rotors in a 13b

and like ur video CLEARLY showed, one rotor face = one piston
so in a 13b that has 6 WORKING faces it equals six pistons

rotor1:
face 1 intake compresion power exhaust (piston1)
face 2 intake compresion power exhaust (piston2)
face 3 intake compresion power exhaust (piston3)
ONE ROTATION

rotor2:
face 1 intake compresion power exhaust (piston4)
face 2 intake compresion power exhaust (piston5)
face 3 intake compresion power exhaust (piston6)
ONE ROTATION

on top of that the rotors are offset, so there are 6 total four stroke events. which would create 6six exhaust pulses.

its 3:37am here, and i couldnt sleep until i put this up
if this doesnt make sense to u then, sheep are skyscrapers, tacos are seacows, and blue tastes like the number 7

Syritis 01-19-11 03:54 AM


Originally Posted by R.O.D (Post 10422700)
Well thanks for the videos,
they prove my point all the more.

u DO know a rotary doesnt fire on just one face per rotor right???????

in that last video, it shows 1ONE face on a rotor doing what 1ONE piston does, right?
and a rotor has 3THREE faces that will all do: intake, compression, power, and exhaust in one FULL rotation. so now we have 3THREE piston equivalences. but there are two rotors in a 13b

and like ur video CLEARLY showed, one rotor face = one piston
so in a 13b that has 6 WORKING faces it equals six pistons

rotor1:
face 1 intake compresion power exhaust (piston1)
face 2 intake compresion power exhaust (piston2)
face 3 intake compresion power exhaust (piston3)
ONE ROTATION

rotor2:
face 1 intake compresion power exhaust (piston4)
face 2 intake compresion power exhaust (piston5)
face 3 intake compresion power exhaust (piston6)
ONE ROTATION

on top of that the rotors are offset, so there are 6 total four stroke events. which would create 6six exhaust pulses.

its 3:37am here, and i couldnt sleep until i put this up
if this doesnt make sense to u then, sheep are skyscrapers, tacos are seacows, and blue tastes like the number 7

watch the video again, and you'll see that the piston motor makes 2 complete revolutions to complete the 4 cycles combustion. where as the rotary makes 1 revolution.
you are overwhelmingly outmatch by your misunderstanding
the e-shaft turns 3 times faster then your rotor. so for every 1 rotation of the e-shaft equals 1 exhaust pulse. the 1 more rotation of the e-shaft equals 1 exhaust pulse for the next rotor face. next rotation is the next face. so 3 rotations from the e-shaft equals 1 rotation of the rotor.
3 rotations / 3 faces = 1 exhaust pulse per revolution.

Syritis 01-19-11 03:59 AM

now what is really going destroy your mind is that a 2stroke pistons combustion cycles last for a little more then 90degrees of rotation. the 4 stroke piston combustion cycles last for 180degree and the rotary combustion cycles last nearly 360degrees.

Aaron Cake 01-19-11 09:19 AM


Originally Posted by jjwalker (Post 10422115)

Anyone else notice he was rotating the engine backwards?


Originally Posted by jjwalker (Post 10422443)
Mullet madness = GT exhaust sound. Sounds plausible!
/joking!

Sounds like perfect Mythbusters logic to me.

AF_H1VLTG3 01-19-11 10:07 AM


Originally Posted by Aaron Cake (Post 10422020)
If you really want your car to sound F1, then you'll need to start with one of these...

http://www.aaroncake.net/rx-7/pictur...eccentric1.jpg

...but you can't have mine!

http://www.aaroncake.net/rx-7/pictur...eccentric2.jpg

Damn Cake, did I count that right? That is for four rotors right? That compatible with 13B housings? Also I have a machine shop in the family with multi axis machines. If you want I could copy the design and help you, Ahem, field test it..... :nod:

jjwalker 01-19-11 06:52 PM


Originally Posted by Syritis (Post 10422709)
now what is really going destroy your mind is that a 2stroke pistons combustion cycles last for a little more then 90degrees of rotation. the 4 stroke piston combustion cycles last for 180degree and the rotary combustion cycles last nearly 360degrees.

Hahahaha!

Sorry, useless post but I found your response is rather comical.

jjwalker 01-19-11 07:27 PM

By the way Aaron, I am surprised you haven't chimed in on educating R.O.D on how our engines work. I know you don't want to feed trolls or anything, but at least try to explain.

Apparently Syritis and I cannot do so.

jjcobm 01-19-11 07:40 PM

Taken from: http://rx7.com/techarticles_displacement.html

Rotary Displacement

As rotary engine enthusiasts, we all know the obvious, intoxicating charms of Wankel wonder. Unique, unusual, lightweight, compact, high revving, what’s not to like? One of the most commonly deliberated subjects is “what is the rotary engine’s displacement”? An excellent question. Here’s our best to make the case for the engine’s displacement.

Conventional reciprocating engines are the standard that most relate to. We all know that these engines are measured by measuring the area of the bore, multiply by the stroke and then multiply by the number of cylinders. Simple as that.

For simplicity, we’ll use the 13B engine as the standard we’re calculating. You can use these ideas and apply them to a 12A or 20B yourself. The rotary engine is obviously unique. The engine has two rotors shaped roughly like a triangle. This makes for three combustion faces per rotor and a total of six for a standard two-rotor engine. Each face has a “swept volume” or displacement of 40ci(654cc) and there are a total of six faces. With this known, the engine displacement should be 40ci(654cc) times six to equal 240ci(3.9L), right? In a way, yes, but that would not be a comparable displacement to the 4-cycle engine.



Thermodynamic cycle breakdown of a Rotary engine.




Thermodynamic cycle breakdown of a piston engine.




The key for comparing the displacement between the 4-cycle engine and the rotary engine is in studying the degrees of rotation for a thermodynamic cycle to occur. For a 4-cycle engine to complete every thermodynamic cycle, the engine must rotate 720° or two complete revolutions of the crankshaft. The rotary engine is different. The engine rotor rotates at 1/3 the speed of the crankshaft. On two rotor engines, front and rear rotors are 180° offset from each other. Each rotation of the engine (360°) will bring two faces through the combustion cycle (the torque input to the eccentric shaft). This said, it takes 1080° or three complete revolutions of the crankshaft to complete the entire thermodynamic cycle. Obviously, we have a disparity. How can we get a relatable number to compare to a 4-stroke engine? The best way is to study 720° of rotation of the two-rotor engine. Every 360° of rotation, two faces of the engine complete a combustion cycle. 720° will have a total of four faces completing their cycle. 40ci(654cc) per face times four faces equals 160ci or 2.6L. That’s a well-reasoned number and now gives us something to be able to compare to other engines. In addition, since four faces passed by in the comparison, it’s like a four cylinder engine.

Now we know, the 13B compare well to a 2.6L 4-cylinder 4-cycle engine.

Aaron Cake 01-20-11 09:12 AM


Originally Posted by AF_H1VLTG3 (Post 10423010)
Damn Cake, did I count that right? That is for four rotors right? That compatible with 13B housings? Also I have a machine shop in the family with multi axis machines. If you want I could copy the design and help you, Ahem, field test it..... :nod:

It is 2 Mazda 13B eccentrics joined 90 degrees apart. Easy to replicate at a machine shop. So easy, I don't know why more people don't do it. Then machine a center iron for a bearing, and Bob's your uncle.


Originally Posted by jjwalker (Post 10424017)
By the way Aaron, I am surprised you haven't chimed in on educating R.O.D on how our engines work. I know you don't want to feed trolls or anything, but at least try to explain.
Apparently Syritis and I cannot do so.

Why, what's the point?

R.O.D 01-20-11 10:43 AM


Originally Posted by jjcobm (Post 10424037)
Taken from: http://rx7.com/techarticles_displacement.html

Rotary Displacement

As rotary engine enthusiasts, we all know the obvious, intoxicating charms of Wankel wonder. Unique, unusual, lightweight, compact, high revving, what’s not to like? One of the most commonly deliberated subjects is “what is the rotary engine’s displacement”? An excellent question. Here’s our best to make the case for the engine’s displacement.

Conventional reciprocating engines are the standard that most relate to. We all know that these engines are measured by measuring the area of the bore, multiply by the stroke and then multiply by the number of cylinders. Simple as that.

For simplicity, we’ll use the 13B engine as the standard we’re calculating. You can use these ideas and apply them to a 12A or 20B yourself. The rotary engine is obviously unique. The engine has two rotors shaped roughly like a triangle. This makes for three combustion faces per rotor and a total of six for a standard two-rotor engine. Each face has a “swept volume” or displacement of 40ci(654cc) and there are a total of six faces. With this known, the engine displacement should be 40ci(654cc) times six to equal 240ci(3.9L), right? In a way, yes, but that would not be a comparable displacement to the 4-cycle engine.



Thermodynamic cycle breakdown of a Rotary engine.




Thermodynamic cycle breakdown of a piston engine.




The key for comparing the displacement between the 4-cycle engine and the rotary engine is in studying the degrees of rotation for a thermodynamic cycle to occur. For a 4-cycle engine to complete every thermodynamic cycle, the engine must rotate 720° or two complete revolutions of the crankshaft. The rotary engine is different. The engine rotor rotates at 1/3 the speed of the crankshaft. On two rotor engines, front and rear rotors are 180° offset from each other. Each rotation of the engine (360°) will bring two faces through the combustion cycle (the torque input to the eccentric shaft). This said, it takes 1080° or three complete revolutions of the crankshaft to complete the entire thermodynamic cycle. Obviously, we have a disparity. How can we get a relatable number to compare to a 4-stroke engine? The best way is to study 720° of rotation of the two-rotor engine. Every 360° of rotation, two faces of the engine complete a combustion cycle. 720° will have a total of four faces completing their cycle. 40ci(654cc) per face times four faces equals 160ci or 2.6L. That’s a well-reasoned number and now gives us something to be able to compare to other engines. In addition, since four faces passed by in the comparison, it’s like a four cylinder engine.

Now we know, the 13B compare well to a 2.6L 4-cylinder 4-cycle engine.

Great, exactly what i wanted to see.
the other explainations, did quite explain it as well, this actually make since.
although im still slightly inclined to believe otherwise, this has help alot.
thanks for finding useful info, and NOT being a dick (club standard)


Originally Posted by jjwalker (Post 10424017)
By the way Aaron, I am surprised you haven't chimed in on educating R.O.D on how our engines work. I know you don't want to feed trolls or anything, but at least try to explain.

Apparently Syritis and I cannot do so.

i had typed out a lengthy rude retort, but i decided that acting that way would serve no purpose.
perhaps, instead of pretending to be such a internet thug, u could pretend u have some manners.
not really sure why so many ppl feel the need to act the way they do, but i will
take the high road and try to act a little more civil
thanks for the help anyway.

Aaron, to be honest i was waiting for u to add something, i know that you have all the know how, and was kind of anxious to hear your thought either way.
if i was wrong, was hoping to hear it and why.
and if i was right, whatever.
but to be ignored by an encyclopedia of the rotary world, and a mod. is kinda shitty
and to be honest kind of expected more from a mod.

Aaron Cake 01-20-11 11:00 AM


Originally Posted by R.O.D (Post 10424981)
Aaron, to be honest i was waiting for u to add something, i know that you have all the know how, and was kind of anxious to hear your thought either way.
if i was wrong, was hoping to hear it and why.
and if i was right, whatever.
but to be ignored by an encyclopedia of the rotary world, and a mod. is kinda shitty
and to be honest kind of expected more from a mod.

Please don't take this as a negative, but I just didn't see the point. I'm not obligated to answer every post made to this forum and felt that others had more than adequately explained their viewpoints.


All times are GMT -5. The time now is 11:57 AM.


© 2024 MH Sub I, LLC dba Internet Brands