This discussion came up in another thread and instead of continuing to thread jack,
i decided to make my own.

here is the debate, found here, https://www.rx7club.com/2nd-generation-specific-1986-1992-17/gt-inspired-exaust-tone-937866/page2/

heres the basic run down, one thought is that the 13b is related to a four cyl. engine.
and a 20b is related to a six cyl. engine, and a 26b is related to a 8 cyl. engine.

on the other hand, another thought is that the 13b is related to a 6 cyl. 20b a 9 cyl.
and a 26b a 12 cyl.

can anyone provide definite answers point one direction, or another?

the posts with videos and text only leads me to believe the way i do. and would like if someone could put a 100% logical definition to this.

do understand that the parties involved in this discusion do understand that the rotary is nowhere close to the same animal as the piston engine.

im trying to post this with a neutral point of view, and will let the reader go through the post found later in that thread provided above and decide based on what they think or know.

thanks

Brendan

 

2 rotor = 4 stroke 4 cylinder
3 rotor = 4 stroke 6 cylinder
4 rotor = 4 stroke 8 cylinder

yes the rotary engine has 3 faces on the rotors. but each face is in a different cycle at the same time. so while one face is starting the combustion cycle, the next face has just started compression. but the fact is that 1 revolution of the e-shaft only exposes one face to the exhaust port. thus a 2 rotor engine has the same occurrence of exhaust pulses as a 4 stroke 4 cylinder.

period.

 

That pulse timing is correct, but remember that rotaries are, in a sense, 6 stroke. 3 complete rotations of the shaft for 1 complete cycle per chamber.

Just a random thought, sorry didn't read the other thread.

 

___________________________________
notice that the "B" is closest to the spark plugs for each ignition. the "B" makes one complete rotation for each face that is ignited. rotary = 1 ignition per revolution. 4 stroke piston = 1 ignition per 2 revolutions. thus a piston engine must have twice as many cylinders to match a rotary.

 

Not sure what you're asking?

The 13B fires every 180 degrees rotation of the eccentric.

4 rotor fires every 90 degrees.

3 rotor is 120 degrees.

Each rotor fires three times per rotor revolution but the eccentric is rotating 3x faster than the rotor so a 1 rotor would fire once per eccentric revolution.

 

basically questioning the standard belief that one rotor equals 2 cyl, based solely on rotation equivalance.

i truely believe that the main idea behind every engine is the parts that actually drive it.
yes, without the crank shaft or E-shaft, there would be no engine, but without the combustion chamber to create the power, we would still would be using horses.
and dont say the same goes for a crank/e-shaft, there are internal combustion engine that function without either


when i look at how the rotary and piston engine work, i see the 4 strokes as the most important area.
i have zero intrest in counting equivalencies in E-shaft v crank, to compare engines.

when i see the engines side by side, i see one face of the rotor doing intake compression power and exhaust,
and with a single piston i see the exact same events playing out.
futher leading me to see that the three faces of a rotor, do the same exact events that three pistons would do.

if these engines are being compared solely based on shaft rotation equivalence.
then i choose to be the Martin Luther (german) of the rotary world, and continue to disagree.

maybe if posed as a question, someone might see my point of view

In a single rotor, rotary engine, how many air and fuel ignitions are there in a full rotation of the ROTOR?
In a dual rotor, rotary engine, how many air and fuel ignitions are there in a full rotation of the ROTOR?

In a four cylinder engine, how many air and fuel ignitions are there in a full rotation of all the pistons?
In a six cylinder engine, how many air and fuel ignitions are there in a full rotation of all the pistons?
In a eight cylinder engine, how many air and fuel ignitions are there in a full rotation of all the pistons?
In a nine cylinder engine, how many air and fuel ignitions are there in a full rotation of all the pistons?

 

crank and eshaft are what gives the true answer here. you can't discount any parts for for opinions. Actually this conversation is pointless anyway. If you gotta do it then use everything in the equation.

 

piston engines are name based on the number of combution chambers, NOT crankshaft rotation.
why would it be any different for a rotaty?

if a six cyl. engine has six combution changers and a two rotor engine has 6 moving combusion chambers, would it not make sense that they are comparable?


^

ok how about a axial vector engine which uses neither crank or e-shaft. and yet its still a 12 cyl engine.
or a spherical internal combution engine, still has neither, eshaft or crank..

so basing engines on crank and eshaft equivalence is a totally incorrect way to look at it.
ALL engines are centered at the combstion chamber, and are named because of the number of chambers

 

It's a rotary engine, in no way is it equal (in geometry or combustion cycles) to a piston engine. A 2 rotor is equivalent to a 2 rotor, but not all 2 rotors engines are created equal.

If you really want to stretch it, it is more like a 2 stroke 2 cylinder.

 

?? thats like saying apples and oranges are completely unrelated...

 

If a bald eagle was a fish, what kind of fish would it be?

 

yup, thats about what i expected.

 

a big *** fish that looks like a punk rocker!..But Flies!
..and 2 rotor?.4 cylinder?..
different engineering,so no comparison.

 

the answer is 9. (Dumb questions will receive equally dumb answers)

 

Why does the comparison even matter? I didn't checkout the other thread, but I would imagine that it was a bunch of people trying to prove why NASA was stupid for not hiring them.

I don't ever try to compare when people ask me, the engines are not really comparable, they perform the same function, but function differently..

 

If this thread doesn't relate to exhaust noise, then what does it matter?

Seriously, compare dyno sheets or something.

 

i always thought of it as a big 6 givin that it makes about as much power as a big 6 like in a jeep. on a properly maintained n/a i would assume it makes like 140 hp and a jeep makes a lil more but its also much bigger. idk i know someone is prolly gonna blow what i said up or w/e but i see where OP is comin from.

 

it is a little apples and oranges, because piston engines are dumb.

a 4 stroke piston engines need 2 revolutions of the crankshaft to fire all of the cylinders. intake and compression are 1 rotation, power and exhaust are the second.

a piston engines displacement is based on the volume of ALL of the cylinders.

a 5.7L chevy has 8 x 716cc cylinders.

a ROTARY engine is also a 4 stroke, but its displacement is rated on the chambers fired on 1 rotation, it takes 2 rotations to be equivalent to a piston engine, and 3 for the rotary to fire all of its chambers.

so a 13B fires 2 654cc chambers in 360 degrees of output shaft rotation, which is 1308cc. 1 firing event every 180 degrees is also like a 4 cylinder piston engine.

2 rotations of the output shaft on a 13B, is 4 x 654cc chambers, and since its 2 rotations of the output shaft, its a nice piston equivalent. you'll see for a lot of the math, we use a 2.6 liter number for the 13B.

in 3 rotations it fires all 6, 654cc chambers, the piston engine has no equivalent here.

the 20B is like a v6, every 120 degrees.
and a 4 rotor should be 90 degrees like a v8

 

the question in the other thread was "a 13b motor has the same number exhaust pulses as a ________?"

the answer is a 4 cylinder.

yet he's still trying to convince everyone that because we have 6 chamber it must be a 6 cylinder.

 

What is the meaning of life?
As Syritis pointed out, the rotary fires on every revolution of the eccentric shaft, where as the piston engine only sparks every 2nd rotation.
So the rotary is firing twice as much...

inho though, there's no comparison between the two at all.. there's no relation other than being internal combustion

 

I think it's a silly comparison because they can't be directly compared.

If you want to get right down to it, a single cylinder 4 stroke piston engine fires every 2 rotations of the crank. A single rotor fires every one rotation of the eccentric. Yet displacement wise, the rotary makes far more efficient use of it's internal volume.

I think the only comparison which can be done is to compare power output per displacement. Or if you want to get really technical, thermal efficiency, specific fuel consumption, or thousands of other factors which make this comparison very difficult when you start looking at it...

They aren't related.

As I recall, a major part of a bald eagle's diet is scavenging, so, a carp?

 

search n00b! apples and oranges are both fruits, and thus are probably cousins or great god uncles or something

 

42

 

i got all the way to the bottom to see you beat me to it /\
did the babel fish tell you that ?

13b = 2616cc = 4 cylinder
and i am also going with 6 and 8

 

Fruit is an arbitrary category created by man. I mean, just look at tomatoes...clearly shouldn't be in the fruit category. Man was drunk that day.