Actual Rotary Displacement Request

[NoDOHC]

As I stated before, it is merely a difference in frame of reference. Each rotor housing undergoes one full cycle during each revolution, but each rotor face will require 3 rotations for a complete cycle.

Because both the housing and the rotor are required to displace air, both frames of reference are valid.

I think that Peter, Barry and Vex have done a very good job of illustrating the concepts that we all need to take away from this discussion. This is a good thread.

[vex]

Originally Posted by NoDOHC

As I stated before, it is merely a difference in frame of reference. Each rotor housing undergoes one full cycle during each revolution, but each rotor face will require 3 rotations for a complete cycle.

Because both the housing and the rotor are required to displace air, both frames of reference are valid.

I think that Peter, Barry and Vex have done a very good job of illustrating the concepts that we all need to take away from this discussion. This is a good thread.

No it's not, and you can't prove I've done a good jorb!

Yeah, I don't understand why people were getting all hot and bothered by this. The only thing I do not understand is where the 2.6L value comes from without using a multiplier. Anyone know?

[Monkman33]

Originally Posted by vex

No it's not, and you can't prove I've done a good jorb!

Yeah, I don't understand why people were getting all hot and bothered by this. The only thing I do not understand is where the 2.6L value comes from without using a multiplier. Anyone know?

I would agree completely. I cant think of any method that would make the 2.6l number viable.

[diabolical1]

Originally Posted by vex

Otto cycle is just the technical term of suck, squish, bang, blow.

no, i was familiar with the term. i had just never seen the graph you posted and i figured i would spend hours trying to get, but after looking at it that night, i had it in less than an hour and confirmed my understanding of it via Wikipedia (for what that's worth - wink, wink )

Originally Posted by vex

The only thing I do not understand is where the 2.6L value comes from without using a multiplier. Anyone know?

get your grain of salt ...

as i understand it, they are using a multiplier - based on the 720 degree theory. by itself, it does seem arbitrary though.

it's funny, when i first got into rotaries (back in the mid 80s), some people used to say two rotor engines were equal to 2.4 liter, 4 cylinder engines (most people i knew primarily messed with 12As at the time), but extending that way of thinking to a 13B, you'd get 2.6L. the thinking was that rotaries were more akin to 2-strokes in nature, so they multiplied by 2. i don't know where the 4 cylinder thing came from.

if you are inclined to think of each rotor face as cylinders (which i know you don't), then with a 2.6L 4-banger, you have exactly two-thirds of a 3.9L 6. so in that context, i guess it makes sense ... sort of. come to think of it, i think i just found the 2616 theory less valid.

[vex]

Originally Posted by diabolical1

no, i was familiar with the term. i had just never seen the graph you posted and i figured i would spend hours trying to get, but after looking at it that night, i had it in less than an hour and confirmed my understanding of it via Wikipedia (for what that's worth - wink, wink )

get your grain of salt ...

Why? I don't like counting grains

as i understand it, they are using a multiplier - based on the 720 degree theory. by itself, it does seem arbitrary though.

it's funny, when i first got into rotaries (back in the mid 80s), some people used to say two rotor engines were equal to 2.4 liter, 4 cylinder engines (most people i knew primarily messed with 12As at the time), but extending that way of thinking to a 13B, you'd get 2.6L. the thinking was that rotaries were more akin to 2-strokes in nature, so they multiplied by 2. i don't know where the 4 cylinder thing came from.

if you are inclined to think of each rotor face as cylinders (which i know you don't), then with a 2.6L 4-banger, you have exactly two-thirds of a 3.9L 6. so in that context, i guess it makes sense ... sort of. come to think of it, i think i just found the 2616 theory less valid.

I'm still not seeing it. With the 3.9 and 1.3 I understand it as the references are stated, but I can only achieve 2.6 with a multiplier. My contention is that if a multiplier must be used then it is less accurate in that it inherently makes assumptions about some process that doesn't come in to play. (I'll have to read over Peters post in more detail, but I was not convinced by the other links attempting to explain it)

[RICE RACING]

Barry your PTO shaft idea is a little off base.

We are not talking about "gearing down" the actual cycle itself, that is a non negotiable part of any engine cycle be it 2 cycle, 4 cycle or Wankel.

I can see what you and everyone else including Mazda is saying (1.3lt for 13B chamber capacity), that is a given. But its an odd engine by nature that it has common combustion chamber, intake and exhaust ports . I only look at all motors in their complete "cycles". See my earlier posts.

Equivalence (just based on the physical displacement to time across all three established engine types allows them to race).

The Mazda 787B only had "good economy" cause it had Group B weight breaks on its side V's the Sauber and Porsche and Jaguar cars, nothing more, it was a smaller and lighter car, and had allot less power (250+bhp less than the Sauber in race trim!)... It was very light weight with moderate power, but with EXCELLENT ROTARY ENGINE RACE DURABILITY. Mazda's have always expolited the rules to get a favorable advantage in racing, the one biggest factor they have had over others is astounding reliability and durability in race trim, rather than any outright speed.

[Libor]

Food for thought
http://www.rotaryeng.net/Ansdale-displacement.pdf

I´m inclined to 3.9 definition Simply saying this is wankel engine and full engine is utilized only after 3 revolutions

[My5ABaby]

I still vote to compare apples to apples we use power/engine weight and/or size (physical, not displacement...).

[vex]

Originally Posted by My5ABaby

I still vote to compare apples to apples we use power/engine weight and/or size (physical, not displacement...).

You mean like TDC to BDC

[Libor]

Originally Posted by vex

You mean like TDC to BDC

I understand your reasoning but doesn´t such approach ignores that rotor housing has two TDCs and BDCs?

Common sense would tell that we examine only intake part, but who knows

I think that wankel engine should be treated as wankel - whole termodynamic cycle is completed only after 3 revolutions. And of course 3 such cycles will be completed, just shifted by 360°.

[vex]

Originally Posted by Libor

I understand your reasoning but doesn´t such approach ignores that rotor housing has two TDCs and BDCs?

Common sense would tell that we examine only intake part, but who knows

I think that wankel engine should be treated as wankel - whole termodynamic cycle is completed only after 3 revolutions. And of course 3 such cycles will be completed, just shifted by 360°.

That's all displacement is measuring. The amount of air injested by the engine when each piston (whether you want to consider a piston the rotor itself or the faces there of is inconsequential) goes from TDC to BDC. We don't count the TDC to BDC of the Compression/Expansion of the piston engines, why would we for the rotary?

Why do we care again about the thermodynamic cycle or how many revolutions it's completed in; when we're worried about displacement?

[Libor]

Originally Posted by My5ABaby

I still vote to compare apples to apples we use power/engine weight and/or size (physical, not displacement...).

Rotary maybe had slight edge in this, some 40-50 years ago

Bare engine may appear compact and light, but whole package is what counts. Engine, intake and exhaust manifolds, cooling system, muffler system, it all counts.

We can´t just say that certain engine is compact and light, when all needed accessories through their bulk and added weight doesn´t make it such viable powerplant.

I would look for advantages of wankel rotary elsewhere

[My5ABaby]

Originally Posted by Libor

Rotary maybe had slight edge in this, some 40-50 years ago

Bare engine may appear compact and light, but whole package is what counts. Engine, intake and exhaust manifolds, cooling system, muffler system, it all counts.

We can´t just say that certain engine is compact and light, when all needed accessories through their bulk and added weight doesn´t make it such viable powerplant.

I would look for advantages of wankel rotary elsewhere

I'm not saying the rotary engine is compact and light. I'm saying that what is needed to make the engine run as intended (i.e. manifolds and engine) is what should be measured. If, as it sits in the car, a 13B weighs 350lb (or whatever), that's what we measure. If, as it sits in the car, an LS6 weighs 450lb (or whatever), that's what we measure.

Originally Posted by vex

You mean like TDC to BDC

Like the weight of the engine including manifolds and such (excluding other drivetrian - tranny etc.) / the horsepower and torque.

Perhaps all this is taking it too far off subject though...

Originally Posted by RotaryGod

The rotary engine as rated by Mazda is 1.3 liters because each individual rotor, following one face of one rotor through the complete cycle, has a swept displacement of 654cc or .65 liters. Multiply this times 2 rotors to achieve 1.3. Since this only accounts for 2 of the total of 6 rotor faces, we multiply our answer by 3 to get an actual displacement of 3.9 liters. However since the rotary engine is a 6 stroke engine and not a 4 stroke engine since it takes 3 complete eccentric shaft revolutions to fire all faces instead of the typical engine's 2, it only does 66% the work of a 4 stroke 3.9 liter engine. Calculating for this we divide 3.9 by 1.5 to get a total of 2.6 liters equivalent work to a 4 stroke piston engine. All of these, from a 1.3 liter in physical size package.

This makes sense to me. Perhaps it's because it's put in non-engineer speak, but whatever.

[RETed]

WTH...
Why did that post reply delete got undone?

This is just a reminder that this is a TECH section.
Anything NOT related to tech should NOT be in here.
Personal beefs should go to PM - don't air your dirty laundry in here.
I'm tired of editing replies, so I'm just deleting them en masse at this point.
I'd hate to get rid of this thread just because a few people can't follow rules.
There's good information in this thread, and it's getting muddied by a few immature kids.

I'D HIGHLY SUGGEST YOU USE THE IGNORE MEMBER FUNCTION IF YOU JUST CAN'T STOMACH READING THEIR REPLIES.
What you can't read can't hurt you.


-Ted

[vex]

Of consequence; this comes from a thread I had going for awhile.
http://www.rotarycarclub.com/rotary_...5&postcount=35