Hello my name is stoo (fellow rotary head) and I have a question. From my understanding, there seems to be an issue with tubocharging in the renesis due to high compression ratios. So my question is this. Is it possible to CNC mill the groove larger in the rotar surface, to allow for a higher intake capacity, and if so; would it not make sense to lenghthen the groove on one side, changing the overall center position of the groove futher clockwise and angled to increase expansion effeciency? I would think the problem people are having is that they are focusing all of their effort on the turbo and engine management. this procedure would not only decrease the rate of effective additional compression caused my forced induction via lowering the tdc(effective) and increasing displacement it would also lighten the rotars as a side effect. futhermore, changing the angle and position of the groove 'could' effectively allow for greater tourque as the exhaust gasses would have a greater thrust angle. I think this product would sell like hotcakes, and as far as i can tell there is no patent or production. please give me a call if your are interested as i'd like to see it come to life. If it ever comes to life and it's origional....... that would kick ass. :lol2:

another question I pose is this- how much of that rotar can be shaved..... I bet you could get a 10,000 rpm 1.8 litre screamer running at 10 psi if this was done right. wadda ya say 500hp renny on pump gas?

I'll wait for your results in doing this. Have fun.

pretty sure that it would have been done by now if it were practical .....

Uhhh - milling out the rotor will not change the engine's displacement. Secondly, the skin thickness of the rotor is not sufficient to further mill out the pocket without creating thin spots. RB does make a set of lightweight rotors but they are still 10:1 compression I believe. Lastly, you can turbo charge 10:1 compression just fine. Sure, it makes it harder to run higher boost, but moderate street turboing is quite possible. Just look at the new BMW 335xi.

The "rotars" are not solid, they are hollow and flow oil.

there is no way your are going to get a quarter of a liter more by shaving rotors. besides, the metal is too thin

:lol: YA NOW THAT I THINK OF IT... what was i thinking. still, i bet new rotar dimensions are more than just possible. I realize shaving may not be the answer, and that actually getting it done may be completely impractical.... but the fact remains, the answer to effective turbo usage is lower compression and i will not take no as an answer (even if it is for the sake of conversation) a complete rotar redesign maybe. I was looking around once and saw a set of race rotars that looked almost the shape of the mercedes benz symbol! the entire rotar edge was convex and it had the shit drilled out of it. so i agree, plan 1 negative response:lol:

and what about the direction the apex seals face.... what if they were tilted to flow with the grain.....

it's these essential internal components, i belive need to be modded before the renesis will be a hot little engine. -It is my favorite of all engines; so don't get me wrong- I just think the internals were designed with an economy factor and the compression issue was the result.... and yayayaya you CAN run a turbo and YAYAY it CAN be done right but ask yourself this, if you can get that far with this engine at x amount of boost imagine the amount of power you'd see if you could just push that boost alittle farther....

okay okay... how about this then.... obviosly you've seen the cross section renesis rotars then. (ofcourse the internal are hollow) but bear with me, inovation requires a good attitude and an open mind-

- it looks as though the it may be possible to intentionally mill out the center section of the rotar completely, so all that is left is the support braces that are left behind... I know this sounds crazy.... but then would it be possible to fab a new rotar face incert, possibly deep enough that it contacts the center ring that rotates aroung the eccentric shaft for support>

before anyone gets smart.... yes i know> week bonds, impossible to weld, but i don't care if it ever goes further than 300 ft for starts. I still think it can be done.

This can only end well.

I think this might be a troll... but I'll play.

Just give up... you might as well be developing a new engine if you're going to toy around that much. Unless you have lots of money and someone to help who knows more then it just wont be worth it.

Quote 1 - get a 10,000 rpm 1.8 litre screamer

Quote 2 - inovation requires a good attitude and an open mind

Maybe stop while you're ahead.....


S

You can't make apex seal grooves "go with the grain", the seal need to be able to move to seal the combustion chamber.

And if you took the rotor face down the hole for the eccentric shaft, how would you seal the side (your side seals would be gone)? It's not even possible, because your compression ratio would be below 4:1.

I was looking around once and saw a set of race rotars that looked almost the shape of the mercedes benz symbol!

all rotors are shaped the exact same way....... provide pics/links and then this thread will get really interesting, troll(now which one of our guys is this?).

okay okay... how about this then.... obviosly you've seen the cross section renesis rotars then. (ofcourse the internal are hollow) but bear with me, inovation requires a good attitude and an open mind-

- it looks as though the it may be possible to intentionally mill out the center section of the rotar completely, so all that is left is the support braces that are left behind... I know this sounds crazy.... but then would it be possible to fab a new rotar face incert, possibly deep enough that it contacts the center ring that rotates aroung the eccentric shaft for support>

before anyone gets smart.... yes i know> week bonds, impossible to weld, but i don't care if it ever goes further than 300 ft for starts. I still think it can be done.

and you are where???? because only two answers might be legit..

and i bet you dont know either..

beers :beer:

You would be better off seeing if you can source rx7 rotors from the foundry before they are sent for machining if they are in a state where Rx8 seal grooves could be machined in or getting a foundry to recast the rx8 rotor with a deeper pocket. That just becomes a matter of money. Assuming you are looking at well over 400 whp in the end (where the compression would be an issue), what are your plans for the remainder of the drive train?

you are in need of some basic engineering classes my friend

I have come from the future. My timeline is from a parallel universe where the events as unfolded to me may differ from yours. In my timeline, the 8th gen RX-8 has 1.8L engines thanks to the work done by CrazyStoo. Do not doubt him. He is the chosen one.

*cue air guitar*

excellent.

You're missing a "d" right there at the end of rotar. :)

Uhhh - milling out the rotor will not change the engine's displacement. Secondly, the skin thickness of the rotor is not sufficient to further mill out the pocket without creating thin spots. RB does make a set of lightweight rotors but they are still 10:1 compression I believe. Lastly, you can turbo charge 10:1 compression just fine. Sure, it makes it harder to run higher boost, but moderate street turboing is quite possible. Just look at the new BMW 335xi.

lol....uuhhhh, yes it will. You tuner guys are great.

I wondered the same thing Stoo. It would affect the power, and the boost capability for sure....just not exactly sure what it would do. Not sure why you guys shoot down innovative ideas, especially on an engine thats very innovative. I the technical stuff is too far over peoples head and its easy to make lame jokes.....never seen another group of people like this in my life. It reminds me of the "no the housings are not plated" thread....and I proved it 30 times over it was fact....LOL. Tuners crack me up.

No it won't. The displacement in an engine is determined by the area change, not static volume of the combustion chamber. For simplicity sake, take a reciprocating engine. Now take a 1/2" off the piston crown. The piston head now comes 1/2" less close to the cylinder head. It has drastically lowered compression. It has absolutely identical displacement because the piston head is ALWAYS 1/2" further from the cylinder head. The swept area of the piston remains identical. Regardless of combustion chamber shape, the rotor displaces the same volume. The Rx7 and Rx8 have identical displacements while having different compression ratios.

^what he said.

This thread has really brightened up my day. Thanks for the hilarity guys :lol2:

The area is increased, which then increases the amount of air/fuel inside the combusion chamber. Rotaries are apples to oranges with piston engines.....

heres a link...
http://auto.howstuffworks.com/rotary-engine.htm/printable

to narrow your search....
Rotor
The rotor has three convex faces, each of which acts like a piston. Each face of the rotor has a pocket in it, which increases the displacement of the engine, allowing more space for air/fuel mixture.

Yeah, because it's on wikipedia or howstuffworks it's true. The pockets on the rotor only affect the compression ratio, NOT displacement :rolleyes:

LOL right....It was a 2 second search, and was direct and to the point. I trust them more than I trust a keyboard mechanics theories.

Don't dig yourselves in any deeper.

Yeah, I know. I've read that article a long time ago--howstuffworks is generally a good site, but they certainly aren't infallible. I don't suppose simple concepts like the definition of how the displacement of an engine is measured matter to you huh? You can postulate performance gains all you want, changing the size of the recess in the rotor faces does not change the displacement of the engine.

LOL right....It was a 2 second search, and was direct and to the point. I trust them more than I trust a keyboard mechanics theories.

Don't dig yourselves in any deeper.

Well, this keyboard mechanic is about to prove you entirely wrong.

The volume of the combustion chamber at any given time is not synomous with any representation of the displacement of the engine. The displacement of a single cylinder is determined entirely by pi²*bore*stroke. In simplistic terms, it is piston face area times distance traveled by piston. If you have a pipet with 2 cc's in it already and you draw the plunger back 8 more CCs, you have caused a diplacement of 8 ccs and not 10. Thus, the displacement is determined by the change in volume and not the total peak volume. In the rotary, the definition is no different. At peak volume (bottom dead center for a piston), the dish in the rotor has a volume of X. The volume of the chamber not in the dish is Y making total volume X + Y. At top dead center (for a piston) or minimum volume, the dish in the rotor has a volume of X. The chamber has a volume of Z making total volume X + Z. Displacement is defined by maximum volume minus minimum volume. In this case, it would be (X + Y) - (X + Z) = displacement. That reduces to X + Y - X - Z or Y - Z = displacement. Where is the rotor dish volume in the final equation? It's not there because it doesn't matter. It never changes and thus is not part of the displacement equation. Furthermore, because of the increased dish volume, the expulsion of exhaust gases will be weaker, the exhaust hold over between cycles will be higher, and the adiabatically compressed charge temperature at top dead center will be lower. In short, the engine will make less power. The only gain is that with lower peak charge temps, you can increase boost pressure until the charge temps at top dead center near the knock/detonation point.

If you want, I can probably dig up a "howstuffworks" reference. Actually, it appears in http://auto.howstuffworks.com/engine7.htm that they don't even acknowledge stroking an engine as a means of increasing it's displacement.

http://en.wikipedia.org/wiki/Engine_displacement
There - you will see that combustion chamber volume and compression ratio are not part of the displacement equation. It also mentions that displacement is defined as "the volume that is swept as the pistons are moved from top dead center to bottom dead center."

If you want, I can probably dig up a "howstuffworks" reference.

:lol:

Well, this keyboard mechanic is about to prove you entirely wrong.

The volume of the combustion chamber at any given time is not synomous with any representation of the displacement of the engine. The displacement of a single cylinder is determined entirely by pi²*bore*stroke. In simplistic terms, it is piston face area times distance traveled by piston. If you have a pipet with 2 cc's in it already and you draw the plunger back 8 more CCs, you have caused a diplacement of 8 ccs and not 10. Thus, the displacement is determined by the change in volume and not the total peak volume. In the rotary, the definition is no different. At peak volume (bottom dead center for a piston), the dish in the rotor has a volume of X. The volume of the chamber not in the dish is Y making total volume X + Y. At top dead center (for a piston) or minimum volume, the dish in the rotor has a volume of X. The chamber has a volume of Z making total volume X + Z. Displacement is defined by maximum volume minus minimum volume. In this case, it would be (X + Y) - (X + Z) = displacement. That reduces to X + Y - X - Z or Y - Z = displacement. Where is the rotor dish volume in the final equation? It's not there because it doesn't matter. It never changes and thus is not part of the displacement equation. Furthermore, because of the increased dish volume, the expulsion of exhaust gases will be weaker, the exhaust hold over between cycles will be higher, and the adiabatically compressed charge temperature at top dead center will be lower. In short, the engine will make less power. The only gain is that with lower peak charge temps, you can increase boost pressure until the charge temps at top dead center near the knock/detonation point.

If you want, I can probably dig up a "howstuffworks" reference. Actually, it appears in http://auto.howstuffworks.com/engine7.htm that they don't even acknowledge stroking an engine as a means of increasing it's displacement.

Great more piston math.

So, let me get this straight....
You think the only way to increase displacement on a rotary(2-rotors) is increase the width of the rotor..(I assume you agree on that, but no surprized if thats wrong also).

You can increase the width of the rotor or the central gearing ratio scale. The gear on the inside of the rotor is mated to the gear on the eccentric shaft in a 3:1 ratio. This must be maintained. So, you wind up with a bigger eccentric shaft, bigger rotors, and a larger case. It is my contention that were the rotor reduced to 3 imaginary dimensionless planes that extended from the center of the rotor out to the apex points, that the displacement of the engine would still not change.

edit - my discription of the geometry change is sloppy at best. I have reference books on this at home I can probably dig up. All this stuff was described at length in the Herges History of the Wankel Engine.

So, let me get this straight....
You think the only way to increase displacement on a rotary(2-rotors) is increase the width of the rotor..(I assume you agree on that, but no surprized if thats wrong also).

You just really aren't very bright are you? You can increase the width of the rotor, or change the dimensions of the rotor housing and rotors. The former would roughly correlate to bore, the latter to stroke. I know, "more piston jargon." Sorry, just trying to make it analogous to something you might actually understand.

Perhaps you should do some research on the 16X engine and how Mazda increased the displacement there.

Throughout Mazda's history, there have only been 3 different eccentricity/rotor diameters used.

First in the list (but not chronologically), there was a limited application 13A which had a rotor diameter of 120mm and an eccentricity of 17.5 mm. The idea behind the higher eccentricity was stronger low end torque.

Next and most recent is the 16x whose dimensions I don't know but I believe is also a higher eccentricity/rotor diameter setup.

All other Mazda rotary engines from the 10A to the 13B use a rotor diameter of 105mm and an eccentricity of 15 mm. The 10A was something like 60 mm wide. The 12A was 70. The 13B family is 80 mm wide.

lol....uuhhhh, yes it will. You tuner guys are great.

I wondered the same thing Stoo. It would affect the power, and the boost capability for sure....just not exactly sure what it would do. Not sure why you guys shoot down innovative ideas, especially on an engine thats very innovative. I the technical stuff is too far over peoples head and its easy to make lame jokes.....never seen another group of people like this in my life. It reminds me of the "no the housings are not plated" thread....and I proved it 30 times over it was fact....LOL. Tuners crack me up.

And you think you know everything, huh?

You've already been successfully pwned, but I'll still clean up.

If changing the compression ratio alters the displacement, then how do T2 FC's and FD's have the SAME displacement (654cc per rotor) yet different compression ratios (9.0:1 and 9.5:1, respectively)? I guess Mazda fucked that up, huh?

And how is when you put a metal head gasket on a piston engine, the displacement doesn't increase, but the compression ratio decreases?

Um, der.

You just really aren't very bright are you? You can increase the width of the rotor, or change the dimensions of the rotor housing and rotors. The former would roughly correlate to bore, the latter to stroke. I know, "more piston jargon." Sorry, just trying to make it analogous to something you might actually understand.

Perhaps you should do some research on the 16X engine and how Mazda increased the displacement there.

Exactly my point, now maybe you should research the 16x a bit more....

And yet another site
http://www.encompassholdings.com/RETI.htm

Each face of the rotor has a pocket in it, which increases the displacement of the engine, allowing more space for air/fuel mixture. The pocket size determines the engine compression ratio.


Looks like I found 2 places that support me....and you guys have only gave me a couple examples of piston engines, lol. Lets see some proof, its odd that no site actually backs up your opinions.................:uhh:
So, till you find actual proof, you can blow smoke up each others asses for all I care. Maybe a dildo displacement comparison is next? :lol:

Exactly my point, now maybe you should research the 16x a bit more....

And yet another site
http://www.encompassholdings.com/RETI.htm



Looks like I found 2 places that support me....and you guys have only gave me a couple examples of piston engines, lol. Lets see some proof, its odd that no site actually backs up your opinions.................:uhh:
So, till you find actual proof, you can blow smoke up each others asses for all I care. Maybe a dildo displacement comparison is next? :lol:

I already have proof. It's called the FC, FD, and the RX-8. Different compression ratio, different sized pockets on the rotor faces, and yet the same displacement.

It's funny because that website you linked to and the quote your provided proves our point more- it says the pocket alters compression ratio.

All this arguing doesn't matter because you were already dis proven by MATH.


And nice comment about the dildos, you always know someone is defeated when they resort to lewd comments and shoot themselves in the foot.

lol....uuhhhh, yes it will. You tuner guys are great.

I wondered the same thing Stoo. It would affect the power, and the boost capability for sure....just not exactly sure what it would do. Not sure why you guys shoot down innovative ideas, especially on an engine thats very innovative. I the technical stuff is too far over peoples head and its easy to make lame jokes.....never seen another group of people like this in my life. It reminds me of the "no the housings are not plated" thread....and I proved it 30 times over it was fact....LOL. Tuners crack me up.FAIL

The area is increased, which then increases the amount of air/fuel inside the combusion chamber. Rotaries are apples to oranges with piston engines.....

heres a link...
http://auto.howstuffworks.com/rotary-engine.htm/printable

to narrow your search....FAIL

LOL right....It was a 2 second search, and was direct and to the point. I trust them more than I trust a keyboard mechanics theories.

Don't dig yourselves in any deeper.FAIL

Great more piston math.

So, let me get this straight....
You think the only way to increase displacement on a rotary(2-rotors) is increase the width of the rotor..(I assume you agree on that, but no surprized if thats wrong also).
FAIL
Exactly my point, now maybe you should research the 16x a bit more....

And yet another site
http://www.encompassholdings.com/RETI.htm



Looks like I found 2 places that support me....and you guys have only gave me a couple examples of piston engines, lol. Lets see some proof, its odd that no site actually backs up your opinions.................:uhh:
So, till you find actual proof, you can blow smoke up each others asses for all I care. Maybe a dildo displacement comparison is next? :lol:

FAIL


your VERY quickly on the road to being the biggest ignorant idiot i've ever seen post here....

Damn, that's 5 FAILS in one thread.

Isn't that a record or something?

Damn, that's 5 FAILS in one thread.

Isn't that a record or something?
no he's done worse in the housings thread and in his REW RX-8 thread, as well as other OP's threads....:icon_no2:

no he's done worse in the housings thread and in his REW RX-8 thread, as well as other OP's threads....:icon_no2:

Oh snap!

He has a bad reputation that lingers like a wet fart.

ewwww, i just did that too... and i've been eating wings and hot everythng for a few days. kinda made my eyes water...

I love the provided "evidence." If it's on the internet it must be true right? How about the fact that these are relatively simple concepts, and anybody with a rudimentary understanding of an internal combustion engine and the terms typically associated with it could figure it out on their own? No? OK, Il'l play along.

Rotary engine displacements seem small when compared to piston engines of similar power. In fact, both displacements are measured the same way. Displacement is the sum total of positive combustion chamber volume increases for one complete revolution of the main shaft (crank or eccentric). In a piston engine, this means the total amount of space swept by its pistons. In a rotary, it is easiest to think about the difference between the maximum and minimum volumes for a single chamber multiplied by the number of rotors (where each rotor has 3 chambers).

http://members.tripod.com/~HARDEBECK/engine.htm


Not that some crap on somebody's website actually strengthens the argument, but in fact the information there is correct. By increasing the pockets on the rotor faces, you're not increasing the amount of volume being displaced, you're merely increasing the amount of space it is being compressed into. The maximum volume is increased, but so is the minimum, resulting in a net gain of 0 displacement. Why does the difference between the minimum and maximum volume matter you ask? Because that is how much air/fuel will be pulled into the engine by the rotor on the intake cycle.

It's so incredibly simple. But I'm sure you still don't believe it... that's fine. Please go machine your own "high performance" rotors and let us know how it turns out. I love being proved wrong.

displacement is just that, the amount of air displaced. since the pockets are in the rotar at all times, during compressions and not, that air volume is constant, it is not displaced.

your talking about engine volume, which is a very different thing


so maybe we tuners know something about engines after all, afterall we do spend most our time working on getting max HP from them

I think this thread must be archived as one of the most swift and incredible Pwnages in the history of teh internetz.

i can scan my automotive engineering degree and post it too if he wants.

im glad howstuffworks is backing him up, when i see at least 10 or so sucsessful car tuners throwing out all sorts of math, but hey what the hell is math. most likely dosent matter just like pistons dont matter. its too bad that internal combustion engines physics dosnt change

I had posted this on another forum because I wanted to know specifically how to calculate displacement for a rotary engine. Sadly, I can't do it with pure calculus as I don't want to look up the integration rules for trig functions. Instead, I used a simple numerical method in excel which is turning into a strong personal preference.



The Mazda rotary engine (all rotaries from 10A to 13B except for the 13A and 16X) have an eccentricity (e) of 15 mm and a rotor diameter (R) of 105 mm. The width of a 13B rotor is 80 mm. Rotor width does vary from 10A to 12A to 13B.

If one were to plot the data points of all values of alpha from 0 to 360, the epitrochoid (rotor housing shape) for a mazda rotary engine has the following equations:

X = e*cos(3*alpha) + R*cos(alpha)
Y = e*sin(3*alpha) + R*sin(alpha)

If you would like to know the location of the 3 rotor tips at any given alpha, the equations are:

X = e*cos(3*alpha) + R*cos(alpha + 2*n*pi/3)
Y = e*sin(3*alpha) + R*sin(alpha + 2*n*pi/3)
where n is the number 0, 1, or 2 depending on which rotor tip you want to solve for.

If you take the rectangular summation of the Y equation for the epitrochoid from alpha = -60 to alpha = 60 and subtract out the integral of the Y equation minus -67.5 from alpha = 210 to alpha = 330, you will have a representation of the swept area of the rotor. Then, multiply by the engine's rotor width (converting from mm³ to cm³), you will have the full displacement of the rotor which is 654 cm³ for a 13B family engine.


*A little note - the equations for the tips of the rotors are important because you can use them to define lines for a theoretically equilateral triangle rotor. You can then subtract the area occupied by this triangle in your numerical methods. This explains the 67.5 in the min volume equation. In the max volume equation, the side of the rotor is vertical and does not intrude into the boundary of the numerically summed area.

**If you want info on rectangular summation, it's a rather boring and simple concept for brute force integrals of known equations.

So let me recap - the inside of the housing is PLATED?

S

So let me recap - the inside of the housing is PLATED?

S

:rollingla

this thread is fantastic.....or craptastic...

meh...same difference

So let me recap - the inside of the housing is PLATED?

S

damn you stealth.

you got the whole monty, rum and diet coke out the nose.

and to all, no meat to be removed from the rotors to lower compression..

a rumor existed about 3 years ago that someone respected did some low compression rotors for our engine. seems it was just a rumor..

beers :beer:

NICE TO HAVE SOMETHING TO TALK ABOUT.... how about this then..... what would happen if you were to fill in the rotar dimension so that it is completely flat.... would that decrease displacement? fact is- i don't know. but how about this... did you know there was a five sided rotary design? and no, i'm not talkign about that silly quadribine with an extra side. i think it was citroen that was playing with the idea breifly. anyone ever consider duplicationg a cast of a rotar and working from there.... meh...

and what about modified ecentric shafts/// has anyone ade these yet? I bet you could do some way cool mods on these! and drilled/dowled housings? no one has done this yet. c'mon guys. stop mocking me- this is the good stuff and you know it.

btw i wasn't really worried about the transmission/rest of car. it's going to power my vibrating butt plug. :spank: :Eyecrazy:

btw i wasn't really worried about the transmission/rest of car. it's going to power my vibrating butt plug. :spank: :Eyecrazy:


That is entirely too much information. Guess that's why you are called "CrazyStoo"

btw i wasn't really worried about the transmission/rest of car. it's going to power my vibrating butt plug. :spank: :Eyecrazy:

ah, it is clear now.

go away crazytroll!

beers :beer:

Mechanics 101...take it please.

unless you widen the rotors and housings, or comeleatly redisign the engine you cannot get more displacement

the end

Thank you Crazy Troll, please leave now.