Prediction on Rotary engine
 

Ok, alll in all I'm very pleased with the rotary engine and generally the overall performence and feeling one gets from drivng it. I'm curious to know if anyone had any idea's what it might be in the near future. Look at the piston engine 100yrs ago and compare it to taday and it's 2000% better. In contrast the rotary is only 50yrs +- and some xxxxbillions/Trillion behind in R&D. Any predictions? Me...

One day it'll surpass the piston.....and it's coming sooner than you think.;)

In the near future, more comman in our cars, and also powered by Hydrogen in some applications, fairly commanly.
In the distant future, limit production due to the near elimination for the internal combustion engine in everyday passanger vehicles.

We wont find out until we run out of oil. Our economy would collapse. Can you imagine what a for sale sign on every corner gas station would do to our real estate market?

The rotary is dead-end technology. The combustion chamber is horribly shaped and there is no way to improve it, so it is doomed because it will never be as efficient as a piston engine will be, or even as they are today.

So enjoy 'em while you can! That's my plan anyway.

Rotaries rule! Someone someday will figure out how to make them extremely powerful and reliable.

Well, as strange as it might sound I don't think that the saving grace for the rotary will come from the automobile engineers. Instead, it'll have to come from the jet/turbine mfg. I suppose there are limits to THIS rotary & how it's built but not necessarily the rotary itself. As demonstrated in other applications in other industries.
I'm curious to know what the theoretical limits of this engine is. Give this engine some serious R&D $$ have Japan loosen the patent application a little to the world, I think you'd be suprised at what's already available.

I think you are right. It will probably develope better somewhere other than cars - so long as they still put them in 7's!

So fix the thermal prob and call it uh fixed. :)

hello guys:

i made that above post i think your server may be having problems....

the rotary of the futre will be PP (as it should have always been) with multiple intake points with solenoid controlled valves, the exhaust port(s) will be similar, the intermeditary housing will be removed as they will serve no purpose anymore, meaning less e-shaft flex they will have bearings around the e-shaft to give better support at higher RPM.

they will most likley be a 3/4 rotor

The planetary gears will have twice as many smaller teeth for smother opperation and will be on both sides of the rotor instead of just one.

the rotors will b 6+ piece parts with the corner triangles being the thickest part, the rotor will be bolted into place to the e-shaft, there will be 200% better oil flow bettween rotors (if the rotos arn't to have split oil sumps)
the sump will be done away with in exchnage for surge cans, allowinf even lower mounting of the engine.

Fuel will be Direct injected at the latesstage possible reducing the amount which is caught by the trailing seal, firing will be made by upto three seperate plugs with at least two next to each other.


Fuel injectors will be designed for three fuel and a custom tank will be designed allowing for the use of Hydrogen and LGP (via a high pressure tank) as well as for conventional Petrol (as a bladder surounding the high pressure tank)
meaning you will have a car that can use any fuel from any where.

the intake will just consist of a pipe to connect the snorkel to the intake port.

The engine will be assisted by means of an electrocharger, a pwerfull electric motor attached to the forward end of the e-shaft (mostlikley by some type of centrifugal clutch) , this motor will keep the engine stable at sub 500rpm idle speeds it will also be able to produce upto approx 130kw of instant torque, meaning instant go at the stab of the pedal, although this motor will not add much at high rpm, thats not it's function it is there to assist in low rpm situations.

the motor will also fucntion when the car has been shut down, by relasing the sparkplugs the electric motor can continue to spin the roros untill they have correctly cooled down at which time it would shut down, it will also be used as a stater motor, and in emergency situation where the car runs out of fuel.

finally, the e-shaft will be hollow it will hold the drive shaft for the front two wheels of the car, the clutch will be a custom designed and will be a donut in shape with no middle, it will feed into the gearbox, within the gearbox thier will a return cog, going to plate within the centre of the donut in the clutch which will feed the driveline which is inside the middle of the e-shaft (th e-shaft will need to be much bigger obviosly) this will feed to a simple differential at the fore of the car and the ussuall rear driveline would be as normal.

The engine would be mounted so far back in the car and so low that the centre of gravity would be in a place providing the best control over the veichle.

well thtas some of my ideas anyway.

oh and the engine would rev to 12,000 rpm smooth as anything.

You will never get away from the fact that the combustion space near TDC is long, wide, and thin, which is AWFUL. Ever wonder why even high-revving production engines use small bores and long strokes? Makes a nice combustion chamber shape near TDC.

Rotaries will have their place... but it will not be in cars, or any other situation where emissions and economy are a concern. :)

I remember when all out race rotaries were putting out 10-20% more power than 2.0 liters, but technology has nullified the rotary advantage. Now even 2.0 liters are putting out 500rwhp on pump and 800rwhp on race gas.

Unique, black art, individualized it may be, but the rotary is dead.

Actually, it won't be just the rotary that will be dead in the near future. All internal combustion engines will be history in 25-50 years.
In the case of current IC engines: No fossil fuel left, increases greenhouse gases.
In the case of Hydrogen engines: Too little output for too much input. Cleaner, but still have heat output that contributes to greenhouse problems. But they could be a stopgap measure.

Unless someone invents something new and easily (read cheaply) manufactured, then the only viable alternative is electric power.
Why?: Conventional IC vehicles can be converted realitively easily. True electric designs (even now) offer a high performance (100% torque at all engine speeds) and economical running, even on conventional battery cell technology. The battery technology is where the most development needs to take place. There just won't be enough lead around to make enough batteries for all the vehicles currently on the road.

I think that this is where all vehicle manufacturers want to be in the next decade or so.

So, enjoy your noisy, smelly, fun engines while you can...

...rotary engine has longer history than 50yrs. Mazda actually bought the petent from a company in germany. Inaddition, rotary engines were/are used for aircrafts.

15B:D

Well one of my idea is to split the rotary combustion chamber into two parts(imagine cupping your two hand together) and adding two spark plugs for each side of the split. This should adress the volume area of the rotary, or create a spark PLATE as opposed to a plug, thus creating a greater area of spark.

And yes the rotary has been used in aircraft engines. NOT to be confused w/a rotary piston aircraft engine which places pistons in a circle. There wasn't a viable Wankel engine before the start of WWII. Still +- a few years of the 50.

I do believe that a theoretical limit will be reached for the rotary as it has for the piston soon. Take drag car, although I'm by no means an expert, it's my underatanding that after a couple runs the engine has reached it's limits of fatigue. Running som 30+ psi will do that to an engine. Even with the aid of titanium, my point is there is a limit in terms of strength, metal fatigue ect..
The rotary with the aid of ceramic, better luburcation, lighter rotors, and better managemnt of the engine will progress. Were just scratching the surface.
For exmple how long have we stayed with the same tricodial shape of the rotor? Look at the new one. Much like the progress of propellers on a boat or the blades on a helicopter the shape og the rotor is evolving. Now the housing has to change also and not treat it as the holy grail that it isn't. If in fact the combustion area is a drawbck do to the volume area ect..change it. but that'l take time.

Should I say that perhaps a marriage of piston & rotary would be blasphme?? Take the best of both world and merge them? Hmm.....

indeed the rotary is dead, i doubt much more developement will be put into it beyond the renesis. it just isnt effeceint enough. no matter how much developement is put into it, it will never have the fuel/thermal effeciency of a piston engine. however, what could be done is a sort of heat exchanger to get the most out of that extra heat.

what could be done is to opperate tho cooling system on pure distilled water under slight vacum, or better yet develope a compound that would boil at about 180f but not freeze until -50f. this coumpound would be boiled off from the heat of the engine and the gas/steam would be used to push a small turbine that would mate to the drivetrain through some sort of hydraulic or mechanical linkage.

- with the recent advent of hybrid cars, we have gotten very good about not wasting any mechanical energy; however, even hybrid cars still waste tremendous amounts of THERMAL energy. this is a new fronteir of furthering the effeicency of cars.

even something as simple as a primitive carnot engine which creates mechaical energy out of nothing more than a temperature gradient could be employed to further the effeciency of EVERY automobile.

in that sence the rotary is dead unless is ability to create lots of heat can be put to good use.

on other fronteirs, i see an RE that uses peripherial and side ports for both exhaust and intake. think PP meets renesis. actuators would be used to switch between and combine the different tracks in order to provide an absolutely rediculous power band and rpm range.

the technology is out there, someone should have attemped this a long time ago.

15 eh? :)

rotary's best advantage is it's compactness. my prediction is that they'll make an extremely small one, like a 04d or whatever. it's sole purpose would be to run several alternators to keep a dc brushless motor running.

one thing i wonder though is why don't they attach rotaries to CVTs. i mean cvt's are bad with large torque and it takes a lot for a rotary to make large torque so it seems like a win win to me. get to sit in your peak power when you need it, and get a slight bump in fuel economy.

I sorta do that with the clutch pedal. I've still gotta shift though. Hmm...

I have pondered this myself at times.
My thoughts go something like this.
Direct injection is a must. add at least one more spark plug per rotor. make the water gap between the outside "skin" and the combustion chamber a little wider with ridges on the combustion chamber side to improve heat transfer.
Now this is where I think it gets interesting. Instead of two rotors, four, but half the width. This narrows the combustion chamber. Then you can design a better quench area for better combustion chamber trubulence and control. I feel this would also improve low end torque (assuming the same output power as the 13b).
A PP is not the way to go. it make it too easy for the spent gasses and the new ones to mix as the apex seal is passing over the port. So this means you have to have the intermediate housings, but now you need more. Now, to get closer to 100% volumetric efficiency, you only have to get half the air in each combustion chamber, but you have the same cross sectional area of the intake port to do that.
Onthe apex seals, ceramic don't seal well enough at low speads and titanium will scrape off a layer of rotor housing with every pass. I don't have an answer to this one. I think every thing needs to be thrown out and start over. some body might beable to come up with something revolutionary, but not me.
as for fuel I think ethanol should be looked into. It is made from corn it is 35% O2 and has an octane of about 115, and it's waste is CO2 and water vapor. It needs to be more wide spead before it can be considered a viable energy source to IC vehicles though. the oil companies won't let that happen. Becuase ofthe higher octane you can of course rase the copression ratio.
Then you give this motor a 9,000 RPM redline and a drive train that can accually handle it and you hvae a great car that doesn't polute.

Actually, the shape of the combustion chamber isn't the problem. It's the fact that the trailing apex quenches a lot of the burning air/fuel.

I'm wondering what you're talking about too when you say that even high-revving production engines use small bores and long strokes. Just about every production engine I can think of that fits that description is oversquare.

Honda B18's are heavily undersquare. Some of them were pretty damn high-revving, wouldn't you say?

Sure there are lots of oversquare engines out there... but they are sacrificing combustion efficiency to get more valve area.

Engines designed for good efficiency are undersquare, or at least have small (80ish mm or smaller) bores. D-series Honda, VW watercooleds, Toyota generic motors (non high performance), Saturns... find engines that make great MPG and more often than not they're undersquare designs.

People like to say that internal combustion engines are "air pumps". Maybe in one sense, but all you have to do is look at what they're called - internal COMBUSTION engines - to see what's important - combsustion efficiency.

Ergh, dammit. I keep forgetting the Honda things are undersquare. Funny because I have one for my daily.

However, I think I dispute your claim that engines designed for efficiency are undersquare. I'm looking at a table of engines from Toyota right now, and there's a great preponderance of undersquare engines for "normal" cars. The big standouts I see that are undersquare are the E series I4s, the M series I6s, the Prius motor, and the ZZ I4s. The V8s and V6s and all the rest of the I4s are all either oversquare or square.

Also, the B-series Hondas are gone. The K-series that replaced them are now square.

Some of the more famous engines in terms of total efficiency are also oversquare... the VQ series Nissan V6s for example. Or the Chevy LS1 or any number of others. Looking at Geo motors, yes they're undersquare, but only just; bore:stroke ratio of 0.96.

Thing is, yes, they're combustion motors. They're also a collection of parts sliding against each other; there's tradeoffs in all of this. Undersquare motors may gain you combustion efficiency, but is the penalty in increased frictional losses worth it? Longer stroke means shorter connecting rods to make everything fit, which greatly increases side load between pistons and the cylinder. Only way to get around *that* is to make the engine larger; taller deck height if you prefer that term. Longer stroke also means higher piston speeds which works against the "air pump" aspect of things.

Newer engines incorporate better combustion chamber shapes that allow the charge to be burned more quickly, so that having a larger bore isn't the handicap that it used to be. Witness how well the newer Chevy V8 engines work with their (relatively) enormous bore sizes.

Unfortunately, we can't translate that into rotary terms, since the technology rather involves getting a good amount of swirl (instead of merely high turbulence) and cramming it all up near the spark plug and the exhaust valve. (Why the exhaust valve? So the mixture nearest the exhaust valve is guaranteed to burn, so less unburned stuff is thrown away when the valve opens)

Our combustion chamber shape is pretty much fixed: roughly 6 inches long by 3 inches wide by maybe 3/4" tall in the center (where the dish and spark plugs are) and changing wildly in the poorly-accessible reaches of the chamber. As opposed to a nice decently-shaped ball of gases swirling around in short distance from the spark plug, and a maybe .060-040" squish forcing everything towards the center at TDC.

You *might* be able to redo the Wankel to be more efficient, but it would be much different geometry than the Mazda rotary. It depends on if Mazda is willing to throw away all the tooling that they've been using. The RX-8 engine still uses all of the same dimensions as the original L10A Cosmo so I don't think they will be willing anytime soon.

Longer strokes don't necessarily mean shorter rods... after all, if you're designing an engine from the ground up, you can make the R/S ratio whatever you want, within reason (piston height and hood height, mainly)

I was shocked when I learned how large the bore is on a K-series... I haven't seen any BSFC numbers of a K versus a similar output B, though. (The K's seem to own the B's as far as outright power production is concerned though!) It's definitely the way of the future.

Well, my point about the rotaries is that the surface / volume isn't the big problme. It's *A* problem, but it's not the big one. The big one, from all the research people have done in looking at combustion chambers, is quenching the burning mixture at the trailing apex.

You're right, larger strokes don't *necessecarily* mean shorter rods but... in practical useage, they pretty much do, for the reasons you mentioned (engine height) But you know.

... and I think the discussion of bore vs stroke kind of just wandered off of any subject related to rotaries. :D

Re: Prediction on Rotary engine
 

Can someone please tell me if there are any advantages to a rotary motor versus a piston motor at this moment?

1. They can rev higher...formular cars can go up to 18000k, winston cup cars can go up to 9000, and my parents Mazda 626 V6 can go up to 7000k in stock form.

2. They are smoother than pistons...i used to think so until i took for a ride a '98 corolla and it was much smoother than both of my rx7's used to be. You would be surprised.

3. They can make more horsepower...all i have to say here is that 4 cylinders have been running 6's in the 1/4 for a few years now, i think v6's and v8's are out of question. I believe rotaries haven't broken the 6 second barrier yet and even if i'm wrong 4 cylinders have been there for a while now.

4. They get better gas mileage than pistons...not really.

5. They are more reliable...maybe in a stock form, without turbos, and even still not as reliable as some honda motors or some v8's.

6. They are cheaper to build than pisstons...far from being so.

7. They get better emissions...hell no!

8. They are easier to build...Obsolutely!!!

9. They are lighter than piston motors...Yes.

10. Rotaries have rotors...no rotor for pistons..damn!


I guess it's 3 to 7 and the pissons are leading. Please someone see if i might have left something out.

the problem with trying to improve the rotary is that no one has the urge or money to think new. when pistons engines were new, they had detachable cylinders. that's where that term comes from. the block only contained the crank and rods (half the time). Think of a rotary without having to bolt the center housing to the two rotor housings? make that all one piece with a front cover (rotor shaped) so you can install the rotor.
how about if you totally changed the standard =O layout? would things be different if the intake started at the top of the engine to make it like this:
*|
-O
that could help out with the 'swirl' of the intake mixture since it's still fresh.
do i have the money to test these ideas? no. does mazda? maybe, but they have to sell normal rotary cars before they'll ever get funding to experiment.

Re: Re: Prediction on Rotary engine
 

If revving higher is what you are concerned about. The rotary that we know (Mazda) starts getting iffy as far as internal loads go over 8000rpm.

If you can make an engine that makes the same power at a lower RPM, the lower RPM motor generally will accelerate you faster since it wastes less energy accelerating itself due to higher rotational inertia at higher engine speeds.



I think a lot of that is exhaust noise. Remember noise is vibration, and a rotary makes a lot of exhaust noise, so you get a lot of sound vibration.

A lot of the boingers nowadays are damned smooth, though! First time I drove a Zetec powered car (a Contour) I was shocked by how smooth a four banger could be. Then I drove its Duratec-powered version (2.5l V6) and was *amazed*.



Rotaries have never been about fuel economy... the main push was better NOx emissions in the 70's, back when meeting upcoming NOx standards meant drastically reduced engine life for boingers.

Then the catalytic converter was invented, and that problem melted away, and the only use was for a small Japanese company's "identity". Which brings us here... :)



Rotaries are VASTLY more reliable than piston engines in racing! They are more overrev tolerant (revs just wear things out faster instead of making things blow up), and they are dead simple which means fewer things to go wrong. Only four bearings, no camshaft drive, no camshafts, no valve springs, no valves...

For street engines, it's a tossup. Most newer engines can do 200k-300k with no problems, just like ye olde N/A rotary.



Well... "it depends".

If you're building an engine from the ground up, for street use, then yes that could be true. If you're building a racing engine, the rotary is much cheaper, especially if you start with a core engine in good condition.



See above. EMISSIONS was the main reason why there was a big push to rotaries in the pre-catalyst 70's. Rotaries are high in HC and CO but that can be solved fairly expediently. NOx is trickier to deal with but rotaries are naturally low in that.

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Not really. Not the way we're given them. :) You could do much better with any assortment of four-bangers.

But then you have the reliability issues involved if you're racing...

That is exactly my point, they don't really have any real advantages over piston engines, so why would anyone try to put a lot of R&D into them and spend a lot of money just to come somewhat close to a conventional engine?

Peejay, most of your responses made sence and some could be argued both ways, like the reliability issues in racing. However, even when building a race engine rotaries are much more expensive. Let me give you an example: look on e-bay and you can find a completely rebuild 302 block that has been bored out, has higher compression pistons, cam, ported heads, etc...all the good stuff for only $900 plus shipping. 900 dollars is what you would spend on a full seal, spring, and gasket set for a 12a, left alone something like a 13brew.

Oh yeah, look at gears for mustangs, they go for like $190 price range compared to like $400 price range for rx7's.

Rotaries are still lighter than I4s of around the same power output. And more compact.

And this 302 you mention... does it have forged internals? Will it withstand several seasons of road-racing without needing to be rebuilt? I kind of doubt it, seeing as how $900 is less than the cost of one good head.

Reliability in racing... talk to people who do road-race piston engined cars, top people in the Production or GT classes. Ask them how much money they spend keeping the engine together. It might be surprising.

A lot of them come with forged internals stock...if you look for the right one.

Kenku, you are right, i did a quick search and the motor comes as a short block meaning without the head but still with everything else and a completely rebuild block compared to just some seals and springs that you would get for a rotary in that same price. I'm not even going to bother to calculate the horsepower and tourque per dollar spent.

But that eBay engine isn't a *race* engine. It'd be a street engine that can handle a little racing because it'd be inherently unstressed for the given HP.

A *race* engine would have expensive pistons, expensive rods, zero-balanced crank, enormously expensive valvetrain parts, real heads, a better block... while a *race* rotary still uses mainly stock parts because they're good enough, so there isn't *that* much difference in price between a stock and a race engine.

Put things into perspective, and part of the reason I went rotary. I wanted to throw a cam into my 429. Well, to do that, I'd have to pull the heads and send them out to have the pedestals machined for adjustable rockers and guideplates. I'd have to *buy* the adjustable rockers and guideplates. And hardened pushrods. While the heads would be off, the valve guides would have to get milled down for higher lift, since you can't *find* any decent 429/460 cams anymore that aren't humongoid lift. Humongoid lift that might have required milling the piston tops for clearance, but fortunately that doesn't require engine teardown. (It Can Be Done!) As well as a gasket set, timing chain, and of course the cam and lifters.

Basically, nearly four figures.

With the rotary, I just pulled the engine apart, ported it, threw it back together with a Mazda gasket set ($92 at the time, I think). And even *that* wasn't necessary since most of the gaskets and O-rings can be made or sourced cheaply elsewhere.

If I wanted to go over 8500 for some reason, I could've sprung for carbon apex seals ($240) and hardened stationary gears (forget, I think $160ish each?) and readjusted my pressure regulator up a bit higher. And then my engine would be most of the way there to being a *race* engine, too.

- Pete (And then I blew the rods out on the 429 anyway...)

I don't know about 429 or what not but have a few friends that are into small blocks. Basically without having to rebuild the motor, in just the main parts alone you would have to spend in the $400-500 range to get close to 400 fwhp. Not sure about durability issues though.

Again this is possible to be argued back and forth. But my point being is that if you took a v8 (ex. a mustang that is being hated on this forum so much) and an rx7, basically you would get more horsepower per dollar spent with a mustang.

Peejay, i think i see the point you are trying to make. I guess rotaries could be made somewhat more durable for a little bit cheaper, but i would say that can vary a lot also.

A couple years ago, SCCA ClubRally's Group 5 champion had a $500 homebuilt peripheral port engine. :)

Ok, now unless he had like 90% of it manufactured somehow himself i would say put the :smoker: down.

I've built the bridgeport myself twice, with my own porting and spending about 800 dollars on seals and gaskets with out replacing oil seals, even with bumping oil pressure without spending any money to 95 psi. That wasn't enough money spent on a properly functioning brigeport, left alone a PP engine. Just the balancing alone for it is like $500. Carbons $250. Intake manifold $250. Machined rotor housings $?? Clearanced rotors..Lighter flywheel..Hardened gears..

Basically it goes like this, it's very possible of building a rotary motor and spending almost 0 dollars. Just so it would run. Hec, i even know someone that did that. But if you want it to perform and last, have a good compression all the time, you would have to get out some major cash.

Here's what he said on specialstage.com... you'll find that most of what you suggested is unnecessary.

IRON apex seals are used because the carbons apparently don't last very long with not-quite-clean air. So if you're keeping the revs below 8000 anyway, you don't *need* all the badass internal modification.

Well i guess he did manufactured like 90% of it. Definetly giving the guy props for that. However this is not a typical motor build up. Also building a PP motor just to have a powerband from 7k to 8k just seems to be a little bit unreasonable but i guess he did manage to win. The dude definetly got my respect for that. I love all the ghetto made things some real skilled people do without having to spend a lot of money.

A PP won't have a powerband from 7k to 8k. :)

NSU P-ports had torque peak 4500, power peak 5500...

Yeah, really. From various sources, pport powerbands seem to beat side ports from around 4k RPM onwards, given large race-style ports. It's just part throttle that they start sucking.

Actually i believe it's the pp motors that have smaller intake ports that might start making more power in the lower end. There were some people in this section providing dyno numbers with smaller and larger runners and the smaller ones start at around 4500k.

Right, the smaller ports make more low-end than the bigger ones. However, even the big ones make more power than the side ports starting at surprisingly low RPMs. Everyone always thinks of pp motors as having powerbands that are unusably high, but it's not the case.

"Someone" was telling me about how his friend with a huge bridgeport would pull away from his -SE starting at a 2000rpm roll.

And a P-port should have nicer low end than a bridge...

well, the 26b in the lemans car had a very usable powerband and a redlineof 9k IIRC. it did have those nifty variable intake runners tho.

how did this turn into a pissing contest? i post a phenomenal idea about how to improve the rotary and it becomes a pushrod discussion! WTF! :)

Actually we have been discussing peripheral ports for the last 8 or 9 posts if you notice.

And this is how it turned into a pissing contest...i quote myself on this one.

Well, okay. First, making the engine one piece with detachable front and rear covers. Problem is how exactly to do that. The rotor housings are aluminum cast around a heavily chromed steel strip. The side plates you *can* make out of aluminum, but if you cast them as one piece with the rotor housings, how exactly are you going to machine them flat? You can't really, as if you cast it as one piece and then machine the side plate flat, you're going to have a lip of aluminum where the steel wear strip isn't... *PLUS* non-uniform rotor housing widths. It's pretty much non-equivalent to making a one-piece cylinder block, because the geometry of the rubbing surfaces is more complicated.

Secondly, changing where the ports are. Well, there's a reason why the ports are where they are. The exhaust port is located so that it's open after combustion when the chamber volume is getting smaller, and the intake ports is located so it's there when the chamber is getting larger. If you put the intake port on the top, it will be open when the chamber is getting smaller... and what *that* means, is that it's trying to pump air *out* of the engine. Now, there's some engine concepts that do that, but it only works with supercharging... Miller cycle engines keep the intake valve open for a while after the piston starts moving upwards, because the supercharger makes up for th compression lost.

Swirl is a specific kind of turbulence in the combustion chamber; the problem is that the intake charge moving past the rotor housing pretty much negates all of that.

There really *HAS* been a lot of research done on rotary engines. And Mazda continues to do more... and believe it or not, other companies do too. It's sometimes a pain to find the fruits of their research, but the data is out there if you know where to look.

about the one piece unit, i don't think it would be tough to adapt modern tools to deburr the inside of a rotor housing. the epitroid could be 'bored' as two very large circles, right?

here lemme show you a BAD redition of my idea...

i know this isn't an epitroid but it's the best i can do with such little time.