Why Do Rotaries Suck?

[Streeter]

I'm sorry I don't understand, piston engines have crankshafts, rotaries have eccentric shafts so there is nothing common there. Why are you trying to make something that is inherently different somehow the same when the fact is they aren't.

Cheers

Gary

read over that a couple of times and maybe you will see the point Im trying to make.

But Ill add my 2 cents of terminology argument anyway...

3.9 litres pfft.

as for eccentric shaft/crank shaft rotations vs displacement thats exactly what most motorsport categories use and class the 13b as a 2.6 litre dont they?

a combustion chamber needs sparkplugs doesnt it? so if they are missing from 2 sides of the rotor, counting them as displacement is just as incorrect as not including them isnt it?

[Streeter]

Also one other thing (after a few beers)

a 2 stroke engine uses the crank case to compress its inlet charge, should we count that as extra capacity? it doesnt have a spark plug in there (just like the inlet and exhaust chambers of a rotor housing)?

[jase-r34]

Where's the spark plugs on a diesel? And they come 2 and 4 stroke.

I do however appreciate the arguments from both sides and applaud the knowledge some of you guys are sharing as a lot of it is new to me and i love to learn! Great reading so keep it coming! haha.

FWIW I do agree with Gary. Also I am keen for a response to this little beauty...

Now would you like to go back and check the 2 litre 4 cylinder 4 stroke engine pumping 2 litres for every rotation of its crankshaft? It actually pumps 1 litre, it takes 2 revolutions of the crank to pump 2 litres. So using your logic of eccentric shaft revolutions somehow making a difference to an engine's capacity, then a 2 litre piston engine should really be rated as 1 litre. Now I don't know about you, but I don't do that for a piston engine so why should you expect anyone to do it for a rotary engine.

Cheers

Gary

[Streeter]

Where's the spark plugs on a diesel? And they come 2 and 4 stroke.

again comparing something that is different, but ok Ill bite.

Glow plug anyone?

also I dont see much combustion happening on the inlet and exhaust sections of the rotor housing?

I do however appreciate the arguments from both sides and applaud the knowledge some of you guys are sharing as a lot of it is new to me and i love to learn! Great reading so keep it coming! haha.

FWIW I do agree with Gary. Also I am keen for a response to this little beauty...

two posts up champ. Its the way most motorsport categories DO calculate and try and compare displacement which means we should double the claimed displacement of 2 strokes (and also add the crank case volume) aswell cause they are all lying?

Edited September 19, 2009 by Streeter

[mad082]

ok, for those not understanding the 3.9L argument, the rotor has 3 sides to it, so it fires 3 times for i full rotation. the 13b has 2 rotors so it fires 6 times. mazda worked out the engine size using the size of the combustion chamber then multiplied it by the number of rotors. however the flaw in this is that they have calculated it as if only 1 side of the rotor is firing per rotation, not all 3. basically it is the same as saying that a 5.0L v8 is only 1.25L because it has 2 banks of cylinders and the cylinder size of a cylinder is 625cc. so 2 x 625 = 1250cc or 1.25L

[Streeter]

^^and for those not understanding, usually displacement means combustion needs to occur there.

They are different to a piston engine. Counting the sides of the rotor and rotor housings that arent involved in the combustion is just as bad as counting the crank case of a 2 stroke. 2 strokes use the bottom side of the piston to compress the air in the crank case and make the engine run... isnt this exactly what is happening in the inlet section of a rotor housing?

we should count this as displacement then!?

Again, they are different, arguing about how we should count displacement Vs a piston engine is just arguing about terminology and what qualifies as displacement. Saying its 3.9 litres is just as 'incorrect' as saying its 1.3 litres. In my opinion 1.3 litre 2 stroke seems to fit the bill alot better than a 3.9 litre 3000rpm engine... but call it and count it how ever you like, still goes the same.

while we are at it, some terminology...

http://en.wiktionary.org/wiki/engine_displacement

so you have to count three cycles of a rotor compared to one of a piston?

I guess you could use that as an argument of why the rotor is good?

Edited September 19, 2009 by Streeter

[Sydneykid]

^^and for those not understanding, usually displacement means combustion needs to occur there.

They are different to a piston engine. Counting the sides of the rotor and rotor housings that arent involved in the combustion is just as bad as counting the crank case of a 2 stroke. 2 strokes use the bottom side of the piston to compress the air in the crank case and make the engine run... isnt this exactly what is happening in the inlet section of a rotor housing?

we should count this as displacement then!?

Again, they are different, arguing about how we should count displacement Vs a piston engine is just arguing about terminology and what qualifies as displacement. Saying its 3.9 litres is just as 'incorrect' as saying its 1.3 litres. In my opinion 1.3 litre 2 stroke seems to fit the bill alot better than a 3.9 litre 3000rpm engine... but call it and count it how ever you like, still goes the same.

while we are at it, some terminology...

http://en.wiktionary.org/wiki/engine_displacement

so you have to count three cycles of a rotor compared to one of a piston?

I guess you could use that as an argument of why the rotor is good?

I'm not comparing rotary capacity with anything else. The facts are quite simple, a 13B pumps 3.9 litres in one complete cycle of its 2 rotors, that's it. Whether or not that's the same as a 3.9 litre piston engine is irrelevant. No need to count eccenteric shaft revolutions, it doesn't matter how many sides it has, the fact is a 13B is a 3.9 litre rotary engine. Supporters of Mazda lies about 1.3 litres try to muddy up the water with meaningless comparisons to piston engines which is exactly what they are, meaningless. It the same as the 2 cycle truth, the rotoary combusts every cycle, not eveery second cycle which is what defines a 4 cycle engine. There is no argument, a rotary engine is a 2 cycle engine, end of story.

Cheers

Gary

[Streeter]

So you count all sides of the rotor and say that each one completed is one cycle? Wouldnt it be just as correct (arguable more so) to say a cycle is intake, compression, power, exhaust? this is 654cc per housing, regardless of what other stages of the process other parts of the engine are in.

Seems you are muddying the water by changing what is defined as a cycle? To complete 3 sides full cycle the rotor has made more than one complete rotation, seems a bit of a funny way to count displacement to me.

[arbess]

Whoa far out! Well I'm a proud owner of a 13B in my nifty RX8. Fuel is shit house but comparable to driving my old monster R32 GTR.

SydneyKid, I have much respect for your membership on this forum so please don't think by what i say on here will mean im having a go at you but rather providing a somewhat educated arguement to this fantastic topic!

From my understanding from aviation and cars, i understand 4 stoke to be the famous quote of "SUCK SQUEEZE BANG BLOW" - that is intake, compression, combustion, exhaust, all a disclosed operation. Whereas 2 stroke is the sharing of the Cycle 1 Exhaust to Cycle 2 Intake. Therefore at the very simplest level, there is a defined difference between 4 and 2 stroke engines.

When, SydneyKid states that "It the same as the 2 cycle truth, the rotary combusts every cycle, not eveery second cycle which is what defines a 4 cycle engine", I strongly disbelieve that as a defined theory.

May I divert some of you to this link that shows the operation of a Rotary (Wankel Style) http://auto.howstuffworks.com/rotary-engine4.htm

Now watch this 4 stroke http://auto.howstuffworks.com/engine1.htm

Then watch this 2 stroke http://science.howstuffworks.com/two-stroke2.htm

Notice, in the rotary and 4 stroke, the intake and exhaust are both separate and disclosed operations. For the 4 stroke and Rotary, there IS a distinct difference between the way the compression and combustion stages occur due to their geometric design, but ultimately performing the same output of exhaust.

I suppose, SydneyKid, there is merit to what you are saying because there is no specific "stroke" between the compression and combustion stages. Therefore to claim a rotary as being a 4 stroke engine is probably just as wrong as calling it a 2 stroke engine.

If we explore just a little more, the only difference I can see between rotary and 4 stroke is the process of compression and combustion. 4 stroke will take a stroke between compression and combustion, whereas the rotary will (by the use of their elliptical movement) will compress and combust in the one movement. This if we all think about it performs the same output and therefore defines the process of a stroke and a turn.

Possibly those in the powers to be could not define the process difference of these two and decided to call a rotary's movement as 4-stroke. I personally believe the rotary is not a 2-stroke.

Cheerio.

Edited September 19, 2009 by arbess

[RICE RACING]

Nice thread

Displacement is here, its written in Layman terms so no one here should have any difficulty

I decided to put this together for the new players who struggle with understanding what a wankel cycle is about and also the true capacity of the engine, a picture tells a thousands words, so I cut up a rotor and a shaft and marked them taking a photo at every 90 degree's of main shaft rotation, following a chamber from firing to firing or one full Wankel Combustion Cycle.

0 degree's TDC No1 chamber firing

90 degree's

180 degree's

270 degree's

360 degree's (one revolution of crank)

450 degree's

540 degree's

630 degree's

720 degree's (two revolutions of crank)

810 degree's

900 degree's

990 degree's

1080 degree's Wankel Cycle is complete ! (after 3 full revolutions of the crank shaft) No1 chamber firing again

From the above you can see each individual separate chamber (3 per rotor) only fires after 1080 crank shaft degree's has elapsed,, this is why the Wankel is so different to ANY other type of engine, 2 strokes fire each individual chamber once every 360 degree's and 4 strokes fire every individual chamber every 720 degree's.

If you look at a 13B with its 654cc per Individual chamber capacity (thus 1308cc) you can see it aspirates this ONCE every single revolution thus you can compare the 13B to a 2 stroke if you must do so on an equivalence basis (but remember you are not counting the other 2/3rd's of the combustion faces!

Now if you compare it to the much more common 4 stroke engine you can see that 2 faces ONLY are being counted in the engine and thus it has aspirated a total of 2616cc over 720 degree's of crank shaft rotation....... nice little bit of info there but it still misses a whole 1/3rd of the engine!

Finally the ONLY TRUE way to look at a Wankel Rotary is to view it in its own cycle! (and not comparing it to something that it is NOT!) this is only over 1080 degree's of crank shaft rotation, where ALL of the working faces can be accounted for (just as when you do a compression test to see if the poor little donk is healthy or not) For it is only when the entire engine has complete one full cycle of work can it thus be rated, be that as functional or in its true capacity sense. You will then see that the humble 13B is indeed 654cc x 3 working faces x number of rotors ! = 3924cc.

Equivalence capacity to time scale (revolutions) for 13B engine, has one power pulse per 360 degree's per rotor

1308cc 360degree's (2 stroke)

2616cc 720 degree's (4 stroke)

3924cc 1080 degree's (Wankel Rotary)

So far as rotaries sucking? Mazda 4 Porsche 0 in the only race that actually proved who made the best road cars (not dressed up fake group A $500,000 cars !) I don't remember ever seeing a Datsun do anything in any of those 12hr production car races nor Porsche, nor Ferrari, nor Lotus ...............

Happy to take on any one of you ladies and your cars at Wakefield Park in any road registered GTR and hand you a lesson is respect and history

[GT-R32]

Decent post.

But remember, Group A was where the money was. We all know (and you of all people in particular) that the force fed 13B would not have lasted at those power levels (600BHP+) to be competitive.

[RICE RACING]

Decent post.

But remember, Group A was where the money was. We all know (and you of all people in particular) that the force fed 13B would not have lasted at those power levels (600BHP+) to be competitive.

No its a little bit of wishful thinking getting in the way of history and facts

When the FD3S was available Group A was in its death throws! so for Mazda to go make a Group A special tweak version would have been stupid as they would miss out on the world wide category prime years in a nut shell (wasted money for what, a series that was in decline world wide).

There would have been absolutely no issue running 550bhp region as Mazda did this in 1984! with their Group C sports prototypes in Japan running 1000km endurance races against Porrsche 956's and so on, these same basic engines were given to Racing Beat and slotted into a S4 RX7 which set a land speed record of 238mph in 1985 so no problem with power or durability as the history states easily.

The FD3S's and Mazda Japans main focus was on showing the potential of the car in its basic form and it dominated ALL comers, even winning the production class at Bathurst in 1999 against GTR, Ferrari, Porsche and many other losers ultimately

I think you boys need to maybe show a little respect towards the Rotary and the RX7 even if you dont like the way it sounds or understand how it works. As a proven racing car nothing comes close to it, and I dont need to remind you all that the only Japanesse winner of LeMans 24Hr was rotary powered

[GT-R32]

A bit of selective history with a mix of 3/4 rotors and turbo charged cars there. That Racing Beat car made 530BHP @ 1 bar, actually. The record took place in 1986. The engine made its mark not in a racing series, but in a short burst. That car ran 1mph faster than the fastest Honda in the world in that catagory. Which also deserves respect. But where does this end?

The rotary is an interesting, but flawed, engine. Its motorsport achievements in the various categories it took advantage of (Le Mans - in what fashion did they win? Where did they qualify?) do deserve respect. But there's no point deluding yourself over it while bashing Nissan's domination in Group A. It looks a touch weak.

While the rotary didn't compete in Group A, it had plenty of time to do so during the 1980s (the FC). The FD won the short lived production series races a few times (and blew up in one of them) - which really was exceptional work from Allan Horsley.

The onus is on you to demonstrate why the two rotor didn't consistently compete at the peak in a top level series where engine power levels were above 500BHP for sustained period. Just leave the bashing out of it and you won't have any issues.

[RICE RACING]

^ Stick to what you know, rotaries is not it

Remember you cant google your way to knowledge and forums are not the place where history is written datsun failed in the real car world and premier race along with every other much more capable sports car maker at the hands of the rotary engine ............ so dont forget the respect next time people go on in worthless cyberspace about how shit rotaries are

Challenge is there to ANY road registered Datsun too, if your man enough you can go to my site and get my details and I shall provide you with a little history lesson out on the track

[GT-R32]

^ Stick to what you know, rotaries is not it

Remember you cant google your way to knowledge and forums are not the place where history is written datsun failed in the real car world and premier race along with every other much more capable sports car maker at the hands of the rotary engine ............ so dont forget the respect next time people go on in worthless cyberspace about how shit rotaries are

Challenge is there to ANY road registered Datsun too, if your man enough you can go to my site and get my details and I shall provide you with a little history lesson out on the track

You came in here. You rattled the cage. You posted selective facts (some of which were incorrect/exaggerated). Then you attempt to discredit while not properly addressing any points. All of that speaks volumes.

t's easy to post a few calls on the net. Take your car to a few tracks and see how you do. There are plenty of road registered GTRs running amazing times in Australia. I'm not sure any one has even seen how your car goes, so a comparison is a touch difficult?

[Zardos]

No its a little bit of wishful thinking getting in the way of history and facts

When the FD3S was available Group A was in its death throws! so for Mazda to go make a Group A special tweak version would have been stupid as they would miss out on the world wide category prime years in a nut shell (wasted money for what, a series that was in decline world wide).

There would have been absolutely no issue running 550bhp region as Mazda did this in 1984! with their Group C sports prototypes in Japan running 1000km endurance races against Porrsche 956's and so on, these same basic engines were given to Racing Beat and slotted into a S4 RX7 which set a land speed record of 238mph in 1985 so no problem with power or durability as the history states easily.

The FD3S's and Mazda Japans main focus was on showing the potential of the car in its basic form and it dominated ALL comers, even winning the production class at Bathurst in 1999 against GTR, Ferrari, Porsche and many other losers ultimately

I think you boys need to maybe show a little respect towards the Rotary and the RX7 even if you dont like the way it sounds or understand how it works. As a proven racing car nothing comes close to it, and I dont need to remind you all that the only Japanesse winner of LeMans 24Hr was rotary powered

Love your Work Rice :-)

How is your build going?

Oh and for people who don't know who Rice Racing is , He is a very well respected turner/engine builder.

[RotarySnail]

Haha nicely done Rice. Was reading these tools going on and wondering when someone would say something with actual knowledge behind it, rather than what wikipedia brought up when rotary was typed in the search engine. How many of you children have ever worked on a rotor, or experienced one?

He's laid down the challenge, so why are all you RB-frothers still moaning? Why don't one of you go show everyone how much rotaries suck. Or is there abit of an issue doing that because your all keyboard warriors who's cars have nothing all that interesting going on?

As for rice and circuit racing. His entire build up of his current car is very well documented and the entire car has been developed himself. How many of you can boast that?

If it ain't a rotor, it's probably some skyline-blower talking trash.

[RICE RACING]

Also remember,

The "touring cars" FAILED against the real sports cars lapped multiple times, Any clown could Group A a heap of turd into a fast car (those same worthless buckets Commodore, Datsun, Ford etc) basically finished nowhere while the real boys went and fought for the title of who actually makes the best sports car in the world.

The title belongs to the rotary engine and the FD3S, end of story. Not bad for an engine that sucks hey

Not much has changed today, sure you can go spend $500,000 and make a Commodore go o.k. does it mean its a Commodore though or is it like the Datsun a failure in its original designed form? You cant fault the rotary engine, its a purist sports car that put Japan on the map! and blew all the pretenders no matter what thier reputation or cars they could muster clean off it !

[GT-R32]

Most of my information comes straight from the horse's mouth. I respect the man, his knowledge and his skill. I don't like the disrespect.

He has built a very nice thing himself, certainly something to be proud. People will ignore that, bash it and resent him for his words if he carries on. And from what I can see it only runs 1.08s at WP, thus far:

http://ausrotary.com/viewtopic.php?f=21&t=91985

A somewhat meagre challenge for a decent drive and a mild GTR. A much quicker car is a black bridge port RX7 from SA, which runs quick times and has 350rwkw.

Also what is a life long dedication for some men, is but a minor hobby for others. Keep it in perspective.

[RICE RACING]

I don't like the disrespect.

Neither do we, when there is just pure ignorance and selective memory towards what we like you can see the reaction.

Facts are, the rotary is flawed, but it is also great as a racing engine in any form... which is one of the things it is exceptional at. < and when combined as a total design concept (car and engine) as in the FD3S it is basically unbeatable even against the worlds best efforts

Edited September 19, 2009 by RICE RACING