Why Do Rotaries Suck?

[FineLine]

There are 4 seasons to a year, the earth revolves around the sun, humans are mammals, rotaries: revolve 3000rpm, pump out 3.9litres and are 2 stroke. These are all facts. Accept it.

There is nothing magical about a rotary. It does not use any state of the art alien technology. It's combustion technique is unique but by no means state of the art. The fuel it uses is just normal fuel, not any special nuclear fuels. So why in the hell can it produce that much power and use that much fuel if it only pumps 1.3litres? How can it spin a massive T01000000 turbo charger with just 1.3 litres? Use your common sense and logical reasoning people!!!

Add also, Why do they use copious amounts of fuel unless all the above is correct.

p.s. I am firmly biased against rotors. anything that sounds like that should be shot or strangled or is in the process of having one or the other perpetrated upon it.

[Jez13]

Oh yeah and another way of seeing the whole 3.9 ltr thing is by not descibing the 3 chambers as combustion chambers themselves. The first section where air is input should be described as an inlet chamber or inlet storage (like a capacitor, it doesnt use its contents, just holds it while other processes are being done) chamber as no combustion happens there. The second chamber should be descirbed as the only combustion chamber, combusting 1.3l of contents and finally the last chamber should be described as the exhaust outlet chamber. Alot of people base 3.9l by saying that all 3 chambers combined are combustion chambers. What if the inlet chamber was 5 x the size (3.25l ) and the combustion chamber only extracted (0.65l) per combustion (so not using the other 2.6l at all until the next phase). By gary's calculations that would be a 9.1l. What I am trying to illustrate is why the combustion chamber should be the only thing measured.

[GT-R32]

Add also, Why do they use copious amounts of fuel unless all the above is correct.

p.s. I am firmly biased against rotors. anything that sounds like that should be shot or strangled or is in the process of having one or the other perpetrated upon it.

They are inefficient, particularly at low revs. The 'copious amounts' really aren't that massive when compared to a RB26 or similar. They use basically the same amount of fuel.

If you consider their full displacement to be 3.9L, you need to understand that they don't get near using 3.9L in anyway similar to a piston engine. At all. And certainly very far removed from a 3.9L 2 stroke, LOL!!

[Birds]

Mate, there is no 'logic'. There is fact and there is not.

What is your definition of large? It is a totally subject term! The same size as a 2.6L piston engines in a similar fashion? For a 13B? Yes, exactly. Albeit (only) slightly better due to heat. RB26 single turbos can be basically applied to 13Bs. Think T04Z, T51R (extreme) or GT35R!

Many people are still ignoring relatives and time equilisers and only ending up confused (yet arguing based on it LOL).

When Revolutions Per Minute is involved, e.g. talking about what RPM a turbocharger spools at, time is indeed quite relevant/relative!

Oh yeah and another way of seeing the whole 3.9 ltr thing is by not descibing the 3 chambers as combustion chambers themselves. The first section where air is input should be described as an inlet chamber or inlet storage (like a capacitor, it doesnt use its contents, just holds it while other processes are being done) chamber as no combustion happens there. The second chamber should be descirbed as the only combustion chamber, combusting 1.3l of contents and finally the last chamber should be described as the exhaust outlet chamber. Alot of people base 3.9l by saying that all 3 chambers combined are combustion chambers. What if the inlet chamber was 5 x the size (3.25l ) and the combustion chamber only extracted (0.65l) per combustion (so not using the other 2.6l at all until the next phase). By gary's calculations that would be a 9.1l. What I am trying to illustrate is why the combustion chamber should be the only thing measured.

That is correct. Combustion chambers are the only chambers that matter when measuring displacement, as per my example of a hypothetical rotor with 100 chambers but only one of them a combustion chamber...it would be very inaccurate to refer to it as a 65 litre engine given the thing only combusts in one chamber. Then you could go on about the production line example, where you put the rotary processes in a straight production line as opposed to a continuous cycle...sending only 650cc worth of air/fuel down the line, it'll go through each stage of the Otto cycle therefore counting as a single yet whole combustion cycle.

Fark I'm still wasting my life on this thread. Go to hell!

[FineLine]

Pokes birdman with stick.

[DRD-00F]

...I can't believe I'm doing this

I think you guys have what Gary was saying a bit muddled up. By my recollection, he wasn't counting the amount of air in the 'intake chamber', 'combustion chamber' and the 'exhaust chamber' as Jez put it, but he was counting the combustion chamber 3 times as that is how long it took the rotor to finish a full cycle and come back to its original state. therefore, it doesn't matter if the intake chamber is 9 billion litres, that would be like counting the plenum on a skyline...

This is why 20 odd pages were about what a 'cycle' consists of, and there was no unanimous decision.

PLEASE don't start arguing again, I just thought that had to be cleared up!

[GT-R32]

When Revolutions Per Minute is involved, e.g. talking about what RPM a turbocharger spools at, time is indeed quite relevant/relative!

Yeah and I agree with that. But merely quoting "the rotary only rotates at 3000RPM" lacks the time equaliser and is misleading, akin to quoting piston speed.

[GT-R32]

...I can't believe I'm doing this

I think you guys have what Gary was saying a bit muddled up. By my recollection, he wasn't counting the amount of air in the 'intake chamber', 'combustion chamber' and the 'exhaust chamber' as Jez put it, but he was counting the combustion chamber 3 times as that is how long it took the rotor to finish a full cycle and come back to its original state. therefore, it doesn't matter if the intake chamber is 9 billion litres, that would be like counting the plenum on a skyline...

This is why 20 odd pages were about what a 'cycle' consists of, and there was no unanimous decision.

PLEASE don't start arguing again, I just thought that had to be cleared up!

His agreement with this concept of displacement and subsequent rating is correct. His understanding further than this is limited. What bothers me is that it has mislead others.

If you say that the engine is that size you need to clarify to those being informed of this new position (to those reading) that it is a 3.9L WANKEL cycle. Nothing at all to do with a 2 stroke as Gary believes. Remitting vital information (or believing otherwise) such as the relatives is misleading:

1.3L 2 stroke reciprocating piston engine equivalent.

2.6L 4 stroke reciprocating piston engine equivalent.

3.9L Wankel.

Or, you can see the logic in Mazda and Dr Wankel calling it a 1.3L. After all, it's like nothing else so they are free to class it as they will, that is the size of the combustion chamber, so you can see the logic if you aren't clouded by thinking it's some kind of conspiracy.

[bozodos]

get a mods opinion

[swodo]

Can i just say this is my first post on here and i only got directed here from a link posted in the improved production forums. (they are constantly having the same argument over the rated capacity of a rotary compared to a 4 stroke piston engine). I just wanted to point out that the inference that a rotary is a 2 stroke because it is completes its inlet and exhaust process at the same time is wrong.

If you look at the three sides of a rotor as seperate combustion faces (much like the top of each of a 4 strokes pistons) then yes definately one is completing the intake cycle while one is completing the exhaust cycle. But if you look at a 4 stroke 4 cylinder for instance when cylinder one is completing its intake stroke, cylinder two (I think its number two, brain isnt working the best after reading 47 pages) would be completing its exhaust stroke, exactly the same as the process that supposedly makes a rotary a 2 stroke.

As far as the swept capacity of a rotary 3.9ltrs is spot on although as said above there are lots of arguments going on as to how a rotary compares to a piston engine in regards to capacity. I agree that they should be compared to a 2.6 lt piston 4 stroke although that is just my opinion. The problem with this argument, especially in regards to motorsport (SydneyKid) is that in racing every one thinks they are being disadvantaged in some way (IPRA for example, turbo guys think the restrictors are a disadvantage, piston guys think that the 1.79 mulitplier for rotaries is a disadvantage etc.) I personally am going to be running a TG Gemini in improved production (cheap fun) and I could harp on for days about how the guidelines etc disadvantage me (example the shitty front suspension on a Gemini) but the fact of the matter is i chose my car for a reason. If you think that the rotary guys have an advantage in racing buy a rotary and move on.

In regards to the original question (which lots of people had already answered within the first few pages). Rotaries dont suck. They are great little engines and are great in the cars they are put in. I personally have never owned one but know plenty of people who do/have and when it comes down to it people are entitled to their own opinion/taste.

As far as Mazda lying about the engines..... who cares? Through forums like this one and others I dont know of anyone who is into cars/engines/bikes or whatever and doesnt know that a rotary doesnt exactly have a 1.3 lt capacity.

Thats my two cents worth anyway and sorry for digging up an old thread. Just wanted to point out another reason why rotaries arent 2 strokes.

Thank you

Ben

[PM-R33]

I miss this thread *tear*

One of the best threads from an engineering point of view (regardless what side of the fence you are on) on these forums. Definetely should be a sticky somewhere, fantastic amount of information and knowledge in here.

[Daewoo]

Geeze... it takes 47 pages to say they sound shithouse and are usually owned by wankers :bolt:

raced against many of them... standard they are a good little machine, and with a standardish exhaust system you don't want to punch the driver in the chops... but once the owner start tinkering with them, they never seem to finish a test without something going wrong... and the only car whose owners can more often be relied upon the be a dick is a WRX...

Cheers,

Daewoo

[GT-R32]

Thread from the dead. Really not keen on attempting to get some people to understand relatives again.

[warps]

but once the owner start tinkering with them, they never seem to finish a test without something going wrong... and the only car whose owners can more often be relied upon the be a dick is a WRX...

Cheers,

Daewoo

Boy, I'd better stay out of your way then . Until very recently, I was the owner of a modified rotary AND a WRX. And I haven't ruled out buying another modified rotary, although if I do, it will have to have a turbo/.

[Birds]

I miss this thread *tear*

One of the best threads from an engineering point of view (regardless what side of the fence you are on) on these forums. Definetely should be a sticky somewhere, fantastic amount of information and knowledge in here.

I'm with you mate. Right or wrong there is more than sufficient information in this thread for someone to make up their own mind about this ambiguous topic, having covered every aspect and analogy/metaphor/example. That is, if they are prepared to read all 47 pages of it lol. One of the few threads on here that didn't turn to shit in the way that most argumentative threads do. This one truly was a discussion.

I settled on the rotary being different enough to have its own rules for measurement and classification. Evidence of this uniquity can be found in the length of this thread - if it was such a clear cut thing for it to be defined one way or another then we wouldn't have the ambiguity we have or strong arguments on both sides. Therefore the only useful things we can do are A. learn about how the engine actually works instead of just reading the paper/surface information that you do with everyday piston engines (e.g. 1.3 litre engine), B. make our own decision on what it is, and C. support using relatives/equivalence to make class adjustments in motorsport.

[bozodos]

daewoo, you've been a member for 3 + years, why decide to start posting NOW? lol

[Daewoo]

daewoo, you've been a member for 3 + years, why decide to start posting NOW? lol

Joined when I was going to build an RA26/30DETT powered 240Z rally car, now I race an R30 so got back in to it.

Motorbikes are still my main interest.

Cheers

Daewoo

[bozodos]

meh bikes, 1000cc or it's nuthin

the debates pretty much gone full circle, surprised it hasn't been locked and sticked yet

[scathing]

Rotaries dont suck. They are great little engines and are great in the cars they are put in

*cough*Roadpacer*cough*

[GT-R32]

*cough*Roadpacer*cough*

The exception that proves the rule?