hey guys
another newbie from www.bcrx7.com up in canada!


I know this is kinda a technical question but, does anyone know?
i think i figured out an answer the other day but i ain't too sure about how correct it is. Does it have to do with the shape of the internal components?

Also how is the displacement measured in a rotary?
i know how to measure the displacement of a piston engine but not a rotary.

 

A piston engine makes 1 power stroke out of every 4 strokes.
A rotary makes 3 power strokes for every single cycle.

Alot of people will argue on this but thats the physics of it.

The displacement in a rotory is measured differently from a piston engine. check out www.howstuffworks.com for more info.

 

umm no the rotary has 1 270 degree power stroke per rotor per revolution. so a 2 rotor during 1 revolution is pushing 540 degrees worth of power, wheres a 4cylinder 4 stroke is only pushing on it for 360 degres in one revolution

 

and its also very efficeint at sucking in air, better than engines with valves

 

Simple, the rotary makes so much power in 13B single turbo form because it is in all essence a two stroke.

True its single chamber displaces 654cc, but when you look at it over ANY given unit of time of you measure a mass flow rate through the engine i.e. CFM you will find it breaths TWICE it rated capacity.

This has been know since Felix Wankel invented the engine priciple in the late 50's originaly as a super charger for a NSU motorcycle, later he turned it into a internal combustion chamber, then the principle as we know it today was refined by NSU engineers, upon which time Mazda carried on the legacy.

In all this time every mechanical engineer & technician involved with this engine principle aknowledge that the engine is most readily described as a two cycle four stroke !, becuase it has a true four stroke principle of operation, but it does this in the main shaft revolutions of a two stroke reciprocating engine.

Getting back to your question then, when you compare an apple to an apple, the wankel is not so powerfull for it's equivalent displacement.

It's like when we talk about 190bhp 500cc motorcyles, we in the same breath mention that it is a two stroke ! The problem with wankel rotaries is that MANY people do not realize that they too do DOUBLE the amount of work compared to a the same "displacement" 4 stroke reciprocating engine.

Hope this helps you, with your question ?

 

in my "OPINION" a rotary is closer to a 2 stroke 2 cylinder than to a 4 stroke 4 cylinder as some people call because it fires the same 2 "cylinders" on every revolution i believe the displacement of one of these "cylinders" to be 654 CCs there for the displacement of 2 of these is 1308 CCs therefore its a 1.3 liter or 79.81 CI, i think this is how mazda arrived at 1.3 liter displacement, if it was like a 4 stroke you "could consider" it a 2.6 becuase for a 4 stroke to displace all of its displacement it needs to make 2 revolutions. but theres no way of reckoning it a 3.9 liter as i heard a couple people say

this was taken from my post on HP vs. Torque

 

Ah yes the neverending debate of 2-stroke vs. 4-stroke and 1.3 vs. 2.6 continues...

 

ah
thanks guys

i think i get it now

 

i think mazda is calling it a 2 stroke because its only 1.3 liters

 

The 2 stroke vs 4 stroke is a different debate then the 1.3/2.6, guys. The engine has basicly a four-stroke working order, but performs this on 3 sides of the rotor. Because the eccentric shaft turns 3 times for one turn of the rotor, you get one powerstroke/one e-shaft rev. That's why people tend to see it as a two stroke.
The 1.3/2.6 thing is just another way of ripping your money. Count it out and it has 1.146cc for a 12A and 1308cc for a 13B. The state laws in many countries double this, mainly because of tax reasons. FIA rules use a more appropriate 1.8 coefficient. Anyway, this has more to do with making it less intresting to own/race a Wankel then it has with tech questions.
Other reasons for high power output: it's a better engine. No discussion. This is an engine stripped to the bare essentials. Camshafts, valves, they all need power, so they are useless. Also, up and down motion means a dead point, or again: power loss. The Wankel is basicly the perfect idea. If it was invented at the same time as the otto (four stroke) engine, we all would be in a wankel powered car now. So the only drawback was the fact that it was invented so much later and therefor needed to evolve too fast. But it seems Mazda got it right this time, with the renesis.

 

hey Im wit rotary emotions, its simply a better motor, and thats all there is to it.

think, when were the very first internal combustioon piston engines started? they produced early cars around 1900 did they not?
therefore at least 100 years of development of the piston engine by many many car companys, governments, armys, everything.

then compare this to the wankel rotary, patented in the 30's, first prototype in 1957, we are looking at an engine with around 45 to 50 years of real development, mainly by one company, just imagine if more companys produced wankels, and did so for another 50 years of development.

then imagine what we would be driving, pistons would be relegated to museums.

 

YEAH NOW WE'RE TALKIN'!

I agree totally with rotary emotions and rota-motor on the better engine part!

hehe
it's got way more potential than the piston engine. But it's not a "perfect" design. The wankel spins in an elipse which limits it's true revving capability.

I am currently working on a solution to this problem.


my target for a prototype is 273 Hp @ 12000 RPM. It's a 1.515L that spins at 1/2 the rate of a wankel(ie. one combustion per 2 RPM, same ratio as a piston engine)

Thanx to u guys I was able to estimate a "goal" Hp rating.

 

I beleive the Rotary to be superior for 2 simple reason's.

1. The overall physics is more efficient for power. A circular movement is more effiecient then back and fourth movements.

2. The lack of a valvetrain.

INMOP these are the 2 fundamental reasons rotarys are superior.

 

hey like canadian said, the design isnt pervfect as the rotor spins in an elipse, the very first rotor was the KKM I think it was called, where the rotor and housing spun around their own seperate centres, thus was perfectly baklanced and everything, they made some ridiculous amount of power considering it was only a single 125cc I think, and it revved to 17,000RPM with 1957 metalurgy technology.

canadian, keep us posted on your progress man, I'm very interested.

but it had a major drawback in that the engine needed to be completely rebuilt just to change sparkplugs

 

yeah i know about the KKM and DKM wankels

his original DKM was wicked!http://www.nsumotor.onlinehome.de/dkm.htm

my model should have the spark plugs either on the housing which is stationary or on the actual rotors

i'd like to put them on the rotors but i'm having enough problems trying to come up with a way to seal the thing well. Because the interior parts become exposed as each rotor spins for cooling, a lot of engine maininence should be able to be done without taking out the engine or dissassembling it.

keep in mind i am only a student and this is a new project started in my spare time(when i should be studying)

 

Now this is getting intresting. At least I found some wankel-guys on the site. I'm getting pissed of with those freaks discussing V8 conversions...
The DKM would indeed be a perfect engine, as it would simply be free of any vibration!!! However I do not see a solution to the spark plug problem. Or well, hey there is one: delete the plugs! Run high compression and use diesel fuel. The injectors would last about the same time as the engine, so problem solved. Of course it can't be that simple, but I really think it's possible. Mind you, I've been designing diesel-wankels for about 13 years now, since I was twelve, and never came up with something that coul be used. Anyway, it could work!!!
Canadian Rotary Man: try this link:
www.der-wankelmotor.de
It's fantastic.

 

the DKM is cool...

hehe
yeah i don't like the ppl talkin' about V8 conversions
tisk tisk, why did they buy an RX-7 in the first place then?

thanks for the webpage. it's really good


there's a company in Richmond,BC. (luckily where i live). That has a brand new type of rotary. It uses something called "rand cam" technology.

www.regtech.com

 

That's intresting. I don't really see how it works, the site seems a bit carefull with designs/drawings...
But it does sound promising. Hopefully someone can let us forget about these old-fashioned piston engines :-)
Well, I still believe that Wankel was a genius, and the Wankel-engine has a potential to become near-perfect. So better then conventional engines. But time and money are needed, and it wouldn't be easy to make profits on short terms. So not many firms will take the risk. Seems Mazda was the only hardliner... And it nearly killed them, that's one of the reasons there's a link to Mazda on the Ford Motor Co site nowadays...
But hey, I'll never buy a non-rotary car again!!! (but I will keep the Mazda 626 as a family car for a while though).

 

go the DKM all the way.
just as a thing about it, how do you synchronise the rotation of the inner and outer rotors as they would be?
thats usually controlled by the stationary gear in the conventional rotor.

if you can get a DKM design workable, then Felix will look down from where he is, and be truly proud of his invention. I believe when NSU went to the KKM from the DKM, Dr. Wankel said something along the lines of his racehorse made into a plow horse.

perhaps you could use the rotor and seals from a mazda motor to simplify design problems?

 

diesels run on detonation so i dont see a rotary making good power with diesel fuel. considering most rotaries make power high in the rev band. the more engine speed thats involved the harder it is to achieve detonation.

 

the modern TDI engines as found in German diesel cars (VW, BMW...) are pretty revvy too. Shouldn't be a problem.
Also, the DKM should make more torque and therefor be able to work at slower speeds too.
But you could of course put plugs in the side housings. You'll need a few, as the DKM has ignition on several spots (both inner rotor as housing rotate). And it won't work with a three or four rotor...

And as an attachment, something to remember all of us why we are here (at this forum) in the first place..
Took the picture in september, in Heidelberg, Germany.

 

yeah
he was the man!

i find it weird that he died in 1988 and mazda sold the most RX-7s in 1988....

and i drive an 88 too