13b displacement
 

what is the displacment of each rotor housing in a 1987 13b?

654cc or 40cubic in

didn't dave colman from sport compact car magazine go on some tyrade about how the rotary is actualy 2.6 liters instead of 1.3 any comments?

its been long debated....but im going with Mazda's answer...1.3 liters

He starts ranting about that whenever the magazine covers a rotary related story :noyes:

If u want more info on this you should do a search. There are tons of threads that go on forever about this. Some pretty heated debates too...makes for good reading ;)

yeah thats my prob. last night I was in a "debate"about this,I thought since Mazda had put 1.3 L on it,that what it was,but yeahI will just do a search on it I don't want to stir up past issues.

here we go.....
 

In my honest opinion the 13b is a 1.3liter four stroke. I've heard every argument out there, but I'm way too tired to talk about it, now.

mazda considers it 2.6L ...
 

each rotor displaces .65L per rev and fires once per rev. in 2 revs, 2.6L is displaced by the pair.

Mazda used a historic 'smoke and mirrors' rating of 1.3L, but recently accepted an award in the 2-3L class:

https://www.rx7club.com/showthread.p...hreadid=251717

The displacement is measured in the rotary by the size of the air post-compression but pre-ignition between the rotor and the housing, is it not?

HUH?? It is rated on one rotation of the crank. Since a rotar fires every rotation, mazda figured that if both/all rotars fired in one rotation of the crank, then that's the displacement.

You rotate a normal production piston engine till all cylinders fire, which happens to take 2 crank rotations. If you rotate the 13b crank twice, you get 2.6 liters.

personally, i go by 2.6 liters to compare apples to apples.

Yah, different types of engines are measured differently sometimes. I say its a 1.3 liter, but I use 2.6 to compare it to pistons.

it sure is nice to say it's a 1.3 when you're beatin up on those stangs..

since ignition usually occurs before compression cycle is complete (BTDC), the period of your volume measurment cycle doesn't exist, and the 'size' of the air between the rotor face in question and the housing would be very small due to the implied TDC firing position.

the volume change at any rotor face is .65L during a full expansion or compression cycle.

Let's truely compare apples to apples here. Let's take a single rotor 13B at 654cc and compare it to uh let's say a Geo Metro or Chevy Spectrum 3 cylinder. Rotate each engine 360º and count how many times each one fires.

The rotary would fire once on one rotor face while the other two would be somewhere in their 'cycles'. The 3-banger would fire once while its other two pistons would be somewhere in thier 'strokes'.

Now what do we have? :)

you have apples and oranges.

the geo-3, if 4-cycle as I suspect, would be just like my '76 triumph trident triple .... an average of 1.5 bangs per rev (3 bangs in 2 revs).

for true apple match, need to add a 3/2 overdrive to the Geo's output shaft. if ea piston displaced .65L, u got very simular apples to compare.

You have a three banger bike? Cool! Are you still running a points ignition?

I should have said Chevy Sprint. Anyway, yes, 3 bangs in two revs isn't like a single rotor's 2 bangs in 2 revs, or a 20B's 3 bangs in 1 rev.

Perhaps the problem lies in trying to compare a rotary to a piston engine in the first place. Heh, now I'm being lazy. :)

impossible to align, short lived, 3 sets of Mucas points were long ago replaced by boyer ignition.

the 3 bangs per 2 revs go to one band per rev if you added, in theory, a 3/2 overdive gear, in the engine, to speed up the output shaft. the 'strokes' also expand from 180 deg to 270, just like the wankel. it is the equivalent, but non-existing, boinger.

I looked up the old info I had about the company in the UK that builds ignition systems a little while ago. I was thinking about using their 3-banger electronic ignition upgrade for bikes on a 20B. Fortunately, I ended up using something else.

Ah, I see what you're saying. Even if such a boinger existed, it would still continue to be a boinger. Interesting to think about though.

Do you know anyone with a Chevy Sprint? I once new the owner of one. That car could accelerate off the line suprisingly quickly. Of course 1st gear was very short. Shifting to 2nd came all too quickly.

The owner was into cars and sometimes would joke about installing a V6 into it. That was several years ago. I still wonder if a 12A would fit.

I'd like to get close to one and eyeball it. Does anyone have any pictures?

I used to own a 1988 chev sprint ,carbed 1.0L, 5 speed trans,great for fuel economy and that is it.I could not get this car to do 100 mph.I had the head resurfaced and new valves put in,I had the cat removed and put a fart can on it and still not much of a difference in HP.You got a question about sprints ? pm me.

Do you have a link for this article? BTW, he was wrong, it's 3.9 litres.

IMO, the best way to compare displacement is on a rev by rev basis. how much air is injested per rev. afterall, that's what displacement is, the amount of air that is displaced. how much air is moved from point A to point B. If you aren't comparing 1 revolution to 1 revolution, or 2 revolutions to 2 revolutions then you are wasting your time. It isn't fair to let one engine rev once and all the others have to rev twice. Forget the whole 2 cycle 4 cycle thing. The rotary engine isn't either of those two options.

There is a big flaw with this method, the result varies for the same engine if the drive is taken off the engine in a differnet way. For example, if you take the drive off the camshaft of a piston motor then its measured capacity doubles, or if you take the drive off the rotation of the rotor the capacity would triple! Basically it would be possible to design the engine to get whatever capacity you wanted without changing the fundemental design of the engine.

I've posted this reply many many times and so far no one has come up with a reasonable response. Most people just re-explain the "air inducted per 2 revs". :)

Re: 13b displacement
 

Each of the 3 chambers around the rotor have a displacement of 654cc. It is definately not the rotor/housing that has this displacement.