PaulFitzwarryne

It is generally known that the 12 and 13 motors were so named after the cubic capacity which rounded out to 1.2 and 1.3 litres, with the a and b representing the engine in that sequence.[recent thread and response by Peejay on 3 motor engines]

However, there is the 13j engines which developed 630bhp @9000 and 378 lb-ft of torque@8000rpm [the later seems low?]. They were 4 rotor engines with a capacity of 2616cc.

My question to anyone with a history of the rotary, what does the ' j ' stand for, why use the number 13 not 26? The sequence number of that engine in the Mazda 767 was m2, does this mean model 2? I doubt whether it meant two motors as the 13j in simple tterms a 13b engine with a additional rotor housing at each end rather then two 13b engines joined together..

riffraff

the 787b has a 26b in it. as far as i know, it is basically two 13b's together

yayarx7

i thought the 12a had 1.1 liters???

just nitpicking

PaulFitzwarryne

Thanks Riffraff, the 787b was of course the Mazda which won at Le Mans in 1991 and featured in a large number of adverts. There is good reference to it in Brian Long's book. In John Matras's book on the RX7, he states the 767b, a 4 rotor machine, finished seventh overall at Le Mans in 1989.

I believe all the early other Le Mans cars in both the 25X and 7X7 series were 2 rotor, and after the success of the 787b the 4 rotor was only used in the RX-792p series which were banned at Le Mans following the win in the previous year. It is interesting that only the 792 had the RX prefix.

You state the 4 rotor was designated the 26b which is logical, but where is the reference and again why b unless the 767 had an earluer engine specification?

PaulFitzwarryne

yayarx, real nit picking. You are partly right, the way Mazda calculates capacity it is 1146cc. Thus, the size is nearer to 1.1 litres than 1.2 litres.

However, 1146 cc rounds up to 1.15 litres, which rounds up to 1.2 litres in the two significant digit format. Note I said 'rounded ' being a good nit picker myself.

You can prove anything with statistics!

nipplebandit45

yea yea yea. Statisticaly speaking you can also prov that as long as it is wearing a purple Tu-Tu a fully drown Elephant can hang suspended 100 feet off the ground because it is holding on to a Rose by its trunk.

Mike

peejay

26B? Haven't heard of that... but anyway if it is called the 26B that means that it's a different engine from the 13J, therefore is the second engine of 2.6l rotary displacement, therefore is a "B" and not an "A".

As for the J... I have no clue.

Felix Wankel

To make it more complicated, the 20B's predecessor was called the 13G

Felix Wankel

What?!??!??!!

peejay

Yeas I knew about that car.. but the name of the engine is R26B, so 26B didn't click with any particular engine. I just call it "the unobtanium race engine that people want to put in their RX-7s even though a decent small block or turbo rotary will weigh less, fit easier, and probably make more power"

smnc

http://mrmazda.members.atlantic.net/cfaqtext.html

PaulFitzwarryne

smnc. Felix's faqs do not cover the query. Why was the engine called 13j?

As Felix says in this thread, the predecessor of the 20b was called the 13g. So there are some exceptions to the standard explanation.

I really like the look of the R26b engine. Wonder what happened to the R26a engine, could that be another number for the 13j?

smnc

Presuamably the J would just be the 10th variation of eccentricity and generating radius that Mazda tried with a 1.3L engine... But I'm just making wild guesses here. I know very little about the Racing engines...

pineapple racing

I don't know about the "j"s origin, but the A and B is an identification for the design of the rotor. Basicly, 2 side seals=A, 1 side seal=B. I know, the 74 and later 12a should have been the 12b, but I think to prevent confussion they did not change it. This info was in some of my training info from Mazda many years ago. Rob

error402

i actually heard the same thing but i cannot recall the source from which i heard it from. so i cannot verify it.

peejay

it wasn't just the number of side seals, it was also the number of distributors (two) and the type of apex seals (6mm carbon) etc.

But basically they couldn't call it a 13A because there already was a 13A... really, they should have called the '86-up engines "13C" because they were also radically re-engineered...

Still no idea why the original 3-rotor and 4-rotor race engines were called 13G and 13J. Hmm, what are the Japanese words for three, four, triple, quad, etc? That might have something to do with it. (Like the W in REW means "double")

smnc

pineapple racing, error402, peejay...
again, I refer you to Felix Miata's page...
http://mrmazda.members.atlantic.net/cfaqtext.html

PaulFitzwarryne

smnc, it really is a funny subject. Like you I have read Felix's page and believed it. But along came a New Zealand trained Mazda mechanic and there was a note in his training book -it related to the seals.