I have seen a few cars recently competing in sports sedan class under 2l in Victoria using 12A rotary engines 'resized'. Can any one shed some light on this, swept capacity is well over 2l for a 12A [2290ml i think], please explain....

Back in the day, Mazda classed the 12A engine as a 1.2L, 13B's as 1.3L

Maybe that's how they are getting around the "under 2L" classification......... not saying that this is the reason, but mearly a suggestion...
Hope you find out

Cheers

what is a resized 12a,do you mean that it has 13 b housings with 12a stamps.please explain how you got 2290ml.
a 12a is a 1.2 litre.
it's mutiplucation factor for sports sedan is 1.75 so the total is 2.1 litre and there is a certain percentage of cubes that are alowed over the 2L capacity and still be legal for it's class.
so theoretically you can run the same cubes for a vw.
i think it is 15%.so a 2.3 vw should be allowed.

Rotary equivalence factors were played around with at the beginning of last year.

It started out at 1.8. It went to 1.5 and then it varied between classes 1.5, 1.75 & 1.8 and then sanity prevailed and it went back to a flat 1.8. So an 1146cc 12A comes in at 2062cc and a 1310cc 13B comes in at 2358cc. Accordingly neither are under 2 litre in standard form. Turbocharging adds another factor of 1.7.

How you would resize one, I dont know. I wouldnt know how to calculate the capacity in the first place! I'm not aware of any fudge factor, but a race organiser can choose their own way of dealing with these things and apply different classing and factors if they so feel. Eg WSCC shuns the CAMS manual and the NSW speed event guidlelines by combining types 1 & 2.

I found this: http://www.ipravic.com.au/bulletin/B06-069_20Rotary_20Equivalence_20Factor.pdf 

Pardon my complete ignorance here ! Why is there a multiplication factor added to a rotary engine's swept capacity for competitioon classes ? It seems like a deliberate class handicap to me.

Wayne

Hey guys thanks for the replys. The engines I am talking about are apparently classed as 'restricted 12A's'. I know the actual capacity [like550ml x 2 for a 12A] is way less then swept capacity, but no matter which way I look at it I can't for the life of me work out how to reduce the capacity of a 12a, or a 13b engine for that matter. I mean volumetric efficiency isn't taken into consideration, and porting size doesn't make an appreciable difference to actual capacity. And its not like a piston engine where you could change barrell size, head space etc

as to why there is a multiplication factor I think it has to do with envy, can't catch them make them heavier/slower/different class etc. uh-hum I mean parity.

Amazer, i know that individual officals can interpret things differently, but as far as i can work out there are a couple of cars that compete at different circuits on a state level with under 2l rotary engines.

anybody?

Mick

Rotary is similar to a two stroke in the way that it fires every revolution. A standard piston four stroke/ cam/ valve engine fires every two revolutions.

that may be it - the distance seal to seal would have to be the same but the meat on each surface could theoretically be made fatter, as in more revolving mass. I have made a few inquiries elsewhere and got no joy. i just wonder how it is effecting the Under 2l guys running vw.s, it may be the field is bigger so that is good, or is the rule dodging causing problems.

There was a reason rotaries were outsized in the first place, they were too competative in the smaller engine capacities.

Mick

[ Edited on 3/4/2007 by flashman ]

there are people running in sports sedans using a 13b motor that has the housing's machined narrower(12a capacity), so basically the motor has 13b housings and 12a rotor's, mazprep engineering builds them in canberra

Hi

Wasn't there a 10A in the early models? They might come in under 2L.

Steve

Hiya Steve,

Yeah there is the 10A engine but try getting parts for them, hehe
Good luck if your going racing, just hope you don't blow it up and damage the rotors or crank!!

Cheers

Hi Deano

What about a rotary from a NSU, they used whale bone rotor seals, imagine trying to buy them, maybe in Japan if your doing research.

The RTA also rates rotaries at a higher capacity. Quote "The engine capacity to be used for rotary engines is the displacement of all rotors x 2." So a 12A would be 2.4 litre and so on.

Steve

capacity cann be reduced by machining rotors and rotor housings makiing them narower and therefore less capacity