I was just curious as to the likeness of both of these engines. Yes, they are obviously both Rotaries, but do their exhaust manifolds bolt up to each? Same compression? What about displacement (apparently the 12A has the same liter size as the 10A)?? Rotor heads, go nuts!

 

No, the rough numbers go as follows:

10A = 1.0 liter displacement (500cc per rotor)
12A = 1.2 liter (1148, as I recall)
13B = 1.3 (1308 cc)

They all have the same "stroke" or e-shaft offset (equivalent of a crank), but the "bore" is increased. 10A has 60mm-wide rotors. 12A has 70mm rotors, 13B has 80mm rotors. Because the engines get longer from one series to the next, the exhaust header spacing grows, too. Each one is 10mm longer than the last on the header, 20mm longer overall. Early 10As had side-plate exhaust which would be TOTALLY different, but I think all the RX-3 engines were peripheral exhast.

Basically, the hole pattern height is the same for each series, and 10mm wider between each engine size.

 

Nice, thanks for the info. I thought that the 10, 12, and 13 designations were from their respective displacements too, but this http://www.ultimatecarpage.com/frame...hp&carnum=1158 says otherwise. Did they post the wrong info?

 

Okay, I finally found what I think you're talking about. There's a typo on the RX-3 that lists the 10A as 1.148 liters. The RX-3 was available as either a 10A or 12A. It's the 12A that's 1148cc. If you look at the RX-2, it lists the 12A as 1148 (70 cubic inches) and any RX-7 shows that the 13B is 1308 at 80 cubic inches.


The displacement on all 10As is the same, whether side-exhaust of peripheral exhaust. 12As are longer and are all the same displacement, whether US-spec, Turboed (jap-spec) or 6-port (also jap-spec), and all 13Bs are the longer still and all the same size, whether carbed, 4-port EFI, 6-port EFI, Turbo, or Twin-turbo. There's tons of varieties, but the displacement never varies for a given engine series.

 

Ok, thanks for clearing that up

 

RX3 10a's share a number of parts with the 12a... oil seals, oil pump, side seals, water seals, you can run the same stationary gear, and the end plates (if you happen to have some 12a twin dizzy plates which are the same). You can also use a later single dizzy front cover and electronic distributor.