79rx_7

Ok, I've thought about this several times and last night I was reading an article on the Pineapple Racing website saying that all Mazda engines from the 10A to the 20B have the same internal dimensions, so the rotors and rotor housings are just wider to get the different displacement 10A=60mm, 12A=70mm, and 13B=80mm. Theoretically, the rear, intermediate, and front side housings should be the same dimensions for every engine from 10A to 20B, only difference is number of ports. So to get to the point, the Renesis engine is just a redesigned 13B so it also has the same internal dimensions as the 13B and 12A in our cars. So why could we not take the irons from a Renesis and build a 12A out of them or on a lesser note swap the 13B 6 port side housings to 12A rotor housings?

Can you imagine a 12A with 6ports and side exhaust ports in our cars!

rotariesrule

you can't swap the 6-port side housings to a 12a because the water jacket o-ring groove was moved from the aluminum rotor housing to the cast iron side housings starting in 1986. now the renesis has the o-ring grooves back where the should be which is on the rotor housings. you may be able to build a 12 with renesis side housings in theory but the renesis rotors have blow by rings (looks the same as the steel oil seal) and the 12a rotors do not but there is an extra groove on the 12a rotors that is seemingly unused. the old engines (i think) used to come with 3 steel oil seals. i know the old rotors came with double side seals.

79rx_7

I have heard about the blow by rings but don't know much about them, could you do without them, arent they just to keep exhaust from getting in the intake charge which happens anyway with a 12a

rOtAryIsbEttEr

the stationary gears on the front and rear housings are different than those of the 12a. they come out farther into the rotor than the stationary gears on 12a irons do. i dont think they would match up very well. if at all. i could be wrong about all that bs tho.
methinks that the exaust ports have been moved from the housings to the irons in the renesis so if you can make the renesis irons work you'd have 2 more exaust ports on the motor.
and you'd need a cuztom header or manifold

rOtAryIsbEttEr

those rings help prevent oil blowby, the exaust ports were relocated to help cut down on how much exaust mixes with the intake.

peejay

No, they are there to prevent the oil control O-rings from being destroyed by exhaust heat.

Somewhat important!

79rx_7

Would it be possible to switch the stationary gears? or maby have the renesis ones machined to the right width.

The exhaust ports on the rotor housings could be plugged, or you could leave them open and make one hell of a free flowing 6 port exhaust. I think if you were going to turbo it you would have to plug them.

79rx_7

Is that heat due to the side exhaust ports? our cars dont have them and they do just fine

rOtAryIsbEttEr

the rotor gear on the renesis rotor looks almost just like the rotor gear on a 12a rotor. i dunno ive been smoking for about fifteen mins now so maybe im tripin
maybe i was looking at the stationary gears wrong or something, sry. looking at this **** again im thinkin itll fit now, but still the renesis rotors are wider so it makes sense that the gears might have to be machined a little

as for those exause ports, it would make one hell of a free flowing exaust, i wouldnt plug them if it would improve performance, id jsut **** with makin a custom heade ot fit man im tripwin now

razorback

i believe youd need a 13b shaft too, since the 12a rotors are narrower than the 13b, am i correct?

also, i think there is one tension bolt difference between the two.

blwfly

iTrader: (4)

lol yo;ur pretty much makin a renises motor by the time your finished

79rx_7

you would not need a 13b shaft because you are using 13b rotors and rotor housings. you are using the shaft housings and rotors from a 12a.

you would basicly be making a 1165cc Renesis, I am interested because it would most likely be more efficient and have a lot more power than you could get from a 13b swap. I think it could make 200hp easy with stock porting.

79rx_7

This is the 12a rotor

The ring looks to be about the same but the pic is crapy so I cant tell

79rx_7

There are 16 tension bolts for both engines

blwfly

iTrader: (4)

ohh i see now its making sense
will the 12a sharft fit ballenced with the Renesis center,back,front parts?

rOtAryIsbEttEr

^thats a good question^

hmm, i guess ill have to build one and measure,lol

blwfly

iTrader: (4)

uhh you got parts laying around...
im gonna go get high cause im depressed now cauze of you

gsl-se addict

iTrader: (3)

There shouldn't be any issues bolting the Renesis irons to the 12A rotor housings. The question is if there is an advantage to doing this and if that advantage is worth the effort. The Renesis design saw gains in power and torque over the other 13B NA engines because of:

- lighter rotors
- higher compression
- design of intake
- side exhaust ports
- higher redline (due to the lighter rotors and such)

Now if you use 12A parts, you will miss all of these advantages besides the side exhaust ports. You wouldn't be changing the redline, compression, etc. so there would be little to no gain in power. You would gain the 6-port intake, but then you would need a custom intake manifold to work with it. You could just make a 6 port 12A with GSL-SE irons (you would also get a place for injectors if you wanted EFI). Again, you would have to do something about the intake manifold. There was a 6 port 12A released in other countries (Japan), but the performance would be less than a 4 port 12A. The next big problem is the exhaust. The 12A has peripheral exhaust while the Renesis has the side port exhaust. You would probably have to block the 12A exhaust ports. Either way, a custom exhaust manifold would need to be made.

If you wanted a gain without going full Renesis, I would suggest the Renesis rotating assembly within an older 13B. You still won't get the full advantages of the Renesis design, though.

Anyway, think aboutit. If you can find a way around these problems and still believe that you could gain some of the Renesis advantages, go for it. It may work better than we think.

Kent

DriftFB

The best part about any idea like this is either the simplicity or the efficiency of the new design. This idea, not that its bad or not fun to think about, has niether of those going for it.

OneRotor

iTrader: (3)

But then again for the cost of a complete RENESIS rotating assembly, you could send your rotating assembly to RB and have them lighten and balance the whole thing, add some hardened stationary gears, raise your redline, and have some coin leftover. You wouldn't get the higher compression, but then again you wouldn't be limited in the future to how much boost you could run.

79rx_7

I just wanted the Renesis side exhaust ports and better tuned 6 port intake on a 12A. and it would make alot more power than the stock 12a just on the fact that you have 2 more intake ports plus all the intake ports have been changed and tuned for better flow, and twice the port area with the side exhaust ports and close the peripheral or 3 times if you leave the peripheral exhaust ports open.

gsl-se addict

iTrader: (3)

Yeah. I am just saying if you had the parts around. Not like the Renesis irons would be cheap either. If you are getting new parts, Renesis parts are often cheaper than the older 13Bs (such as the rotors), though. Currently there is a large supply of good used older 13B parts, but a shortage of used Renesis parts. In a few years, it will probably be more balanced.

79rx_7: You have to realize how all the parts are made to work together. The Renesis intake is tuned to work with that engine. It is where much of the power comes from. The intake won't work with 12A rotors/housings. Also, power is related to both torque and RPM. The torque in the Renesis is a bit higher than the other NA 13Bs, but not by a huge amount. Some of the torque increase is due to higher compression rotors. The major change is the redline. The higher redline, with an intake that can flow enough and is tuned, is what makes the majority of the power increase in the Renesis. The additional ports would offer you little or no power gains. As I said, they had a 6 port 12A in Japan, but the power is going to be less than what your 4port 12A can do. Yes, there are more ports, but the ports are much smaller. The reason for the 6-port setup is to have a wider powerband. Two of the secondary ports stay closed during low load/low rpm situations. This keeps the air velocity up and increases low end torque. At higher loads, the additional two ports open up for high end power. The 4 port engines are similar to having a 6 port with the additional ports open at all times (little less low end, about the same relative top end).

Having more exhaust ports isn't going to really help things. If you leave the stock exhaust ports in place, the exhaust gases are going to take the path of least resistance (the 12A ports), because the 12A is a single large opening and the gases don't have to exit the side and make several turns. Getting an exhaust manifold to work with that setup would be complicated.

Anyway, I think you are best off porting/modding what you have. You can add EFI, have rotors balanced/clearanced, ported, and so on and have a real nice NA 12A. Other options would be either the full Renesis setup (would be cool, but it would be easier, cheaper, and get more power from a TII setup) or some hybrid setup (S5 or Renesis rotating assembly, 4 port irons, FD housings for example). Many people prefer the 4 port engines because you can port them further. Also, for forced induction, the 6 ports offer no advantages (all the stock turbo setups are 4 port).

Kent

rOtAryIsbEttEr

the only renesis part that i have is a flywheel and its hanging in my bedroom on the wall.

oh, and im higher than you
im still getin my hands on that new orleans weed that them refugees brought with them when that hurricane did whatever hurricanes do.

gmanuser

*read this*
it is very important to understand that althought they me the same demension they would seize, because they are made out of alluminum and you other housings are made out of cast iron from your 12a and by doing that you cause, 1. leakage, 2. seizure and most likely never be able to take apart engine agian, 3, warpage due to reasons 2 and 1

gmanuser

*sequal to above comment*
in other words the rotors would hit stuff and long story made short it would go BOOM!!!!