boog

I ve heard from different sources that both are better than the other...can anyone give me some detailed info( ive researched through search and it seems the 12a is less efficient) I was wanting to know because i wanted to see if i could turbo my 12a(it has 84,000 miles , is that out of the question to turbo) with jdm parts from jdm engines and just obtain the jdm factory horsepower output......im personally unexperienced with turbos so give me a break... : ) God bless

RexRyder

iTrader: (10)

im sure some guys in the 1st gen section could help. as to answer ur question why 12at's are scarier than 13b's: The FB (or SA22) is a lot lighter, but then again it all comes down to what turbo each engine has.

HEns

the 12a likes to rev alot more then a 13b and is let prone to warping at high revs, as for scarier, im not sure what you mean, if you talking about outright power a 13b is still the way to go.

Bitteliten

Just a small taste of what you "can" have with a 12a turbo

http://www.simtechracing.no/prosjekt_616rx2.htm

Enjoy!

boog

sorry, i mean that it sounded like people were saying 12a's hold up better when turboed

RexRyder

iTrader: (10)

not really, it depends how u build it

13btnos

iTrader: (1)

Look at this link http://rotarynews.com/node/view/107 like the previous post dependability relies on how well built the motor is. My next street motor that I would like to build would be a 12A turbo. Just something a little different than what others have.

moremazda

iTrader: (4)

Displacement, displacment, displacment. You can not make power unless the motor displaces air. A 13b is bigger than a 12a, we all know this. Reliability is in how the motor is built and then treated. Everything that is done to high horse power 13b must be done to a 12a to make it just as reliable. The problem lies in the fact that all 12a parts sold here in America are produced to be used in a naturally assperiated motor. Bearing, side seal, rotor to side plate clearnces are all different in a turbo prepared motor. So all of this time and money put into the smaller of the two rotor choices will net smaller torque and horse power numbers. Unless you crank up the boost on the 12a to compesate for the DISPLACMENT, and now your reliability begins to deteriorate.

Now I'm not saying 12a turbos aren't cool, I'm saying you are spinning you wheels if you are doing for any other reason, than to be cool.

13btnos

iTrader: (1)

Man what are you talking about that all 12A parts are only made for N/A applications. You can clearance the bearings, side seals, and rotors. Bearings and side seals can be done on your own if you have the know how. Rotors don't need to be clearanced unless your going to be holding the motor above 8500rpms for extended periods of time. You can get hardened stationary gears from Racing Beat relatively inexpensive or you can get a stock set cryo treated and clearance the main bearings yourself. On rotor bearings use 1993 rotor bearings because they have the most clearance even more than the MFR race rotor bearings. Well built 12A Turbo can make a reliable 400rwhp on the street and in a FB body that would kill a lot of cars on the streets. Reliablility is all in how well you build your motors. Compensate for DISPLACEMENT then build a V8. I build rotarys simply because I like the fact I can build a small displacement motor that can run with big displacement motors. And a little 12A motor that can eat up most cars on the street would be very impresive. And I know someone putting down 450rwhp with a 12A on the streets and hell there is a guy on hear claiming 680rwhp 12A. 680rwhp sounds a little far fetched but I would not doubt it.

Jesuscookies

iTrader: (1)

I believe there is a dyno run floating around here that backs up that claim

moremazda

iTrader: (4)

You are totally correct!!

Now take all of that time and money (because were not talking about a couple of hundered dollars here) that you just took to build a RELIABLE 12a for turbo charged purposes and compair that too a 13b that you could have thrown the same time and dollar figure at. Yes you have a very reliable well built 12a turbo that at the same boost level, from the same turbo, will produce between 15% and 20% less power than the 13b.

13btnos

iTrader: (1)

Yeah but who cares if your making 400rwhp whether it be a 12A or 13B it's still going to accelerate the the car very quickly. What's wrong with doing a 12A turbo it's something different and if you have the money to do it why not. Why don't you look at this previous link http://rotarynews.com/node/view/107 now tell me if he wasted his time. He runs 8.27 with a 12A and consistently runs those times and I have seen this car personnally. You can make power with a 12A, yes a 13B will make more power than a 12A, but you can't say your wasting your time building a 12A. You probably don't build your own motors that's why it would cost you soo much. It's going to cost you a couple of thousands to build anything with real power. Hell I'm into my 13B turbo in my Datsun 1200 over 10g's and I'm still not done with it. Like the saying goes how fast do you want to go? Well how much money do you have?

fitzwarryne

MoreMazda- Your view that there is a 15-20% difference in potential power between the 12A and 13B is not supported by evidence.

It is really difficult to make comparisons because if differences in porting on stock models. For example the 12A NA output fell by 20% over the years before it went into the RX-7 mostly caused by more restrictive porting.

The difference between the early 12A and a carby 13B 4 port of the same vintage was around 9%. The 83 12A turbo efi produced about 140hp, adding a 13B intercooler gave around 166hp, compared with the 87 13B T, a difference of some 8%. Later 13Bs had increased power due to improvements never incorporated in the 12A as it had gone out of production.

Yes, there will always be a difference in power due to their capacities, but I suggest all things being equal it will be around 9-10%. Still a significant difference not fully offset by the engine weight difference.

I don't think the scary part comes about because of the engine. My view is that it is the Gen 1 body and suspension. It is not so rigid with marginally lower handling and braking characteristics. A Gen 2 model with the same power to weight ratio is a more solid predictable car. However, I prefer the Gen 1 as it feels like a sports car of my youth, driving a stock gen 2 feels like driving my Suburu Outback, civilised! transport!