Yeah I don't know much about that area either lol. I'm definitely going to take off some of the peripherals and such to explore a bit before installation :P

 

awesome! I'm glad you picked this up, it's so rare

 

the 12at is neat, ive owned some stuff from them and have seen pics...

1. the LIM basically looks like the carbed 12a intake, although it might be a bit taller? think of a t2 intake with a 4 barrel carb flange on top, and you're close

2. no coolant for that turbo, oil inlet i dunno, outlet goes into the front cover. in the US we got the casting boss for it

3. not sure about the injectors, i had heard they were green? rail SHOULD look like the gsl-se

4. hard to describe the manifold, it looks like a manifold... its like the size of the s5, but non divided

5. http://cp_www.tripod.com/rotary/pg18.htm there were two turbos, both ht18 variants, i guess the FC turbos are larger and a bolt in

6. the throttle body looks just like the gsl-se throttle mounted on a downdraft carb intake (don't the nikki carb and the gsl-se TB share the bolt pattern?)

7. not sure about the idle control, in the evolutionary chain the 12at is BEFORE the gsl-se engine, but it would seem they did them right after the other, so the electronics are really similar, with the 12at being slightly more primitive, with its emissions control box AND ecu, something that was integrated for the -SE

anyways pics would still be much cool... wait until you see the ports

 

technically the red piece is before the throttle plates so I guess it's not an upper intake manifold, just a cast elbow piece connecting the compressor outlet to the throttle body. I think I see an IAT sensor in that cast piece. The TPS looks exactly like the other TPS sensors from the era. It seems like the basic TB design begun with the 12a T continued for 20 years, all the way until the series 8 FD left production in '02. Rx-8 is a single butterfly drive-by-wire TB. The secondary ports are opened by vacuum (secondary shutter valve and vacuum chamber/solenoid) and the auxiliary ports are controlled by a motor.

I can see that the 12aT doesn't have much of a plenum really, unlike the GSL-SE and later 6 ports. Later on the s4 Turbo II had a plenum after the sidedraft style TB, with slight modifications in the s5. FD 13B-REW has long runners and a small plenum, Cosmo 13B-RE had a much larger plenum volume. Both had bigger throttlebodies.

Solenoid rack and ACV look familiar.

My Greddy 720's clearly say "Denso" on them. They are a light blue but that could look greenish if they were old enough I bet. They are the exact style as the early series 4, same impedence and exact same early Bosch style connector. I think it was Keith from KGParts (which makes a lot of FD fuel kits) who said that the Greddy 720's are GSL-SE injectors. It wouldn't surprise me given that the GSL-SE's are 680's.

I don't know if you've seen the s4 manifold. The s4 turbo is actually divided but the manifold isn't. The manifold has a flapper that closes one of the turbine housing passages (the larger passage) in low rpm operation. The FD exhaust manifold is similar--it has a big flapper that closes when only the 1st turbo is running (the Turbo Control Valve). It also has a small flapper that opens in mid rpms as the secondary turbo is just starting to spin up ("precontrol valve"). That's controlled like a wastegate. FD has dual boost control solenoids.

Interesting. I wonder which turbo the OP has? That's a good site btw. The FC turbos may not bolt in. The series 4 and series 5 have different flanges, so one of them won't work for sure.

I'm guessing the emissions box is for the ACV etc like on the 12A. The fuel injection on 12A T and GSL-SE is really crude. Two batch fired injectors is very imprecise, especially compared to the duty cycle-based injector staging of the series 6 and later RX cars.

For spark control, I know the GSL-SE just modified the vacuum signal to the distributor some. I presume the 12A T is the same?

 

1. it would not surprise me if the greddy's were the same part as the 12at, the greddy injectors must have come from SOMEWHERE. gsl-se injectors are orange, ive had new ones, used ones several of the cars, 100% they are orange. its like a carrot color. oddly we had 4 of em cleaned and flowed, and they came out at 700cc... it'll be interesting to see what the 12at has

2. ive had s4/s5/fd's and the 12at looks like the s5 but the turbo is more centered, and its undivided. it does not have the twin scroll or anything like that either. it looks like a t3 flange too, but i bet its not. ive read you can use the FC turbo as an upgrade, i do not know if its just the wheels, compressor or what. if you do a little searching on ausrotary you'll get a bunch of hits on it. boost control is like s4, its just the wastegate spring

3. i actually had the ecu's and one box looked just like the gsl-se ecu, the other box looked just like the US spec 12a emission control box. i found a wiring diagram and it appeared (it was japanese) that this is exactly what they are. they are piggy backed together too, some things like rpm, are shared by BOTH boxes, its really funky.

4. yep, all of the rotaries have a solenoid between the vacuum source and the vacuum advance. so they can turn it on and off. i have never checked a gsl-se, but i did check a 12a, and its very simple, vacuum advance is OFF at zero throttle. the 12at has different vacuum advances that allow retard as well as advance.

one would presume the 12at uses the same strategy, but i don't actually know.

 

I have all the parts for the 12AT in my basement, and i can tell you this much:

- The injectors are actually light green and sized 850!
- The dizzy is unique, and very much sought after down under..
- Turbo is a Hitachi HT18 unit, two different versions were available.
- It has a very primitive knock control system, never really looked into it
- Centre plate ports are tiny! Secondary ports are the same as other 83-85 12A
- Rotor housings are also unique to the 12AT. It has provision for oil lubrication on top, like the 13B

If there is interest, i could find a camera and take some pictures?

 

Please and thank you

 

When will you be needing these parts? I have an 85 GSL-SE running and I am going to make a NASA ITS out of it. So I will be ridding it of the ECU and harnesses. I don't know what it is really worth other than Ebay prices.

gd

 

The tricky thing about injector flow ratings is that it depends on what fuel pressure they are tested at.

Here are the Greddy 720's:



They probably aren't the same thing. Unless Mazda put two different sets of injectors on the 12a T? If they had two different turbos I suppose it's possible.

Any 12a T pictures you could post would be awesome. Clear closeups of specific parts or specific areas of the engine bay would be nice... I think we've all seen full engine bay shots.

 

found a thread on 12aT injectors: https://www.rx7club.com/1st-generation-specific-1979-1985-18/12at-800cc-shouldnt-660cc-212285/

I can't find any consensus on this issue.

It would be awesome if someone could find a part number on their 12aT injectors and post a pic.

 

Found mine, made a thread!

 

Any more pics on the 12A turbo I am very interested

 

Ask what you need and I'll take a pic.

 

Haven't updated this much.

Things I have done so far...


Street ported the engine a little, and painted.
Had a buddy make a custom T4 turbo manifold for the 12a.
Just put the engine into it's final resting place. Going to start making stuff happen in the next month or so.

First picture is just a joke.. I was excited to finally get the engine in so I threw some pipes on it.






Still need to get some fittings for my fuel rails, a TII starter, coils, modify my driveshaft, set of gauges, BOV, etc. But it's finally starting to come along.

 

So how did you get the TII manifold to line up? Does the lower part of the 12at manifold bolt directly onto the top part of a TII? If so, couldn't you have put a 3rd gen manifold on it?

Did you tear it apart and port it? 2nd gen CAS?

What ecu setup did you end up with?

Thanks, sorry for all the questions

 

For the intake I used an adapter plate like this one,

You can find them at tweakit. I don't think it can use the 3rd gen's LIM, but I could have modified a S5 LIM to bolt to a 3rd gen UIM.
I am probably going to weld the adaptor plate to the TII LIM because the extra inch between the block and the LIM is causing some clearance issues that wouldn't be there otherwise.

Me and a buddy took it apart and replaced seals and ported it.

I'm using a 2nd gen cas.

Going to run a wolf3d ecu.

 

Looks as though the work done on it was really good, and that makes me happy. Since you're replacing pretty much everything with the engine, however, I have to ask why you didn't just start with a normal 12A and make all the same adaptations? Either way, it will put down some good power with that gt35r. Prior to my selling my FB I was going to use a gt30r, and hope for around 250-300 horsepower. I was also going to run a blow through setup, though, rather than going EFI. I had everything ready for it but had to move, so I had to sell the car that didn't run.

Enjoy the car.

 

I don't know why lol.. I bought the 12AT and was going to keep it stock but things took a change, and the 12A I had had almost 200k miles on it so I decided to just use the 12AT.