12A turbo hybrid, center plate questions!
 

Ok, im currently building a new engine for my 12A turbo. Im planning on using the 12A turbo housings, and front and rear irons. The center plate however, is a bit of a problem.. It has the smallest ports i have ever seen, and i really want to use a tallport center instead. Pics below shows the difference in port size:

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As seen, the difference is huge! But.. It also does not have the center bolt fitting for the manifold, and it also has a extra hole where the newer centers has injector fittings.. Im planning on using a adapter to a Turbo II manifold, so the injectors will be placed here, but what im kinda worried about is the lack of the center bolt going trough the manifold and the "extra" hole..

So what do you guys think? Will it work?

BTW, the engine will be studded, 10mm Xtreme rotaries, and dowelled (8). Planning on something like 500 BHP..

I'm not quite clear on what you are doing about primary injectors. I THINK you said you plan to install them into the adapter plate for the TII manifold.

If you look at the TII manifold, the primary runners have a smaller area than the big 12A ports. This will not net more flow and will decrease the velocity. It will also complicate the fuel atomization for the primaries, where it is most critical. The center housing looks identical to a GSL-SE housing... If it is, the timing is the same as the big 12A port despite the smaller port size. The injectors are also placed in the optimum position in the primary ports. I'm gonna side with the smaller port housing.

A streetport on this housing will net a port closing of around 50 degrees ABDC, up from the stock closing of 40 degrees on both housings. I would also open the entrance of the port runner (manifold side) to match the TII manifold and to blend that into the stock port. Just make sure you are mindful of the EGR port and water jackets.

After porting all of the intake ports on this engine your porting will closely resemble that of a streetported TII engine and will retain streetability as well.

Good luck and keep us posted! I'd love to hear more about your setup, specifically details regarding what your are doing to strengthen the block.

I assume you are using the lower compression 12A-T rotors.

I'm building a 12A PP engine that may someday see *some* boost and am very interested in your project. Here is a thread detailing my setup:

https://www.rx7club.com/naturally-aspirated-performance-forum-220/peripheral-port-project-716989/

Thanks for the interest! Sounds like you have a interesting project as well!

I actually just got back from the workshop, finished the adapter and the inserts for the injectors, ill take some pics tomorrow, so you know what im talking about.

Ill also port the inlet manifold to match the intake. The engine will most likely be half-bridged..

As to the strengthening the block, it will be dowelled in 8 places. Its basically just inserting more dowels around the known weak areas. Its just boring the tension bolt holes out to a bigger diameter, and inserting dowels here. Ill try and get some pics when its getting machined.

And yes, im using the 12AT rotors..

Ill get some pics asap

Thanks! I'm very interested in what you are doing as far as doweling the block. I'd love to see some pictures and some details if you don't mind when you get a chance.

i'd say use the non-turbo 12A intermediate. there's a reason why some hardcore racers go through the trouble of getting them (12A side housings) to work with REW rotor housings for big power 13Bs.

i, too, would like to see your dowel-work. sounds like a great project you're getting together.

Ok, so i decided to use the tallport centre. Since im running the a plate between the engine and manifold, i machined it to accept two injector fittings. The adapter is 20mm thick, and the fittings are 18mm. Bored out two 16mm holes, and machined the fittings down to 16mm. They are press fit, but i decided to add some high temp epoxy to ensure its tight. Turned out ok:

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I also made fuel rails, but havent gotten around to mounting them yet, pictures to come when its done.

Regarding dowel pinning. I know a lot of the builders down under use the original dowels and simply machines the holes to accept these. Im going the same route, but im getting the dowels made this weekend (hopefully..). I have also been thinking. I know that the normal way to do this, is to use a dowel that goes only half way trough the lenght of the engine (end plate - housing - center). I also know that some builders has used custom dowels that goes all the way (custom) and since im having it made, making them go all the way trough, is not a problem.

Anobody have any suggestions/opinions? Im thinking all the way would be stronger, but i really dont know.

i wasn't aware that some people made dowels that go all the way through. the only potential problem i see with that is maybe harmonics. however, i'm not well-versed in mettalurgy at all so it may not even be an issue.

Finished the rails, except for fittings and brackets for the primary rail.. Turned out ok, bit tight, but it works.

Attachment 719919

http://i4.photobucket.com/albums/y11...elrails002.jpg

Fitting the secondary rail so high, means i have to make another set of sleeves for the injectors, that "raises" the hole a bit. No biggie, doing them this weekend.

Attachment 719920

I have also wondered about the original TB. I guess its big enough for the level of power im shooting at, but its kinda bulky and has a lot of, well "crap" attached to it. I have some 3" Audi TBs lying around, and they are quite nice and basic. I really want to keep it as simple as possible. I have also been looking at other options, for instance 85mm Ebay items.

Any opinions/suggestions?

You can still make good power with the 12aT intermediate plate. I made 497rwhp with one. Like has been said above, when you use the 13bT inlet it has smaller ports in the centre anyway. I got mine extrude honed and then port matched them to the ports on the motor.

It looks like i have a bit of porting to do then! I know the original centre can make some some awesome numbers, it just seems like its easier to do it with a tall port centre.

BTW, i noticed you are running a light steel flywheel. Of the top of my head, i cant remember if the 12AT rotors are lighter than the NA ones, and if you would have to get a counterweight from a 12AT specific automatic vehicle to do this? Or are they the same weight as the NA? I do have access to both type rotors, but i cant find a accurate weight around the shop..

I kinda dont want to go hunting for a Cosmo 12AT counterweight..

the 12A turbo rotors are the same weight as the 84-85 12A n/a rotors(the ones that have a "N" in the combustion pocket)... i have one if you cant find one(12A T counterweight)

i like your project but i prefer the clean look of individual thottle bodies, oh and with the individials there is no worries about making enough power :)

Yeah I am using a 12aT counterweight. It took me a while to hunt one down too.

So what you are saying, is that you have a automatic counterweight for a 12AT?

Id also like separate TBs but, im trying to keep the look somewhat original, since this is a street driven car, that could be towed in for an inspection by the Norwegian DMV..

The is plenty of cars in Oz making well over 500rwhp with the 13bT throttle body if you want it stock looking.

Seems like im going with the stock TB (turbo II). And since im not a big fan of all the "extras" on this TB, im wondering about removing the vacuum operated butterflies, and plugging the holes. Anybody done this?

Since im not going to be running cruise control, i also want to remove as much as possible, basically i just want to keep the throttle and linkage to the lower butterflies. And cut the rest.. Ill take some pics and show you what i mean!

BTW, its not going to be a daily driver, more of a trackday car and the occasional cruise, so i dont really care about lumpy idle etc..

thats exactly what im saying.. i have 12A turbo rotors too :)

You want to sell the counterweight then?

everything i have is for sale my friend :)

I tried to clean up my throttlebody a bit too by taking the unnessary gear off it that I wasnt going to use. No vac butterflies either.

Thats exactly what i want to do! Thing is, i already have a TB housing thats powdercoated, but i have to swap some parts over to get it functional.

12AT, is your motor studded/dowelled? One of the others in my garage has built a 600 BHP 12A, and he started cracking the rear plate when he went past 350-400.. Im kinda building my motor like his, and have already went for the Xtreme rotaries stud kit.

Robert, how much, and do you take VISA? :)

The motor was studded, isotropic finished crank, bridgeported etc, etc...

I gave up on trying to have a compromise between street car and race car so I went back to a street port and a T66. The bridgeported motor is in bits in the garage until I can build a car worthy of putting it into.

Well, i finally got around to cleaning up the TB a little. Removed everything i figured i didnt need, except the dashpot. Also threw a TPS on there, not quite finished with the bracket. Also removed the cruise control lever, still have to make some plugs where the vacuum operated butterflies where. Result:

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Oh yea, my airfilter arrived!

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Next up is a new cone for the TB.

your car is definatly top notch for a fast street car!

Thanks Robert.



Anymore progress mortenf??? Seeing your build up inspires me to get motivated on my own project.

Progress.. Well, the guy making the dowels is taking his own sweet time getting done.. Not much right now, ill post some pics when i have some serious progress on the project!