82t/a,
I have contemplated adapting a 4 barrel Holley or FAST TBI throttle body system. Seein as you could use the RB Holley carb manifold engine management is where I come to a hitch, since the ecm most come with is meant for small block V8's. I get pretty good power and mpg in my GMC pickup running the factory TBI system and it is basically self contained unit. Is there any viability to this idea perhaps?

Sent using RX7Club for Android.

 

Yeah, that's one of the easiest ways to do it. The only issue you'll have with the holley or any of those other "generic" TBI setups is that they are too big for a stock port 12a. The stock Nikki is something like 320cfm, and I believe a fully built Sterling was like 450cfm. Most of those TBI setups start in the 650-700 range. You would need to choke it down somehow (or port the engine to make use of it...)

Another option would be to do some research to see what cars came with a smaller TBI setup back in the day and adapt that - something closer to the stock Nikki sizing. Basically everything American back in the 80's and early 90's used a TBI setup, I'm sure you could find something to work.

Something else to consider - you would want the TBI to work like a carb in that it has primary and secondary butterflys, and you'd also want to have 4 injectors (someone will argue with me, since SE's only had 2...) and stage them as well. Thankfully staging the injectors isn't too hard since basically all the aftermarket ECU's (and stock FC ecu's if you were thinking of using one of those somehow) support that.

Anyway, just some food for thought

 

I have experience with the GM factory TBI systems and although V6 came with smaller TBI units all are 2bbl downdraft setups so to do that you'd need to work out a dual 2bbl intake or single 2bbl intake, now would a "restrictor plate" be viable to downsize the cfm or couldn't you just downsize the injectors or tune for the larger throttle body, fd/fc guys run some pretty big ones. As for injector staging on the 4bbl aftermarket units I belive they are staged primary secondary like a carb but, I'm not 100% on that. Just a question to end haven't a few tuned 600 Holleys to run on stock port 12a's? (side note my 12a has a large street port with a 465)

Sent using RX7Club for Android.

 

If/When I buy another FB it will have a dash and five letters in the trim designator....my GSL will die with a 12a in her.

 

I'm sure a restrictor plate would be an option. You can probably tune around a lot of issues if you are experienced enough (I am not) but I feel like even if you did tune it to make good power etc the throttle would be absurdly "touchy" since even a slight movement of the throttle would result in a large amount of air suddenly going into the engine.

You're right, there are a bunch of FC/FD guys running some really big TB/injector combos, but honestly I think the focus there is on making big horsepower - not smooth streetable throttle response. Many of the "street tuned" FC/FD's still have the stock TB's, or perhaps a modded version of the stock one. Personally I had a modded TB on my T2 engine for a little bit, and while the throttle response was very quick, it was almost too quick and made the throttle so touchy that it was difficult to drive smoothly...

I can't really comment on a holly 600 on a stock port 12a since I have no experience with them firsthand, but I believe you're right that some people are running them. Again though, I'd question how touchy the throttle is.. Maybe I'm just picky lol

 

I'm in the process of making my 12a EFI, but I got a 12a --> 13BT Intake Manifold adapter & I'm welding on injector bungs on the UIM. It's a boosted setup. Running it with a MegaSquirt.

 

couldn't have stated it better. 12As will always have a place with me. it's funny how I spent so many years trying to get the next 13B only to end up now chasing 12As.

 

Everyone asks me why I haven't swapped out the 12a, and I just like the fact that it's the original motor, and I'd like to retain that. It also just has it's own character. To be honest I will miss my Weber 48 IDA with boost, there's definitely something special about carburetors. Hopefully when my EFI setup is up and running without hiccups, it will be just as rewarding.

 

The 12a is a great engine. Its reliable as hell and while the engine parts are starting to become rare, the carb definately has some old school sex appeal I'm going with an s5 setup in my daily driver, but I'm holding on to my 12a for my other car.

 

While the 12a is a great and reliable motor, the scarcity of housings available for rebuilds has forced me to switch to a 13b. My mechanic used the old 12a irons and 13b housings and S4 rotors. I opted for a carb instead of going EFI at this point because of available funds.
When I have enough saved for another step in my project I'll be going EFI and boosting her also.

 

I'd keep the 12a as long as possible. Nothing like having a simple set up.

 

Maybe slightly crazy.... Well considering the fact that you have a rotary that is already apparent

 

A 12a with a Sterling is all I need to eat Miatas, Porsches, Subarus, and Hondas for breakfast at autocross events. I think I've gotten pretty good at doing more, with less.

Stay with the 12a, for bragging rights if nothing else...




.

 

That was my reasoning exactly Mark, when it comes to HP, it ain't what you got, it's how you use it.

The SA/FB was literally designed around the 12A.

That's what makes the 1st gen RX-7s the very best true sports car out there, Miatas, Vettes and MGBs included.

Put in bigger engines, a heavier chassis, ditch the Nikki for EFI and add too many "luxury" items and the SE happens, followed by the FC.

The death of a truly great sports car.

12A people are an elite club, membership gets harder to obtain every year.

Keep the 12A.

 

My SE isn't as quick as the 81 S model was, both with 4 port 13Bs and the same RB long primary exhaust. Now I have to make more power just to get back to the performance level the 81 did effortlessly. I'm bemused but determined.

Just today I finalized how the fuel lines go to the fpr for an eventual blow through Nikki. Right now it has the big hogged out race prepped Nikki (bigger than a Sterling or Yaw) for NA test purposes, which I also tested in the 81 and was very impressed - not so much in the SE.

At least I'm using a Nikki in this GSL-SE. Kinda makes it worth while. I really don't like EFI.

 

this is true, the Rx3 is simple, and they made a bunch of improvements and got the 1st gen Rx7, and then they did this quantum leap to get the FC, and its a really complex car.

when you're building an FC, you're always looking for some oddball part that is either really expensive new or hard to find.

the 1st gen 12A is just perfect, because its simple, fun and it works...

 

and keeping a carb set-up over EFI means you can still drive it home even on limp mode as it is much easier to troubleshoot. the rest, AAA towing it is.

 

Ive owned my SE since Jan 89. Always thought it was superior to my 12A brethren, but i can see your point as to simplicity. My SE has had flooding issues and idling issues for a LONG time. Dont get me wrong, i love it, but with all the complicated stuff that can go wrong, it takes the right kind of owner that is willing to work around the problems and stick with it.

 

I like carbs too, sound cool look cool. But for an everyday car FI is a no brainer..
The 13b is a better engine for a street car. build or find an early 4 port.