MattG

iTrader: (2)

I am sick to death of carbs, I want nothing to do with them anymore. I can never get them tuned right. One day they are great and the next day they blow *****.

I want to go to TBI!!!

Who all on here has gone to throttle body injection on thier 12a?

Also I know robert at rotaryshack sells them, but who else does?

Discuss


Im off to go work on my pinto

rxtasy3

iTrader: (2)

i've too have been thinking of going to FI, but lack of funds is keeping me from actually doing it. i'm sure megasquirt will run TBI and i would think any of the other stand alone ecu's will run one. i've been looking at the holley projection setups too.

LokiRx7.1

iTrader: (1)

You my friend are in need of a carb rebuild Do it once, and you will find that carb is very simple, and there is a reason for everything. My Carb'd setup is every bit as relaible as a FI setup. You just need to get a feel for it...

85rotarypower

IMO, carbs are great. I was in the same position as you a long time ago, when I was having all kinds of problems with my Nikki on the original 12A, but I finally worked it all out and have found that carbs are actually very easy to work with. FI may be easier to tune, better on gas, and run more reliably, but the initial cost is normally outrageous. This is the main reason I am going with a carb on my streetport 13B. The stock FI system had more bugs in it than my Nikki could ever throw at me.

The 12A never came with a FI type manifold, so your going to have to put something together to work with a TBI setup. The best bet is probably a RB holley manifold with a 4 barrel to TBI 2 barrel adapter and a TBI throttle body and injectors from a small block chevy V8 from the early 90's. The adapter can be found at nearly any performance parts shop. For control, best thing to use would probably be a megasquirt setup with ignition control, use the 2nd gen CAS and DIS coils. You'd also have to set up the gas tank to be used for fuel injection, which means installing special baffles around the pickup tube and also installing an aftermarket fuel pump capable of over 50psi. I can guarantee that there will also be other things to go with this as well.

trochoid

iTrader: (6)

I have been slowly thinking of a configuration for FI on a 12A and my thoughts are leaning towards the wrap around intake for the 2 barrels carbs, replacing the carb with some sort of double opening throttle body. Injectors could mounted on the runners, one in each, and staged like the 86+ 13Bs.

MegaSquirt is developed well enough to handle the electronics, or most any other standalone for that matter. My problem is I am not that familiar with setting one up or what size of TB to use. Once the intake, TB and injectors are set up, along with the fuel system mods for FI, it's just a matter of tuning.

Those that are familiar with piston engine TBs, for sizing and flow characteristics, could chime in with recommendations for the appropriate TB, then it's a matter of making the adapter and setting up the linkage.

The nice thing about developing a setup like this is boost would be a much simpler add on.

So gents, put your heads together, eventually we should be able to come up with a parts list that can be adapted to make this work.

NTRX7

this is the stk setup that just come off my 12at, im now running series 4 13B turbo manifolds.



Paul

rxtasy3

iTrader: (2)

i kinda like this style, and i wouldn't have to get another intake.
http://www.auto-nomics.com/cgi-bin/s...rt=10850-002-D

renns

A couple years back a guy on the Megasquirt list mounted a TBI setup on a 12A. He had it working well as I recall, but lost the car in a fire.

If you guys are going to pursue this further, spend some time at your local auto wreckers. Look under the hood of TBI-equipped cars in your target hp range to get the right size. Also consider the mounting of the TBI. Can it be easily adapted to the stock intake, and still allow room for air breather/hood clearance? An aluminum spacer plate could be used to assist in port-matching the TBI ports to the 12A. Bring an old 12A intake along, and check fitment right at the wreckers.

If you can find one that meets those requirements, grab one and get to work. The TBI setup with its integral injectors and pressure regulator would be a very easy way to efi on your 12a. Remember you will still need to upgrade your fuel system, and purchase a standalone to tune it. The base Megasquirt can handle that easily for a couple hundred dollars. Leave the stock dizzy for ignition until you run out of things to fiddle with on the fuel side.

Hades12

What about something like this? Made for a Weber style intake.

dantheman

iTrader: (4)

I have thought about this a few times. I just dont want to have to take the car down long enough to make a custom harness to control everything. Megasquirt is the easy part if you ask me. Alot of people make ITB setups that would bolt on with ease, just use a weber lower manifold. From there all you need to do is change over your fuel pump to a higher pressure one, pull all your carb stuff, and convert your lines over. install your sensors and start running megasquirt.

The harness wouldn't be hard to make, just time consuming. Also, you might have issues if you still run the AC.

trochoid

iTrader: (6)

I've looked at that, and like it, except the price. Iirc, isn't it in the $750 range by the time you get all of it. I would like to figure out a parts lists where the entire setup, including MS, fuel mods and the TBs w/injectors could be put together for less than 750.

renns

Yeah, that setup is really in a different league than the TBI setup mentioned above, due to high new price, and limited supply on the used market. I think Mike Robert (pmrobert on this forum) runs a similar setup that was a less expensive alternative. Try contacting him for details.

Slammed_GSL

iTrader: (14)

I got a 600cc GSXR throttle bodies on Ebay for $45, 2.0 Megasquirt w/harness, FC coils, CAS and other goodies cost another $500. Got it all waiting for me to make the manifold tubes to fit my TWM dual carb manifold. I'll let you know when I get started in the late summer.

rxtasy3

iTrader: (2)

the 4bbl throttle body looks nice too. but i didn't see any prices on anything.

rotary632

iTrader: (1)

Is this et up for sale?[



QUOTE=NTRX7]this is the stk setup that just come off my 12at, im now running series 4 13B turbo manifolds.



Paul[/QUOTE]

steve84GS TII

I run TBI on my 2.8L V-6 Samurai.
The GM/Rochester stuff is super simple and quite reliable.I dont know how well the ECU would react to running on a rotary,youll likely need to run a 4 cylinder ECU which fires the same sequence.The 4 banger TBI setups were 1 barrel with a single injector,but I understand that the dual injector 2 barrel setups fire simultaneously anyways.So long as the driver will handle 2 injectors,you should be OK.
The TBI unit for a 4.3L S10/CK V-6 outta flow plenty of air for a 12A.Thats right around 500CFM going to all 4 ports full time,and you wont have to worry about low speed bogging since its fuel injection.
TPS,idle control and pressure regulator are all built into the unit.Just add the MAP sensor,ECU and a few other things and your ready.TBI only needs 12-14psi,so fuel delivery is easy enough.
Painless Wiring makes a universal TBI engine harness that makes wiring a breeze.Hell,I originally swapped the TBI V-6 engine into my old GLC when I was 17 with no prior EFI experience.Ran awesome for 10 years...

The toughest part to this swap is going to be finding an ECU that will run a rotary correctly.There may not be a factory ECU that can do it.Being speed density EFI,the computor needs to have maps for everything since it has little real time info to tune from.
Having a chip burnt will probably be required....if thats even possible considering its a completely different engine/configuration than what the EFI is designed for.No doubt a standalone could run it and be perfectly happy,but thats more $$,and a low buck,factory component type TBI swap sounds much more appealing.Someone just needs to do the legwork and experimentation to see what works, and what has to be custom fabbed/programmed.....

HadaGSL-SE

iTrader: (6)

Damnit Steve now Im jealous. You have a beautiful turbo FB (which I soon hopefully will have) and a hopped up samurai (which I really want).

I demand pics.

steve84GS TII

Sure,why not.
Sorry to hi-jack,but its kinda relevent....and yes,there are several RX-7 parts applied to my FrankenZuk....

85rotarypower

Actually, you would have to get another intake, unless your already running something that fits a squarebore holley. The stock nikki is a spreadbore carb, of a sort anyway. There is really nothing else made that will fit the stock manifold. This throttle body is WAY too big for a stock 12A anyway. This would be good for a bridgeport on a 13B, mabey even too much for that. These are probably pretty expensive anyway, more than you would want to spend just to get rid of your carb.

The weber style throttle bodies are big money. I've seen the throttle body with injectors go for $700 alone, not including anything to really make it work. Unless your going for all out power, don't bother with this throttle body.

As for the FI setup from a 12A turbo, don't even bother with it. For the price you would pay to get one, and the amount of hassle it would take to get working, its not worth it.

I feel my original suggestion of a TBI setup from an early 90's chevy V8 is probably the cheapest and easiest way to do it. You can't use the stock computer for it though. You will have to use some sort of aftermarket stand alone unit, and megasquirt is probably the best for this. Oh ya, this is mostly just my opinion, but I'm sure others will agree.

trochoid

iTrader: (6)

Toys and more toys, eh, Steve.

The MS is extremely cheap compared to the other standalones. A prebuilt one with harness can be had for about 500. If you want to build your own, the components are about 1/2 that.

My problem is I am not familiar with the modern FI setups, ( have enough trouble with the 2nd gen somedays) and I don't know what is out there. Did I understand you correctly, that the tbi runs 12-14 psi and not in the range of 40, like the fi 13Bs? I didn't think the injectors would flow at that low of a psi, let alone have any kind of useable spray pattern. I'm also assuming that if boost is added, the fuel pressure needs to be upped by a 1:1 ratio.

steve84GS TII

Yup,the Sammy is my second vehicle,I drive it almost as much as the RX.Its pretty fun to see people look twice when they hear it,and they really stare when I haul my 17' runabout.Most guys at the lake dont think Ill make it out of the water until I lay into the throttle and go flying up the ramp with the boat in tow! I'd dare to say the Sammy is as quick as a stock 1st gen,its only about 2200lbs after all!Those are old pics,shes currently more decked out for trail running,just in time for this years Fordyce run...

Heh,heh....modern EFI!?
J/K....but seriously,TBI is ancient stuff.Its SUPER easy to understand and work on so long as you know whjat each part is....and there aint many of them.
Basically it amounts to an electro-mechanical carburetor, and since most of them are speed density,the wiring and sensor systems are also minimal.
The FC's Bosch EFI is metered type and much more picky/overly complicated.The idle circuit and overall layout of the Rochester TBI makes it about the simplest and easiest EFI one could imagine.

TBI uses showerhead type injectors that lay out a cone of fuel spray on the top of the throttle plate.They dont really need much pressure since the fuel is delivered well before the intake valves,in a heavy spray.
When at idle,the fuel doesnt really atomize at all,it just runs down the walls of the barrel,around the closed throttle plate,and when it is pulled through the tiny gaps around the plate,it gets swept up in the airflow and "kinda" atomized.Under more throttle,the airflow really grabs ahold of the thin fuel "cone" and its immediately picked up and drawn down the intake where it mixes.
The intake manifold is wet style so theres likely always going to be some puddling and fuel out of suspension.But damn if my idle isnt a rock solid 750RPM with nary a missfire, and I still get full power to a 6K redline and an average MPG of 20.

trochoid

iTrader: (6)

Like I said, I don't know much about efi. If it's not carbed, it's 'modern' to me. Sounds like it's time to buy some more books and catch up on the last 30 years.

rxtasy3

iTrader: (2)

i'm already running the RB holley setup on a sp 13b, that's why i said i wouldn't have to get another intake.

85rotarypower

Oh ok. I wasn't sure of that.

Chamele03

talk to this guy,
http://cgi.ebay.com/ebaymotors/MAZDA...QQcmdZViewItem

dont know him just found it and thought of this thread