I'm certain this has been covered many times - but I can't find the info I need. How do I put fuel injection on a carburated 12A or 13B (four port)?

All the info I keep finding is electronic or programming in nature - mine is mechanical. ie, How do I actual get a fuel injected manifold for a 12A or a 4 port 13B?

All of the megasquirt sites I've found sell parts for the ecu, sensors etc.

Currently have two cars that need help - a stock 85 12A, and a 1980 with a 1976 RX4 13B. The 80 is street ported with RB header/exhaust & Holley intake & carb.

Appreciate any help in pointing me in the right direction.

Henry

 

You need to modify the manifold to accept injectors by adding bungs, and then replace the carb with a throttle body. And obviously, install an EFI fuel pump and lines.

You can then decide to either trigger the 'Squirt from the dizzy or convert to electronic ignition. Triggering from the dizzy is easier, going to electronic gives you computer control over the timing curve and a better set of coils.

 

OK - weld on bunts and a throttle body. Do you know which TBs would fit on the stock manifold? I was hoping maybe an old style GM TB could be made to work. Alternately, how bout the RB 4BBL manifold?

On the old 4port 13B, do you know if the T2 intake fits?

 

There are no throttle bodies that will fit on the stock manifold without modification.

If the RB lower intake will take a Holley style carb, then there are a number of aftermarket throttle bodies which will do the work. Check Edlebrock, etc.

The TII intake will not fit an older 4 port 13B without modification.

 

Aaron,

great information.

As a bit of background, the 80 with the 4 port 13B is my car. The stock 85 12A is a customer car. Low miles (74K) but not run in 10 years. After pickling the engine, it has fair compression. Stock carb, with all of its ancillaries for emissions, is junked up and I simply would prefer to not even have to work on it if a system is around to get FI on this thing. The current owner is the son of the original owner, and has an interest in getting the car back on the road but has a limited budget (who doesn't?).

The RB intake on the 1980 with the 4 port 13B is the Holley setup - and I've looked at FI kits from Holley/Edlebrock etc. & frankly the price is the issue as those things are expensive (at least from my perspective) - hence the interest in the megasquirt ecu. Has anyone stuck GM throttle bodies (the ones that look like a carb but have injectors built in) on the rotaries? If feasible, these have interest as to their affordability - but I don't want to waste my time if this option has been tried/researched and is a dead end.


On a totally different line, I am also evaluating the feasibility of the megasquirt on a turbo 1.8 Miata and a NA 1.6 Miata built for SCCA road racing. currently running an AEM (bought back when I had some money ) but would like to standardize on one platform as I don't have the time or brain power to be conversant with all the ecu's out in the world. With the SCCA current rules, I think a megaquirt is also legal for an ITA Miata. We have several SM's, and are looking at converting one to IT just for grins and giggles.

Lots of things we are looking at (and research is the most affordable thing going right now) but the Megasquirt ecu system is a common thread that ties all of this together.

cheers

Henry Payne
Dread Nought Racing
Pelzer, SC

 

If you really want to take a shortcut, you can use the stock carb as a throttlebody. Just don't run fuel into it and there you go. It isn't optimal but it can work until something better is used.

 

Does it have a TPS?

 

I'm not referring to getting a complete Edlebrock/Holley EFI kit. I've seen those before and they are junk compared to what we normally run on the rotary. But they do sell EFI throttle bodies to fit most aftermarket manifolds that will accept a Holley carb. Or, you can get a suitably large throttle body from the wreckers and make an adapter plate to fit it to whatever manifold you want.

You're talking about using throttle body injection. That's something I've not considered before. I would suspect that having the injectors so far away from the ports would mean a lot of fuel ending up on the manifold runners, causing fuel loading at low RPM.

 

yea, especially when cold, you want to be spraying the fuel as close to the inlet ports as possible, because otherwise you're just wasting it b/c it doesnt vaporize and just runs down the walls. It becomes quite the tuning problem.

Another option would be motorcycle ITB's. I know that the honda CBR600F4i's have the injector bungs mounted in the throttle bodies, and they are essentially tubes with throttles and injector bungs (with a few vac nipples etc), so you can use flexible couplings to mount these to tubes of a similar diameter.

 

TPS is definitely not mandatory. MAPdot will work just fine for most folks.

 

Aaron, depending on where he is (NC I think?) the "distant injector" scheme may or may not work. I'm in S FL and have my injectors in the TB (but not throttle body, Weber Alpha) on a wraparound manifold, 17" from the side housing ports and haven't had much trouble tuning it. The main issue that took some tinkering with was Warm Up Enrichment. I'm absolutely sure that wall wetting was the issue that made it a bit difficult. That and the fact I can get one cold start per day and we get below 50F maybe 14 days out of the year. Moving to E85 now, that should be ... "interesting".

 

You might be able to use the nikki (gutted of course) as a throttle body. I've seen someone do that with a holley carb.

EDIT: whoops, didn't read the posts just above :P

but you could maybe put some kind of tps on it if you really had to

 

http://www.injectionperfection.com.a...nt/view/22/70/

Its a good time to import it too! We are trading at $1AUD=$0.68USD

Thats what I have on my car.

 

If you go the ITB route, make sure to factor in a plenum to your fabrication list. Trust me when I say it makes ITBs much more livable at part throttle.

 

I have one already, and its actually on the car but I also have stacks and foam filter socks. Are you talking plenum above or below the throttle bodies?

 

Both will make a huge difference. The thing is that if you put it below, whats the point of ITBs? It does have to be properly sized though.

 

I have a bud doing a low budget Megasquirt on a 12A in an '82 GSL. To keep the initial costs down, he's using a 2 bbl GM TBI unit and is making an adapter plate to mount that on a stock 12A 4bbl intake. If it works out (no reason it shouldn't), later on he'll upgrade to an IDA TB. The good thing: since it's a mechanical OMP he doesn't have to worry about triggering an electronic OMP, just have to make a cable.

 

Just pick up a 13b out of a 2nd gen or a GSL-SE. Drops right in. 2nd gen requires that you put a 1st gen oil pan and front cover on it for clearance and fitment.

That will cost you at least half of what t would cost to build a Weber IDA stand alone set up.

 

If the OMP actuation becomes too much work, premix has worked very well for my EFI 12A. 1oz/gallon, you're good to go. This also allows you to use synthetic for the main rotating parts/eshaft/oilpan. Al always, YMMV.

-Mike

 

The throttle body is off a 86 T-Bird. The manifold is stock. The adapter is custom built. I will keep you posted as to how it works. It is getting close to being ready to install and wire. This is just a simple start to see if I can make it work. Next will come the custom manifold and multiport injection. Here are some current pictures.

 

No, no, no. The throttle body is off of a ThunderTERD, not a ThunderBIRD.

 

I'm considering the same thing as the O/P. I've 'squirted cars before, and my '79 just so happens to need a carb rebuild anyway. So I could either learn carbs, which I know NOTHING about, or do what I know.

I'm looking for the holley intake manifold right now. It looks like just a standard square bore mount from what I can tell. Holley sells an adapter (part #17-45), that adapts square bore to GM TBI. Complete TBI's sell used for $20-30. Then I just need another MS board and harness. Weld a bung into my exhaust header for an O2. I still haven't looked up what kind of fuel pressure the GM TBI systems run to know if I'll need a pump. Kinda psych'd right now. My goal is to get everything done for the same cost as a Sterling modified carb.

 

Belt, how did that plan turn out? I'm planning to do a TurboII motor swap into my '84 down the road, but I'm curious about removing the carb and converting the 12A to FI (I have MUCH more FI experience than carbureted). If your project worked well, it might be worthwhile for me to convert the 12A to using the Megasquirt and then when I get the TII motor built I (theoretically) won't have to use the FC ECU.

Has anyone else done similar (either using the MS on a 12A or using it in place of the TII ECU)? I'll be doing a thorough search on using the MS with a 13BT when I get home from work.

Sorry for the thread necromancy, though two months isn't as bad as some of the undead threads I've seen here