EFI with Megasquirt on my 85 GS 12a
 

Now that I have succusfully installed megasquirt on my Turbo-GXL I feel comfortable enough to try it again. My current problem with my FB is I was a dumb @$$ and sold my racing beat intake and 600cfm holly. My factory 12a engine has a broke apex and I installed my race ported 12a last weekend, I have everything to get this car running again accept the intake and carbs.

I need ideas to get this EFI thing to work on the old 12a. My first thought was to use the 6 port intake that was in my GXL and get an adapter plate to fit it to my 12a that I saw on ebay, but now it's sold... so i need more ideas. Should I just stick a 13b in it?

http://www.chromeaccount.com/rx7/new.JPG

hey Rus, it's Ken, AC's friend, my vote would be picking up a TWM stlye throttle body and a sidedraft wrap around intake ...either that or there are TB's that fit a holley bolt patern that would work on a RB intake. Either way TB inject is the way to go since 12as don't have injector bungs in the irons and you're going to need secondaries for that big port job. Time to spend some money brother!!

I dont know how much time, effort, or money you're looking to put into this, but if it were me, I'd pick up a set of CBR600 f4i (just cause im familiar with them) throttle bodies and make a custom manifold to match. The TB's have injector bungs incorporated into them, and running them with a custom, short-runner manifold would not only look awesome, but im sure would match the quick-reving characteristics of a race-ported 12a, and be more responsive to part-throttle than one large TB.

You can get pieces of steel cut for the engine-end of the manifold, run some thin-walled pre-bent steel tube (of the same OD as the TB's) inside them, and have them all come together up at the top to hose-clamp on to the bottom of the TB's (thats how its done on the bike anyway). Then you'll either need to rent a welder (if you dont have one already) or have someone weld it for you, and machine the engine-side of the manifold plate flat... but now you have a very custom setup that should flow quite a bit.

I have another option, I will try and find my photos

This is a common way a 12AT is done in Australia

http://img65.imageshack.us/img65/2759/13btqk5.th.jpg

You can see there is a ~1" thick bit of aluminium that bolts to the 12A motor, then a 13BT intake bolts straight onto the adaptor which is allready bolted onto the motor.

You can have injectors placed inside the adaptor. The adaptors themselves cost about $130AUD probably only $100USD.

You get progressive throttles, and you can easily use 550cc primary injectors combined with 1600cc indy blue secondary injectors. I'm using siemens 870cc secondaries which are a harder fit however.

My intake has since been cleaned painted, and had the primary injectors installed in the adaptor plate.

ooh, that looks nice! I wasnt thinking along the lines of going turbo, but that is pretty clean. Where did you get the replacement for the stock TB elbow? Is that a one-off special, or something I could pick up somewhere? I don't have access to a welder myself, so i just have to be content with buying some things.

I can get you the sellers details, might be difficult for you to pay however.

It was about the same cost as the adaptor place

ok...i like both of their ideas better than mine... I'll shut-up now... ;)

Oh great u just had to say something about using motor cycle TB with a RX7,i have a set of gsxr1000 TB i am looking at right now :) ,guess i will be spend the next few days seeing if i could get them to work with the electric controlled secondary plates:wallbash:

electric-controlled secondary plates? it'll probably be pretty hard to implement that, are you planning on using a stepper motor to do that with some sort of aftermarket module, or are you converting the whole thing to throttle by wire? Id think it would be easiest just to hook up some sort of mechanism to delay the opening of the secondaries similar to the stock TB.

steper motor for the second plates are already on the tb its oem gsx (2002 i think), primary throttle plates are cable driven,injectors are on the tb also! Now how to control them throttle plate angle to rpm based who know that's what i would have to look in to (big head ache) i really don't think it will happen, just an idea!

Their position is RPM based? Hmm, could you link a picture that shows them? im sure with a little searching you could come up with an frequency (aka RPM, just use the tach-out pin on the MS) to PW converter that you could adjust for full-open at whatever RPM etc.

42 mm bores times 4 168mm total,fd 1 46mm and 2 50mm =146mm total, fc is 46mm times 3 i think 138 total! also older 98-99 gsxr 750 don't have the electric second throttle blade and i believe the bore size is 48 or some thing bigger 2000-2001 tb have cable controlled electric secondary plates 2004 and up are spaced differently, busa tb are even bigger yet (don't know how big) and the old ones dont have the second electric tb plate!tps got cracked some how(opsie)!
http://i58.photobucket.com/albums/g2...4_115733AA.jpg
http://i58.photobucket.com/albums/g2...4_115718AA.jpg
http://i58.photobucket.com/albums/g2...4_115706AA.jpg

Using quad throttles you lose the progressive action of the secondaries and you also loose being able to tune by MAP because there will be no way in hell you will pull decent vacuum with throttles that big.

In Australia we also use 48IDA Manifolds with 45,50, and 55mm twin throttles sitting on top. They make more power than the stock FC setup, and have less of an addition in size than your figures :S Think that tells you that adding the size of the throttles like that doesn't work, you'd need to work out the surface area not just add up the radius's.

Another option is contacting someone like www.xtremerotaries.com they make some very nice gear ($pricey)

yeah, ITB's make it difficult to get any kind of decent MAP signal unless you get vacuum from all 4 throttles, and run that into a small "tank" of sorts.

most bike TB's do have a collected vacuum signal, and I think i've figured out a way to get more progressive throttle opening on the primaries, and delay the opening of the secondaries until about half-throttle, although testing it will have to wait til i get my next car and start setting it up (either an FB, or my "project" car that is waiting for more time and $)

I'm going to think about this for a while. The first bit of money I get i'm taking the GXL to the dyno to get tuned. So i'm in no hurry to get the fb together yet. I do like the RB intake with TBI setup the best so far. remember fellas, megasquirt was created for the budget minded, i'm not looking to spend $1000 or more to get this thing back on the road when I can go the usual route and have it done faster and cheaper. But it will be cool to have an EFI FB with a 12a in it.

Guess u could just use rpm vs tps (alpha-n) instead of rpm vs map (speed density).I think the bikes are set up to use the map only on very small throttle opening then some how switch to tps instead of map.But if the secondary plates were controlled electrically rpm based i think u could work around the weak map signal, some what,only problem there is you could not control each 2nd throttle plate separately they are all hooked together , then i guess u could take the two center secondary blades out so u would be using only two 42 mm tb until engine demands more air flow sorta like the 5 & 6 ports on the na's except electrically controlled for example at 3500 the two otter 2nd tp are open 10% then at 4000 they are open 20% so on and so forth, just like a vacuum secondary holley carb the secondary open slowly with engine air flow demand . lol now just figure out how to make the manifold runner length change with rpm like the 4 rotor Mazda r26b (TIMS) and you are all set. Any ways this would be a big pain to do any way and with no way to control the secondary plates like this (that i know of) is there any way to do this Ken (soft ware wize)? Really i think his best bet would be to adapt a s4-s5 manifold and tb over to the 12a!