DIY turbo on a 12a
 

Ok so I have decided I would love to take on a prone t of modifieing my 12a N/a engine with a turbo. This is a budget build keep in mind I have 5 kids so money savers is big here. I have a turbo that is to push 16.5 psi off a Turbo Trans Am. I have the the powder coated elbows from the original set up and turbo and turbo I take plate. I am going to buy the weld les and steel for the custome mainifold. My big questions are about the carb on my 12a and anything else you all might contribute to this build in knowledge. Keep in mind it's my first turbo set up. I am a mechanic but havn't self with a lot of turbo chargers, a few here and there. Thank you to everyone for there help in this.

what are the specs on the turbo off the T/A - particularly the turbine size? you need to make sure it's worth trying on rotary.

the truth is you may want to just do what a lot of guys do and set something up with a T2 turbocharger and the Nikki if cost is that big of an issue.

The TII turbo is probably the way you want to go for a budget build. The stock TII exhaust manifold is easy to mod to fit the 12a engine, and you can pick the turbo up cheap, probably less than you can sell the trans am turbo for. The stock nikki actually works pretty damn good with a few mods and bigger jets. The biggest cost is the fuel system and all the random hoses and fittings. I'll try to list all the things you need to do

Tap the front cover for the turbo oil drain. There is a spot near the oil metering pump(remove and block off the OMP, run premix) that's perfect to drill and tap for the fitting. Remove the front cover to do this. Be very careful re-installing, put some heavy grease on the front thrust bearing to keep it in place.

Turbo oil feed line, you can either get a T fitting for the oil pressure sensor and run a -4 line from there, or better is to get an oil filter adapter with an outlet on it.

If you have the beehive oil/water oil cooler, it's not good enough. Get a front mount oil cooler if you want the engine to last more than 20k miles.

Bigger fuel pump, stock GSL-SE is BARELY enough, walboro 255 is better. Pressure regulator to go with it, mallory's are cheap and work good, aeromotive's are nice but $.

Lock the timing advance on the distributor. Cap off the vacuum lines on the advance pots, and remove the springs inside the dizzy for the mechanical advance, don't bother welding the weights, as soon and it spins they'll be locked out anyway.

Modify a stock TII exhaust manifold(grind bolt holes and exhaust ports inward to fit 12a gasket) or make a new one.

Intake manifold, you'll either have to space the turbo away from the manifold, space the manifold away from the block, or use a 12aT intake manifold and modify the flange to fit the nikki carb.

Spark, the stock plugs don't work without better ignition coils. The cheap way is to get NGK B8EG motorcycle plugs, gap them to .010(close gap so it's tight on a razor blade) and get a thinwall plug socket to fit them, or grind down a normal plug socket.

Exhaust, custom downpipe/full exhaust is basically the only option.

Clutch, I like a 6-puck with a sprung hub and a heavy duty pressure plate. You might be able to find a full circle disc that'll hold up and engage a bit smoother.

I HIGHLY recommend getting a wideband O2 sensor to keep you from blowing everything up.

I'm sure I missed a few details, but that's most of it. Check out the first couple pictures in my build thread to see how a cheap turbo setup looks, I have more pics of it on my cardomain page, www.cardomain.com/id/coldy13

If you want to go the TII turbo route, I have some parts I can get rid of CHEAP that'll help you out.

The stock TII turbo will get you very close to 200rwhp on a stockport 12a. The BNR upgrades will get you quite a bit more, but you'll probably want to port the engine at that point, only so much air can go through those little holes. Then you'll need to switch to a TII transmission if you havn't already, you WILL break the stock 12a trans :) Then if you do lots of hard launches the rear end will go next...

Renesis... more N/A power cheaper swaping the engine than turbo. If I wasn't up to my balls in turbo II housings with turbo's sitting everywhere I'd get a nice Renesis.

but if you're dead set on turbo ^^^ its already been said. :P

Word of warning, I've got at least $1500 into my 12a turbo project so far. That's using the stock carb and a TII turbo and doing all the work myself.

There is no really cheap or budget when you say turbo in a 1st gen. Unless your buying one already done.

https://www.rx7club.com/attachment.p...1&d=1365320305

tanks guys I will take all this into consideration I just had the turbo sitting here and was thinking about it so this gives me some great things to think on before I dive in.

http://i996.photobucket.com/albums/a...psb24a9903.jpg

Here is the turbo I was thinking about installing... compressor side is a AiResearch A/R .60 and the exhaust side is an A/R .81 by what I have read about them I should be boosting around 3000rpm with a max of 20psi...

This should be a nice boost to the 12a.

Now I have been noticing that a lot of people are using a waste gate system on the exhaust. Do I need that with this turbo? The reason I ask is because I am going to make my own exhaust manifold, and I just want to make this correct the first time.

You should be able to make a nice little blow through setup with that. Research into your carb hat and exhaust manifold, they will both end up being custom jobs unless you want to shell out too much money.

Ok so on every 12a manifold I have found they have a plate for the turbo and one other pipe coming off... Am I to assume that once I go through the turbine of the turbo it meets back up with this other pipe coming off the manifold and then out to the rear of the car or I am missing something like a waste gate and then to a y pipe and out to the rear of the car?


http://i996.photobucket.com/albums/a...pse2b3266f.jpg

http://i996.photobucket.com/albums/a...ps3f5f4de3.jpg

the third pipe is for an external wastegate. if ur turbo doesnt have an internal wastegate, you NEED an external. end of story lol. no wastegate=no boost control. the downpipe comes out of the back of the turbo. you'll probably want to get a flange to fit that too.

Thanks for the information. I will look into boost control then and see what I can find.

no prob, im here to help lol(to the extent of my abilities)

Got an Intercooler last night looks in good shape and I think it should fit just fine with a little bit of modification to the car to duct it through the right front side...

http://i996.photobucket.com/albums/a...ps544de759.jpg

^^ good find.that would fit real nice in front.

I am in need of a wastegate. Anyone have an extra or usable old one. Please let me know. I am on a small budget due to the fact that I am also into a repaint/dent repair on this carat the moment. The last owner thought he was a Drift King and slide this thing into a fence and ditch. LoL

I'm going to keep an eye on this build. Always been curious about a DIY Turbo set up. Parts are fairly easy to come by, getting good advice is priceless.

Found a 4S engine and trani today with turbo manifold for $400.00 going to pick it up next week. Comes with complete wiring harness and ECU now I just need to find an empty 3rd gen to fit it in... or maybe a high powered FB?

whats a 4s motor? did you mean s4, it would be one helluva downgrade to try to fit in a FD!:scratch:

Well that's why I was thinking of putting it in my FB.

Dave, what's going on with your project? Is it on hold?

Yes at the moment it is. I have a moster celica I am building for a customer and I also purchased my old GSL back and currently stripping it down for the boneyard. So my time is quite full right now. I am hoping here in the next month I can clear some things out and get back to it... I did however find a guy that will build me a custome stainless manifold for my turbo setup once I get to that point.

I guess this thread died, along with none of the pictures work either

Sorry I didn't know the pictures stopped working. I will get some new ones up soon still searching for a good turbo manifold and ordering some goopy seals for the rebuild. And also getting a 74 spec port template made. Lots of things in the works but nothing to show at this time.

I went a different route compared with coldy13b and have a better setup in my somewhat humble opnion. :)

Hmm let's see. First it's a 13B but it has a Nikki on it so it can work as an example. It has an NO J-spec intake manifold intended for a hitachi carb, which I drilled and tapped for the Nikki pattern. The manifold looks a lot like a typical SA manifold, complete with channels of equal size and no it doesn't cover over the ACV port so it's filled in with quicksteel in the engien. Put some freeze plugs in the rotor housings too.

Now to compare advice/setups with coldy13b:

S5 turbo, yep.

Nikki with bigger jets yep, but only to match the bigger venturis I cut. The jets need to keep the engine alive at whatever boost you're running, so get a wideband so you don't go too big or too small. Do the Sterling accel pump mod, choke flapper removal, mechanical secondary mod etc. There is info on the forum for boost prepping Nikkis so I won't go into it here.

I kept the OMP. There is no reason to remove it. It supposedly works up to 10psi. I'm only making 7psi (stock wastegate spring of an S5 or there abouts). Will crank it up to 10psi when I get an intercooler.

I drilled and tapped my front cover before the oil pan went on. I used a nice 5/8" brass nipple NPT fitting (3/8" NPT thread tap) with a 45 degree angle and mated it to the S5 oil drain pipe like stock. It works darn good.

Any reason to pull the front cover to drill etc? No. Not really if it's too much work. Just clean out all the aluminum debris really well. It is light and sticks to oily surfaces. Pro tip: No need to deal with the thrust assembly if you leave the front cover on. Duh.

Oil filter adapter is what I did. The blue anodized RB one they sell for the RX-8 etc. Probably going to switch to the older version later to free up the blue one for another project.

There is not enough volume at the oil pressure sensor hole. My buddy tried it with a Camden and it locked up the bearings. Now I understand a turbo requires less volume but do you want to risk it?

The beehive works ok. I deleted the coolant thermostat though. Did the RB recommended bypass block off and no thermostat. Electric fans too. We'll see.

Don't get a walbro. Been there, done that. It is too much for the mallory 4309 pressure regulator. I swapped to an MSD pump. Much better. Now it goes down to 2.5psi. Perfect. In my opinion nothing else should be used.

I had a semi locked dizzy I got with some parts. It only goes out to 10 degrees. Perfect. Idle is at 0 like it should be. Then in boost it only is at 10 degrees. Best of both worlds. I recommend this and will be doing this on a couple dizzies soon.

Don't cap the vacuum diaphram things. That's stupid to do. What happens when you go up a mountain?

If you semi lock by adding weld to the slot(s), then all the stock springs, weights etc can be retained.

Do direct fire. I'm running DLIDFIS. You can too, or do an MSD 6AL or whatever.

I had to add a 7/16" spacer to my S5 manifold and grind some aluminum off the intake manifold and compressor housing. Your Nikki mani might need similar treatment. I added a set of FD studs to make up for the extra length. Also needed a MOOG idler arm because stock doesn't fit. The MOOG gives tons of room.

Using stock BR8EQ-14 spark plugs and stock Diamond coils with stock J-109s. No need for oddball motorcycle plugs or a thinwall socket. Just stock components in direct fire runs perfectly NA and in boost. Not sure why folks keep trying to reinvent the wheel. Good plug wires help I guess?

He doesn't say anything about exhaust pipe size. Then I will. Go 3"! That is all. Well, one more thing. The DP must be 3" while the rest could be 2.5", but might as well go full 3". Mine has three muffling components and the bass at idle isn't bad. I suppose the RB PR Extreme muffler at 2.75" inlet can work too.

My clutch components are, get this, a 215mm centerforce pressure plate, stock disc and an RB light steel flywheel. I can break them loose in gear on dry road. Plenty clutch capacity for me. Old tires though. I've got a 225mm street strip pressure plate, ACT "modified street disc" and aluminum or a light steel lined up for when/if the current one slips. So far it's holding up fine.

Trans is an S5 NA because it was in the car and healthy/low miles. This NA trans is holding up perfectly so far. Fellow forum user PercentSevenC had a 12A trans that held up to even more power than what I'm pushing through mine. No need for a T2 trans... unless you want to get one and install it.

I dont just highly recommend getting a wideband O2 sensor, I 100% insist you get one. Nothing like driving blind to sober you up.

Oh my engine is ported to 74 spec. That is the same timing as the secondaries of a T2 or FD engine, but on all four of mine. My exhaust ports are GSL-SE timing so not quite as large as T2 spec, but my sleeves are such a size as would not allow you to go all the way out to T2 spec and still retain an anti-reversion lip. Kind of important with a turbo to keep the lip if possible.

Oh I forgot to mention I'm talking about two turbo setups. One is done and running perfectly. The other is getting pieced together now. It's got the beehive and the deleted thermostat with the bypass hole blocked. It's in a baja so cooling back there is important. The other option is to forget the baja and throw it (the turbo) in another FB. Going back and forth on this one due to concerns that the 3 rib bus trans is almost too weak for an NA rotary let alone a turbo, but things like the fuel system were completed just the other day so it's one more thing checked off the list. The nice thing about the mallory fpr is it's compatible with NA and boost. I also used EFI hose (as should you where applicable) because it doesn't go bad (crack, leak) unlike carb rated hose which starts to get hard as soon as it has gas go through it for the first time. Still have to make some carb hats too.

Speaking of which, Robert at rotary shack is on ebay these days and sells aluminum fabbed carb hats for the Nikki with a 2.5" inlet. It's certainly an option for us, and I'd think with ebay's buyer protection, if he doesn't ship, you get your money back. Probably a pretty safe bet to buy through ebay. I'd consider it myself but figured out a way to use a stock blue air cleaner base seal and a 4" round tube to make my own hats out of steel. The first one I made worked fine. 1/4" top and a 2" inlet as 2.5" is kinda big, and it turned out really tall (pretty much wants to hit the hood but just enough gap that it doesn't). My next ones might try for 2.5" and be a bit shorter. We'll see.

Man it took me a long time to get into turbos but I'm glad I finally did. Once you drive a turbo, a good well set up one, anything else is just slow and lame.

wow, Jeff, i guess i've been away longer than i thought. i like this though. :)

Ok that's a lot of information Jeff thanks I will go trough it all before I continue. I am in the middle of restoring a 1972 dodge charger for a customer, so my time is being eaton up in that project but once I get that in primer I will be getting back to my rotary projects. I did make a cap for my carb also. I will get a picture of it up for you to see. Made mine out if steal but I also used a 12a rotor to make the shape templates from cardboard and then cut out the steal. Let me know what you think of it...

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Any plans to go turbo yourself? It's actually pretty easy once you get over the initial learning curve.

I'm convinced the Nikki can do practically anything now. No need to get V8 carbs or italian racing carbs anymore. :D The secret, which is not even a secret, is to make the venturis bigger than stock and do other air/fuel mods (all covered here and there on the forum). The resulting carb is able to handle boost or NA equally well. Seriously. That's one of the points mentioned earlier about how you don't really need to swap in bigger jets unless your wideband tells you to, and then only if you increase the air coming in with the usual mods (bigger venturis, booster supports trimmed and airfoil mod, removed choke flapper, and maybe thinned throttle shafts but I don't do that mod as it's not necessary unless you're looking for extreme max flow).

I can literally take one of my boost prepped Nikkis and run it equally well on an NA setup and then swap it onto a boosted setup. Or use the carb in NA mode to break in a fresh rebuild, then after a few miles, swap in a turbo and a carb hat and not have to change anything in the carb, unless the wideband tells me to. Such convenience.

Heh. :)

Would a charge pipe fit the inlet? If so, maybe you can use it as your carb hat. Does it have a seal against the top of the carb? It needs to seal well there. Maybe cut a slit in a piece of vacuum hose and wrap it around the lip. Superglue the two ends where they butt up. It could work.

anyone hear need a turbo carb hat set for a nikki? also fits holley's iirc. not really trying to sell but im not using it and figured if anyone would be interested they would be in this thread!

if not sorry for going off topic, i was planning on going turbo myself but on US spec 12a's if you push more than 5psi you'll blow the seals out and destroy the engine, just went the porting route. Best of luck with your project!

You know if you rebuild the engine with goopy seals and solid corner seals that won't happen.

uhhhh I dont know if they just explode with over 5 psi haha. I know guys who threw turbos on stock 80k+ mile blocks and still run them today around 10 psi:nod:

Its just like anything else, though. How its built is critical. Safe boost, good fuel, good timing etc.

Ok, then.

I didn't let an artificial road block derail me. I'm running stock wastegate pressure of around 7psi on an engine that has 9.4 compression just like a US-spec 12A, and I've got 2mm apex seals which are supposedly easier to break and "destroy the engine", and they're longer, being a 13B and all, which makes them even more likely to break... but they didn't. Oh yeah, the exhaust port is wider too, letting the seal bow out a bit more, and they didn't "blow out" and "destroy the engine". Hmm...

Jeff your such a smart... You all thought I was going to swear there didn't you?... Such a smart rotary guy. I love your jokes with real information included in them. I am currently searching for a turbo manifold and turbo from a stock 13b turbo II or a newer model such as the S5 almost had one and the guy backed out of the trade at the last moment. Once I get that part I will start porting and building the engine. Until then I am on hold with other projects making the money part of the build needed to finish the build. Budget builds are ok but I have found in the last year of being in here learning and taking notes that money does make these builds a lot easier to complete and I think I will be more satisfied if I wait for the correct parts for my build. DIY doesn't just mean that you build everything from scratch. It's more about taking something everyone else says doesn't belong and make it work anyway. Like a person before me post that it would destroy the engine. HHHMMMM I guess if I had listened to people like this I wouldn't have even lined my car up against most of the cars I destroyed racing them. Come on. I was told I couldn't smoke a eclipse GT what ever killed him with in the first 150 feet. And I was turning out behind him when we started. Oh how about those Civic Si hahaha he got me off the line but I had him after 250 feet. So to you people that say it can't be done unleash physics says otherwise we will continue to do it. I will turbo this 12A and it will not blow up. That's that. With the help of people like Jeff and a few others I will be turbo'd by the end of this summer.

i'll be brief since this is neither the time nor the place to speak with great detail. suffice it to say, yes, do plan to have a turbo rotary project at some point, but right now i have more engines than cars. i'm juggling a whole lot of things at the moment so there's no real rush on it. i have 80% of a pretty pristine REW block and i buy parts when i can, so things are cooking ... just slowly.

I too have more engines than cars. I have an FD shortblock, dissassembled and ready for whatever I want to do to it. But I really like the current R5 13B with the S5 turbo on it. My biggest concern is whether to throw the other S5 turbo in the rotary baja because it has a 3 rib bus trans which are not known for lots of strength. I'd rather not break it with a turbo, you know? But doing a turbo on it is child's play compared with the REPU which needs some kind of power adder, and the Camden is in another vehicle, plus it's not nearly as good of a power adder as the basic simple S5 turbo. The engine bay is very narrow and very short. It also already has a full long primary that actually does enhance low end grunt, which this sorely needed.

I'm thinking if I had not already invested so much time/effort in the REPU and was just starting out with my current list of available parts (Camden, S5 turbo, other) I'd have an easier time deciding to throw the turbo in it, but as it sits, the Camden literally bolts in, in a few minutes (or more like an hour but you get my point). The turbo, on the other hand, would take days and weeks of careful planning, custom tubular exhaust manifold, carb hat fabrication (not gonna buy the rotaryshack one for this) and a complete fuel system redo. Heck I just finished a complete fuel system install in the baja and that was no picnic either. But the baja is done and 100% compatible with a blow through turbo (MSD pump, mallory fpr, 5/16" send and proper 3/8" return all in EFI rated hose as mentioned before). I even have a boost prepped Nikki ready for it. Just need a carb hat is all. But the beautiful part is I can run it NA with a dead gutted turbo housing and an RB spun aluminum air filter assembly for engine break in which I suppose does technically free up the turbo for the REPU. The REPU can't use the stock S5 exhaust manifold due to its narrow frame rails but all that stuff fits perfectly in the baja. Decisions, decisions...

So I just secured $1,000 in a restoration job. Wife is getting some but how about you guys help me spend the rest on my car. LoL. I should probably spend it in a turbo setup. Any ideas as to what I should purchase to get going. Possibly a kit out there?

Good luck finding a kit, im about to go turbo on my fb and am going to have to buy the parts myself and put it all together, I would like to go fuel injected but costs too much for my budget so im going carburated and im a welder so I will be making some of the parts myself

Turbo kits for the 12a are out there, you just have to know where to look :nod:

Your probably right but I havent found any, guess ill jus have to piece it together myself

So I am thinking of going with a 13b turbo manifold. Stainless steel. What size wastegate should I be looking at. Seams to me that everyone is talking about using a 44mm wastegate. But I have no idea as to what this does besides bypassing the turbo to control it. Is that all this part does in the turbo system. And then the blow off valve relieves the pressure on the intake side correct. Sorry for all the questions but I just want to get this right the first time. This will be a lot of money I am dropping into my engine.

I hope I don't get in trouble for this if this thread is already to dead? but if I may ask and put my 2 cents in but couldn't you use an old 83 saab 900 turbo's turbo charger.

I have one sitting around but it needs to be rebuilt with a new wastegate and exhaust side but I could give it up for like $50.

that's if this thread isn't so dead I get in trouble that is xD

If not then I could rebuild it and have a welder buddy of mine make me a manifold to fit the turbo I got.

its like a t13 turbo its very small but can produce quite the punch when I had my old saab running that is xD

can't remember how big the turbine was or how big the waste gate was but max boost on the turbo was maybe 20psi if you could tune it out right on the APC Box and get an Intercooler running.

but it ran stock on 8 psi think I could slap one of those on to it?

also I guess I should say its the same size as a T2 rx7's stock turbo but I would have to compare them side by side and not with just a picture but saab turbos were garret turbos back then and they were good and almost bullet proof unless you abused them I guess. but anyways if anyones interested in that look them up and try to compare them if you want. they look to be about the same. I just remember being told long ago its a T13 garret turbo and it was the biggest they offered at the time on saab cars stock.

It's not dead just slowed down. I just cleaned up a Mitsubishi turbo yesterday to try out on my engine. Going to the metal shop today to get flange plates cut so I can make a new manifold for this turbo to test. I will let you know how it does.

One thing it want to ask if you can make me one of those neat rotor carb attachments would be cool to have

I can but I need to destroy the ild blue one for the carb base. And I could make another one. Let me figure out what I have in one and time also. We can work something out. PM me and we will talk about it more.

ok will do

and if anything dave I have been planning the same thing but need to get me a winter car first so I can tear this 83 mazda down now. been hoping one would show up for some time now though so I can get my hands on a 2nd first gen and just build one up for boost or a bridge port and then get it driving again then just rebuild the other motor for the normal everyday driving on a nice streetport and some exhaust.

but first gens are not just popping up like i'm hoping xD

Update for all of you. I FINALY built a turbo header. Here is what I have...
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That is some thick pipe. Or is it tubing? What are the dimensions? SS? Mild?

Dave, I'd also like to know if you can make a rotor shaped carb hat for me!