1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

DIY turbo on a 12a

Old 04-04-13, 08:10 PM
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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.
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Old 04-06-13, 04:40 AM
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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.
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Old 04-06-13, 02:40 PM
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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...
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Old 04-06-13, 08:58 PM
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Renesis... more N/A power cheaper swaping the engine than turbo. If I wasn't up to my ***** 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
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Old 04-07-13, 12:10 AM
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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.
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Old 04-07-13, 02:40 AM
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There is no really cheap or budget when you say turbo in a 1st gen. Unless your buying one already done.

Attached Thumbnails DIY turbo on a 12a-image.jpg  
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Old 04-10-13, 09:06 AM
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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.
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Old 05-29-13, 10:59 PM
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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.
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Old 05-29-13, 11:04 PM
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KY

Originally Posted by Dave.Martin2008 View Post


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.
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Old 05-29-13, 11:33 PM
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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?




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Old 05-30-13, 02:12 AM
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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.
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Old 05-30-13, 07:08 AM
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Originally Posted by bikeordie092 View Post
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.
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Old 05-31-13, 03:12 AM
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no prob, im here to help lol(to the extent of my abilities)
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Old 06-02-13, 12:43 PM
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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...

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Old 06-02-13, 01:33 PM
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^^ good find.that would fit real nice in front.
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Old 06-08-13, 09:38 AM
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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
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Old 09-05-13, 04:35 PM
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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.
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Old 10-04-13, 12:04 AM
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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?
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Old 10-04-13, 08:31 AM
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Originally Posted by Dave.Martin2008 View Post
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!
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Old 10-04-13, 02:24 PM
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Originally Posted by Shredduuhh View Post

whats a 4s motor? did you mean s4, it would be one helluva downgrade to try to fit in a FD!
Well that's why I was thinking of putting it in my FB.
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Old 10-27-13, 11:14 AM
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Dave, what's going on with your project? Is it on hold?
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Old 10-27-13, 12:01 PM
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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.
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Old 04-30-14, 12:18 PM
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I guess this thread died, along with none of the pictures work either
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Old 04-30-14, 12:49 PM
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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.
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Old 05-01-14, 02:44 AM
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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.
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