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N/A to Twin turbo conversion HOW TO

Sun 12 Sep, 2010 8:34 pm

So you want to do the TT conversion? Well, be ready for the long task ahead of you  ;)  Heres a list of stuff you need
A location to work on the car. Inside is recommended
A good set of tools-1/2", 3/8" and 1/4" socket sets. Screwdrivers, pliers, side cutters, multigrips. You get the picture
Various lengths of galv pipe (size to fit over power bars and ring/open end spanners)
Pry bars, levers, pinch bars, crow bars. Whatever you can get your hands on will help a sh*t load. Trust me
A decent trolley jack and atleast 2 axle stands (4 would be nice)
*Optional* A set of ratchet spanners-honestly, you might only use them a few times in the swap, but they make that one stupid bolt a breeze to get off. You can pick up a semi decent set for <$100
Something to cut a hole with-hacksaw blade, cold chisel, angle grinder, reciprocating saw-anything will do

Im sure ive missed a heap of stuff, but thatll do for now. Obviously, the better your tools, the easier the job will be. Until you get under there and look, you wont know what will work for you. Lets get started

Step 1. Find a decent TT wreck. I really wouldnt bother just getting parts from a wrecker, because
a. You will be putting the wreckers children through university with the overly expensive prices they charge
b. You never know what parts you will need during the swap

A good wreck will set you back anywhere from $1500-3500. Dont mess this up-get a bad wreck (damaged drivetrain, shady engine) and your prized posession will turn into an unreliable black hole of money and parts. Better off to pay the extra money now than down the track when it implodes.

Step 2. Start pulling the engine.
-First up, drain the fluids. Coolant, all the drive train oils and engine oil. Its a good chance to change them anyway. Remember to take pics of every hose, plug and anything else you take off. Label your plugs, label the hoses, label your bolts (in boxes or bags). It makes reasembly way easier

-Pull the radiator, and (if its in one piece) set it aside carefully. Youll need it later on

-Remove all IC pipes, and the intake ducting/piping. Use your common sense here. Remember, you are pulling the engine out so only take off the stuff that will be in the way, or is stuck to the car itself. Set aside

-Disconnect shift linkages and unbolt its transmission mounting bracket. Move to the side.

-Disconnect both fuel lines, heater hoses and set to side with shift linkages

-Take a photo of the vacuum solenoids on the firewall, then unbolt them from the firewall and tie to the engine-dont disconnect any vacuum lines, theres no need to

-Disconnect wiring, and pull wiring harness out of the way with your shift linkages etc. Take notice of the extra things the TT harness has plugged into it, like the boost/fuel solenoids, injector resistor, and the things by the fuse box in the engine bay

-Remove any leftover vac lines (clutch/brake booster lines and stuf)

Your engine bay should be looking fairly empty now. Go through and remove your mechanical stuff-
-Remove front half shafts from transmission-No need to remove the knuckle at all. Just pop off your wheel, take off the centre axle nut and unbolt the strut from the knuckle. You should now have enough movement in your knuckle to get the driveshaft out. It might be rusted into the splines of the hub, so just give it a tap with a block of wood/soft hammer. Same deal on both sides.
The left side has the carrier bearing mounted to the block, held on by two 14mm head bolts and the shaft will slide out of the gearbox. I had to disconnect my rear turbo oil feed line and gently move it out of the way a little to get the bearing mount to slide out.
The right side (drivers side) is held into the trans with a circlip. You need to pop this out with a lever. Just lever against your inner CV tulip (not the boot) and the gearbox and the shaft should pop out and slide out. Put them aside- you need them

-Loosen drive belt tensions, and remove alternator. Unbolt A/C pump and PS pump from engine and tie up out of the way. Dont disconnect the piping. Remove belts and set aside

-Remove downpipe-disconnect at turbo precat housings and catalytic converter. Keep any gaskets (unless you intend to replace them)

-Remove transfer case. 5 bolts, and lever it off the transmission. the 5 speed ones not that heavy at all, just be ready for it when it falls off the dowel pins. Slide it off the output shaft spine, swing it down and slide it off the prop shaft.

-Disconnect clutch hydraulic line. I found it easiest to remove the 10mm flare nut from the master cylinder and keep the lines on the engine itself. Remove the master cylinder while you are here and put it somewhere

-Loosen engine mounts and lift out engine. Your front engine mount (the one on the cambelt side) has to come right out (unbolt from engine and chassis and remove whole bracket, not just remove the through bolt). Same deal with the transmission mount- the bolts are accessed through the wheel well (behind the 4 rubber bungs) These mounts must be removed to allow the engine/gearbox to swing out otherwise you dont have enough room

By now, it should be something like this

Mount your chain up on the two lifting hooks provided. No need to remove plenum. FYI, heres Mitsubishis steps on removing the engine incase I missed something

Step 3. Strip everything else you need from the TT wreck-
-Wiring harness. You should have everything disconnected in the engine bay by now, and hopefully you have the harness ready at the firewall grommet to pull through. Jump inside the car, remove the centre console side covers and then the ECU. Unplug the ECU and put it aside. Unplug all wiring on the engine harness up to the grommet. Once you have it all disconnected, pop out the engine harness grommet from the outside (its clipped in with a plastic clip) and slowly feed the harness out of the car (it comes out through the engine bay, dont try pulling it out the inside). Its handy having two people do this, one feeds it out on the inside and one pulls it from the outside, however you can do it alone.
Once out, it will look like this


Put it in a box with the ECU and put them away somewhere carefully.
Now be prepared to get a little rough with the wiring. Particularly if the car has ABS, you will have a fun time trying to maneuverer the wiring out of there with the lines to the ABS modulator being rigth in the way. Just persevere and remember the wirings really not as delicate as it looks. Just dont go overboard with the pulling and it will be fine.

-Clutch booster. You should have the master cylinder unbolted. The booster is removed by removing the 3 nuts shown (red circles) and then the split pin and clevis pin (green arrow)
The clutch booster should now slide out from the firewall. You also need to unbolt the pedal and mount from the vehicle. Stick your head under the dash and have a look. You already took off 3 nuts that held the pedal on, theres on more bolt that bolts it up to the chassis, then the pedal and its mount should slide out. Put them aside
If you have removed your NA master cylinder, you will know by now that the mounting point on the firewall is very different. This picture shows the difference

-Fuel pump-Remember, loosen the feed line from just infront of the tank underneath first, this allows the fuel line to rotate as you remove it from the pump itself

-Diff and prop shaft.
Before you drop out your rear end drivetrain parts, just remove the rest of the exhaust. Honestly its just a PITA if you leave it there. You should be able to find the mounts yourself, and drop it out. Remember your O2 sensor wiring is still inside the cabin so you might want to pop them out so you dont break them. Take it right out of the way somewhere. Dont leave it under the car. Youll thank me for this later  :lol:

The propeller shaft is held onto the diff by a flange and 4 bolts. Put match marks so you know which way it goes. Unbolt flange and remove the 4 nyloc nuts holding the hanger bearings to the chassis. Remove prop shaft, and move it out of the way.

Next up, disconnect the rear half shaft flanges from the companion flanges on the back hubs. Again, 4 nuts and bolts, put match marks on them before you remove them
Put a jack under the diff, and take the pressure off the mounting bolts. Remove bolts shown
ImageOnce bolts are removed, let down the jack and the diff and half shafts should come down as one. You can pull the half shafts out of the diff before you take it out if you want, theyr just clipped into the diff like the front half shafts are. No oil will come out when shafts are removed
If your TT has 4WS, the pump is attatched to the top of the diff. To avoid a mess, remove the bolt holding the pump to the diff, not the fluid lines coming from the pump (they will piss P/S fluid all over the place)

Right so the diffs out, and prop shaft is out. Last but not least, you need the companion flanges, pictured here
Reason being, the TT ones have a much larger PCD to accommodate the larger TT rear half shafts. To get them off, put the hand brake on, and remove the big hub nut (refer to picture). The flange itself is just on splines on the rear hub. A tap with a hammer should see them popping right off.

Oil cooler, I/Cs-pretty straight forward

Front (radiator) and rear (firewall) engine mounts-they are different on the TT. Unsure why, but the NA ones seem to have random chunks of metal welded to them (youll see when you do it). Anyway, keep your TT ones and swap them over because these chunks of metal sit right where your turbos will be

Misc items youll need-clutch/brake booster vac lines, clutch vacuum tank, Evap canister. You might also need the power steering pump (we'll cover this later)

Step 4: Rip into your NA
Once youre done with your TT donor, wheel it out of the workshop, and sweep the floor. Bring in your soon-to-be twin turbo, and get to work. The best thing i did was pull off the front bumper. It just makes it that much easier to lean over the front of the car. Remember, cover your guards or you will ruin the paint work

Once again, pull it all apart and whip the engine out. Same goes with all the drivetrain.

Step 5: Pre-Reinstallation stuff

First thing i did was swap over my harness, while there was no engine in there. Same deal as before, pull it out, feed the new one back in. Plug it all in inside and mount up your TT ECU. Now is a good time to pull apart the ECU and check for leaky caps. You will also have to swap the other thing over from your TT (not sure what its called, its on the passengers side of the centre console, and its a metal box thats plugged into your engine harness. The plugs will be different between the NA and TT one)

Next, youll have to make a hole for the left IC piping to come through. Its right next to the A/C receiver dryer, and its in a prick of a place. Unbolting your A/C line mounting brackets will allow you to swing the hard line out of the way. Your NA will look like this (minus my hacking away
And you want it to look like this (this is the TT)
Im not sure what tools will work for you when you do this. I didnt have a lot of cutting tools, so ended up using a drill, a hacksaw blade and a cold chisel. Others have used dremels, reciprocating saws. Whatever you can get to fit in there, use it.

Nows a good time to mount up your I/C's and oil cooler. Check to ensure your hole is big enough/in the right place. It has to have enough clearance around the metal piping of the IC to clamp a rubber hose to it.

Time to attack that clutch booster  :lol: Remove your NA clutch master, and look at the hole. Now look at your clutch booster mounts. Look again. Throw tools to the ground, and go have a beer...just kidding (sort of). First up, you should know that the TT hole is not concentric with the original NA hole. So best thing to do is pull out your NA pedal, and mount up your TT one (youll only be able to get the one bolt in at the top but it will do) to give you a rough idea where you need to place the hole. Again, use your trusty cutting device and cut out the hole as needed. I used a 3mm drill bit and drilled about 50 holes around the circumference of the hole and knocked it out with a hammer and cold chisel. A big hole saw would be handy here. To get your three mounting holes, put some paint on the studs of the clutch booster, and touch it up against the firewall.

With the clutch vacuum tank, the TT had two metal tabs welded to the subframe for it to mount up to, and my NA didnt. I was thinking about cutting these tabs off and welding them to mine, but decided it wasnt really that necessary so just left it off and plugged the vacuum hose with a bolt.

From 93 and up, the power steering pumps were driven by a serpentine belt, and before 93, a V belt. In other words, if youre swapping a 1st gen motor into a 2nd gen body, chances are your PS pump pullies will be different. I had a look at the pulley and it seems that they are pressed onto the pump shaft itself, so I opted to just swap over the pump.

Get those engine mounts swapped over now, because once the engines in, youll be swearing at them.

Check your A/C compressor mounting bracket. On mine, the bracket was completely different on the TT engine, and my pump would not mount up to it, so i had to swap these over too. Its not too bad to do with the engine in, but check them out anyway. Its the one circled

Step 6: Refitting the TT engine

Cross your fingers and hope like hell you havent forgotten anything. Plop that bad boy into there

Before it gets forgotten, put in all your mount bolts, and tighten them. Refit everything to the engine. This is where your labels and  pictures come in handy. Check your drive belts. Its a good chance to replace them while theyr off. Once you get your shift linkages, vac lines, heater hoses, electrical connections and all that sorted, pop your driveshafts in and reassemble your hubs then put the front wheels back on. Don forget the carrier bearing

Clean up your banjo bolts and hook up your oil cooler. Replace the washers if it looks like theyv been leaking.

Mount up the radiator and connect the upper/lower hoses to the engine BEFORE doing the intercooler pipes.

Sort out the birds nest of I/C piping, and hook it all up. Tighten every hose clamp as you go, dont leave any loose as they will be forgotten in the mess.

Replace your evap cannister with the TT one

Refit your solenoids to the firewall, double check vac hoses are still connected to them

Mount up the injector resistor pack

Double, then triple check everything. Let the front down.

Step 7: Reinstalling drive train
Swap over your companion flanges first. Same deal, take the nut off and tap off the old flange, the TT one should go straight on there with no problem.

Now go ahead and mount up your TT diff. If your one had 4WS and your NA body doesnt, you want to remove the pump from the diff and make up a blanking plate out of something solid (atleast 3mm steel plate). Bolt it into the original mounting hole, and cover it with RTV so it wont leak. Put it on your jack, and get it in there. The mounts are the same for TT and NA. If you can, tie the diff to the jack somehow, to prevent it from slipping. If that diff squashed your hand against a concrete floor, youd have a sore (and flattened) hand.

Pop the half shafts into the diff, bolt them up to the companion flanges.

Mount up your prop shaft. get it bolted up to the diff.

Once this is all done, mount your exhaust back up (from the cat back).

Let the back down, jack the front back up. Mount up the transfer case (slide the prop shaft into it first!). It might take a little bit of wiggling to get it on there. To prevent it from rusting onto the output shaft/mounting dowel pins, smear some grease onto them prior to installing.

Refit your downpipe. If youre reusing exhaust gaskets, use some exhaust sealant. The downpipe will bolt up to the stock NA exhaust from the catalytic converter back. Im not sure how restricting this is compared to the TT exhaust system, you may want to swap them over. Im using the NA at the moment and it seems to be working alright. Push your exhaust wiring back through, secure the grommets. Check the earth strap to the exhaust while youre at it. Mine was broken so I swapped that over from the TT

Drop the front back down, and start refilling your fluids. Bleed your clutch, dont forget the Power steering fluid. Remember to bleed the cooling system properly (fill it up, idle until thermostat opens, continue filling until it stops taking coolant. Use a 50/50 mix of antifreeze/water)

Replace your NA fuel pump with the TT one.

Connect your battery terminals. Hop in, make sure its in neutral and hope like hell you havnt forgotten anything. Turn the key, make sure youve got all the lights on the dash. Crank it over and listen to the sound of 300bhp roar into life  :D

The radiator fan problem
1994+ Gtos used the ECU to switch the radiator fans on/off based on readings from the engine coolant temperature sensor, and older ones used thermo switches mounted in bottom of the radiator to earth the fan control relays.

If you have the 1st gen TT radiator intact, you should use it. This way, the stock control system can be easily transferred to 2nd gen. First of all, your 2nd gen radiator fan connector is only a 4 pin, the 1st gen has 6 pins. The two extra wires (green black and blue black) are the earth wires for the fan control relays (high and low) which run through the two thermo switches.
What we want to do is cut the 6 pin plug and wiring off the 1st gen harness, and join up the four wires (the ones we originally had) to the 2nd gen harness. Then you have to find the earth side of the relay control winding (in the fuse box) and cut the wiring to that, and join them to the two left over wires coming from the six pin plug (green black and blue black).
I havnt actually done this myself yet (i still have to buy a TT radiator) so youre on your own if you do it.  ;) Once I do it, I will post up pictures on what to do.

Alternatively, you can buy an aftermarket fan controller which comes with its own temperature probe and this can be used with the 2nd gen radiator. Probably the easier way to make it work for those of you who are less inclined to attack the wiring harness with side cutters and a soldering iron

SOMETHING MUST BE DONE OR YOUR RADIATOR FANS WILL NOT WORK. Dont just do nothing and assume it will be fine, because the radiator fans just wont go, and you could cook your TT engine  :o

STEP 8-installing stock boost gauge
In a nutshell, pull the whole dash out

and pull out the factory NA combination gauge cluster. Fit the TT one, and plug it in. It will work without any wiring on the standard NA dash harness. I would highly recommend pulling out the dash completely, or you risk breaking/scratching your gauges on various metal tabs. Before you put the dash back together, check you have the backlight illumination and that no bulbs are blown. If you put it back together and have a blown bulb, you will be swearing at it

FAQ (not really an FAQ, just answering the questions I had before I did the swap)
Q.Are the TT diff and tailshaft the same as the NA ones?
A. Nope, they are different and have to be swapped

Q.Is it necessary to swap over the body harness and fuse boxes (the harness which runs down the inside of the drivers side guard), or will the ECM and engine harness swap be sufficient (the harness that goes through the grommet in the firewall)?
A. Just swapping the engine harness and ECU is sufficient. Just take note of the radiator fan problem

Q. Does the dash wiring have to be changed to run the center gauge cluster (with the boost gauge) or is all the wiring present on an NA?
A. No. Dash and body harnesses appear to be the same for NA and TT

Q. Are the 5 speed NA and 5 speed TT shift linkages different? I assume they must also be changed over
A. Yes they are the same

Q.Will the TT clutch booster, master cylinder and pedal bolt straight up to the NA body?
A. Modification to the firewall is needed to mount the booster, pedal and cylinder fit fine

Boy that was a bit of typing. Hope this helps someone. If ive missed something, give us a yell and Ill sort it out  :D Cheers
Last edited by box on Sat 12 Oct, 2019 12:27 pm, edited 1 time in total.
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Re: HOW TO: Twin turbo conversion

Sun 12 Sep, 2010 8:57 pm

... nice write up ;) - sweet work on the car too btw.
Never forget: 2 + 2 = 5 for extremely large values of 2
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Re: N/A to Twin turbo conversion HOW TO

Fri 29 Oct, 2010 12:01 am

Extremely detailed write up, must of read it 3 times now... :lol: :lol: :lol: Thanks..
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Re: N/A to Twin turbo conversion HOW TO

Fri 29 Oct, 2010 8:09 am

Wow impressive work and writeup!! :)
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Re: N/A to Twin turbo conversion HOW TO

Fri 29 Oct, 2010 7:34 pm

cheers guys :D

Will put up a bit of info regarding the radiator fans tomorrow
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Re: N/A to Twin turbo conversion HOW TO

Fri 29 Oct, 2010 9:29 pm

Nice work dude. Excellent write up.
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Re: N/A to Twin turbo conversion HOW TO

Thu 09 Apr, 2015 9:22 pm

Thanks again for taking the time to do this writeup, especially stopping to take pictures which I know is a royal pain in the a**.

The swap would've taken me three times as long without it and I'd probably have wound up missing half a dozen parts.
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Re: N/A to Twin turbo conversion HOW TO

Sat 11 Apr, 2015 9:55 am

Good read.
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Re: N/A to Twin turbo conversion HOW TO

Tue 08 Oct, 2019 10:57 pm

Hey box, do you still have the original photos for this thread?  I wouldn't mind re-uploading them with iforce.  If you CBF you can just send them to me and I can do it.
au naturel.
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Re: N/A to Twin turbo conversion HOW TO

Wed 09 Oct, 2019 1:45 pm

Hmmmmm, I'll have to have a nosey. I guess photobucket holding the others to ransom....
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Re: N/A to Twin turbo conversion HOW TO

Thu 10 Oct, 2019 2:58 pm

yeah it's gone a bit weird.  This is probably the most important thread in the forums in my opinion!
au naturel.

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