Non Turbo to Turbo (NA-T) FAQ

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Supramania Contributor
Feb 26, 2006
You will notice that I have cleaned it up a bit so there's less scrolling and less reading. I removed the GE electronics part because I figure it's very risky and not worth it for most people who turbo their cars. I'm pretty sure the reason most people look at this FAQ is because they are new/don't know how to do it, so GE electronics is most likely not for them. Here it is.

"7M Swap Info" from
This is my attempt to provide all the info you should need to drop a 7M-GTE into your NA MKIII Supra. Read it all before asking questions, this page should answer most of them.

Toyota was fairly nice when they built the MKIII- there are very few differences between the NA and turbo variants. The differences are (other than the obvious turbo/IC associated parts):

lower compression pistons (NA- 9.2:1 vs. turbo- 8.4:1)
piston oil squirters
oil cooler
transmission (NA- W58 vs. turbo- R154)
clutch setup (flywheel, pressure plate, release setup, slave cylinder, slave cylinder softline), ironically the clutch discs are the same...
differential ratio (NA- 4.30, may be LSD vs. turbo- 3.91 (<'88) or 3.73 ('89+) LSD)
10 blade cooling fan
different tachometer driver board

NOTE: '86.5 cars are considered the SAME as '87 - '88 cars for conversion purposes. My car is an early model year '87, effectively the same as an '86.5 and I had no problems. '89 cars are a problem- '89 was a transitional year. Early '89s have a lot in common with the <'88 cars as far as wiring is concerned, later '89s have more in common with '90+ cars.

Here is a fairly complete list of stuff you will need, approximate prices are included after each item:

7M-GTE long block- intake manifold, exhaust manifold, turbo, sensors, etc.
CPS (cam position sensor, may be included w/long block)
Coil Pack (may be included w/long block)
Engine Wiring Harness- must be from same year as your vehicle (either '87-'88, '89 or '90+) drivetrain doesn't matter
ECU- must be from same year as your vehicle (either '87-'88 or '89+) and same drivetrain (auto or manual)
Accordian Hose (AFM to turbo inlet) your best bet is to pick one up from a toyota dealer.
HAC (High Altitude Compensation) sensor->only needed for '87-'88 models, is inside the ECU on '89+
Downpipe (pipe from turbo elbow to first cat)
Oil Cooler
Oil Cooler piping (or you can use hoses/ss braid)
Intercooler- make sure the piping and the intercooler are from the same year as your car. '88 (and maybe others) is different from other years
Intercooler piping
Oil cooler and Intercooler brackets- there are holes already in the chassis, they bolt right up.
PCV/ISC hard and soft lines- may be included w/long block
Power Steering Reservoir and lines- its different on the 7M-GTE, it mounts near the thermostat
Stock "Blow off valve" (really a bypass valve..) (may be included w/long block)
Throttle linkage (the thing sitting on the cam covers, throttle cable and cruise control actutor connect to it), it's different on the 7M-GTE.
Throttle body connections, JDM TB connections are different (different throttle cable routing). You can either swap just the connections off the TB or the whole TB with a USDM one.

All total you should budget at least $2,000 to cover everything seen above and all the many misc. pieces that you will end up buying along the way.
Here are my recomendations of things to change during your conversion:

Clutch- the stock NA clutch will last about 3 weeks at elevated boost levels (ask me, I know). Your best bet is to replace it while you have it out. Stay away from Centerforce, as I have yet to hear a good thing about them. The RPS stage 3 (turbo carbon claw) didn't work for me either. I have had good results with my Clutch Masters Stage IV, but beware, it has very harsh engagement.

Head Gasket- its quite easy to swap out the head gasket w/the motor out of the car. you might want to think about getting a metal head gasket if you are going for big power, just remember to get the head and block refinished otherwise the metal gasket will not seal.

Timing Belt- this one kind of goes along w/the head gasket, its much easier to do w/the motor out of the car and its required every 60k miles so you might as well save yourself the trouble later.

Seals- you might as well replace the front and rear main seals, cam seals and oil pump shaft seal along with any other gaskets you feel like changing.
Water Pump- while I have yet to hear of a 7M water pump dying, you might as well swap it out.

Now for some notes: the swap is straight forward, pull out the NA engine (I recommend pulling the engine and the trans together, its much easier, unplug the engine wiring harness from the ECU and pull it through the firewall), remove the flywheel/flexplate from the NA engine and install it on the turbo engine (along with the clutch, etc.), swap over the transmission, drop in the turbo engine, remove the NA ECU (its above the glove compartment), put in the turbo ECU, remove NA ignitor, install the turbo ignitor, remove the NA AFM, install the turbo AFM, install the downpipe to the turbo elbow, the down pipe should mate up to the stock NA catalytic converter though i wouldn't recomend using the stock NA exhaust as it is way too restrictive, install the intercooler and oil cooler and respective piping, fire it up!

As far as transmission choices, you can reuse whatever trans your NA had. The W58 (NA 5 speed) will bolt up to the 7M-GTE w/no problems (just use the NA flywheel/clutch assembly). The NA auto trans is basically the same as the turbo auto trans, just some subtle differences in the clutch packs, etc. to hold the extra power. If you do have an auto trans you might want to think about rebuilding it or replacing it w/a 5 speed as it will hold only about 300rwhp. The W58 should hold upwards of 400rwhp and the sky is the limit w/the R154.

If you do decide to switch over to the R154 (from the W58, for auto to manual conversion go here), you will need a few things:
R154 transmission
R154 flywheel
R154 clutch disc
R154 pressure plate
R154 throw out bearing
R154 clutch fork
R154 slave cylinder and soft line
R154 drive shaft (its a bit shorter than the W58 one with different input splines)
R154 engine to transmission support "wings"
R154 flywheel inspection cover
R154 transmission crossmember

the NA tach does not work with the turbo engine->the difference is in the ignition systems (distributor vs. CPS and coil pack). In order to make the NA tach work with the turbo engine you have to change some resistances in the tach PCB itself. I figured out the rewire for the NA tach, see it here.
There are some weird year to year differences in the chassis: <'88 seems to be all the same, '90+ seems to be all the same, '89 is the problem year. From my experience, '89 was a transitional year: the chassis wiring is like the <'88, but they use some newer style plugs here and there AND they use the '89+ ECU. Be careful when you are doing the swap on an '89 or buying parts: treat '89 as its own special year.

"GTE Electronics" by BryzonKriz
1.1 Introduction:
7M-GE to 7M-GE/T with GTE electronics – This is what my project involves. Keeping the GE head and block, I transferred over all of the mechanical and electronic portions of the GTE. End product is basically a GTE with the GE block/head, resulting in higher compression. More customization can be done this way (oil lines, filter, cooler, piping, compression, etc) but involves more fabrication of parts and a much higher price tag. Recommended to users with moderate/high knowledge of 7M engine , slightly higher knowledge of mechanics in general, and a higher knowledge of custom fabrication.

1.2 Gathering Parts
This can either turn out to be one of the most time consuming, or quickest parts of the project. The best is to find a 7M-GTE that’s developing BHG (Blown Head Gasket), or has some sort of damage to the rear end. Either way, don’t start with a car that has 200k miles on it and has failing parts. Each of these options gives you a relatively good engine with minimal damage for a low price. You may think the initial price of buying a parts car is too high, but after tracking down all the parts individually, it adds up. If you can’t find a parts car, look for parts that come from a reputable source. Someone claiming a great CT-26 turbo with fast and furious stickers on E-Bay with a zero feedback rating is probably something you should stay away from. Now is a good time to think about some of the possible goals for the car. 550cc injectors could be bought at this point to save yourself from finding used 440cc stock turbo injectors and so on. Due to the price tag of these aftermarket parts and the current price tag of the project, this might not be realistic. I started out with 440cc / stock AFM / stock intercooler with my project, due to a lack of funds at the time.

1.3 Parts list from the GTE engine
Here is a list of the parts you need to locate off of a 7M-GTE engine. Try and stick to the same year (87-88/89-92) for your parts. Some things such as the wiring harness and ECU need to be the same year/model to work as well. Safest way to avoid complications is just to find the same year parts for the major electronic pieces. Items with a year in front of them indicate these types of parts. 1989 is the year used for example:

· 1989 GTE 5spd ECU
· 1989 GTE 5spd Wiring Harness
· GTE CPS (cam position sensor)
· GTE Coil Pack
· GTE Igniter
· CT-26 Stock Turbo
· CT-26 O2 Housing/elbow
· Downpipe / exhaust system
· Oil Cooler
· Oil Cooler piping
· Intercooler
· Intercooler piping
· GTE Exhaust Manifold
· GTE O2 sensor
· GTE Fuel Pressure Relay
· GTE Boost pressure sensor
· (6) GTE 440cc injectors (1989 7M-GE fuel rail)
· BOV (blow off valve)
· Various Hoses/Clamps
· Oil filter housing
· GTE Tachometer electronics

1.4 Various parts list
After gathering the parts from the GTE engine, there are a few other various parts you should gather to save you complications for the long run. I will go into greater detail later.

· Toyota Thermostat
· W-58(N/A) or R154(Turbo) upgraded clutch
· Aftermarket or Resurfaced Flywheel (W-58 or R154)
· ARP Head Bolts
· Toyota Head Gasket or better
· Toyota intake / exhaust manifold gaskets for the GTE (depending on application)
· Toyota rubber coolant hoses

1.5 7M-GE Engine dismantle
With the parts in hand, you can finally park your Supra to go under the knife. Remove all the electronics on the car that have some sort of connection to the wiring harness. Other electronics already hooked into the body of the car (such as the windshield wiper motor etc) will work regardless. The wiring harness extends over through the firewall on the passengers side of the vehicle. Make sure you disconnect/remove the battery before attempting all of this. Removing the glove box allows easy access to the GE ECU. Remove various intake and exhaust components to view the naked head and block. Remove head for resurfacing and remove transmission for upgrade (R154 turbo transmission) or replacing the GE clutch. The head gasket will not last very long under boost conditions, along with the GE clutch. Learn from my mistakes and replace both during the dismantle process. Personally, if you are aiming under 400-450 RWTQ, the W-58 (N/A) transmission should be fine. Keep all of the bolts and various parts together, as you will never know when you might need them again. Replacing various coolant hoses and replacing the thermostat at the same time would be a wise decision. As always, clean all of the parts thoroughly, such as the radiator. Years of driving accumulates large amounts of dirt, leaves, and other foreign objects on the front of the radiator resulting in cooling problems.

1.6 Head and Block preparations
To start off, i'll give you a brief history of my prior experience with the 7M motor with higher compression under forced induction. With ARP head bolts torqued to 72 foot-pounds, and a brand new OEM Toyota Headgasket (some say redesigned, i would be skeptical about that) I believed the way to prevent headgaskets blowing would be to control detonation. So with enough fuel in hand, I went the route of the stock headgasket. The Head was milled by a local machine shop 6 thousandths of an inch, and the block was cleaned. By that, I mean that I removed all the old gasket material on the block. Within 1000 KM, my headgasket was blown again, with deformation around the intake side of the gasket even worse than prior. With further research, I came to a conclusion that even though I did control detonation, that the way the 7M motor is designed, specifically the different expanding and contracting rates of the aluminum head against the cast iron block, along with the design regarding cooling passages on the OEM headgaskets, that a inferior product such as the OEM headgasket cannot last under these boosted situations. Some have used the OEM headgasket with proper torque with success, but under a high compression application, I would suggest against it.

With my 2nd headgasket blown, and knowing I was just getting started at 300 horsepower, I soon realized that the OEM gasket would not be the way to go. By taking the head into a local machine shop again, this time shaving 5 thousandths of an inch off, the head was ready to be installed. But having some time on my hands, I purchased new valve stem seals, and replaced my old ones accordingly. If your engine has a lot of wear, or if you are slightly smoking oil out of your exhaust, I would suggest to change these as doing it with the head on is much more difficult. I also received a five angle valve job with reground valves at this time, for better airflow. On the 7M motor, they come stock with a somewhat three angle valve job, which is much better than most stock engines. For the average supra owner, if you are tight on cash, I would advise against this modification, unless you can do it yourself or a reputable shop will do this job for cheap.

When going for “more-than-stock” power, there is no substitute for a properly installed Metal Headgasket. A few companies make these gaskets for the 7M, specifically GReddy and HKS. These headgaskets are of a much better design, regarding cooling passages, and come in various thicknesses. Unless you are confident with your judgment, order your headgasket after all of the block and headwork has been done. That way, you can select the right size to normalize or decrease your compression ratio. Remember, the higher the compression ratio, the more prone you are to detonation and pinging when running positive manifold pressure. Don’t expect to run 20psi on N/A compression and dodge extreme detonation.

For the block work, inspect the block for major crevasses in the block, paying close attention to the firerings around the cylinders, and damage around coolant passages. If it looks like the block is in decent shape, you can follow Reg Riemer’s guide to lapping your block at , where you will find a more in depth guide to metal head gaskets, and their installation into the 7M.

1.7 Engine Assembly
Assuming you have gathered all of your necessary parts and did the required work to your engine, you are now ready to start to reassemble your motor. After installing the head, disregard any manuals regarding the 7M-GE motor, especially regarding the electronics. From now on, you will need to refer to 7M-GTE manuals for help. Things that change would be the replacement of the distributor with the cam position sensor, new addition of a coil pack, addition of the igniter, replacement of the 7M-GE AFM with the 7M-GTE AFM (housing and electronics), addition of the fuel pressure relay, and replacement of injectors. Don’t forget as well, you will need to swap over the 7M-GE tach circuit board to the 7M-GTE circuit board. From now on, things are pretty standard and self-explanatory. With your ECU and wiring harness in place, you can plug in various sensors and electronics. When installing new sensors or electronics, such as the igniter, it works best if you place the item close to the stock location on the 7M-GTE, due to the length of wire from the wiring harness. There are a few sensor connectors you can disregard that are on the GTE wiring harness, such as VSV’s on the intake side, and auxiliary fan sensors on the water jacket housing.

Now, depending on which setup route you took, regarding intake manifolds, both turbo and non turbo upper intake manifolds will bolt up to the lower intake manifold. If you choose the turbo intake manifold, it is smart as well to go with the turbo valve covers as well, and the rest is self-explanatory. For the non turbo upper intake manifold, the sensors such as the cold start injector, and ISC valve work on the GTE wiring harness. If you choose this manifold, you will notice that the Y pipe takes up a large portion of room, with no stock mounting points for the coil pack. The coil pack can be mounted sideways, but requires a special mounting bracket to be fabricated, and the coil pack wiring needs to be extended for the connection to the wiring harness. In order to use the stock 7M-GTE spark plug wires, you will need to re-arrange the order of the coil pack so it is backwards from the stock configuration. It will be tight, but stock length spark plug wires will reach. From there, you should have no other things to worry about, and can be reassembled just like you would a normal 7M-GTE.

Some useful posts from other threads/general sources:

CRE said:
Hey, you should add that the GTE's ISCV check valve fits in the GE's plenum. You need to replace the spacer/O-ring with an O-ring that's 2-3mm thick in place of the one on the GTE that's 7mm.

The dimensions of the O-ring are: 35mm OD, 25mm ID, and lets say 3mm thick.

It replaces part #90210-26001 here.

I went through hell trying to find a check valve that would work that wasn't $100... ended up building a ball valve but it was bulky and I don't know how much boost I was leaking before it would close. The GTE's check valve is the best option, IMO.

supraguru05;1031026 said:

my write up not the most clear but it should work

and there was a post about the stater question i am not sure whether there is a difference NA to turbo starter.

i belive i am running a NA starter on a r154 im not sure tho so this a question someone needs to answer i know the flywheel is different r154 to w58 so the starter should be to

also my code 52 has cleared so you can run just one knock sensor splicing the wires together works

viper92086;1031307 said:
i'm going to shed some light on my na-t experience....

1. it is only worth na-t IF you have a low mileage motor (not that JDM crap) and you know its in GREAT condition OR if you just dont care and dont mind blowing the motor.

2. you will need all electronics from a gte if you want it done right, as for the knock sensor you can wire it so it is just using the stock single na one or you can drill into your block and tap for a second one altho this could be dangerous... i took the single knock sensor route

3. Don't expect more than 300rwhp on a na-t with a stock block if you want it reliable. I've been running mine at about 300rwhp 13psi for just over a year.

4. it may be a good idea to go maf-t or pro (i'm maf-t)

5. get the rabidchimp oil line kit, it helps a whole lot

6. get a new clutch

7. watch your oil, i can't stress this enough. You forget to check.. bye bye motor

Here's a list off the top of my head that your going to need:
electronics (harness + ecu)
intercooler and piping
custom oil lines
turbo manifold
downpipe (upgraded 3" w/ elbow is highly recommended)
walboro 255 is highly recommended

i can't think of anything else at the time, but you can use the stock NA intake manifold if you want but your going to have to figure out your bov situation. You SHOULD NOT use a vented BOV with the stock afm setup, it'll be more of a pita than anything. my solution maf-t.

btw there are other ways of doing a na-t setup, but i feel this was the most reliable way even if your running stock boost. (your not going to stay stock boost for long, thats what i told myself and now i'm at 13psi)

Poodles;1044910 said:
As I'm usually not in this section, I missed this.

A few corrections.

-The GE and GTE starters are the same
-The oil squirters as put in for durability reasons to keep piston temps down. With forged pistons more than likely you'll be fine (the Group A racecars ran GE blocks with forged internals, so no oil squirters)

The heads are the same. The blocks are actually the same, but are missing drilled and tapped holes for the turbo lines, knock sensors, and the oil squirters.

The oil pumps are different (GTE is higher flowing)
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