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1990 N/A Auto :(

2470 Views 6 Replies 3 Participants Last post by  Jeeves
This was the only supra i could find in great shape over here in vegas. (car hunting here sucks) I originally was searching for a really good honda, maybe a crx si or prelude. Couldnt find any decent ones so found this supra. Its silver and very clean. I feel like making 300hp but dont know how to get there. I am very familiar with hondas and nissans but i never walked into the toyota side. Is there any inexpensive routes to take? Engine swaps seem a bit pricey though. I dont know, gimme some numbers and info. Thanks
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You're best bet to power, would probably be to step up to the 7M-GTE swap. All and all (since you'll need an ECU and such) it will be a tad pricier than my $1100 Gte->Gte swap. The big problem there, however, would be finding you a wiring harness. They are still sold for the post-89 model cars, but you don't want to even guess the price...

N/A's can be made swift, but as with any vehicle, the higher you start from the easier it is to reach that same HP goal. has a great FAQ on N/A options.. I suggest you poke your head in over there.

7m-gte swap seems reasonable. what numbers are we looking at here? i wont be doing the work myself, but i got a mechanic. I have an auto tranny, and i REALLY want to swap to a 5spd, so that's 2 swaps in one, tough job there. I dont know too much into what parts are involved. What other extras would you suggest i get? Where could i find a dependable motor? Sorry for the noob q's. thanks
Your best bet is to check out This Thread. It's been explained better than I could ever do. But for posterity, I'll quote it.

As for the power output:

N/A Specs:
Horsepower: [email protected]
Torque: 188
Weight: 3400-3600
Engine: 7M-GE 2954cc
Transmission: W58
Injector Size: 380cc
Spark Plugs: NGK BCPR5EP-11
Compression: 9.2:1
Cylinder Pressure: 156
Fuel Pressure: 33-40psi

Turbo Specs:
Horsepower: [email protected] (232 89+ models)
Torque: 246 (256 89+ models)
Weight: 3600-3700
Engine: 7M-GTE 2954cc
Transmission: R154
Boost: 6.8psi (Autos run lower boost because the tranny doesn't put as much load on the motor -- more like around 4 - 4.5psi)
Turbo: Toyota CT-26
Spark Plugs: NGK BCPR6EP-N8
Injector Size: 440cc
Compression: 8.4:1
Cylinder Pressure: 142
Fuel Pressure: 33-40psi
Fuel Cutoff: 11.4-13.7psi

Trust me, that extra torque is where the power is at. From what I've seen, you'll be hard pressed to get 300hp out of the N/A motor. It would be much easier to transplant the turbo motor in and do just a few minor mods. To get an idea of how many mods you would have to do to an N/A click here.

jong said:
I've been receiving lots of requests for information regarding this. So, I'm creating this thread to clear up any confusion regarding this type of conversion and to pool information because some threads lack important info. If you have anything to add, please by all means do so, just keep it civil and of pure logical importance. :)

The following is information i gathered before and after doing my 1/2na-t. This is how i did it, the mistakes i made, and better ways to do things. Don't assume this is the "best" way to perform the 1/2na-t, this is simply my experience with it.

First and Foremost, i think its necessary to let people know that this is not an easy project. If may look easy, but don't let the conversion checklist fool you. This could ultimately make or break your car. Half-assing will not be tolerated by your engine. If you are to do this conversion, you must take your time. This sort of thing can't be rushed. You must also have a good undestanding of what you are doing. I would suggest you read "Maximum Boost" by Corky Bell. This book will really help you understand turbochargers. Then i would suggest you rent the book "Vehicle and Engine Technology" by Heinz Heisler. Thats about an $85 book with almost 780 pages. Written by a professor from london, its very very helpful in learning about tuning and engine theory. Just touch a few chapters in that book, he beats a few topics to death. :p Again, i would like to stess the fact that i researched and read for almost a year before doing this conversion to my car. Its important to know what you are doing and that lefty is loosey and righty is tighty.

Another topic that often comes up in discussion is cost. heh, cost... Most supra owners will tell you NEVER EVER add up receipts, well... i did. The 1/2na-t cost me $1239 total. But... I got the following items for free; 440 injectors, fuel regulator, exhaust manifold, HKS downpipe, stock bov, stock tubing. I also got insane deals on a rebuilt ct-26 (175), safc (150), and intercooler (60). Also one thing that i forget to budget for this project is mistakes.. Heh, mistakes cost me at least 50 total. Just for broken bolts, nuts, new gaskets, silicone, hose clamps... over time it all adds up. I would say, a safe budget would be at 1500-1750. Its always better to have too much money for a project than too little. :bigthumb:

Okay, here is the 1/2na-t Parts list that i worked off of. I collaborated this list 4 monthes before i did the project and then modified it after i did it. Its fairly accurate.
The ½ NA-T Conversion
Performed on a 1986.5 mk3 Toyota Supra

Parts Needed From Mk3 Turbo
-CT26 turbocharger
-Stock Piping
-Exhaust manifold
-440 injectors (better get them now)
-Blow off valve w/ tube assembly
-Oil inlet and outlet lines
-Coolant in/out lines

Optional Parts from Mk3 Turbo
-Stock BOV (probably easier to put aftermarket on)

After market necessities
Items marked with * can be optional but just make life easier
-Boost Gauge
-Fuel Pressure Gauge*
-Air/Fuel ratio Gauge
-New free flowing exhaust*
-A’PEXi Super ACF fuel controller (SAFC)(HIGHLY RECOMMENDED)
-2mm Metal head gasket (MHG) Tighten your stock to 72 ft/lb. and you should be good*
-Fuel Pressure regulator of some kind! Generally a rising rate fuel pressure regulator (RRFPR) but I think a mechanical one will work fine but will require careful tuning
-Oil Cooler*
-Aftermarket Downpipe*
-Aftermarket Blow Off Valve (BOV)*
-¾” rubber hoses for oil outlet*
-Turbo NGK Spark Plugs gapped at 29
-MSD ignition Boost Timing Master (BTM), this will eliminate detonation and take the guesswork out of retarding the timing on the car.*

Tips and N/A modifications to ensure the proper operation
-Tighten your AFM so the turbo doesn’t constantly suck it open
-Retard timing 2-5 degrees if no MSD BTM is used
-Re-Route PCV hoses and plug up where they enter the throttle body, if this isn’t done you’re car will smoke like no tomorrow
-For the Oil, take oil from the pressure sender unit, just screw in a T and get your oil feed from there. For the oil drain, you can either; a) remove the block plate for the oil cooler return and use that, which is easier but may not flow as well, or you can b) remove the oil pan (PITA) and insert your own drain fitting
-Start out with a stock boost pressure and get the car running for a while before you crank the boost.
-Cranking the boost is not recommended

Alright, if you have any questions regarding information on this list, it can most likely be found in SF, so just search. If it doesn't appear in the search, ask me, and i'll add it to the list if i think its important. :)

Okay, next i'll include the installation checklist i used during my 1/2na-t. Its not very specific because most of the stuff i had in my head, but it'll get you started in the right direction. :cool:


½ NA-T Conversion Checklist

-Check Compression, using TSRM, if not good... Do NOT proceed

-Remove all NA intake and exhaust manifold, throttle, ect.
-Clean engine
-Remove valve covers
-re-torque HG (get instructions for this)
-Clean throttle, intake Y-pipe, and manifold (carb cleaner, just get carbon out)
-Install RRFPR and injectors (make sure to put the rubber washers on the bottom of the injectors)
-punch hole for oil drain or use existing oil drain (easier and safer to remove oil pan for this)
-Install oil feed T-coupler into oil pressure sender
-install intercooler and oil cooler
-install EGT probe and other probes/gauges
-Gap and install spark plugs (autolites, NGK, but NO BOSCH!!!!!)
-install ex. manifold, turbo, elbow, DP (may need new bolts, nuts, and gaskets)
-install Intake manifold, y-pipe, and throttle
-install hoses, BOV
-Adjust AFM
-Add Octane booster (toluene, xylene, ect)
-Adjust timing
-tune, and get to idle
-check oil pressure for turbo
-grace tuning


The following are mistake i made along the way and how to correct them....

1) Oil feed... i used an oil filter reloation kit to feed oil to my turbo. That proved too much oil too soon, and it forced oil past the seals, into the intake. bad idea. I now have oil coming from a feed installed in the oil pressure sender. much better

2) Oil drain... I punched a hole with a punch into the side of my oil pan then jammed a fitting in there. I'm a little embarrassed by this, because it's probably the dumbest thing i've ever done. Oil leaked everywhere and my GOBS of silicone glue didn't aid the problem at all... I removed the oil pan and now have a nice, clean, secure fitting in there. It doesn't leak a drop.

3) dyno.... this was rushing in its purest form. I completed the 1/2na-t in a week and set a dyno appointment for the end of the week. It sucked. The car ran poorly because i tightened the last bolt 5 minutes for the dyno. A huge manifold leak and throttle blockage caused miserable, embarrassing, and depressing numbers. To fix this... simply take your time.

4) BOV... I vented a stock BOV to open air.. enough said... that caused nice vac leaks and inconsistant boost. To fix this... get an aftermarket or plumb the stocker into the intake.

5) I didn't search... I pestered the heck out of people from SF, over AIM and on the phone. I was a real PITA, asking dumb questions. This made a lot of people uncomfortable with talking to me, and kinda annoyed with me. To fix this problem... just search, read, and learn because that will answer most questions. :)

okay. thats most of my information regarding the 1/2na-t. the rest is up to you, because most of it is just Supra Knowledge and Know-How. ;) If you need pics, search SF, i've posted quite a few. Have fun with this and be careful!

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damn that was a lotta readin. cool you put it up though.

I read it all! didnt take me to long. Just a few more hurdles now, Where is a reputable place to find a motor/swap? i looked at this site and they sell a 7m-gte pretty cheaply, but it doesnt come with the tranny i need, nor the ecu. I think it is also missing some other things? Very informative article however, thanks.
The article pretty much says all the stuff you'll need to do the swap. You'll need an ECU, wiring harness (to match the same year as the ECU), R154 Tranny... etc. Your best bet is to go check some junkyards. If you just need a reputable JDM motor shop, I suggest
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