3SGTE: MK2 NA > Turbo Write-Up

[Basement Digital]

This writeup details my experience installing a '93 JDM Turbo 3SGTE into a '91 US NA MR2. There are some differences between model-year engines and cars. Attempt at your own risk!

I'd like to start by saying that I'm a pretty novice mechanic and by no means an electrician. Those of you whom have read my posts know what I'm talking about. I work on vehicles strictly as a hobby and with a bit of time and a lot of tenacity – my work has paid off. Forgive the lamens terminology and please feel free to correct and contribute.

From the moment I purchased my 1991 NA MR2 I knew that it was destined for an engine swap. In fact, I found the stock power plant to be the only disappointing thing about it. So I waited for an excuse to perform an engine swap – which came soon after in the form of a broken timing belt.

Money is a big determining factor for me, so the 2nd gen 3SGTE was the most viable option in terms of affordability/performance ratio. [If you're still considering swap options; trust me on this one!] The only problem was that I could find very little information online for this swap! Most of the write-ups I read seemed to assume that you'd purchased an entire rear clip. While buying a clip may be ideal; it was not feasible for me. I did not have a means of transporting it, storing it, or money to afford it! So I decided to take a leap of faith and purchase the components that I thought were required to complete this conversion - without really knowing what was needed.

Since I needed to do this on a budget, I set out to prove the following [and did]:

• You can perform a NA>JDM Turbo swap for less than the cost of a rear clip.
• The NA fuel pump works fine for the stock boost of a 3SGTE.
• The 3SGTE fuel pump relay/resistor is not required. It adds resistance to the fuel pump at idle (The 5SFE lacks such a feature).
• The NA radiator is fine too.
• The 5SFE 5-speed tranny can handle the added power of the 3SGTE.
• The wiring required to get the new motor running is pretty easy to pull off.
• You do NOT need a 3SGTE body harness (Just re-pin ECU plug “A”!)

Basic items needed for a clip-less swap:

• Engine w/ uncut ENGINE-harness and ECU.
• Intercooler, intercooler fan & appropriate piping.
• Intake & exhaust.
• Turbo or '91 NA automatic ECU plug “A” for adapting body harness to new ECU.
  If using 5SFE tranny:
• 3SGTE flywheel and pressure plate. 5SFE clutch disk (preferably ACT) & axles.
  If using 3SGTE tranny:
• 3SGTE axles and hub assemblies (rear suspension).
• Or - 3SGTE axles w/ adapted CVs for NA hubs.

The first thing I did was drop the engine. This gave me a reason to be in the garage (which I enjoy) and prepare my car for its new motor. If you've ever put a clutch into your MR2, dropping the motor isn't much more difficult.

Keep your BGB handy if you haven't done this before.

Start with a LARGE floor jack and jack the car up as high as it will go from the rear suspension x-member. Once it's in the air put a couple jack stands under the rear jack points. Next unbolt the rear suspension x-member and lower it down with the floor jack. From this point you simply need to unbolt the igniter, coil and other misc items from the rear firewall and unplug the ECU from your trunk. Once you pop the plugs thru the firewall and disconnect your shift linkage, coolant hoses and the like – the motor is ready to drop down with a complete engine wiring harness attached to it (so cool!). Leave the body harness and fuse box in the engine bay, though! There are a couple of wires you'll need to add to the fuse box to get your 3SGTE to work with it – but more on that later.

And so I started doing my shopping for the items mentioned above. I found a great deal on a JDM motor for about $1500 shipped to my dock at work which included the engine, tranny, engine harness, relay box (huge deal for required mod mentioned later) and ECU. It was described as a 91-92 MR2 3SGTE so to this day I'm still not exactly sure which year the motor is from, although the tranny came with an LSD and I hear that's rare for a 91. (EDIT: I've since learned that my motor is a 93). I also sourced the intake, intercooler and exhaust online and stowed them away in my garage.

Given my experience with other vehicles, I was surprised by how many parts are interchangeable. Motor mounts, coolant hoses, shift linkage and throttle cable, for example. This makes the installation simple, really. The wiring is essentially the only thing that stops it from being plug and play.

Next I mated my 5SFE tranny to the 3SGTE with a 5SFE ACT clutch disk in between. This keeps things cheap and simple – and someday when my 5SFE tranny blows up I might have the cash I need for a 3SGTE ACT and custom axles. Although, now that I know a few more MR2 people, it seems as though the 5SFE tranny is used fairly often with other motors – but usually with hybrid gear combinations in that the stock gears are quite short for the 3SGTE's powerband. One benefit is that the 5s tranny is considerably lighter.

Now if you have any experience with so-called JDM “30,000 mile motors”, you know to replace some components prior to stuffing one in your car. I ended up replacing the timing belt (PN:13568-79045), idler bearings (PN: 13505-88383 & 13503-63011), water pump (PN: 16100-79126), thermostat (TRD PN: PTR01-35050-01), plug wires and yes... the oil filter too (PN: 90915-YZZF1). (EDIT: I've since learned that I should have also replaced "The Hose from Hell" aka HFH (PN: 16283-88381) and the HFHOE (PN: 16282-88380)). Follow the BGB and you'll do fine.

EDIT: The rest of this write-up is primarily wiring related. I have a created a supplemental thread located here: http://www.mr2.com/forums/na-5s-fe-3...tml#post499539 detailing some new experience I've had since.

Before you toss the motor in, hop into the engine bay, disconnect your fuse box from the firewall, open it up and flip it upside down. The following wires need to be added per my diagram. If you're lucky you'll have a 3SGTE relay box to pillage. If you're wondering why I didn't just swap the 3SGTE fuse box out with the 5SFE – open the fuse box and you'll see. Adding these wires is MUCH less work. If you trace them you'll see that they're required to get power to the igniter.

NA fusebox bottom:


Turbo fusebox bottom:


Wires to swap comparing the two:


One more thing to address prior to installing the new motor would be the Fuel Pump Relay and Fuel Pump Resistor. I have attached a picture (located at the bottom of this writeup) to help you locate these items.

First off, both the FPRelay and FPResistor are part of the body harness. The interesting thing is that they are attached to the same bracket as the Injector Resistor Pack, which is a part of the engine harness. This means that if you purchase a motor and engine harness, the FPR&FPR will be either missing or have cut wires. In my case it had cut wires so I simply removed the FPR's from the engine bay.

If you're wondering; all the relay does is click the resistor on when the motor is at idle. This allows the fuel pump to take a break, kind of like a thermostat controlled cooling fan. My assumption is that NA's do not have a FPR/FPR setup because their fuel pumps don't work as hard, but that is just speculation.

Ok, now you can hoist the motor in and hook stuff up!



All that's left at this point is the ECU wiring. Have a look at the image below.


As you can see, there are two wiring looms that enter the trunk from the engine bay. The Body Harness loom and the Engine Harness loom. The Body Harness is comprised of ECU Plug A and one side of the EA1 connector. The Engine Harness is comprised of ECU plugs B&C, the starter relay, the intercooler fan controller and the other side of the EA1 connector.

ECU plugs B&C will work with the 3SGTE ECU since they came with your motor. Unfortunately Plug A will not work because the 5SFE ECU is different. This is where the wiring comes into play. You have to hack off Plug A and splice on one that will work. This of course requires that you remove this plug from another vehicle (Plug A from either a turbo MR2 or '91 NA Automatic).

EDIT: hoodain has contributed this source for purchasing this plug & pins, brand new!!!


You may notice that I labeled each wire for clarity. You could easily do this to each side to make the process even more brainless - but honestly it's pretty easy while you have your nose in the service manual (or you could use the diagram I created below).



Most of the wiring from plug A is shared between models.

Pins shared between 91 NA & 93 JDM Turbo:
(Wire colors listed are from the NA body harness side)

• BATT: 12V constant. - White w/ Red
• +B: 12V keyed. - Black w/ Yellow
• +B1: 12V keyed. - Black w/ Yellow
• * FC: Fuel cut (circuit opening relay). - Green w/ Red
• ELS: Engine idle up Diode. - Black
• W: Warning light. (check engine light) - Green w/ White
• SPD: Speed sensor. - Purple w/ White
• PSCT: Power steering. - Blue w/ Yellow
• PS: Power steering. - Black
• A/C: Air conditioning. - Black w/ White

Unused NA pins:
(Tuck these cut wires away and tape over them!)

• VF: This pin is located on the engine harness plug 'B' for turbo models. - Purple w/ Yellow
• ?: Mystery pin. According to my 91 service manual this wire should not exist. I've rewired two 91 NA's to turbo now and found this wire on each car. - Pink w/ Green

Unused turbo pins:
(These are not present on the NA plug and are unessential)

• ABS: Anti-lock brake system.
• STP:
• RLY/FPR: Fuel pump relay.

Different pin:

• STA: Starter. You must run a wire from this pin on the ECU to the the starter relay pin pictured. This is because turbo models utilize plug 'A' and NA's utilize plug 'C'. If you skip this step the car won't start!

* Fuel cut is shared between plug A on US NA's and JDM Turbo's but is located on plug C for US Turbo's. Simply put; don't worry about this if you are going from a US '91 NA to a '93 JDM gen 2 turbo.

One more thing worth mentioning is that I have removed my AC, CC and I don't have ABS or PS – so that simplified things considerably for me.

More information regarding the EA1 connector (not used in my swap):


Contributed by M1ke:
Originally Posted by Jim King
Ok, its the "EA1" connector. Here's what I found in my 93 wiring diagram:
Pin - Color : Desc.
1 - ? : ?
2 - not used
3 - L-O : Engine bay fan sensor
4 - L : Engine bay fan sensor
5 - L-W : Fan warning light (to instrument cluster)
6 - not used
7 - W-B : Ground
8 - R-G : Engine hood switch (for factory alarm)
9 - not used
10 - V : Speed signal (from speedo to ECU on 91-92 car)
11 - L-B : MAP ("boost sensor") to stock boost gauge
12 - L-B : FP diagnostic (to check connector)
13 - not used
14 - not used
15 - G-W : Check Engine Light (to dash)

L = Blue
G = Green
O = Orange
W = White
B = Black
R = Red

So there you have it. I've been driving my MR2 for a few weeks now. It idles great, runs strong and passed DEQ. I'm as happy as a clam.

Good luck!



PS
I cannot take credit for creating this attachment, but it should be helpful for identifying many of the components mentioned in this writeup!

[Maruki-kun]

what? wow. good job.

[PhatBoyMR2]

sticky this?

[ghostrida3]

i thought there would be more responses for this, this is the 1st one to go into details on the wiring which is the toughest part of the swap. great job, ille defintly refer to this when i do my swap.

[goddom]

I think I am going to do a swap and this is gold. Thanks.

[snowghost440]

you just saved my life. im doing a swap for my freind, and this helsp a ton. what would you recommend i do witha cut harness tho? the one he bought said they wouldnt cut it, but once it arived i immediately noticed harness chopped in half.

[no_name]

i'm looking at purchasing a half finished NA - JDM turbo swap for mega cheap - owner started and got lazy with the wiring / had no idea what he was doing - so this is my golden ticket! thanks!

[hmong337]

Originally Posted by PhatBoyMR2

sticky this?

x2


this is great information for swaps.

[Basement Digital]

Originally Posted by snowghost440

you just saved my life. im doing a swap for my freind, and this helsp a ton. what would you recommend i do witha cut harness tho? the one he bought said they wouldnt cut it, but once it arived i immediately noticed harness chopped in half.

Where is it cut?

My swap came with a fuse box attached that had a bunch of hacked wires on it. This freaked me out initially because the description of the motor that I ordered had "uncut harness" in it too. The hacked wires ended up being the body harness from the JDM car, and the fuel pump relay/resistor. Since I wasn't using any of those things, I simply removed them from the motor before proceeding with my swap.

If you're lucky that's what you're noticing on your motor.

[pxiong22]

Do you think this setup would be able to pass CA smog??? I really need to do a swap on my 91 N/A too, it leaking oil like crazy

[Basement Digital]

Originally Posted by pxiong22

Do you think this setup would be able to pass CA smog??? I really need to do a swap on my 91 N/A too, it leaking oil like crazy

Doubtful. JDM motors have no EGR. Also, your SW21 body means there shouldn't be a turbo in the engine bay. I wouldn't be surprized if they knew to look for that. I live in Oregon so I'm not 100% sure - but I have friends that live in So. Cal and register their cars in other states to avoid these ridiculous rules.

In my mind, if your car runs clean; who cares what's under the hood?

Just move to Oregon like the rest of California.

[Hiighboost2]

I havent had a chance to read through everything,
but im having trouble with my wiring because the old owner hacked everything up,
hopfully now i can figure it out with your write up, thanks!!

[Brokenline]

Very cool thread!

[Davis]

That was a good read.

[braydo]

K so i followed your instructions on wiring my swap..
Its in a 91 N/a shell with a 92 3sgte full swap (including tranny.. jdm ecu etc.)
FOr some reason when i hook car up to power with key in off position battery, check engine light, and intercooler fan come on.. when the key is switched to on, all that turns off and radiator fans and normal stuff come on...
Could someone PLEASE help me figure out what is wrong...

[Basement Digital]

Originally Posted by braydo

K so i followed your instructions on wiring my swap..
Its in a 91 N/a shell with a 92 3sgte full swap (including tranny.. jdm ecu etc.)
FOr some reason when i hook car up to power with key in off position battery, check engine light, and intercooler fan come on.. when the key is switched to on, all that turns off and radiator fans and normal stuff come on...
Could someone PLEASE help me figure out what is wrong...

That's odd. Do those indicator lights come on with no key in the ignition? How old is the battery? I would also check your grounds either way. Does the motor turn over?

[braydo]

Originally Posted by Basement Digital

That's odd. Do those indicator lights come on with no key in the ignition? How old is the battery? I would also check your grounds either way. Does the motor turn over?

Yeah they come on with no key in the ignition. What grounds do you reccomend i check? I haven't tried to turn the motor over because of this issue. Didn't want to fry anything.

[M1ke]

has anyone figured out how to hook up those last two white plugs? I think one of them might be the CEL and my trunk/ecu wiring looks just like yours. I'm having boost problems and the car is in safe mode and I cannot read out codes because my CEL and wiring might be suspect.

[M1ke]

found this on "the other boards"

Originally Posted by Justin311

For anybody new to the MR2, there are FOUR main connectors at the ECU. There are (3) that actually go INTO the ECU (1 from the Body Harness, 2 from the motor harness).

The FOURTH plug is what this thread is intended to discuss - it is called "EA1" and connects the body harness DIRECTLY to the motor harness, just below the ECU. I have noticed it is VERY confusing and not talked about much in the forum, EXCEPT when somebody has a swap or wiring problem. From what I can gather, the Toyota BGB does NOT have a diagram for this particular plug. I cannot answer why. People have deciphered the wiring colors and you can find bits and peices througout the forum, but I want to have a centralized knowledge base around this plug and figured I'd just make a thread.

I will start out with the best information I have found on the subject, posted by Jim King:

I assume from his description this is a 93 Turbo, since he has "engine bay fan" listed in there.

I am interested to find diagrams or lists as posted above for the 91-95NA, 91-92T and the GenIII. I have yet to double check my 93bgb but will shortly. Then I will update this first post with the aquired information. So if anybody can add info, such as wiring colors for their particular year and model of car...please do so!!

GenIII EA1:

[Basement Digital]

Originally Posted by braydo

Yeah they come on with no key in the ignition. What grounds do you reccomend i check? I haven't tried to turn the motor over because of this issue. Didn't want to fry anything.

Any updates? I just got back from vacation.

The more I think about it, the more your problem sounds like a bad battery. You might take it in to a battery shop to have it checked out/replaced.