GDII's 1990 G-Limited

[GDII]

Final fit of the 3D printed bracket I designed and printed by @midnight.3d. Now the OMORI boost gauge pressure sensor has a place to live and it is well fixed in place and a clean tidy look.

Next is to build a wiring harness for the GEN4 3SGTE swap and incorporate this into it. Quite a simple setup but if the car was already turbo it would be even easier. Being NA I am missing a wire so I'll just use another redundant wire to transmit the data from the sensor to the gauge. More on that later once I actually get around to installing the gauge and building the engine harness.

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[GDII]

I guess now is the time to start building the wiring harness for this GEN4 3SGTE. Without this the whole build would be futile.

Here on the floor is the GEN4 3SGTE engine harness I took from the Caldina GTT the engine came in at the bottom and at the top is a GEN2 3SGE engine harness which is the same as the one I have in the MR2 right now. It's missing a few bits but they are not required for the swap.

Going back to 2019 when I had this idea of doing the GEN4 swap I was aware I had to have a wiring harness that was compatible with the engine and car. I know there are a few places around the world that specialise in these sorts of swaps but I'm in New Zealand and we don't have anyone local who does this. So I took it upon myself to learn how to do it myself.

I'd already done a basic swap with a GEN2 3SGTE from a REV1 SW20 GT onto a REV2 SW20 G-Limited but using the MR2 harness back in 2014 for @clanfever. Only around 8 wires to change to make it work.

So I found a *T21* wiring diagram book in Japan and purchased that with help from @coolstylemaster. It covers all aspects of wiring for the ST215, ST210, AT211 and CT216 from 09/97. Using this was good as it expanded from the ST215 ECU only diagram found online. It has all the body harness stuff and the power systems.

I proceeded to figure it out while cross referencing an SW20 harness and the ST215 harness. Then @1996_mr2 wanted to do the same swap but was actually in possession of the parts needed and was further ahead in the build actually having an engine to put into his car. So he trusted me to build one for him and learn. That was successful and after a slight wiring hiccup that wasn't part of the harness merge I did he had a running engine.

Since then I've built 8+ GEN4 3SGTE wiring swaps into various cars for great people like @enuf_psi and helped @frostbite_mr2_build with his 2GR wiring swap. Recently building a harness for @haydoss.nz putting a GEN3 3SGE harness onto his GEN3 3SGE that was running GEN2 3SGE electronics.

Why haven't I done my own one yet? I was never at that point in the build. Thanks to the people who have trusted me to bring their projects to life I am now ready to do my own.

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[GDII]

This is good!! I sent off my CT15b to MR2 downpipe to Cerakote NZ in Tauranga to get it coated with Cerakote V series V168 Cobalt heat cure coating.

It's a dark charcoal with a fine metallic which gives a unique finish that actually closely resembles the coating on the TRD 3SGTE muffler I have.

Sparkles!!

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[GDII]

Time to start removing all the covering off the GEN2 3SGE harness in preparation for stripping out all the unneeded wires and plugs.

45mins later you end up with what is shown in the last photo.

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[GDII]

A before and after of the GEN4 3SGTE engine harness being prepared for the MR2. Typically I wouldn't remove so much of the original tape on the harness merges I do but I have some slightly different ideas in mind for this one.

The next step is to strip the unneeded wires out of it.

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[GDII]

Stripping out all the unneeded wires from the GEN2 3SGE harness in preparation for the merge with the GEN4 3SGTE.

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[GDII]

Inside this blue junction block is engine oil. This block lives inside the car under the glovebox next to the ECU. Why is there engine oil here?

It's because the cam position sensor leaks oil internally due to a bad OEM seal design. The oil leaks from inside the engine, through the inside of the sensor, into the black plug body and through the terminals into the wire sheathing and transmits its way all the way to the end of the wire inside the car. Luckily there is this junction block between the sensor and ECU otherwise you'd have oil inside the ECU which can't be good.

I have resolved this leak on the engine with the @driftmotion1 seal and I will be replacing the wire with a new one. It's a dual core shielded wire too so not the most straightforward swap but nothing I can't handle.

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[GDII]

Going full on OEM replacement for the plugs on the GEN4 3SGTE harness. The old ones are dirty, damaged and old making them brittle.

The only downside here is the plug colours don't match the OEM for all of them. They are white and grey where the OEM are a combination of black, grey, blue and brown. But then new and genuine is better than old, damaged or full on broken.

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[GDII]

Another set of hose clamps. This time for the heater hoses and the filler hose that leads to the radiator or pressure cap.

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[GDII]

I'm replacing the cam and crank position sensor wiring with some tefzel milspec M22759/32 22AWG twin core shielded wire. The cam sensor wire is full of oil from the sensor leak (which won't be leaking anymore) and the crank sensor, mostly because I can so I will.

This wire is significantly thinner than the OEM stuff as it has a more tightly packed copper conductor strand and much thinner harder more resilient insulation vs the OEM PVC.

I have to shorten the wires anyway so I still have to do a bit of work to get the 2 wires reconnected and shield grounded to the correct place.

This wire I got from @mselnz a while back for another project I worked on but also purchased enough for this one as I knew I'd be replacing the old wire due to oil and heat damage.

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[GDII]

I've decided to replace the twin core shielded wire for the crank position sensor even though the majority of it is fine. The new wire slims it down.

The plug end needs replacing anyway.

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[GDII]

I am using Raychem DR25 heat shrink covering over the branches on the GEN4 3SGTE to clean up the OEM harness. I'm not trying to seal the harness, rather improve the finished appearance and reduce the bulk of the old coverings.

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[justsomeguy]

Am a little bit jealous and a very large bit in admiration of your skills and knowledge. Amazing how much work goes into these restorations.

[GDII]

Am a little bit jealous and a very large bit in admiration of your skills and knowledge. Amazing how much work goes into these restorations.

I am learning a lot of this for the first time. There are definitely reasons this is taking years and not months.
I'm happy to share the detailed process. It's good for record keeping and if it helps anyone just a little bit then that's great too.
During this process as I present this project to the world others have reached out and provided suggestions and information to help me. There is no way that I know everything here.

[GDII]

I purchased some Raychem DR25 and SCL heat shrink from MSEL for the GEN4 3SGTE wiring harness build.

The Raychem DR25 which is a heat shrink that remains flexible when recovered and is chemical resistant. It has a 2:1 shrink ratio.

The Raychem SCL is a dual wall (with black sealant/adhesive in the middle) and it recovers down at a 3:1 ratio and goes very stiff. It will be used in short lengths at the ends of the DR25 near each plug.

DR25 sizes i got were 3/16, 1/4, 3/8 and 1/2.
SCL sizes are 1/4 and 3/8.

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