1G 1g Wiring Harness

[SigSauer]

Hey guys, need a little clarification on the 1g harness before I begin my projects.

I have a 91 auto nt and a 90 manual GST. I'm going to first swap the 90 manual trans into the 91. (If my research has been correct this will not require swapping the wiring harness and ECU.) However I do plan on swapping the turbo over to the 91 as well and this will require the 90 wiring harness and ECU.

Can I make this work with what i have without having to purchase a 91-94 harness and ECU? Really not much for a budget, hence why I bought the whole parts car. Thanks for all your help guys.

 

[CrackedDSM]

Turbo and trans don’t care about the harness.


However to use a 90 trans in a non-90 car you need the shifter base, cables and the bracket from a 91-94 car. They’re different on a 90.

 

[19Eclipse90]

In some light, the comment that the turbo and transmission don’t care about the harness may be true. But if you were trying to use the 1990 harness in your 1991 auto non-turbo without swapping anything else, it would matter quite a lot.

I’m still a big advocate of using anything and everything you can from the donor vehicle as it will make the swap so much easier. Could you make the auto harness work? Sure. But it will be more of a struggle, IMO.

Also consider the gauge cluster in order to get the tach working (make sure you keep track of the noise filter) after the harness swap and motor mounts as well. See: Please identify these!

 

[97egl]

As far as the transmission I would attempt to use everything from the 90. Shifter, Cables, and Trans. Make sure the shifter base has the same bolt pattern. I'm pretty sure they are IIRC but if you don't want to drill new holes just check.

You will have to remove the brake pedal bracket and swap it over to the one with the clutch & brake. Also you'll need to drill a hole out for the master cylinder.

As far as an ECU you will have to buy an ECU if you plan to put a turbo on an N/T engine. Even if you swap the entire harness (which I would recommend) you will still need an ECU that can be tuned because the 90 turbo ECU is programed for a car with 7.8:1 compression and the N/T engine has 9:1 compression. You could put the pistons from the 90 in the 91 and this would solve that issue if being as cheap as possible is what you are looking for that is what I would do.

 

[SigSauer]

As far as the transmission I would attempt to use everything from the 90. Shifter, Cables, and Trans. Make sure the shifter base has the same bolt pattern. I'm pretty sure they are IIRC but if you don't want to drill new holes just check.

You will have to remove the brake pedal bracket and swap it over to the one with the clutch & brake. Also you'll need to drill a hole out for the master cylinder.

As far as an ECU you will have to buy an ECU if you plan to put a turbo on an N/T engine. Even if you swap the entire harness (which I would recommend) you will still need an ECU that can be tuned because the 90 turbo ECU is programed for a car with 7.8:1 compression and the N/T engine has 9:1 compression. You could put the pistons from the 90 in the 91 and this would solve that issue if being as cheap as possible is what you are looking for that is what I would do.

Honestly, drilling new holes for the shifter equipment seemed to be the only thing that would hold me back from using the 90 parts, so no big deal. I might just hold off on the turbo swap and rebuild the turbo engine to go with it.

 

[bastarddsm]

As far as the transmission I would attempt to use everything from the 90. Shifter, Cables, and Trans. Make sure the shifter base has the same bolt pattern. I'm pretty sure they are IIRC but if you don't want to drill new holes just check.

You will have to remove the brake pedal bracket and swap it over to the one with the clutch & brake. Also you'll need to drill a hole out for the master cylinder.

As far as an ECU you will have to buy an ECU if you plan to put a turbo on an N/T engine. Even if you swap the entire harness (which I would recommend) you will still need an ECU that can be tuned because the 90 turbo ECU is programed for a car with 7.8:1 compression and the N/T engine has 9:1 compression. You could put the pistons from the 90 in the 91 and this would solve that issue if being as cheap as possible is what you are looking for that is what I would do.

That's not really right. For the most part the ECU and turbo don't really care about the compression. What all that will really care about is the n/t 190cc injectors and maf that will overrun at about 15lbs/min.



Steve is the man when it comes to the 90 stuff. His info is 99.9% rock solid gold. 19Eclipse90 also knows his shit.


I've personally done the n/t auto to m/t turbo swap. Just like the OP, but mine was 91-91. I build these transmissions professionally and deal with 90vs91 stuff a lot.

Please if you do not have have 100% rock solid i've done it info, keep your finger off the keyboard. It makes the signal to noise ratio poor, and the guys that do know don't bother.

For the atx to mtx swap and wiring you will need to connect the starter wires together at the connector for the prndl switch. I'm not 100% if reverse lights are there or at the shifter on an auto. This all assumes you keep the atx engine harness. Also something happens with cruise and it doesn't work anymore IDRC what it was though, IIRC you can do some jumpering or install a clutch switch and hook it up.

OP If you want to convert your n/t harness to a turbo you can. you will need to add a shielded cable for the knock sensor, the injector resistor pack, and the 1 wire for the maf reset, along with swapping to a 8 pin connector there. You will need a turbo ecu, injectors, maf and resistor pack. The pitfalls of this are that the harness will still be an auto harness

Now for the rest of the story, your chassis harness will be different than the 90 mt turbo. Meaning inside the car there is a connector near the ecu that sends stuff to the cluster and pedals. That connector is not the same, and you will need to swap connector bodies and repin. it's not hard, but not fun. And you chassis harness will still be a an ATX harness, I'm not 100% if your dash/chassis has the wire for boost gauge in it, plus it will also not have the clutch switch wires in it for cruise control.
And then you will still need to deal with the 90 specific stuff.

If I were you I'd probably convert your n/t atx harness to a turbo m/t harness, and find a 91+ ecu, and not have to deal with the 90 stuff. If your donor was a 91+ I'd 100% swap the engine harness and repin the chassis harness to match it.

Changing the chassis harness is a BIG BIG job. Like unreal big.

 

[SigSauer]

That's not really right. For the most part the ECU and turbo don't really care about the compression. What all that will really care about is the n/t 190cc injectors and maf that will overrun at about 15lbs/min.



Steve is the man when it comes to the 90 stuff. His info is 99.9% rock solid gold. 19Eclipse90 also knows his shit.


I've personally done the n/t auto to m/t turbo swap. Just like the OP, but mine was 91-91. I build these transmissions professionally and deal with 90vs91 stuff a lot.

Please if you do not have have 100% rock solid i've done it info, keep your finger off the keyboard. It makes the signal to noise ratio poor, and the guys that do know don't bother.

For the atx to mtx swap and wiring you will need to connect the starter wires together at the connector for the prndl switch. I'm not 100% if reverse lights are there or at the shifter on an auto. This all assumes you keep the atx engine harness. Also something happens with cruise and it doesn't work anymore IDRC what it was though, IIRC you can do some jumpering or install a clutch switch and hook it up.

OP If you want to convert your n/t harness to a turbo you can. you will need to add a shielded cable for the knock sensor, the injector resistor pack, and the 1 wire for the maf reset, along with swapping to a 8 pin connector there. You will need a turbo ecu, injectors, maf and resistor pack. The pitfalls of this are that the harness will still be an auto harness

Now for the rest of the story, your chassis harness will be different than the 90 mt turbo. Meaning inside the car there is a connector near the ecu that sends stuff to the cluster and pedals. That connector is not the same, and you will need to swap connector bodies and repin. it's not hard, but not fun. And you chassis harness will still be a an ATX harness, I'm not 100% if your dash/chassis has the wire for boost gauge in it, plus it will also not have the clutch switch wires in it for cruise control.
And then you will still need to deal with the 90 specific stuff.

If I were you I'd probably convert your n/t atx harness to a turbo m/t harness, and find a 91+ ecu, and not have to deal with the 90 stuff. If your donor was a 91+ I'd 100% swap the engine harness and repin the chassis harness to match it.

Changing the chassis harness is a BIG BIG job. Like unreal big.

Appreciate the backup on keeping the thread credible. Time is not something I have an abundance of and I like a driving project, not something that sits layed up for a couple seasons. I'm going to mtx swap first. With that being said, all manual components swap over from the 90 mtx and i will need to connect starter wires, get reverse lights squared away and figure out the clutch switch or jumper to retain cruise for electrical and ideally it is mtx?
This will also buy me time for sourcing parts for the turbo swap in the future While still having a driver.

 

[bastarddsm]

Yes. It's been 20yrs since I did mine so it's a little rusty. You'll have to check the wiring diagrams out in the FSM and see what's the deal, but IIRC theres something in the shifter or tcm that gets unplugged and doesn't let the cruise come on. like a switch to turn cruise off if you bump into neutral or something. the mtx has a switch on the clutch pedal so that if you touch the clutch it turns cruise off and doesn't just rev to moon trying to keep speed.

 

[Spleen8urLSX]

I used my cars non turbo harness and added the missing things as bastard mentioned above, I 100% recommend this route over swapping the whole harness over. Adding the few wires and such can seem intimidating but I assure you isn’t bad, or nearly as bad as switching the whole harness with brittle 30 year old connectors. If you have a little basic wiring know how the stuff you need can be added in a few hours taking your time on a rainy Saturday.

 

[SigSauer]

Yes. It's been 20yrs since I did mine so it's a little rusty. You'll have to check the wiring diagrams out in the FSM and see what's the deal, but IIRC theres something in the shifter or tcm that gets unplugged and doesn't let the cruise come on. like a switch to turn cruise off if you bump into neutral or something. the mtx has a switch on the clutch pedal so that if you touch the clutch it turns cruise off and doesn't just rev to moon trying to keep speed.

Understood, I'm not too worried about that part. I'll find the fix to that to retain cruise control to keep it factory as possible. Appreciate all the help!

I used my cars non turbo harness and added the missing things as bastard mentioned above, I 100% recommend this route over swapping the whole harness over. Adding the few wires and such can seem intimidating but I assure you isn’t bad, or nearly as bad as switching the whole harness with brittle 30 year old connectors. If you have a little basic wiring know how the stuff you need can be added in a few hours taking your time on a rainy Saturday.

Appreciate the input. I'll likely keep the na harness, I take pride in my wiring abilities so I'm sure I will over engineer it .

 

[CrackedDSM]

For the record I’ve actually done the NA to turbo swap, and my current DSM is a weird hybrid of 90 and 91 electronics and wiring. If you have any current questions you want asked now, or want to compare yours vs mine hit me up. Be happy to take pics.

I’m also a huge auto guy, while guys bragged about buying auto transmissions just to melt them down for scrap, I was figuring out wiring and info on them.

Also: spleen is a huge NA-> Turbo resource. He keeps pulling new info to help me out all the time. Good dude there. Same with Steve and 19eclipse90.

 

[SigSauer]

For the record I’ve actually done the NA to turbo swap, and my current DSM is a weird hybrid of 90 and 91 electronics and wiring. If you have any current questions you want asked now, or want to compare yours vs mine hit me up. Be happy to take pics.

I’m also a huge auto guy, while guys bragged about buying auto transmissions just to melt them down for scrap, I was figuring out wiring and info on them.

Also: spleen is a huge NA-> Turbo resource. He keeps pulling new info to help me out all the time. Good dude there. Same with Steve and 19eclipse90.

Thank you so much for the help. I'll be reaching out once I'm on leave in a month and back to wrenching. Just for shits though, does the 90-91 differences have a production beginning and ending dates? Just wondering if I'd get lucky based off the productions date...fat chance I know.