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Doing a +t conversion on an unopened RB25DE NEO (R34 GT)


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Short answer: Daily driving? No.

Longer answer: It could theoretically be done, but you'd have to get absolutely everything spot on perfect, and anyone who can pull that off has enough self doubt to want to verify the setup works correctly... by tuning it.

A Nistune is what you want. If you cannot afford a Nistune + Tuning time, or a plug in ECU for the Donor ECU you are using (Haltech, Link or similar) then this project is out of reach.

Yes, its a large expense for a DE+T that might make 200kw. This is also still the cheapest option.

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On 16/08/2020 at 12:49 PM, Kinkstaah said:

Correct, this issue happens because

1) The NA Auto ECU cannot accept a Nistune
2) A GTT Auto ECU cannot natively run the Auto gearbox from the NA car, because the NA car has a seperate TCU.

You can wire the the inputs to the NA TCU into the GTT ECU on the correct pins and bypass the NA Auto TCU. Nissan have the wiring diagrams of both units available in the shop manual.

This has only been done successfully a couple of times. It isn't that hard, about ~20 wires. All clearly labelled in the shop manual. People just never tried it, or had need to.

So does this mean a better option for an R34 de+t is to run a stand-alone ecu (power fc, adaptronics, link etc..) or still better to run the gtt auto ecu with nistune?

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A Nistune is kind of a stand alone ECU. You'd want some kind of tunable ECU, it doesnt have to be the bees knees, but you'd need to tune it to do it properly, because a NA+T is _not_ a stock car/tune, and even stock GTT cars get tuned anyway.

Just keep in mind the GTT auto ecu will NOT run a NA auto without wiring the standalone auto ecu that is in the NA cars, directly into the GTT ECU. Which may only work in theory, but the same pins exist in the GTT ECU that are seperated (for some reason? Maybe a good one!) to the GT standalone TCU.

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On 22/09/2021 at 7:29 AM, Kinkstaah said:

A Nistune is kind of a stand alone ECU. You'd want some kind of tunable ECU, it doesnt have to be the bees knees, but you'd need to tune it to do it properly, because a NA+T is _not_ a stock car/tune, and even stock GTT cars get tuned anyway.

Just keep in mind the GTT auto ecu will NOT run a NA auto without wiring the standalone auto ecu that is in the NA cars, directly into the GTT ECU. Which may only work in theory, but the same pins exist in the GTT ECU that are seperated (for some reason? Maybe a good one!) to the GT standalone TCU.

Okay I feel like I’m getting more confused as this goes on haha, so from what you’ve said above: to use the gtt auto ecu you need to wire it into the tcu to control the auto. ORRR you can keep the NA TCU and run a completely different ECU seperate?

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If you have an auto (which most people do when asking this question it seems) you cannot use the GTT ECU to control it plug and play.

You also cannot just leave it as is, and let the TCU control itself. The TCU by default wants to talk to the GT ECU.

If you want to use a GTT ECU *only* you have to wire the TCU into the GTT ECU.

If you want to use a standalone ECU for the engine, you either piggyback that off the GT ECU (gl with that) or have a complete aftermarket TCU to control the gearbox.

Go manual.

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On 22/09/2021 at 12:41 PM, Kinkstaah said:

If you have an auto (which most people do when asking this question it seems) you cannot use the GTT ECU to control it plug and play.

You also cannot just leave it as is, and let the TCU control itself. The TCU by default wants to talk to the GT ECU.

If you want to use a GTT ECU *only* you have to wire the TCU into the GTT ECU.

If you want to use a standalone ECU for the engine, you either piggyback that off the GT ECU (gl with that) or have a complete aftermarket TCU to control the gearbox.

Go manual.

Okay that makes way more sense. Obviously manual swap is the way to go, but for now with the basic power I’m looking for I’d like to retain the auto (grown to enjoy the tiptronic). I’ve already got the GTT auto ecu so will just sort out the wiring side of things.  Thanks for taking the time to reply.

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Keep in mind noone has ever documented actually doing it. But if you have the NA ECU/TCU diagrams and the GTT ecu pinouts you can see that the GTT has extra pins that correspond to the exact pinouts of the NA TCU.

I am ASSUMING you can join/bridge these up. ASSUMING.

At the time I noticed this, I already had an aftermarket engine ECU, and an aftermarket Transmission ECU. I noticed this when I was re-wiring in the aftermarket transmission ECU as I swapped from a GT chassis to a GTT chassis.

I too, wish I knew this information before I bought a haltech, and a $2000 aftermarket auto transmission controller.

If it doesn't work, go manual, the NA box won't live long behind a turbo motor anyway. Even if built. I know that one too, from experience.

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I was always of the same opinion as Kinkstaah that using a GTT auto ECU would be complicated. If you've got the R34 service manual, pages EC11/12 show that GT auto and manual have the same ECU wiring that uses a separate transmission control unit and the GTT auto has the transmission control built in to it. Page AT3 states that plainly. As per the diagrams, wiring for manual GTT ECU is same as GT auto/manual so that's what I used on my auto NA+t. It works fine and just uses the original GT transmission control unit to look after the auto box. As mentioned above, popular opinion is that there could be problems if the transmission circuit inside the GTT auto ECU creates conflict or doesn't talk with the GT transmission control unit still in the car. Pages EC13/14 will show you which pins are different and what they control. On page EC11, pin 79 of a GTT auto ECU (multiplex communication) is shown as only being for TCS/ABS but on page EC12 for non-turbo it also goes to the separate GT TCU. Pages AT8/9 have the transmission circuit diagrams (top right corner on page AT9 shows the connections from separate TCU to ECU). If you're gonna give it a go, those refs might help and if you get it working report back to feed the knowledge base. R34Nur posted a couple of weeks ago and said it worked fine with auto GTT ECU but that does go against popular opinion.

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I think it can certainly be done, and upon reading the manuals you can see how it could very conceivably work as above. The workshop manuals are very direct and easy to interpret, surprisingly so!

I think it becomes hard because people do not read the manuals, do not have the gusto to compare the wiring diagrams and think "Well what if I...." and assume it will plug and play, which it won't.

It may however, be a wire-in job. It probably is, the only thing that throws me (personally) is wondering why Nissan went to the extra work of making two seperate systems in the GTT and GT. There could be some reason, but it may have absolutely no effect.

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  • 2 months later...

It's your idle air control. Both for idle speed control all the time and for fast cold idle via a wax pellet valve that also lives inside. It goes on the back end of the DET plenum. You cannot live without it if you are using a factory ECU. You can live without it if you're using an aftermarket ECU, but you will need to do soomething else for idle control. From a simple 2-wire idle air valve, all the way up to a proper e-throttle.

 

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@Jack_Dubz if you're planning on running Drive by Wire sure launch it. However I suspect you're not so that needs to go into your plenum as that's the idle control valve.

Also I recommend installing OEM coil packs OR Splitfires OR R35 coils, whatever you have there will end up being another topic on SAU asking why your car is misfiring.

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On 07/12/2021 at 11:54 AM, GTSBoy said:

It's your idle air control. Both for idle speed control all the time and for fast cold idle via a wax pellet valve that also lives inside. It goes on the back end of the DET plenum. You cannot live without it if you are using a factory ECU. You can live without it if you're using an aftermarket ECU, but you will need to do soomething else for idle control. From a simple 2-wire idle air valve, all the way up to a proper e-throttle.

 

too fast, too furious

The Price of EVERY Car From 2 Fast 2 Furious! - Ideal

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