Z31/300zx ECU/MAF to 280ZXT swap guide

[Afshin]

Adapting a 1984 300zx turbo/Z31 MAF and ECU to a 1983 280ZXT harness:

 

Disclaimer: First, electrical shorts can burn out your EFI and/or cause a car fire. I have no interest in anyone doing this and don’t know if it will work for you or not. I have no formal training and am only sharing what I did for myself. There is no guarantee nor should any inference whatsoever be made that anything posted below is correct or safe.

 

Purchased parts: 1984 Z31 turbo ECU, MAF, any 84-89 300zx crank angle sensor/chopper wheel (the wheel has a top and bottom, do not reverse or car won’t idle properly) and MAF and ECU connectors with several inches of wire attached.

Also need wiring diagrams of both cars.

 

Nomenclature:

Mass air flow sensor = MAF

Air flow meter = AFM

Fuel pump relay = FPR

z = from 280ZXT

zx = from Z31 / 300 ZX

Example: zx 30 y/b = # 30 wire/pin which is colored y/b (yellow with black line) on the 300 ZX system

Also, I crimped every cut wire to connectors so I could plug and unplug all the changes.

 

CONNECTING THE MAF:

Cut the wires to the AFM a few inches back from the clip

Take clip and wire from MAF then:

1) Connect MAF Position A/wire 30 y/g to 30 y/b wire from z harness

2) Connect MAF Position B/wire 31 b to 31 y/r wire from z harness

3) Connect MAF Position C/wire black to body ground

4) Connect MAF Position D/wire 26 b to 26 b wire from z harness

5) Connect MAF Position E/wire 27/35 b/w to any ignition activated + powered wire (pin 27 and 35 are + ignition wires on the same circuit, they are b/w (black with white strip) and can be tapped into from either b/w wire going to the 2 V.C.M solenoids that are located under the AFM bracket

6) Connect MAF Position F/wire 12 r/w (for cleaning cycle) to 33 y/l wire from z harness

 

CONNECTING THE Z31 ECU to the Z HARNESS:

There are a few of the ECU connector pins that are different. I got an ECU connector clip from the junkyard and then cut it open and took out three metal pins with several inches of wire to it so I could plug them into the empty connector slots of the z harness.

 

1) Insert new pin into slot 12 of ECU connector then cut wire 33 y/l before it goes into ECU connector and attach to new pin #12. So 12 pin from the Z31 ECU thru wire 33 y/l will be connected to the 12 r/w wire on the MAF (marked as F). Now the ECU will be able to go into auto clean mode and keep the NAF filament clean.

2) Insert new pin into slot 34 of ECU connector then connect it to a new wire going to the + coil terminal

3) Insert new pin into slot 3 of ECU connector then connect to a new wire going to the – terminal of your coil. The car seems to run OK without this step, but I still wired it since it was done on the 300zx. I have a MSD and the car is doing well with it

 

 

CONNECTING THE FPR TO THE Z31 ECU:

This way if the car stalls out, the fuel pump should shut off as it’s supposed to.

Now on the 280zx the FPR is always grounded and does not get turned on until the ECU thru pin 16 l/r (blue wire with red line) sends a + signal. On the 300zx it is reversed, the + is on whenever the ignition is on, and the ECU thru the fuel pump modulator sends the – signal to activate the FPR. Hence, I needed to rewire the + and – signal used to turn the FPR on.

1) Black wire (- source used to turn on relay) wire cut right before FPR, connect to new wire and take to pin 108 on the ECU connector

2) 16 l/r ( + source for turning on relay), wire cut right before the ECU connector end and connected to + ignition source (I tapped into the b/w wire going to my 280zxt fuel pump modulator which sits above the ECU).

 

Now the ECU controls the – power that switches the FPR on thru the ECU pin 108, and the 16 l/r wire is ignition + to the FPR. Now I have no explanation for this part, but according to the book, pin 20 from the Z31 ecu should activate the FPR, which then loops back thru the FPR to pin 108. This did not work for me. However, it worked perfect when I connected the new wire going to pin 108. Again I don’t know why pin 108 is working for this and pin 20 did not, but it sure is working well on my car.

 

Also I disconnected the knock sensor and did not switch any of the injector wire.

 

Lastly, to run the air regulator, it was controlled thru pin 108 on the z set up (which control the FPR in the z31 set up) as opposed to pin 16 on the Z31 set up. So I connected the 16 pin/wire coming out of the ECU connector to the 108 z harness wire (black which goes to the air regulator) and now the Z31 ECU will control the air regulator from ECU pin 16 thru the 108 wire. (While ECU pin 108 now controls the FPR)

 

I hope this helps others map out there own swaps (there are many ways to do this). It would be most useful if others who did this could add in their tips, cautions and related experience reguarding this swap such as Z31 maps/ chip burning, adaptations for 370cc injectors, data on actual HP/torque gain and timing/tuning for the set up…..

[Guest ZmeFly]

Ive been waiting for this Afshin. Thanks a MILLION!

[slownrusty]

Afshin - Beautiful write up!!! I have been waiting for that bro.

 

Did you get my email on the brakes?

 

Now I have my next project lined up.

 

Thanks again - Yasin

[Guest Paul Felker]

cool maybe i will attempt my install after all now, thanks a lot!

[Guest bastaad525]

Any way this can be made a sticky or moved up to the top section or whatever?

[Afshin]

Here are a few pictures

 

MAF wires

 

 

 

 

picture of new pin and wire inserted in the ECU connector

 

 

 

picture of new wire goint to the fuel pump relay

 

[240ZinTN]

Great post Afshin. This will help tremendously on my upcomming conversion. The pics are a nice bonus. Sticky status is a good idea.

[Guest bastaad525]

can someone PLEASE make this sticky? 99% sure I'm gonna need this later and I bet I"m not the only one... a very cheap and effective mod for those on a budget.

 

 

Afshin - damn dude those pics... make me feel good about my wiring Hey Afshin does the MAF's inlet and outlet diameters match the stock AFM's? Looks like your using the stock boots from the ZXT on both ends... that would be a sweet bonus... thought that stuff would all need to be changed out.

[240ZinTN]

Afshin, Is there any chance you could post or Email copies of the Z31 wire diagram and pin codes? I bought a Chilton manual like Sleeper recommended in previous posts on this topic but mine is missing the wire diagrams. I have the diagrams for the 83ZXT and 73 240Z already. Does the year of the Z31 ECU matter? I have no idea what year mine is from since I bought it on Ebay.

[Afshin]

Afshin, Is there any chance you could post or Email copies of the Z31 wire diagram and pin codes? I bought a Chilton manual like Sleeper recommended in previous posts on this topic but mine is missing the wire diagrams. I have the diagrams for the 83ZXT and 73 240Z already. Does the year of the Z31 ECU matter? I have no idea what year mine is from since I bought it on Ebay.

Unfortunately I don't have a scanner to send an electronic copy. Check section 6-75 on the chilton manual. If you can't find a diagram locally drop me a pm with your address and I will send you a photocopy.

 

There is a difference in the year ECU

84-86 are the same

87-89 have the same pins, but I think the 88-89 years use a 16 bit processors (as opposed to 8 on all others) and are digital, which offers higher resolution and more accurate maps. I already had the 84 turbo ECU, but I will switch to an 88-89 turbo ECU whenever I find a cheap one.

 

You should be able to use the guide for the 84 set up for the 87-89 ECU, the only difference that I can see is that on the 87-89 pin 19 (as opposed to 16) controls the air regulator (which most don't use) and pin 16 (as opposed to 15) is for the fuel temp. sensor (which I have not used).

 

Also you have to use the 87-89 O2 sensors for those year ecu's, but I think all those may work with only the main black wire (one of three) hooked up (I'm not sure of that however). The 84-86 work with the 280zx O2 sensor. I remember reading that the 87-89 thread for the 02 sensor may be different, but I don't know if that's the case. Maybe someone else with a 87-89 ECU can chip in and make sure that I'm not missing something.

 

To answer Bastaad's question, yes the inlet and outlet on the MAF are the same as the AFM. And the wiring pictures were from the initial test set up. It's been cleaned up since wise guy

[Guest bastaad525]

Afshin - heheh just jivin dude... trust me my wiring could definately use some cleaning up as well! Well I'm VERY glad to hear that the inlet/outlets are the same... z31 setup just sounding better and better every day. Well... now actually the only thing keeping me from doing it is cost. Unfortunately I'm screwed in one way... I have an '81 setup, which means crank mounted CAS and a fake dizzy. So I gotta get my hands on a '82-83 dizzy first and foremost, which is fine, been meaning to do that anyways, but it's just one thing on my list of things to do. Just makes the whole thing a bit more expensive though and still outta reach for the time being. But now I'm 100% that I want to do this on my car, I think it will run GREAT with this setup.

 

Afshin - one other Q, I've never seen the inside of the later dizzies... how hard to do the chopper wheel swap, and is there some good way to be sure you line the z31 chopper wheel up correctly?

 

Mods - make this sticky already or we're gonna keep bumpin it!!!

[Afshin]

OK I got more info relating to the O2 sensors:

84-85 all models use Zirconia type which is the same as the 280ZXT

86-89 non turbo also use the older zirconia type (same thread as well).

86-89 TURBO models use Titania type which is non-compatible and has a smaller diameter thread

 

Has anyone on the site adapted the Zirconia O2 sensor to the 280zxt flange ? if so how did you do it , and was it difficult ? (weld a new flange....?)

 

It would be easy to use a non turbo 16 bit 88-89 ECU since the sensors are the same, but then the ecu would not retard the timing (under load/boost) like the turbo ecu would. Is it better to use an older ECU with turbo map or 16 bit newer one with a non turbo map ? I don't know.

JWT uses non-turbo 88-89 ECU's , but then they remap them anyways.

 

Also as bastaad pointed out, anyone with a 81 ZXT (crank trigger ignition)set up will need the distributor assembly from an 82-83 year. The chopper wheel from the Z31 just drops in and take 5 minutes to swap. I will take a picture later to show which side is the top of the wheel.

Another point for the 81ZXT harness, you need to add a pin in the ecu connector slot position 114 and hook it up to a constant 12V + source (white wire with black line) so the ecu memory stays on when you shut the car off.

 

A few more notes, for 280zxt with fuel pump modulators, it is now being bypassed, I forgot in the first post to remind you to ground your fuel pump to the chasis. (the relay will control the + line going to the pump).

 

Also, I realized that the Z31 ECU does not control the VCM (which controls the AAC valve) properly, so you should disconnect the VCM modul (the same thing is done with the JWT set ups, car idles fine)

 

Lastly, don't forget to disconnect the battery when doing any of this

[Guest bastaad525]

Another point for the 81ZXT harness, you need to add a pin in the ecu connector slot position 114 and hook it up to a constant 12V + source (white wire with black line) so the ecu memory stays on when you shut the car off.

 

is that only for the 81 harness? Funny enough, I'm actually running an '82 wiring harness and ECU, even though I'm using an '81 dizzy/CAS

[fl327]

for the later type 02 you could always just weld a nut to the dp.

I got a 84 and an 87 turbo ecu, the 87 and up ones are harder to find.

the 87 was complete, except for the diff

Did get more 370s though

[Guest bastaad525]

Question: is it at all possible to adapt the z31 MAF to work with the '81-83 ECCS? I think this alone could be a nice little mod... everyone and their mother always saying how the flapper AFM can't be good for performance/air flow. I know (well, I think I know!) that they work opposite, right? Like one reads from 0-5v and one from 5-0v, right? Couldn't you just... reverse the wires or something?

[Afshin]

As far as I know, the two systems are not compatible and just changing the wiring for the MAF won't work. It's only a few more wires to hook up the Z31 computer anyways, which is much better (I got mu ecu for $34 from the junkyard).

On a side note bastaad, I think if you car is running a 82 ECU, you should be running an 82-83 distributor. I would imagine that the 82 ECU would not get the right signal and/or advance/retard timing appropriately with the crank trigger 81 system.

[Tim240z]

Worthy of STICKY status!! 8)

[Guest bastaad525]

Dude Tim where ya been we been sayin that for weeks!

[fl327]

All the s130zxt ecus interchange pretty freely. To do the z31 on a 81 setup, you have to change it to the CAS in the distributor from 82-3, because as you know, you need to use z31 CAS chopper wheel and the 81 has its CAS external. Ive run 82-3 ecus on the 81 harness, but I noticed that the car will sound like its misfiring when I let off the throttle, and it totally went away with the 81 ecu. The 81 also uses a external resistor pack for the injectors located in a small steel box that comes off the harness on drivers side-I think if it was bypassed that would be the way to swap ecus correctly to later models.

[Tim240z]

Dude Tim where ya been we been sayin that for weeks!

 

Generally don't read the L-6 nonsense

 

Tim