So my buddy is offering me his motor out of his 02, with the harness, a turbo kit, and his standalone, which would be swapped into my 96. I've read the megathread a bunch of times now to see how its done, but I've had one question for a while now. I know it would be easier to use the 96 harness and rewire the coils, but because he's also offering me his ecu if I went that route I obviously wouldn't be able to use it. So I guess I'm wondering if its viable to use the vvt harness for this project, or if would have to go and get a new ecu

 

Many other things will be difficult, including the dash cluster and pretty much everything else the harness plugs into.

 

You want to keep your ‘96 chassis harness and get an ECU for it. I’ve done a **** ton of wiring on Miata’s from 90-05, and that’s definitely the easiest.

i do like to splice the NB harness into the NA, since the NB has single neat harness exit by the back of the intake manifold. But it’s a lot of work stripping down both and splicing them together.

The NA has some plugs by the back for coils, injectors, and then another harness by the throttle body going to TPS, IAC, the useless crank sensor, and PS switch.

I guess what I’m saying is, you can splice in the NB pigtails individually at their source, or use the entire harness and do all your splices in one place.

 

Is it possible to use the nb2 me442 I have? I don't mind splicing up the harness. I just don't know what the difference is pinout wise between the ecus or if it would be compatible with the na harness

 

Sure, anything is possible.

You're going to need the following two harnesses, engine and injector. These are random pics from eBay by searching "miata engine harness", and "miata injector harness" and looking for NB2 listings




The big white square plug is what plugs into "other" chassis stuff. This one:



Quick count shows this plug has ~54 pins in it. You're going to need to cut this off, and continuity check between each pin to find it's destination. It'll go towards things like grounds, powers, OBD2 plug, instrument cluster (temp, oil pressure, CEL, etc), purge valves, fuel pump relay, 2nd o2 sensor, etc. You'll need to make the decision as to whether or not your setup needs it, and if it does, where it needs to go on your NA. There is no "master plug" like this on the NA, the engine harness disappears into miles of electrical tape without connection, and you'll need to run the required wires out of these ~54 individually to each device. A couple to the dash, a couple to the OBD2 plug, one to the fuel pump relay, etc.

Another thing to think about is the length of the NB harness. Your NA doesn't have the hole for the large grommet on the engine harness, and your ECU isn't in the same location. I don't think this will reach behind the passenger seat where yours is, but you can put it in the NA6 location by the passenger foot area. You'll have to contend with that extra length of wire and zip tie it up so it fits there.

The above issues and headaches are why it's considered easiest to buy the ECU for your chassis, and run the two extra wires required for VVT. If your ECU is a nice one, it'll have an output pinned to the purge valve in the engine bay already, so it's just a matter of splicing a foot or two of wire to the VVT solenoid, swapping TPS/IAC/coil/Cam/Crank sensor pigtails, and away you go.