SE motor into NA8 - prep questions

[StanTheMan]

I was under the impression the Haltech has a plug & play solution for the NA Mx5.
https://www.haltech.com/product/ht-1509 ... a-mx-5-na/

.

They do, but the problem is that at one end or another the plugs wont match.,


The NA Haltech will plug into the NA loom, but the NA loom wont plug into an NB-SE engine.
So you'd need to do a lot of cutting and splicing at the engine end to match sensors etc up.


Conversely, if you had the SE loom handy, it plugs into the engine fine, and you then can use either the OEM SE ecu, or a Haltech ECU to suit an SE.


and the third option is to just custom wire the lot.



Also, OP, if you want I have a spare ECU plug to suit NA (will confirm NA6 or that has about 6ft of wire pre-terminated.
so you'd just need to wire the sensors on the end where needed.
PM me if you want more details.

OK right.

yea I must have bough about 6 or 7 new plugs & spliced wirse & so on to make it fit. its a days work I suppose

I got my connectors & stuff from
here
https://www.bmotorsports.com/shop/static.php/post/miata

[hks_kansei]

I'm not convinced that for that sort of Money you still have to do all the wiring to all the sensors.

yeah, but it's a matter of:

Haltech Elite 750, cheapest plugin they have = $2000


Loom and ECU from a wrecked SE = probably around $500, maybe a bit more from a wrecker or something.

[greenMachine]

My 2c. I have just had an Autronic SM4 installed in my SE. I paid the tuner to build a patch harness to connect the SE engine loom to the Autronic. Win.

I would look closely at what you NEED to run the SE engine, and then what the NA8 ECU supplies to/from the ECU. This will tell you what additional wiring you will require (at a minimum). Do not think you will absolutely need all the wiring for the sensors and controls on the stock SE. Be aware that getting the engine harness out requires (at least in an NB) removal of the dash.

I have an SE ECU surplus to requirements, but trust me you do not want it - the tune is poor, and getting past the immobiliser would be a major problem. Ideally, to do this you would need the keys, ignition lock and immobiliser that are linked to that ECU. Fairly obviously, I would not be suggesting that you use an SE ECU.

My suggestion:
Step 1 Choose ECU.
Step 2 Choose tuner, discuss wiring options - patch harness to NA8 loom plug plus extra wiring; or, new harness built from flying lead harness for selected ECU (cut engine harness off at firewall, and as much as you can reach between heater and firewall - unless getting an NA harness out is easier than an NB).
Step 3 Pay lots of money.
Step 4 Enjoy car.

Good luck.

[hks_kansei]

A third option, which is the least wiring.

Use the SE block, use your existing NA8 head (assuming that's not the part that blew up), and then bolt the SE turbo setup onto that head (you'll need to keep the NA8 intake manifold)

Then your existing NA harness will plug straight in like before, and you'll only need to add a Map sensor and maybe air temp sensor.

[CrazyRacer]

From where you are I reckon its going to be easiest to buy your preferred ECU with a complete wire in harness kit and start from scratch. Otherwise you're going to be patching into the existing loom at both ends and will probably have to add extra bits that don't exist in the NA loom anyway.

Starting from scratch works out a lot neater and with fewer issues. You'll need to source new sensor plugs, but if you didn't get them with the engine you'll need to do that anyway.

I did a complete rewire when fitting a Toyota 3SGE into a Datsun 1600 with a Motec. Its not that difficult but you have to be careful doing it to avoid mistakes. Its a little time consuming but very satisfying when the car fires up for first time.

[StanTheMan]

double post

[StanTheMan]

yea I thought the OEM ECU was a bad idea...



first of all there is this document
https://www.flyinmiata.com/support/instructions/misc/1.8swap.pdf
its for the 1.8 into an NA6 chasis. but its a good read. will give you some hints

then there is the mega engine change thread on Turtbo Miata
thats an awesome read. might even mention your engine
https://www.miataturbo.net/engine-performance-56/definitive-vvt-swap-into-90-97-chassis-megathread-80469/

loads of other info on changes.

one of the most awesome threads on connectors
https://www.miataturbo.net/general-miata-chat-9/connector-witch-hunt-70034

a google doc with all the connectors summarised
https://docs.google.com/spreadsheets/d/15J89EFBYnflI0PudPuKPvdpzoCgeF7ScK5Vkm-e10r0/edit#gid=0

[JZP]

Sheesh. Many ways to skin a cat, it seems.

Rectum I’ll need to speak to the tuner first.

Much like the discussion and varied responses on this post, I’ve spoken to a few people who’ve suggested different ECU’s. So, ease of tunability and industry versatility would be a consideration (eg: tuner is sh*t and need to go elsewhere).

Given the NA8 is pretty old school, I’m kind of thinking that the old stuff needs to go and be modernised.

BUT, I’ll give a few tuners a buzz and kick some ideas around. Just need to collect the mechanical ancillaries and decide on the ECU path in the meantime.

Really appreciate everyone’s perspective and input. Great stuff.

No doubt I will be back to ask more questions and let you know how I’m travelling.

[bruce]

I would get OEM loom and fit a Plug'n'Play aftermarket computer.
Whilst you have the dashboard out to remove the old loom, I would fit an SE/NB dash and interior to update the car.

[JZP]

I would get OEM loom and fit a Plug'n'Play aftermarket computer.
Whilst you have the dashboard out to remove the old loom, I would fit an SE/NB dash and interior to update the car.

I actually considered updating the interior with an NB when I eventually buy a salvage donor car. But I realise these cars will become desirable from a nostalgic perspective, so I’m thinking keeping the interior reasonably period correct ( yes I’m aware the turboing blows that theory out of the water, but what can you do when you hear the call of more power? ...I’m only human).

I’m hoping I can hand this car down to my daughter when she is old enough (she’s only 6, we probably won’t be allowed to drive then).

[StanTheMan]

I recon changing the loom is a monumental piece of work. You need to then figure out how to work the pop ups.
If you're going splice part of the loom it is the same as changing the connectors. At the end. Just heaps more work

There are pehaps some sensors you can transfer from the old engine. Or just change the connectors.
You've only got a hand full of sensors if that....

If of course this will be a concourse contestant.... we'll. I'm totally with you then.

While of course this is what I should do cause the underneath of my dash is a butchered piece of nightmare.

Ohhh and the NB8C dash.....mmmmmm...yea

[StuwieP]

Just take the whole loom out if everything is coming out.

You'll avoid causing yourself more headaches down the line if you've been able to trace everything properly.

[beavis]

The engine will bolt right in, physically. The metal backing plate may no perfectly align with the bolt holes for the 5spd trans & starter... double check that before it's all in the car and trim as necessary.

You need to swap the NA8 alternator onto the NB engine, pretty sure it'll bolt right up. (unless you end up with an ecu that controls the NB alternator.)

I'd suggest grabbing a Megasquirt PNP for the NA8 loom, (check how many plugs your ECU has as it changed over the years for the NA8).
I can recommend a tuner with good experience in the MS products in Melbourne for your consideration.

Wiring wise on the engine side you should be able to retain the standard wiring for the following 5 items, but they my need to be pinned to suit the NB connectors:

• TPS
• IAC
• coil packs
• coolant temp (just swap your NA8 sensor onto the NB engine?)
• oil pressure (just swap your NA8 sensor onto the NB engine?)

I'm fairly confident the wiring for the NA's mechanical CAS (on the back of the head) can be split apart and then re-pinned to suit the NB CAM and Crank angle sensors, there's docco on what wires go where somewhere on the internet.
I have a 36-2 trigger wheel which makes resolution even better if you end up with the NB crank sensor and MS ecu.

Fuel injector connectors are the same. I don't believe anything else needs to be done wiring wise, other than perhaps run a wire for an electronic boost controller.

A stock clutch will hold up fine, consider a lightweight flywheel and exedy HD for extra "bite" but stock like performance.

The 5 speed box will likely be fine for your power level.

[plohl]

https://www.miataturbo.net/engine-performance-56/definitive-vvt-swap-into-90-97-chassis-megathread-80469/

for a vvt engine, but most of it will be pretty similar.

[bartmanftw]

The simplest way to do this is to get your choice of aftermarket ECU for your year NA8 and just swap a few things from the NA8 engine onto the SE engine so that you don't have to change anything on your OE harness.
Would need to swap over:
Throttle body
Coolant temp sensors (dash sensor and ecu sensor)
Coil packs (should bolt onto SE engine)
CAS (fits into exhaust cam once a blanking plug is removed)
Alternator since the NB alternator needs ECU control

Optionally you could also convert to the NB style cam/crank sensors and the SE (or aftermarket) coil packs.

The VTCS manifold the SE engine comes with doesn't need anything hooked up to it. Can just leave the butterflies in the default open position. Better option would be to swap in a VICS or flat top manifold.