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Author: Subject: MX5 donor ECU wiring
Hammy360

posted on 23/5/18 at 08:49 AM Reply With Quote
MX5 donor ECU wiring

Hi all,
I am building my kit with a PWS car loom and keeping the engine loom and ecu from my mk2 1.8 MX5.
Has anyone else done this and have a guide / how to?

Any tips, links or threads appreciated
Cheers





Hammy

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miskit

posted on 23/5/18 at 10:23 AM Reply With Quote
Right now I am stripping down the MX5 loom for my Sandrail engine conversion (1600 beetle engine to 1.8VVt Mk 2.5 engine). So I have a lot of information that can help you - and it is fresh in my mind.
They changed some things from Mk2 to 2.5 - mainly around security and most of the wiring diagrams are US so some of the colours are wrong I have a 2003 Miata diagram

Where are you at the moment - have you stripped the MX5? What does the PWS loom provide ?

This is what I started with



Which then progressed to this


I expect to be finished in the next few days. I am keeping the instruments but have my own wiring for head lights etc.

[Edited on 23/5/18 by miskit]

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Hammy360

posted on 23/5/18 at 04:10 PM Reply With Quote
Thanks mate the donor is stripped and the Exocet chassis on the car, the OEM engine loom is still fitted the engine.

The PWS loom does everything else, output to OEM ecu for power from the PWS loom

Cheers





Hammy

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miskit

posted on 23/5/18 at 08:29 PM Reply With Quote
Ahh Ok it's an Exocet. Loads of help over there - I was looking at building one (that's how come I have an MX5 engine) - wiring is their favourite subject!

Big question - have you got the immobiliser and key - as ECU is useless without? I assume you have the whole loom not just the Engine part? Are you using the stock ignition barrel?

Main power comes from the Engine fuse box (Ign Key fuse) W/R to Ign barrel, then the Blu wire from Ignition barrel - (start or run) feeds the 2 fuses you need in the dash fuse box - these are the "Meter" and "Engine" Fuses. The only other one you need is labelled "Room" and is Always on - feed from Main fuse box.

Unfortunately it is not as simple as just throwing power to the ECU loom. I got some work done on it today is this is what I have left (still got a bit of temp hook up to do to see if it still starts, but this is just for the engine and instruments). The blue block mid top is the Engine/ECU connector - everything below is from the main looms



and this is what I have left over....




Have to ask - what is the benefit of using the PWS loom over the stock one ?

[Edited on 23/5/18 by miskit]

[Edited on 23/5/18 by miskit]

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ianhurley20

posted on 23/5/18 at 09:20 PM Reply With Quote
I used everything from the MX5 that I could - a 1998 Mk 2. I laid out the loom and started by stripping out the wires I knew I would not need - electric windows, audio system etc and kept the rest. Worst part was stripping off the tape covering the loom - then used a few cable ties that can be released to keep the wires together. Eventually I removed miles of wire it seemed and ended up with a great bundle behind the dash, most of which I shortened but left lots at full length as intend to put a screen on so things like wipers and heater were left full length and just bundled. All the switches were left as standard like lights and indicators the only one I changed was the horn which I led to a new button. I added DRL to the system and they just turn on with ignition, when I get to mot time I'll add a relay to turn them off when the headlamps go on. I couldn't find much on wiring loom diagrams so just took it one wire at a time and traced it back to source and either removed or left it.
Time consuming but it worked





My build blog http://ianhaynes20.wordpress.com IVA passed 3/10/16

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