Hi folks just joined the forum to see if I can get some help with this. I am fitting a 98 mx5 engine into a 73 Jensen Healey, engine and gearbox is in place now need to wire it to suit, engine bay is fine but will need converted inside car to Jensen anyone got any thoughts on this? An auto electrician told me it won’t work and the ecu would need remapped to take out the immobiliser?? Any help much appreciated
Thanks Gavin
Hi - I believe that the ECU needs to see its matching immobiliser or it won’t work. Immobilisers are coded to specific ECU, so need to be acquired as a pair. (If it’s an import, it might not have an immobiliser though.)
You would need the loom from under the dash for this.
I believe that someone sells an immobiliser emulator, but that you still need a ‘magic number’, specific to the ECU to code into it.
I have the complete loom from the car that the engine came from so was going to fit that then change it to suit the Jensen gauges etc?
Could always use an aftermarket ecu
As long as it has the immobiliser module in it still then it should work.
I have the ecu from the car as well which I am told is ok
Ahh! I had sort of assumed that you already had the ECU! 
Might be worth looking on one of the Locost / kit-car forums as they must experience this all the time when using an MX5 as a donor.
Is that not going to be heavier than the Lotus Engine, which has an Alloy Block?
Yes might be but when I bought it the Mazda engine was sitting in it but not finished, the guy had started the project but not carried it on so I just kept going with it. It’s the same horsepower I think around 140?
Thanks for the tip on the Locost kit car forum I have joined so will see what comes of it
Was surprised to see how many parted out Healy/ Eclat ect ect 907 engines there are these days. 
Hi guys where would I get a wiring diagram when I search for one and put in 1998 MX-5 it seems to come up with a 97 or 99. The reg of the car my engine came out of was X395 TST which comes up as a 1998 on eBay when you enter it when searching for things!
According to the mot history search and car tax search, that reg was on a black MX-5 first registered September 2000. At last mot(in 2021) it had 77000 miles on it. you may find the wiring info here: https://www.mellens.net/mazda/index.html most likely this one https://www.mellens.net/mazda/mazda_miata_extra_manual/2000_wiring.pdf
Yes that’s what the guy said the miles was thanks for the info👍