I'm installing an 89-91 model turbo rotary in my 1976 MGB and i'm still trying to figure out exactly what hooks up to what and what i will need to do to actually get the engine running in the car. It has the complete harness on the engine and i know that 2 of the 3 big plugs that come off the harness plug into the ECU but i cant figure out what the other goes to I'm also not sure where to hook power from the battery to and also don't the ignition coils with ignitors just plug into the harness?

 

You'll find complete wiring diagrams in the FAQ.

The other big orange connectors go to the body harness in the passenger foot well.

Using the wiring diagrams, you'll want to strip down the harness of anything unnecessary like the wiper motor wiring.

 

you only have the engine side harness there is another harness that comes out the drivers side of the firewall that hooks up to all the coils and light and everything.

and as far as the battery goes you need the positive battery cable harness. if you go to a junk yard you will see what i mean.

 

I was looking at a wiring diagram i found in the FAQs. Could i not just run my own cable from the positive terminal of the battery to the starter as it would be with the stock harness? Shouldn't hooking the positive up to the starter and then grounding everything else appropriately provide power to everything such as the coils and ECU when they are plugged in? Also regarding the third large plug that connects to the body harness, can i get away leaving it unplugged? will the engine still run properly?

 

There is a lot more then that for wiring hope you got the sensors and relays that go under the dash their is also the under hood harness that originally goes fuel pump relay and throuhg the radiator support behind head lights and throuhg the driver side firewall then goes to fuse box cpu and inside fuse box and ignition, you have to go throuhg the electrical manual and figure all the wires you need to hook up just for the engine to run then you will have to figure out gauges run stock rx7 or custom after market,check in the forum for the wiring diagrams good luck.

 

wow that sounds like a lot of stuff but i did find some wiring diagrams so i guess i will have to spend the time translating it... if anyone has some hints on basically running a race car setup (no headlights, radio, cruise control, turning signals, etc.) please let me know!

 

What I do in this case is strip the emissions harness down to just injectors and sensors, then make an additional harness that houses the CAS wire and coil power/signal wires. I bring all the powers and grounds back to the ECU and set it up so that there are only actually two connections that go to the car's electrical system: 12V and ground. That ground also needs to be tied to the engine itself.

Never run the positive wire to the starter. Voltage drops way too much during cranking, there is a lot of noise, and it's just generally sloppy. Take another supply wire off of the battery, install a breaker, and then connect it to a distribution panel to run all of your engine related stuff.

Have you considered going to a full standalone? That will allow you to ditch the stock ECU and wiring harness. The downside is the cost, and the fact that you need to tune it. But of course, being able to tune it is the greatest advantage.