I just purchased a 13BT as a replacement for my seized engine. This stock was a S4 GTU. Bolting in, everything seemed fine until I attempted to wire everything back together. Not only are there not enough connectors to fit my own ones, but the engine bay harness is too short to go all the way over to the right side where my ECU is located. I don’t know what to do. Is this really just an s5 engine with a simple fix? Or is it a LHD and I’m screwed… please let me know

Old ECU socket

Full engine pic

Fully extended ECU harness

Power steering gore

 

I little more information is needed, Has the car already been converted to a turbo and if so, which series turbo engine was it using, or are you replacing your S4 n/a engine with a JDM S5 turbo motor?
Did this Turbo engine come with an ECU? You will need a S5 turbo ECU regardless as the S5 harness won't plug into either the S4 turbo or n/a ECU and you can't run the turbo engine on a n/a ECU anyway.
It is too short because it is LHD. I'm not sure what the best path is. Easiest would be to find a US S5 TII engine harness but I think they are hard to come by. A S5 n/a harness can be made to work as it plugs into the S5 turbo ECU but some connectors go to different locations and some wires may need to be extended. Still may be easier than extending every wire on the harness but that can be done as well.
Also, the S4 dash harness doesn't plug into the S5 ECU. IIRC it's just a few wires that need rewired or re-pinned to get it to work but maybe someone who has done it can chime in. I've only read about it.

 

Thanks for chiming in. It was originally an s4 n/a, and I have both s5 and s4 ecus. The engine came with one. There were so many wires it looked like the engine came with all harness stuff included, minus the front chassis harness.
I’ll look into a new harness.

Two follow-up questions:
What is an IIRC? And is there a plug-in spot for the whole harness? I.e. like an unplug and plugin connecter to the engine?

 

IIRC = If I Recall Correctly
As far as I know the engine harness plugs directly into the ECU. as does another plug that goes to the dash/ body. Unfortunately, it isn't compatible with the S5 ECU. It my plug in but the wiring is not right. I think details about it are on here from people who have successfully put S5 TII engines in S4 cards. A US S5 TII ECU would be best but you should be able to use the JDM one that came with your engine. It may not work initially though as there was an issue where JDM ECU wouldn't always work in US cars. I think it may have been the JDM cars had a speed limiter, and the US cars had something else on that pin so it had the ECU thinking it was going over 180km/h and thus the car wouldn't run right.
This thread details it.
I'll try to dig up the wiring differenced between the S5 n/a harness and the TII harness later in case you can't find a U.S. S5 TII harness and want to try to build a harness from a n/a one.

 

if you compared a US S5 harness and a JDM S5 Harness, they sit on the engine exactly the same, but the difference is where that main branch comes out.
on the JDM harness it comes out under the oil filter, and the US harness comes out with the AFM wires, and then goes along the shock tower. i'm pretty sure that the JDM harness is actually longer
pretty sure that if you can get it to come out of the rear instead of the side of the engine, it will reach. you might need to move the firewall boot (unwrap the tape)

the other difference is that the JDM harness uses only one plug to go between the engine harness and the body harness. the difference between the US and Japan is that the Japanese harness does not have the cruise control wiring on the engine harness so its only the one plug. also i think the wipers are on a different harness. The US harness is actually three, Turbo, NA Manual, and NA Automatic, but the JDM cars only use the one. basically the pinout of the plug to the dash harness is a combination of the US models, and uses the same wire colors, so its not bad to figure out.

if you want/need cruise and wipers, its really easy to de-pin one of the connectors, and then you can just take those wires and put them in the harness you're using.

i'm running a JDM S5 harness in my car, but its not an FC engine. i have it coming out the back, and it goes along the firewall.

 

Historically with people with s4 car with s5 engine, they have gone with s4 electronics on the s5 keg to keep the compatibility all s4 electronics. Think one drawback is if using all stock ecu, no piggybacks the s5 keg is higher compression, not sure if split timing differences matter, but are things to consider.

With parts being more difficult to find, it seems some people have been able to wire up a s5 harness to a s4 car. S5 t2 harness will probably be difficult to find. S5 na harness can work on a s5 t2 engine as noted above, only a few wires need to be lengthened on the sensor connector side, and maybe 2 pins swapped on the ecu side.

Maybe there’s another option where you lengthen all wires on the jdm harness…? I had a post where I posted the supplier part number for s5 ecu pins, if needed.

heres a link to all the factory service manuals. I don’t think they’ll have info on the jdm pinouts, I believe I’ve seen the jdm info on this forum though. https://foxed.ca/indexmobile.php?page=rx7manual

 

I think j9fd3s may have posted them once upon a time. I thought I saw a post while looking for the JDM ECU issue but can't remember if the wiring was for a S4 or S5.

 

its been done. variety of ways to do it, but since you can just buy all the connectors, maybe some kind of adaptor is the easy way

actually this PFC adaptor might be good start, https://www.banzai-racing.com/store/S4_PFC_adapter.html