JDM motor swap Japanese engine
 

Ive spent the last couple days on here, and haven't found what I'm looking for. I'd imagine quite a few have done this swap I'm looking for alternatives to having a spare engine, plan on building a spare motor for when mine pops. So far from what i have read the egr is disabled on jdm motors, the jdm engine wiring harness is for a 16 bit ecu, and that it is possible to run just an apexi power fc to control engine management as an alternative to spending the time tearing the engine apart to convert the rats nest.

The reason I ask is because I recently purchased a 1994 jdm motor, it came with an uncut wiring harnesses both for the ignition and engine. The harness looks similiar to the us spec was wondering instead of going the pfc route for the short term if it would be possible to run just the jdm ecu instead.

only later models have the 16 bit ecu.

is there anyway you can buy a front cut then yo ucan change everything over with fewer hassles whilst having spares.

a 94 motor will drop straight in..

no worries

You serious, SWEET!! Well that makes sense because the ecu harness looks similiar to the one I have.

Yes, the same company sells front clips but, I really don't need to go that route as I don't have room for the extra parts plus its about an extra $2000 counting the added weight for shipment. It would be worth it though for a right hand conversion.

The smart way to tackle it is to strip the engine down to the short block, compare parts from the new and old engine, and use the best parts. Just dropping in a full long block is foolish - you have no idea what the condition of all the components are. Much easier to go through everything on the engine stand.

In general, there's little difference between the JDM and US engines. Short blocks are identical, there's some changes in the intake manifolds due to different emissions regulations in Japan. I would probably use your US wiring harness - it will take some work to make the JDM harness fit and work properly in a left hand drive car.

BTW, the "16-bit" ECU's are only on the '96+ engines. Most of the core components on the later engines are identical. All FD short blocks are the same.

Dale

Dale

I agree, that is good advice, as far as making a comparison and installing the best components of the two.

As far as the wiring harness goes I made a comparison of the two lengths. The wiring harness on the jdm motor is actually the same length, as the us spec only that it is stretched behind the transmission and bolted down with clamps so that it could be entered into the left side. It is mearly a matter of unbolting the clamps and unraveling it through to the right side, not much work involved, although I did notice one wire may need to be wire-stretched I think it was either the knock sensor or the oil pressure sending unit, but that is it, from what I can see right now. Everything appears to be exactly the same, I don't think there is any difference at all. Although once I break it down further it may prove to be different. I'm going to trace individual wires and make comparisons of each harness. But If I can I'd be better off using the jdm harness because it isn't stiff and brittle like the one in the car right now. In fact everything on the motor seems much more fresh as would be expected.

Wow! I am suprised there isn't much information on here related to this subject, As it would seem a decent alternative to replacement engines. Well I made more progress in comparing the two JDM to USDM. The JDM motor I have indeed is a 92-95 jdm version since I was able to find it carries a n3a7 wiring harness. Some of the things I noticed, like others have mentioned here 1) is it does utilize a version 8 bit ecu and easily plugs into the original usdm ecu, 2) however on the blue connection there are two extra pins on the left side, not sure how to get around this other than rewiring possibly to the usdm connector. 3) It does not have the egr valve, or four vacuum lines that connect under the uim, ("3" vacuum connections instead) due to the fact there is no egr. I'm not in a smog area so I'm not too conerned with the egr, even though my usdm had the egr solenoid. but was disabled 4) Also it does not utilize activated warm-up system (aws), 5)it does have the double throttle control valve, 5) and also the wiring harness attached to the left side which is a simple fix as mentioned above. I'm curious if anyone has information on if this will be a problem with running this setup on the stock usdm ecu, based on the minor wiring differences.

I'd like to see if there are any other problems before I go and drop it in to something.

Ottoman you said it will drop right in what information or source do you have on this?

looking for someone who has been there done that.

Help
 

I am running into the same problem. I made the trany wires longer and I thought that this was the only difference, but as you said the blue connection (near the ecu) is different, and a few of the wires are moved around a little. (also, I think there is more wires on the JDM one) I also was wondering if I could take the connectors apart and hook the wires up in the correct spots on the US plug. Does anyone know???

I got my car as a roller, and I didn't take the engine harness out, so I don't have one to compare it to.... I was going to use the JDM harness. (so I might need this US plug if anyone has one to sell)
I think this blue connector is for the injectors, or tells the ecu when/how to operate the injectors.

I finally found the answer, check it out:
https://www.rx7club.com/showthread.p...ht=ecu+harness

its just drop in. its not that hard. there are only a few things that are different. just run the engine with its jdm ecu and you wont have problems.

since u have time before your motor goes, maybe u should try rebuilding that jdm engine. usually they have bad coolant seals or something nasty..

I think you need to change all the harness or re pin it to fit the jdm ecu, my car was done when I got it so im not 100% but I have the wire diagrams showing how to rewire the hole car and it looks like they did.

Well the verdict is in its just the blue connection that needs to be rewired, I simply repinned the us spec into the jdm motor and vwalla the engine runs beautifully, also the throttle linkage had to be tranferred over as the jdm is in the opposite direction, a few other minor things and I am running the us spec ecu. THe engine runs great no rebuild or anything, I'm really impressed with this motor. It doesn't have a badass streetport like my old motor, but I am pulling this one out to redo the internal port work and all seals while I'm at it, this will just be a temporary install. Thanks guys for your help.

needed this

lopedl, if you're still around the forums, i was wondering what your compression and vacuum at idle was? Im trying to get a good idea of avg decency or jdm engines