Why, when doing a swap, can't the factory ECU and harness be used? I have searched for the answer to this question and have never come across a thorough answer.

If you have the factory ECU that was programmed by the factory for that engine and you have the harness that is designed to work with that engine and ECU and you are using all the sending units/sensors that the ECU is programmed for it seems to naive- me that the whole thing could just be dropped in (mild oversimplification).
What is it that I'm missing?
This is, of course, if you are only planning on factory hp. But for a DETor even a VVL swap it seems that it would work, after all it worked from the factory with different sheet metal wrapped around it.
The post about the VVL swap using an SE-R ECU has me baffled.
I'm not being sarcastic, just curious. Can someone school me?
:confused:

one of the things to think about is The Fuel Rating over seas.

I think we have crap 92/93 over hear where they have even higher over there.

But your right if you use all the sensors, MAF, TB, Ect. I would think you could use the ECU no problem, as a matter of fact I belive there are a lot of cars running around with the Jspec ECU running JSpec motors.

Really? I guess I haven't heard of anyone using the stock, DET or VVT ECU. It seems that everyone is using JWT or black boxes.
I'm not sure if I agree that the US has inferior octane gas. I don't recall seeing higher than 91-92 overseas, but that was a few years ago. Perhaps you are right though.

Well...I actually have 4 friends with Silvia swaps, which is the same for the FWD and everything(for those who didnt know). But anyways... They are using the stock SR20DET ECU from factory(Japan) and the cars run f&ckin strong. The gas octane actually isnt that much of a problem. I mean running 93 is just fine. I was actually gonna use the stock BB ecu if I cant come with a JWT BB ecu soon...The only problem there is, is that a BB is OBDI and our cars are OBDII(since it says u have 99) So, there is some work u gotta do. If you want more details PM me or e-mail me. Ive researched it quite a bit and I know.... Besides, if you get a sr20det motor...Why not use the stock sr20det ecu, you know? Its just pulg&play with the JWT ecu and much easier. But PM and ill tell ya more.

What if I have a '92 nx2000 I'm swapping a BBDET in? If my DE ECU is OBDI, and the BB ECU is OBDI too, it should work right?

don't worry! it will work fine.
la seule différence avec le ecu de JWT c'est qu'il aute le speed limiter.

that's good.

It's sad Sonny has so much trouble with his swap, but on the other side, I would have had liked to have his JWT!