USDM ECU to JDM

[oldmansupra]

I have a JDM engine running with the EGR removed. My car is a 5spd and has an automatic wiring harness. I did the necessary conversions to make the harness work but.

What I want to do is order a JDM ECU. I found a good condition JDM ECU but it's from an AT. Is it okay to use the JDM AT ECU with my 5spd?

 

[90mkiiisupra400hp]

I am not positive but I believe the only thing you will have to do is bypass the neutral safety switch other than that it should work fine. Also using the JDM ECU will be better because it is tuned for no egr. I may be wrong on all of this so I would wait for more people to chime in, but I think it's right.

 

[bioskyline]

no real difference. ive ran a at ecu on mt car for years with no probs, and devin is running a mt ecu in a auto car. the tranny has its own computer seperate from the main


only thing is the jdm ecu does have speed limit though (180km/h)

 

[oldmansupra]

Interesting, do all JDM ECU's have the limiters? I heard HKS makes a product that eliminates that

 

[bioskyline]

yes all jdms have that, and oddly enough all jdm speedos normally stop at 180k aswell. you need the hks SLD (speed limit defender)

 

[oldmansupra]

Alright, well good to know I can run an AT ECU. I'll be ordering that soon.

 

[noel]

Its great to know that a A/T JDM ECU can be used with a 5 speed just not the other way around. From what I can see pre-89 supra's have yellow plugs but some post-89 supra also have yellow plugs so be careful.

 

[3p141592654]

There are quite a few differences between AT and MT ECUs, but unless you know what to look for its probably not obvious. Idle control is quite different between them. Also the way they handle trailing throttle is quite different, such as when you change gears in an M/T and close the throttle briefly, the MT ecu goes open loop, the AT will not.

 

[Nick M]

Idle can not be ramped up to compensate for A/C when in drive with the brake on. Or you could hit the car in front of you. Especially the millennials on the board. As an example to what PI said.

 

[suprarx7nut]

There are quite a few differences between AT and MT ECUs, but unless you know what to look for its probably not obvious. Idle control is quite different between them. Also the way they handle trailing throttle is quite different, such as when you change gears in an M/T and close the throttle briefly, the MT ecu goes open loop, the AT will not.

Idle can not be ramped up to compensate for A/C when in drive with the brake on. Or you could hit the car in front of you. Especially the millennials on the board. As an example to what PI said.

While these things may be true, I ran an Auto ECU on my 88 "Undead" mk3 for a few thousand miles over a summer and never noticed any hiccups. Idle always seemed good, gear changes were just like normal. :shrug:

While you may have some missing functionality somewhere in the ECU programming it's nothing that would harm the motor or cause daily driving hassles - at least in my experience.

 

[Nick M]

Right. And he is letting you know they are not the same.