I have nearly completed a S5 TII Convertible swap. The only thing that is really holding me up at this point is the computer. The computer (N374) is from a Japanese market TII. The problem with this ECU is that it will not "fire" the #2 primary injector. This is actually the 3rd N374 ECU that I have installed in this car. The first ECU had no spark on the rear rotor. Since the ECU caused the rear rotor to have no spark, I never checked to see if the ECU was operating the injectors properly. The second ECU would not "fire" the #2 primary injector. And now, as you already know, the 3rd ECU also will not "fire" the #2 primary injector.

The car's old S5 NA computer runs the car just fine, so it would seem that the wiring is correct. Also, I am using the S5 NA harness with modifications for the knock sensor and the duty solenoid. The rest of the harness has been untouched.

Evidently I am not the only one that has had this problem. Here is another thread in which someone complains of an identical problem. He solved his problem by repairing the computer, but since I have gone through 3 computers, two of which definitely had an identical problem, I am concerned that the ECU may actually be good, and that a difference exists between the US market na wiring harness and the j-spec harness.

Another thing that I have wondered about, but that I have not tested yet, is whether having the knock box disconnected might cause this problem. I would be surprised if that was the problem, but at this point...

If you want to take a look at the project so far, I have a web page dedicated to the build process. Jacksons Garage

Any assistance is appreciated whether it be, "Here is why your setup is not working..." or, "You're an idiot, your computer is broken!!" :P

Thanks,
Brian

 

Brian,

stock ecu when they sense knock they fuel cut the rear rotor. compression testing proves the rear rotor to be the most worn out due to its control over the engine.

if you eliminated the knock box..... you have your problem. re attach it to the harness... and see


You need a knock input on the stocker unit. JDM ECU differer only lightly to the US market. NOT in wiring though.

Boosted application for a stock ecu require the knock input

George

 

Thanks so much for the reply. I will reconnect the knock box and see what happens.

 

Wait a minute, S5 turbo cars don't have a knock box do they? If that is the case, what the heck is this box that came attached to this N374 ECU I have?

another thread describing a similar problem:
https://www.rx7club.com/showthread.p...ght=inside+ecu

and another one:
https://www.rx7club.com/showthread.php?t=518542

I assume it is an N374 ECU anyway... All of the numbers are washed off of the tag. In fact, all 3 of the ECUs that I have gotten from this supplier have had the numbers washed off of them. I wonder if these ECUs have all been S4 computers.

So, on an A-Spec S4 computer, is the little black box that is attached to the computer actually a knock box? I am getting the impression that the black box on this S5 J-Spec computer is not actually a knock box. And even if it was a knock box, I am using an S5 harness, so the harness has no provision for this box... what ever it is.

I have a feeling that I am going to just have to either buy an N370 ECU to get this thing going, or replace the #2 primary injector driver on this N374 unit. Truth be told, I'd rather install an N370.

Sigh, sorry for the information overload guys. Any ideas? Or has this question already been answered, and my searching failed to find it?

 

At this point, I am wondering if the pin outs for the rear injector on the vert are different from that on a coupe. do any of you guys know if that might be the case?

I think I'm going to try the N351 ECU (S5 NA coupe) that I have lying around too. Hopefully that thing still works. I drove through a car wash with it sitting in the back of my truck. :P