I am trying to get an S4 (apparently an 88 based on the injector clip shape/color) turbo engine swapped into my 88 vert, and get it to run on the original (to the car) N338 ECU and wiring harnesses. What sensor/input does the ECU use to determine which map to run (turbo or NA)?

From what I've read, when in "turbo mode", the pin I/O's are the same as an N332 or N333, and in "NA mode", the pin I/O's are the same as an N326. Is this correct (and thus the emissions harness will need the standard S4 NA to Turbo wiring done)?

What are the inputs to and outputs from the knock control box (not the knock sensor), since my emissions harness is missing that plug.

Also, what wires need to be run to get the turbo fuel pump resistor relay to work on the NA front harness?

Icemark, your solutions/input to this would be very much appreciated, since you have completed this swap. Thank you very much!

 

Knock box wires to pin R of the 24 pin ECU plug.

Fuel pump resistor relay is controlled by Pin 3D of the 10 pin ECU plug. Some 88 verts will have this already wired with the black/red of the 10 pin already running to the Green/Red at the fuel pump resistor relay. A few verts (and I have not been able to determine which by VIN or production date other than built before 9/87), will have the fuel pump resistor relay alredy in there.

Although I have run a Turbo motor with no issues on the N338 (for about a year in my vert) I lately have been working on breaking the coding of the N338's processors and I am not convinced anymore that it really can tell the difference between the turbo and non turbo motors.

In theroy the AFM and pressure sensor (boost sensor) should be feeding different signals for a Turbo than a non turbo, yet I have not been able to see what the ECU uses for a change.

The thing that is throwing me for a loop, is that if you use the standard 87-88 convertible 079753-0286 and 0276 chips (fuel and timing maps) You should be able to swap them with the Turbo chips. You can't. Or if the Turbo chips won't work, then the non turbo chips should. Nope doesn't work either.

So I am leaning more towards they used tweaked conventional non turbo timing map, while using a tweaked Turbo fuel map chip (for economy). From what I have been able to reverse engineer of the code so far this theroy seems to match, but I could just have my head up my *** and am not understanding the code at all. I just have not spent the time on it much as I have also been playing with Megasquirts (trying to get them true plug and play with all emissions and accessories functioning - with some cool extras).

 

so the N338 will advance timing in some instances then, even while running a turbo? interesting...

I also read on here that the brake booster vac line needs to be swapped with that of a turbo, but only in one place so it confused me because no one else mentions it when doing a swap. I'm going to assume that its not needed, unless told otherwise.

Thanks, and good luck with both the megasquirt and figuring out the N338. Is there a way to get the megasquirt to run the leading/trailing split on a rotary? I havent heard of other 7 guys running with one.

 

The brake booster vac check valve should already be in place.

For some reason a few people that wrote up the swaps didn't understand that even the non turbos had the check valve from the factory.

And yes there are people running mega squirts on FC's. It is mostly software for the split. I am actually trying to get rid of the split at under 1000 RPM and have the coils all fire at the same time at that RPM, but that is another thread.