I figured I should update this a bit, since I have something to update.

Well, the original plan for the MS was to install it on my LX9 in my Datsun, but since that's been broken since December with no sign of getting back together anytime soon, due to reasons, which are beyond my control right now, I installed the MS on my T-bucket (283+.030" V8) which I converted to EFI about a month ago using GM components, including a '7747 ECM. I used the Delco to start with because I knew that it should be close and could drive it on the stock tune, or tune it a bit better, and then switch to the MS. Both of my widebands were also loaned out in other people's vehicles at the time and didn't want to try tuning the MS blind, so another reason to start with the Delco at the time.

Well there were mechanical issues that needed to be worked out and at this point should be pretty much solved. I got sick of the '7747 losing connection with the AutoProm and lack of reliable datalogging. There might be an issue with the ECM itself, but I was just sick of it. This was last Friday. I went home and started on an adapter to jumper the '7747 harness to the MS. I'll post pictures later.

Sidenote: When I installed the Delco EFI I knew I'd be going to the MS shortly so I added wires at the time for the IAT and a couple extra grounds.

On Sunday (I was lazy on Saturday lol) I finished the adapter harness and ran a vacuum tube for the MAP sensor that is built into the MS ECU. I was able to get the engine to start and run ok, in trying to tune the '7747 I discovered that increasing MAP AE worked very well to get rid of a lean pop through the intake with large throttle changes, so I started there by figuring out how to enable the MAP AE in MS. Turns out that there's a slider in the AE menu that controls the blend between TPS and MAP AE, and you simple slide it towards the MAP AE table...

One thing was always a miss though, above about 3000 RPM, the revving became REALLY sluggish, and no matter what I tried with VE or spark nothing changed it considerably for the better.

I checked base timing and decided to adjust it. I ended up with a weird thing where with the bypass connected the engine would not start, the MS was not getting or at least was not acknowledging any RPM (DRP) signal. Bypass disconnected and the engine would start and run the way that was expected.

In this I decided to check whether the EST signal was good from the MS, which I used my JimStim and connected the EST signal to a spare LED on the JimStim board and observed the LED pulsing... for hours, in fact overnight the EST signal was still triggering in the morning... oopps... lol

I also discovered that the MSExtra manual is wrong where the bypass control circuit is concerned. Using the board modifications and the external connections shown will have the timing control work backwards, as in ECU controlling timing during start, but not during run. *facepalm* This is why the engine seemed lazy above 3000 RPM, because it was running on base timing! In other documentation there is often a relay suggested to control the 5V signal on the bypass line, usually the relay is suggested to be controlled by the ignition switch, so that 5V is provided to the bypass wire only while running, so that base timing is still used at start. diyautotune.com suggests connecting the bypass wire straight to 5V and have the ECU control timing during start up.

I went a different route. The built in settings for the HEI control will turn on the transistor that controls D16 (Q8) 5 seconds after the engine starts to run, or more specifically after the threshold that is set under "Cranking/Startup Settings" called "Cranking RPM" has been exceeded. IIRC stock setting is 700 RPM, I set this to 400 RPM. As I mentioned before the way the MSExtra manual suggests to connect it will not work correctly. I modified the circuit by installing a 2N3906 PNP transistor to provide the 5V on the bypass line that is needed for the ECU to control timing through the HEI module. I have not tested this on the engine yet, hopefully tomorrow I will be able to. On the bench it works it works perfect and I can't see the HEI module needing anywhere near the 200mA rating of the 2N3906 transistor.

I will post pictures and hopefully a schematic tomorrow, once I get a chance to get them onto my computer.