MicroSquirt Wiring Help Options

[913B]

Hello members,
I am in the process of wiring it up and I need a good 12v switch power for the main relay and ECU.
I could guess and pick one but I thought maybe I can ask in case anyone BTDT

I would appreciate the input.

Thank you

[GregAmy]

I can help. I'm traveling so cant get verbose right now but select the link in my sig for what I did. Wiri8ng diagrams and details toward the end.

Back home early next week.

[Montreal914]

I used something like this. It has an adjustment (arrow) where you can bump up the voltage to simulate the ~13V on the car if you want.




https://www.amazon.com/Hosyond-Universal-Re...F9tdGY&th=1



Here is a picture of my "bread board". Unfortunately, I abandonned my MS conversion and moved on to a different engine. Best to rely on Greg's thread. (IMG:style_emoticons/default/smile.gif)

[GregAmy]

If I understand your question correctly, you're asking how you should power your main relay and the ECU.

TL;DR answer: the stock D-Jet ECU and injectors are run off of the 4-pin T-4 connector on the relay plate. The ignition, of course, is a standalone coil that leverages ignition power. You can run the MS ECU off of T4-I. You can also use that to latch your relay.

Do note in there how the MS ECU is so efficient that it will run just on current drawn backwards from the battery through the GEN light bulb. You'll need to install a diode...

Not-so-TL;DR answer:

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-6.html

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-7.html

https://tgadrivel.blogspot.com/2020/04/on-m...14-part-10.html

[913B]

I used something like this. It has an adjustment (arrow) where you can bump up the voltage to simulate the ~13V on the car if you want.




https://www.amazon.com/Hosyond-Universal-Re...F9tdGY&th=1


Here is a picture of my "bread board". Unfortunately, I abandonned my MS conversion and moved on to a different engine. Best to rely on Greg's thread. (IMG:style_emoticons/default/smile.gif)

Thank you, but I am wiring it in the car, I am to dive in and raw dog my harness, fingers crossed. I know this not the final harness, there will be improvements along the way, then I will know it works.

[913B]

If I understand your question correctly, you're asking how you should power your main relay and the ECU.

TL;DR answer: the stock D-Jet ECU and injectors are run off of the 4-pin T-4 connector on the relay plate. The ignition, of course, is a standalone coil that leverages ignition power. You can run the MS ECU off of T4-I. You can also use that to latch your relay.

Do note in there how the MS ECU is so efficient that it will run just on current drawn backwards from the battery through the GEN light bulb. You'll need to install a diode...

Not-so-TL;DR answer:

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-6.html

https://tgadrivel.blogspot.com/2020/03/on-m...914-part-7.html

https://tgadrivel.blogspot.com/2020/04/on-m...14-part-10.html

Thanks Greg,
It appears, it triggers the Fuel pump relay from the Djet ECU.
I wired the MS main power supply and straight from the battery.
I was searching for a simple switch 12v input to MS.
I think I am going to use the (+) wire from the regular DJet coil for now.

Wish me luck, its just only been a few years. (IMG:style_emoticons/default/chair.gif) (IMG:style_emoticons/default/headbang.gif)

[Montreal914]

I remember a safety discussion at some point concerning the powering of the fuel pump and how the D-Jet was cutting it off for safety in some scenario or after a while? (IMG:style_emoticons/default/idea.gif)

I believe the MS setup wasn't providing this element of safety. @GregAmy , do you recall something as such?

[GregAmy]

I remember a safety discussion at some point concerning the powering of the fuel pump and how the D-Jet was cutting it off for safety in some scenario or after a while?

That is correct. The D-Jet ECU grounds the fuel pump relay solenoid when the engine is running via the T4-III wire, activating the fuel pump; as I recall it does this when the ECU is sensing the engine turning via the trigger points.

The Microsquirt does the same thing for fuel pump control. It comes with a fuel pump relay ground circuit when the ECU detects the engine turning via the crankshaft position sensor. I am using that same T4-III wire to the MS ECU to ground the factory fuel pump relay solenoid and thus control the stock fuel pump. So, when the engine stops turning, the MS ECU opens that circuit and the fuel pump is de-energized.

I do not use the T4-II wire, as the MS ECU is sufficiently powered through the T4-I keyed power. I do not use the T4-IV as MS does not incorporate a CSV, it varies the injector dwell and 'pre-loading" the injectors at "ignition switch on" for additional start enrichment.

Wire / D-Jet Use / MS Use
T4-I / Keyed power, ECU and injectors / keyed power to ECU and latching external relay that powers injectors and ignition coil
T4-II / starter circuit power, signal to ECU that key is engaged to start position / unused
T4-III / ground for factory fuel pump relay / same
T4-IV / starter circuit power to cold start valve / unused

It is really remarkable how similar D-Jet and Microsquirt are in concept and operation. It really shows you just how advanced D-Jetronic was for its time. The only thing D-Jet was missing was modern sensors (looking at you, MPS) and more computing and tuning capabilities.

[913B]

I remember a safety discussion at some point concerning the powering of the fuel pump and how the D-Jet was cutting it off for safety in some scenario or after a while?

That is correct. The D-Jet ECU grounds the fuel pump relay solenoid when the engine is running via the T4-III wire, activating the fuel pump; as I recall it does this when the ECU is sensing the engine turning via the trigger points.

The Microsquirt does the same thing for fuel pump control. It comes with a fuel pump relay ground circuit when the ECU detects the engine turning via the crankshaft position sensor. I am using that same T4-III wire to the MS ECU to ground the factory fuel pump relay solenoid and thus control the stock fuel pump. So, when the engine stops turning, the MS ECU opens that circuit and the fuel pump is de-energized.

I do not use the T4-II wire, as the MS ECU is sufficiently powered through the T4-I keyed power. I do not use the T4-IV as MS does not incorporate a CSV, it varies the injector dwell and 'pre-loading" the injectors at "ignition switch on" for additional start enrichment.

Wire / D-Jet Use / MS Use
T4-I / Keyed power, ECU and injectors / keyed power to ECU and latching external relay that powers injectors and ignition coil
T4-II / starter circuit power, signal to ECU that key is engaged to start position / unused
T4-III / ground for factory fuel pump relay / same
T4-IV / starter circuit power to cold start valve / unused

It is really remarkable how similar D-Jet and Microsquirt are in concept and operation. It really shows you just how advanced D-Jetronic was for its time. The only thing D-Jet was missing was modern sensors (looking at you, MPS) and more computing and tuning capabilities.

Thank you Greg, very good explanation on the T4 plug.