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The second post now has a how-to on modifying a pre-assembled ECU patch harness

The wiring diagram picture, in this first post only, is wrong!
Pins 10 and 7 on the ECU need to be switched.


As promised, even if a bit late.

This is the procedure I used to install a 4 channel ecu into a USDM Legacy SS. This has been tested with both a BC5 EJ20G ECU and with a EJ20G Apexi Power FC aftermarket ECU.

First you will need to add 2 pins to the 26 pin factory ECU connector (F47). The 4 wires going up in the pictures are the ignition outputs. The black wire on the right is pin #1 and the brown wire on the left is pin #13. The two factory channels are the Green/white @pin 9 and the Yellow/blue @pin 10. You will need to add the two wires located @pin 7 and 8. (I chose red/black and black). These wires will need to be harvested from a spare harness/ECU connector.


This is the tool I made to extract pins from the connectors. It's just an allen wrench ground to shape.


Once you have added the needed wires to your connector you need to add the igniter. I chose to use a SVX igniter. A JDM WRX or tandem factory Legacy igniters will work just as well. Follow the following diagram to wire them in. Basically each output from the ECU gets it's own igniter channel. After the igniter you can bond cylinders 1&2 and 3&4 together. Remember to ground your igniter/s.


I chose to do this all inside the car right at the ECU location. I also used a jumper harness to avoid and permanent harness modifications. In this picture you can see 4 channels coming out of the ECU, but only 2 channels returning to the harness.


Igniter location. Just stuffed up there in this picture.


Now that you have added new igniters to the circuit, you need to remove the factory igniter. You can go under the hood and either splice (or jumper) it out. I chose to keep with my no-permanent-mods theme and gutted a factory igniter. Solder the inputs to the outputs and you've made a reversible jumper.


This is pretty much all that needs to be done with the ignition. In fact the car should now run, but most likely throw a code. It turns out that the pressure sensor is wired slightly differently on our USDM cars. The solution is to remove pin 5 on B48 and join it with pin 21 on B48. This could easily be done with a conversion harness also, if desired. Sorry no pics of this step, but should be a no brainer if you've got this far.

That's it. The car should now run and be code free. The rest is all detail work. Mounting, wrapping and making it looks good. You will most likely decide to deviate slightly to make the conversion suit your needs exactly, but hopefully I've given everything to get it up and running.

Using a commercial patch harness

I've just finished modifying an off-the-shelf ECU patch harness for 4 channel ECU operation. I'll post the play-by-play for those that may be interested.



On the big 26 pin connector label the stated wires as follows:

Pin 7 > "#4" on the ECU side
Pin 8 > "#3" on the ECU side
Pin 9 > "#2" on the ECU side, "#3 & #4" on the harness side.
Pin 10 > "#1" on the ECU side, "#1 & #2" on the harness side.
Pin #15 > "Ground" or "GND" on both the ECU and harness ends of the wire.

For the 22 pin connector, label as follows:

Pin 5 > "MAP GND" on both the ECU and the harness ends of the wire.
Pin 21 > "TMP GND" on both the ECU and the harness ends of the wire.


Double-check that all wires are the correct ones and labeled correctly!!




Pin 1, Yellow/blue > "#1 in" on connector A, "#3 in" on connector B
Pin 2, Green/white > "#2 in" on connector A, "#4 in" on connector B
Pin 5, Blue > "#2 out" on connector A, "#4 out" on connector B
Pin 6, Red/green > "#1 out" on connector A, "#3 out" on connector B

Pin 3, black > Igniter ground, eventually goes to pin 15 "GND"
Pin 4, yellow > Not used, left unconnected. Can be trimmed off.

Double-check that all wires are the correct ones and labeled correctly!!



Only the 4 ignition channels are shown cut in the photo above.



Attach your preferred connector (or prep for soldering) to the ends of the 4 ignition wires on the ECU side of the patch harness. I prefer to use crimp connectors with heat-shrink weather resistant ends.




Attach the "IN" wires on the igniter connectors to the prepped wires on the ECU connector.

Igniter wire "#1 in" > ECU wire "#1"
Igniter wire "#2 in" > ECU wire "#2"
Igniter wire "#3 in" > ECU wire "#3"
Igniter wire "#4 in" > ECU wire "#4"

This gives each ignition channel out of a 4-channel ECU it's own igniter channel. The igniters have built in diodes that keep them separated on the ECU side when we join them on the output side of the igniter.



I suggest using a type of quick disconnect for these steps. That way you can easily correct the firing order in case of a mistake.


For the wires labeled "#1 & #2" and "#3 & #4" on the harness side of the adapter you will need to make small "Y" harnesses. Each of the mentioned wires needs to have TWO quick disconnects attached.


The opposite type (male/female) of quick disconnect needs to be used on the igniter output wires. Each igniter output wire "#1 out", "#2 out", "#3 out", and "#4 out" needs the proper connector to plug into the "Y" harness we just made in the above step.

Double-check your connectors and wires!
It is very easy to mistakenly make an igniter output wire that cannot plug into a harness-side "Y" adapter.



Connect the black ground wires from the igniter connectors to the adapter wires labeled "GND". I suggest that a bit of length be added to keep the total length even with the other groups of wires. All FOUR wires should be connected together when finished. These ground the coils (charging them) when the ECU energizes the igniters.



Connect the igniter outputs to the harness side connector. The proper order is:

Igniter output wire "#1 out" and "#3 out" > connector wire "1 & 2"
Igniter output wire "#2 out" and "#4 out" > connector wire "3 & 4"



The last area that need to be addressed is the MAP sensor ground wire. BOTH the "TMP GND" and the "MAP GND" from the harness side of the adapter need to be connected to the "TMP GND" wire on the ECU side. The "MAP GND" on the ECU side is not connected to anything anymore.


THAT'S IT
The jumper harness can now be installed between the vehicle harness and the 4 channel ECU. Then install a pair of normal Legacy igniters and replace the factory igniter with the bypass. Start it up and give it a test drive!

I'll add a how-to on gutting the factory igniter to make a bypass.

In the meantime here's a vid for Kimo, because that's who's getting the PhyrraM 4Channel Adapter(tm) sn#001.

Startup

Only thought/suggestion is that the ignitors get hot with use, and could use a heat sink.

Yes, I've thought of that too. I left the ignitor attached to the factory SVX bracket just for this reason. After an hours drive it is still cool enough to hold in your hand. I'm guessing the lower temperature in the cabin vs. under the hood is helping things alot.

Also, no EMI interferance that I can ascertain from the in-cabin mounting.

So what does rewiring the pressure sensor do? Are you tricking the ECU to make it think that the sensor is working or are you just making it work with the 4 chan. ECU?

The 4 channels ECU are expecting the signal ground to be on a different pin than our harness. We are just making our harness match the JDM/Aussie/Euro harness.

As an update....

If you are following this with the plans to install an Apexi Power FC, I would like to point out that, contrary to my logic, the "boost control kit" setting should be set to installed or "yes".

Even though our cars (or all EJ20Gs) do not need any additional hardware to sense or control boost, it appears that turning off the option also disables the code to do so in the ECU itself.

So, to repeat, even though our cars have a factory MAP and boost soleniod (which can be used up to about 17psi), and we DO NOT need the optional boost control kit, the boost control kit SETTING in the PFC menus MUST be on for the PFC to actually control boost. (It will read boost just fine either way.)




I have a feeling that the 1.2 kg/cm (~17psi) spikes I have been fighting on my non-intercooled, stock EJ22T contributed to it's headgasket failure!

Yes I feel like a dummy, but I figured "no kit installed, physically" = "no kit installed, electroncally" in the settings.

Thanks PhyrraM! This will be really useful when I copy your setup. lol

Cool Write up.

Too bad I sold off all of my EJ20G ECUs :(.

Would using USDM coil/ignitors requirs less wiring (not that this is really alot of wiring) as I have a EJ20G in my SS?

This uses the factory SS coil and all wiring, except for the mods mentioned (all @ ECU). It essentially converts a 4 channel ECU to 2 channels. Dropping to 2 channels allows you to use the exsisting harness and coilpack.

You can use 2 Legacy ignitors (2+2), an SVX 6 channel (2 not used), or a JDM 4 channel. As long as you have 4 channels total, it will work.

any updates on this?

Who is it running phyraaM?
anyone else done this? success?

i've done it with dual legacy ignitors, but mine is yet untested as I still need an ecu, injectors and maf. someday tho.

So then What's the purpose of this whole process? better spark?

it's so you can run a 20g ecu with wasted spark ignition instead of doing a coil on plug conversion.

Yup, there are programmable options with EJ20G ECUs. Revtronix was the only game in town for EJ22T ECUs.

The coil on plug conversion requires running wires out to the motor, which can involve pulling the dash, front bumper and fender. This keeps all wiring changes near the ECU and can be done with a jumper harness, meaning ZERO wire cutting on the car. NO permanent mods. That was important to me.

Mine has been going for just about 2 years now, with zero problems. It even spanned 2 motors, the original EJ22T and the EJ20G (kept wasted spark). And for testing purposes, it worked with every EJ20G ECU I tried (Legacy EJ20G, WRX EJ20G and two different PFCs).

ive got a chipped 20G ecu coming for my car, ill post up how i works once its installed...

Followed this exactly, but my car wouldnt run right. I had to swap wires 10 and 7 at the 1st ignitor in order to get it to run on all cyls. idk why that was, but it fixed and it runs very very well....

Bump for a brand new second post describing how to modify a pre-assembled ECU patch harness.

Also added warning about a typo to the original post. Thanks Mike! I checked my original install and found that it has always been as your needed to be. The error stems from the Legacy FSM I used for the wiring diagrams. It states the pin 9 and pin 10 correlate to cyls 1&2 and cyls 3&4, so that's what I put in the drawing. Sometimes the FSM is even wrong.

You are awesome Jess! I'm excited. Just need my TD05 kit from ebay and I'll get it all back together for a test drive.

can anyone explain me the purpose of this?
what is it for?
look like a lot of effort doing it, must worth it

It's to convert the ignition system to work with spark plugs instead of coil on plug ignition.

yazmo, this changes the ignition setup to allow for higher hp. It's not really necessary unless you're revving high rpm's or are pushing above 300 hp.

When I originally set out on this project there were no options to add programability to to the stock EJ22T ECU. Revtronix was not around then, and in fact, is already gone. Also, there were a few of us running EJ20G motors on the stock EJ22T ECU, workable-but not ideal. The need to have a programmable ECU available to us was growing.

The (early) EJ20G ECU is a very close relative of the EJ22T ECU. The only real difference is that the EJ22T is wasted spark/coil pack (AKA 2channel) while the EJ20G is coil-on-plug (4channel). There were, and are, many programmable ECUs designed to work with the EJ20G.

The traditional way of running an EJ20G ECU was to run new wires for the extra ignition channels. I, personally, prefer to not make any permanent (non-reversible) changes to the car. This project is to allow use of any type of EJ20G ECU, or programmable replacement, to be used with the factory Legacy SS wiring harness and wasted spark coil pack, with no cutting of factory wires.

? I thought this was specifically to do the opposite so you can use an ECU from a coil on plug engine on a wasted spark engine?

You're correct. I misread the title.