Adapting an EJ20G ECU

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rob
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Adapting an EJ20G ECU

Post by rob »

Hi all,

I thought it would be good idea to capture all that is required to adapt a JDM WRX EJ20G ecu to a stock ej22t.

There are five areas that need to be addressed;

*ECU wiring changes
*Ignition changes
*Injector changes
*Fuel Pump changes
*MAF changes
Each are described separately below;


ECU RELATED CHANGES

Image



----- DE-PIN FROM CONNECTOR ------

- Purge Control (F47-6 ; White-Blue) :: Remove from the ECU plug. Purge control does not exist on the JDM EJ20G ECU. This pin is used for the 5th injector control on the WRX RAs (although it not used on any stock ECU). I am not sure what the consequence will be of losing control of the purge system.

- California Pin (B56-11 ; Green-Black) :: Remove from the ECU plug. This pin is used for the JDM EJ20G accelerator pedal switch. It has no impact on the behavior of the EJ20G ECU.


----- DE-PIN AND MERGE WITH ANOTHER ------

- MAP ground (B48-5 ; Red) :: Merge with
B48-21. B48-5 is used for the stock JDM EJ20G cat efficiency EGT sensor. Not having an the stock EGT sensor has zero impact on how the ECU runs. The EJ20G harness combines the MAP sensor ground with all other sensor grounds at B48-21.

----- OTHER ECU DIFFERENCES THAT CAN BE IGNORED ------

- N/A (F47-4) :: Nothing to be done. On the EJ20G ECU, this is the Fan #2 control.
- N/A (F47-16) :: Nothing to be done. On the EJ20G ECU, this is the steering pressure switch input.
- N/A (F48-12) :: Nothing to be done. On the EJ20G ECU, this is for the EGT cat efficiency warning light.
- TPS shield (B58-7 ; Black) :: Nothing to be done. On the EJ20G ECU this pin is unpopulated in the connector. TPS shield it is located at B48-21, but B58-7 will work as well as both pins are connected inside the ECU.


----- MOUNTING ------

The mounting between the two ECUS is quite difference. What I did to make it fit is basically use the top half of the EJ20G case and the bottom half of the EJ22T case and fit them together.

Here is the stock EJ20G ECU;

Image

Remove the six screws from the side. These are fairly soft material and threadlocked in. Its very easy to strip out if you do not use the proper size phillips head. If they do strip, then it's out with the vise grips!

Once off you have access to the ECU board.

Image

Remove the two screws that hold the ECU down to the bottom half of the case. Then put the board back in the top half and use the two matching screw locations to reattach to the case.

Image

Lastly, take the bottom half of the EJ22t has ears on either side that can be fitted around the edges of the top half. This provides a pretty snug fit. I wasn't so thrilled that the ECU board wasn't as secure and possible susceptible to vibration, so I jammed a bunch of bubble wrap between the bottom of the board and the bottom half of the case. Sounds ghetto, but it works the treat! Lastly to make sure the two halves didn't want to pop apart I put a little duct tape around the seam.

Image

Viola!

IGNITION CHANGE


The EJ22T ignition system is a 2 channel "wasted spark" setup with an external coil pack and an external 2 channel igniter. The ECU sends out two alternating trigger signals to the igniter. Each of those causes the coil to fire on one of the two pairs of cylinders. The cylinders are paired to the coil such that the spark arrives on the compression of one and the exhaust stroke of the other.

The EJ20G setup is for is a four channel coil on plug (COP). There are four coils each of which are molded to the sparkplug boots are physically located in the spark plug wells. Each coil has two wires, +B and the output of the igniter. Each coil pack is grounded through the mounting bolts to the head. There is a 4-channel external igniter that outputs to the individual coils and also takes as input four trigger signals from the ECU.

To boil it down, the EJ20G ECU will send out four igniter triggers, each 90deg apart when the EJ22T igner is expecting two 180deg apart. It is not possible to simply plug the EJ20G ECU into the EJ22t harness and expect the ignition system to just work.

The two approaches to resolve this are:
1) Either to use EJ20G coils/igniter and adding the necessary wires to the harness. This is only an option if your engine uses different heads; EJ20G, EJ20H, EJ20R, and EJ25D are all known to work. Technically this is the best option and made even better if you skip the EJ20G components and go directly to the GD COP conversion. You can check out my coil conversion thread on Nasioc Besides the coils being superior to the older G coils, This route makes install a bit easier as it completely eliminates the need for the external igniter and the associated wiring. One would only need to run the four wires from the ECU pins directly to each coil, a common +B wire to all the coils (most likely from the +B wire from the removed EJ22T coil pack), and a grounding ring from the coils to the mounting bolt.

2) Modify the igniter trigger signal output from the EJ20G ECU to look like the equivalent 2-ch signal and keep the rest of the EJ22T ignition system intact. The easiest solution is to use my 4to2 converter box that does exactly this. It is relatively simple to install and is smart enough to run both ECUs without removal or modification. Follow the link above for more info.

PhyrraM has a real good write-up of how to use two seperate igniters to achieve the same result.

INJECTOR CHANGE

Match the injectors with the tune. Stock EJ20G uses grey top 450cc/min injectors. They are drop in compatible with the EJ22T rails.
http://bbs.legacycentral.org/viewtopic. ... +injectors

If you are running my "550" tune you would use yellow side feed injectors from an '04+ STi (or LGT/OBX/FXT from the same vintage) which technically flow 525cc/min but are commonly incorrectly referred to as 550cc injectors. These require EJ22 NA rails or EJ22T rails with adapters.
http://bbs.legacycentral.org/viewtopic. ... +injectors
http://bbs.legacycentral.org/viewtopic. ... +injectors

These are NOT to be confused with the yellow side feed injectors from the EJ20K JDM STi motors. Those are 480cc/min and fit the same as the grey top injectors.

FUEL PUMP CHANGE

You will need to match the FP to the uprated injectors. '04+ STi fuel pumps, Walbro 195 or 255 are common choices.

MAF CHANGE

You will need to match the MAF to the ECU. If you are using the stock EJ20G ECU, then match it to Subaru part 22680AA160. This is also referred to simply as a JECS MAF or a green label MAF; both for obvious reasons. The good news here is that these are simply plug and play. They fit the same physically and electrically as the stock EJ22T MAF. The other bit of good news is that they are very common parts, so they are cheap and easy to find. Here is a list of the models that used this MAF; http://opposedforces.com/parts/info/22680AA160/.
Last edited by rob on Mon Jun 29, 2015 5:53 am, edited 28 times in total.
kimokalihi
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Re: Adapting an EJ20G ECU

Post by kimokalihi »

Do they sell a harness extension that you can plug into your stock harness and then repin the side that plugs into the ECU so you can keep the factory harness the same and allow you to swap in your old ECU by removing the modified harness?
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91 SS EJ20G Engine/Tranny/Diff Swap Build Thread Here
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rob
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Re: Adapting an EJ20G ECU

Post by rob »

I have seen them on ebay, but for something like $130. It's really looks to be a small number of changes (5 + the ignition changes). You could do this in a way that would make swapping back to stock pretty easily.

-Rob
kimokalihi
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Re: Adapting an EJ20G ECU

Post by kimokalihi »

Yeah $130 is out of the question lol.
98 Metro Hatch Daily Driver :)
91 SS EJ20G Engine/Tranny/Diff Swap Build Thread Here
"Your testes are close to your bottom but you still play with them all the time." Jeremy Clarkson
Legacy777
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Re: Adapting an EJ20G ECU

Post by Legacy777 »

Rob,

Removing the Purge control really shouldn't matter. The pressure in the tank will increase a little, but it shouldn't cause any harm. I've had the vent line on my car plugged up since putting in the Link.

Regarding the AT/MT identifier pin. It appears to be wired the same between the JDM & USDM ECU's.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

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rob
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Re: Adapting an EJ20G ECU

Post by rob »

So the MT harnesses don't have a wire in that location? Is it an input or an output?
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Re: Adapting an EJ20G ECU

Post by Legacy777 »

The MT harnesses should not have a wire there. If they do, I'm not sure where it would go. It should not be grounded though.

It's an input to the ECU. Grounding that pin tells the ECU whether the trans in the car is MT or AT. The ECU will alter idle speeds/loads and timing to properly adjust idle. There may be some additional minor stuff that the ECU changes, but I don't really have any info on that.

Subaru apparently put both sets of info/code into the ECU. When I did my AWD & 5spd swap, I was using my 90 AT ECU hooked up to a MT. All I had to do was snip that MT/AT identifier pin. Everything worked great.

One thing to note. The later first gen non-turbo legacies 92+ apparently had reversed AT/MT identifier pins. They were reversed from what the 90-91 MY's had, and were incorrect when compared to the factory manual. However, that issue does not affect the turbo ECU's, all years 91-94. I bring this up in the event someone is swapping in a turbo motor into a 92+ non-turbo legacy and keeps the existing harness.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
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rob
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Re: Adapting an EJ20G ECU

Post by rob »

Thanks for the insight Josh. I removed the AT/MT pin concern from the list.

-Rob
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Re: Adapting an EJ20G ECU

Post by cj91legss »

rob wrote:I have seen them on ebay, but for something like $130. It's really looks to be a small number of changes (5 + the ignition changes). You could do this in a way that would make swapping back to stock pretty easily.

-Rob
A person could just go to a junk yard and snip out the ecu connectors and grab the ecu from an N/A and make their own harnes.
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
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Legacy777
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Re: Adapting an EJ20G ECU

Post by Legacy777 »

cj91legss wrote:A person could just go to a junk yard and snip out the ecu connectors and grab the ecu from an N/A and make their own harnes.
Trust me! That is much easier said than done. Those pins are extremely fragile.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

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cj91legss
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Re: Adapting an EJ20G ECU

Post by cj91legss »

oh i bet but a couple hours work and some patience is worth more than 130 bucks
91 L-TW Wagon with a full Swap -RIP
92 SS Prefaced, GD dash swapped, 22T/205 Hybrid 20 psi - BEAST!
93 SS Bone Stock Gone!
94 TW Bone Stock Gone!
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Re: Adapting an EJ20G ECU

Post by klin7757 »

Agreed. I've made a conversion harness out of a junk connector and ecu. Not bad, just takes time. Oh and be sure to epoxy the soldered end for durability.
94TW red.
rob
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Re: Adapting an EJ20G ECU

Post by rob »

I don't see how its worth it. If you forget about the ignition changes for now, you have;

2 pins to simply remove from the connector
1 pin to move to another location
1 pin to remove and splice into the above relocated wire.


That's maybe 10 min of work. Plus, it's not like you are hacking up your harness. In fact if you wanted to go back to stock, you could leave the TPS shield wire spliced into the MAP ground, so that take out one of the steps.

I am working a way to make the ignition switch over easier, so even considering that, I cant see it being worth effort to build a patch harness.

-Rob
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Re: Adapting an EJ20G ECU

Post by PhyrraM »

A few days late to the conversation, but as someone who has done the "scavanged ECU parts" jumper harness.....I will gladly pay $130 to not do it again.

As far as the purge, TPS and California pins? I didn't do anything with them and have seen no ill effects in almost two years. I only did the ignition pins and the MAP ground pin. DISCLAIMER....most of that time was with an EJ20G spec Apexi PFC with only a few days testing with OEM EJ20G ECUs (although no ill effects were noticed during that time either).

Rob's idea of just modding the stock harness, in a controlled way, is likely what I would attempt if I was to do it again.
'93 Winestone SS Auto, '91 Pearl White SS.
'93 Pure White SS EJ20G slanty intercooled, SIDESWIPED! In stasis.
'94 FWD and '95 AWD Laguna Blue SVXs.
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Re: Adapting an EJ20G ECU

Post by Legacy777 »

PhyrraM wrote:A few days late to the conversation, but as someone who has done the "scavanged ECU parts" jumper harness.....I will gladly pay $130 to not do it again.

Yeah...unless you have done the jumper harness....or tried, it sounds a lot easier than it actually is.
Josh

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Re: Adapting an EJ20G ECU

Post by PhyrraM »

Here is a list of cars with the same ECU connectors as the Legacy. This list can be used to search for patch harnesses, harness side connectors/wires/pins, or cheap ECUs to disect for male ECU connectors.

91-01 ACURA NSX (MAIN ECM CONN ONLY)
94-96 DODGE STEALTH
94-97 MITSUBISHI 3000GT
00-05 MITSUBISHI ECLIPSE 2.4 MANUAL
96-99 MITSUBISHI ECLIPSE TURBO
03-05 MITSUBISHI LANCER EVO VIII US MODEL
96-98 EAGLE TALON TSI
96-97 LEXUS LX450
93-95 MAZDA RX-7
97-98 SUBARU FORESTER
92-96 SUBARU IMPREZA EJ20G
90-94 SUBARU LEGACY EJ20G
93-96 SUBARU LEGACY EJ20H
1996 TOYOTA 4RUNNER 4CYL AUTOMATIC
97-98 TOYOTA 4RUNNER 4CYL
96-97 TOYOTA LAND CRUISER
95-98 TOYOTA T-100 4CYL
95-97 TOYOTA T-100 V6 MANUAL
95-97 TOYOTA TACOMA 3RZ AUTOMATIC
95-97 TOYOTA TACOMA V6
'93 Winestone SS Auto, '91 Pearl White SS.
'93 Pure White SS EJ20G slanty intercooled, SIDESWIPED! In stasis.
'94 FWD and '95 AWD Laguna Blue SVXs.
2017 Pure Red BRZ Limited w/Performance pack
Legacy777
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Re: Adapting an EJ20G ECU

Post by Legacy777 »

Good to know. Thanks for the list.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

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MikeyMeyagi
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Re: Adapting an EJ20G ECU

Post by MikeyMeyagi »

PhyrraM wrote:A few days late to the conversation, but as someone who has done the "scavanged ECU parts" jumper harness.....I will gladly pay $130 to not do it again.

As far as the purge, TPS and California pins? I didn't do anything with them and have seen no ill effects in almost two years. I only did the ignition pins and the MAP ground pin. DISCLAIMER....most of that time was with an EJ20G spec Apexi PFC with only a few days testing with OEM EJ20G ECUs (although no ill effects were noticed during that time either).

Rob's idea of just modding the stock harness, in a controlled way, is likely what I would attempt if I was to do it again.
I too only changed the ignition and the map ground.... my car has been running excellent for over a month
94 Supra Turbo 6 speed. build in progress
98 Lexus GS300, single turbo 2JZGTE swap. daily driver
93 Impreza wagon, home brewed n/a-t ken block themed winter drift missle

*sold*
94 Alpine Sport Wagon... STi conversion, rotated turbo etc
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Re: Adapting an EJ20G ECU

Post by 93forestpearl »

If one is hell-bent on making a patch harness, the ECU header can be removed easily with a propane torch. You sacrifice the board of the ECU you are taking it from, but the header comes out in a snap. I have two of them on my workbench, actually.


However, I won't be using them since it really would be a major PITA to do it properly. Since my car will never be stock again, I don't care about cutting my harness up, since it will be significantly modified in other ways. Heat-shrink butt connectors are where its at.
→Dan

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rob
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Re: Adapting an EJ20G ECU

Post by rob »

updated first post;
rob
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Re: Adapting an EJ20G ECU

Post by rob »

As I have now successfully done this conversion myself, I have updated the original post.
-Rob
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Re: Adapting an EJ20G ECU

Post by impreza_GC8 »

I thought there was a lot more involved in the ignition side of things in order to run the '20G ECU. The EJ22T and the EJ20G control spark differently from previous writeups I have read.
-'97 Outback - EJ25 block/pistons/HLA heads, EJ22T crank/rods/ECU, EJ20G intake manifold/fuel rails/440cc injectors, VF8 @ 11psi. . . . Fuel cut > me
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Re: Adapting an EJ20G ECU

Post by kimokalihi »

Depends which EJ20G you have. My 97 Forester EJ20G had wasted spark just like the EJ22T. The WRX EJ20G uses coil on plug I believe.
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Re: Adapting an EJ20G ECU

Post by rob »

impreza_GC8 wrote:I thought there was a lot more involved in the ignition side of things in order to run the '20G ECU. The EJ22T and the EJ20G control spark differently from previous writeups I have read.
Yes there is. That's why I said;

----- IGNITION CHANGE ------

More info coming...


I am prototyping a simple converter circuit that will allow the retention of the factory coil pack setup while using an ej20g ECU. When I have it finished I will post the info.

-Rob
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Re: Adapting an EJ20G ECU

Post by Florin1 »

Thanks for the update Rob. Any ball park ideas as to when?
1994 Legacy Sport Sedan.
1991 Legacy Sport Sedan.
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