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Old 01-31-2007, 05:26 PM   #1
rob
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Default ej20G coil conversion

THE WHAT:
This is an example how to convert an old EJ20G to work with '02+ WRX ignition coils.

THE WHY:
The EJ20G coils are notorious for failing with age and causing misfires. I had misfires at anything over 0.8 bar, that was traced to two coils that developed cracks in the housing. Below is what I found (I removed the cracked piece on the one on the right to see what was on the inside).




THE HOW:
The old style ignition incorporates an external igniter, the newer style has the igniter built into the coil housing. The old coils have 2 wires; coil trigger and +12V. The new coils have 3 wires; ground, igniter trigger, and +12v. There is a little bit of harness hacking to make it work, but it's pretty straight forward. Here are the basic steps;

1. Cut connector off of old coils
2. Wire the old pigtails to the new coils; Power to power, trigger to trigger. Wire the ground signal to a ring connector and attach to the mount screw
3. Install new coils and connect up to the Ej20G harness as usual
4. Remove the igniter, and snip the 2 connectors from the harness and merge the harness.

Details of the steps above:

1. This is pretty straight forward, just clip off as much of the pigtail from the old coils as possible.

2. The easiest solution is if you have the matching connectors for the new coils from the '02+ harness. I didn't, so I soldered new wires directly to the coils, then attached the old pigtails to the new wires.



Using the above picture as a reference, the pinning is as follows from left to right:

Pin1 : Pin2: Pin3
+12v : GND : Trigger
Red : Blk : Green <--- wire colors I used in my picture
RY : BY : GY <--- '02 WRX harness colors


After soldering the wires, I globbed in a bunch of high temp epoxy to prevent corrosion and to add some strain relief for the pins:



Next comes connecting the old connector to the new coil. You have two colors on the old pigtail, Red and Yellow (one of them might have a stripe, can't remember). Here's the tricky part of this, the wiring diagrams only show the wiring *up to* the coil connectors. The problem is in the diagram, the yellow wire is the +12V, but after the connector, on the coil side, the yellow wire turns into the trigger signal.

** To wire the pigtail to the new coils, connect the Yellow wire to the trigger pin on the new coil and the Red wire to the +12v pin. Put a ring terminal on the center pin wire.

Lastly I shrink tubed and put the ring terminal on the bolt (after cleaning the corrosion under the bolt flange)



3. The coil fits in the early WRX heads perfectly, however there are some fitment issues with the Liberty version of the motors. The engine harness has two coil connectors for each side. The grey connector is for the front coil, the black is for the rear.




4. Last part is to bypass the igniter. I chose to simply cut the connectors out of the harness and merge the harness. The igniter is on the backside of the mounting bracket containing the MAP sensor and boost control solenoid.



Cut both connectors out of the harness and remove the igniter. There are 5 input wires into the igniter from the main harness and 4 output wires leaving the igniter to the engine harness. If you are following from the wiring diagrams, this is a very confusing wire up. The signal pins on the ECU are labeled coil 1, 2, 3, 4. The wiring to the coils are also listed as Coil 1, 2, 3, 4. The trick is that they use different conventions. For the ECU, the pins are labeled in *firing order*. For the coils in the diagram, they are listed as the actual cylinder number. The correct wiring is:

ECU side :: Coil side
---------------------
Yellow-Blue stripe (YL) ---> Red-Green stripe (RG)
Green-White stripe (GW) ---> Blue (L)
Red (R) ---> White-Red stripe (WR)
Black-Red stripe (BR) ---> Blue-Green stripe (LG)
Black (B) ---> no connect

Wiring diagram for reference:


THE RESULTS:
So far my high boost misfires are gone and I am back to 1.1 bar. I still need to open the gaps back up to see just how good they are, but so far I am very happy with the conversion.
UPDATE: I peak up to 1.30 bar now and still not a hint of misfire.

-Rob
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Last edited by rob; 02-07-2010 at 12:37 AM.
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Old 01-31-2007, 06:51 PM   #2
snowman4us
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nice write up!
you get a banana

i defenetly plan on using this
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Old 01-31-2007, 07:20 PM   #3
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awesomness!!!

this is going to be one of the many things i do to my swap when it gets here
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Old 01-31-2007, 07:49 PM   #4
kbahus
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Very sweet, thanks for the write up!
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Old 01-31-2007, 11:59 PM   #5
rob
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Thanks.

A couple things I would like to add.

If you solder the wires directly to the pins, I would suggest tinning the pins and the wire ends first, then all you need to do is place the wire on the pin then apply heat to the side or underside of the pin and the solder will reflow in both parts. Only for those with a steady hand.

On my engine at least, I had a biotch of a time getting cyl #4 coil in place. The head to rail clearance is litterally a couple mm too small. I found the easiest way is to take a long bar between the head and the rail and shove the motor just enough to slip the coil in place. It's important to make sure to get the coil boot on the plug while the you have the engine moved over.

-Rob

Last edited by rob; 04-05-2007 at 05:00 PM.
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Old 02-05-2007, 05:11 PM   #6
Matt Monson
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This is a great little write up. The longer my swap sits in the corner waiting for me to love it, the more appealing this conversion seems. Since I haven't converted my ignition yet, this would be even simpler on my '91 SS.
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Old 02-05-2007, 05:58 PM   #7
Jaxx
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i tried to get the mods to sticky this .. sigh

yeah it would make sense to do this when you do the initial wireing if you were to do such a thing
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Old 02-06-2007, 04:36 PM   #8
rob
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So just an update, I have been running this for about a week. I have had no issues. When I first experienced the ignition cut-outs on the old coils, I dropped the gaps down to 0.025" as a temporary solution. I have since opened them back up (NGK coppers) to 0.030-1 and filed back the ground electrodes a bit. I have no ignition problems at 1.1bar and all the way to 7k. Keep in mind this is 8.5:1 motor. In the end, I am very happy with the results.
-Rob

Last edited by rob; 04-05-2007 at 05:00 PM.
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Old 02-06-2007, 05:50 PM   #9
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this needs to be stickied!
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Old 02-08-2007, 11:19 PM   #10
kbahus
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So I have a question. I finally have my car almost tuned and ready to roll. I have been trying to adjust the pfc boost to 1.0 bar and no matter where I set the duty cycle I get what feels like fuel cut at .75 or so. I am starting to wonder if this is not fuel cut, but really the ignition breaking up as it feels just like the soft -touch rev limiter on my Camaro. The only weird thing is it goes lean and not rich on the wideband when this happens, so that confuses me. What symptoms did your car experience rob?
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Old 02-09-2007, 09:02 AM   #11
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Seems to me like its your coils also. I was having the same issue as you, at about .8bar it would cut out. So i lowered my gap to .025 and it got rid of the issue for about a week. Then it started cutting out at 1.1bar. So last night i pulled out my coils, and i found 3 BAD coils. 2 of them fell appart when i took the rubber boots off, and one had a small crack in it. Luckely i had 2 spare coils to fix the problem with. Now im running 1.2 bar, tapering off to 1.1 by redline and i have yet to feel even the slightest hesitation.
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Old 02-09-2007, 04:05 PM   #12
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Yes I would have cut out and missing around 0.8 bar. Sometimes it was mild, other times more violent bucking. And as snowman suggested, try dropping your gap down to 0.24-5 on new copper plugs. If it goes away, or improves, then it's likely the coils.

Snowman, try moving your gaps back up to .030 and see if it's still clean.

-Rob
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Old 02-09-2007, 04:45 PM   #13
kbahus
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I already have my gaps dropped when I put plugs in it a few weeks back. Matt's got some coils laying around, I am going to pull mine apart this weekend and see what's going on.
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Old 02-11-2007, 03:18 PM   #14
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Go figure. Every one of my coils are cracked, most in multiple spots. One just totally fell apart. Heading to Matt's soon to get some new coils. haha

update, replaced all four coils, it doesn't break up under boost, but still stutters and hesitates under 2k and occasionally up top.......never ending

Last edited by kbahus; 02-11-2007 at 08:12 PM.
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Old 02-12-2007, 06:47 PM   #15
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did you try new plugs. being that they are only 10bucks, you cant go wrong putting in new ones.
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Old 02-20-2007, 10:09 PM   #16
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Would 04+ sti coil packs work the same?
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Old 02-20-2007, 10:20 PM   #17
rob
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should work the same.
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Old 02-20-2007, 10:34 PM   #18
kbahus
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Sweet, my car is breaking up under boost again, even with the new coils, so I am gonna try and do the conversion to something better. No sense in continually battling this. Thanks Rob.
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Old 02-21-2007, 12:44 AM   #19
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Quote:
Originally Posted by kbahus View Post
Sweet, my car is breaking up under boost again, even with the new coils, so I am gonna try and do the conversion to something better. No sense in continually battling this. Thanks Rob.
+1

My car under cool moist conditions on a cold start still needs some help to start. Me thinks it is the coils.
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Old 02-21-2007, 01:42 AM   #20
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Quote:
Originally Posted by kbahus View Post
So I have a question. I finally have my car almost tuned and ready to roll. I have been trying to adjust the pfc boost to 1.0 bar and no matter where I set the duty cycle I get what feels like fuel cut at .75 or so. I am starting to wonder if this is not fuel cut, but really the ignition breaking up as it feels just like the soft -touch rev limiter on my Camaro. The only weird thing is it goes lean and not rich on the wideband when this happens, so that confuses me. What symptoms did your car experience rob?
Fuel cut
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Old 02-21-2007, 02:55 AM   #21
rob
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Quote:
Originally Posted by sixpack subaru View Post
Fuel cut
He has an Apexi Power FC, not the stock ECU.

-Rob
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Old 02-21-2007, 02:57 AM   #22
rob
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Quote:
Originally Posted by kbahus View Post
Sweet, my car is breaking up under boost again, even with the new coils, so I am gonna try and do the conversion to something better. No sense in continually battling this. Thanks Rob.
Sure. At the very least you can put the ignition question to bed. Mine still runs sweet after the conversion.

-Rob
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Old 02-21-2007, 10:40 AM   #23
kbahus
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No way it is fuel cut, the boost control is turned off in the pfc, no fuel cut period.
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Old 02-25-2007, 12:21 AM   #24
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Just to make sure before I go through with this, I need to merge these wires at the igniter:
ECU side :: Coil side
---------------------
YL ---> RG
GW ---> L
R ---> WR
BR ---> LG
B ---> no connect

?
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Old 02-25-2007, 01:07 AM   #25
rob
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Quote:
Originally Posted by kbahus View Post
Just to make sure before I go through with this, I need to merge these wires at the igniter:
ECU side :: Coil side
---------------------
YL ---> RG
GW ---> L
R ---> WR
BR ---> LG
B ---> no connect

?
Yep that's right. Are you just double checking my work, or seeing something different?

If you want to do it the safe way, do one coil at a time. That way if you run into trouble it's easy to diagnose and move back to stock if you get into a bind and need a running car. That's what I did initially.

-Rob
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