1998 Subaru Legacy GT EJ25 6/7 96-pin Plug & Play

[thebigmacd]

We will add more info as we compile a list

VEHICLE (stock)
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Year: 1998
Make: Subaru
Model: Legacy GT

ENGINE (stock)
-----------------------
Code: EJ25 Phase 1
Valves: 4 per cylinder
Cams: DOHC (Stock)
Displacement: 2.5 L
Induction: Natural
Injector: Stock 27# (280 cc/min)

ELECTRICAL
-------------------------
Connector: 96-pin stock
Fuel Relay: Stock
Fan control: Megasquirt 2-stage
MAP: Onboard
IAT: GM
CLT: Stock (Use Bosch [Saab] setup in sensor config)
ignition: Stock Wasted Spark Ignition Module
Crank: Stock 6-tooth (LM1815 conditioner)
Cam: Stock 7-tooth (LM1815 conditioner)








Specific TunerStudio Settings:
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Spark Output: Going Low (Normal)
Idle Valve Mode: Inverted 100%=Off

[turboed22]

Sweet!!! Thanks for the link over here from NASIOC. How is it running?

[thebigmacd]

Sweet!!! Thanks for the link over here from NASIOC. How is it running?

It ran great for 30-40 mins on the highway at 110-130 km/h, then suddenly shut off. We're pretty sure it was caused by the 5V regulator not being heat-sinked (jsmcortina warned about this;)). We simply coasted to a stop on the shoulder, plugged in the stock ECU, and were on our way again. Didn't matter because my laptop ran out of battery right around then too, so no more tuning any.

The VE Analyze Live feature of the latest TunerStudio works very well.

I am currently researching the best method of building a 12V-16V DC-DC power supply, so we don't have the laptop issue happen again.

The funny thing is due to an O2-related code, the stock ECU is running way worse in some sort of limp mode than the Megasquirt was running when it shut off.

[a73camaro]

I am currently doing that exact same ECU case/MSII mod to a '98 Impreza. Good to see that the idea of stuffing a MSII into a factory case dose work.

I am curious on how you brought your MAT signal to the ECU via the factor wiring harness. My thought was to install a MAT sensor on the outlet end tank of the intercooler and use the MAF wiring that goes to the ECU.

[a73camaro]

I had no luck getting the 96 pin through the perf board. Ended up soldering the wires to the pins.

[thebigmacd]

I am currently doing that exact same ECU case/MSII mod to a '98 Impreza. Good to see that the idea of stuffing a MSII into a factory case dose work.

I am curious on how you brought your MAT signal to the ECU via the factor wiring harness. My thought was to install a MAT sensor on the outlet end tank of the intercooler and use the MAF wiring that goes to the ECU.

We just brought an extra wire right into the ECU case through one of the heat-sink mounting holes in the side. The other side of the sensor we just grounded to the engine.

[thebigmacd]

I had no luck getting the 96 pin through the perf board. Ended up soldering the wires to the pins.

The 96-pin connector is metric spacing I think. We spread some pins apart and pushed some closer together with pliers.

[thebigmacd]

This thread deserves a proper update, so here goes:

Broken

Soon (minutes) after we took that last photo I posted, the car conked out; at 130 km/h in the third lane; with a passenger that really had to pee. Fun. We coasted over to the shoulder. The trigger logger told us that the signal from the CKP sensor was gone. Flatlined. Great. We threw the stock ECU back in and started up just fine and we continued with our trip.

Stock ECU Sucks

Now being able to use the stock ECU at a moment's notice is all fine and dandy, except that this whole megasquirt thing started because the stock ECU is screwed and the car gets about 13 mpg and stumbles around with it in.

Worse and Worse with Fixes

The next logical step was to reflow the solder to that circuit, check for shorts etc. Which we did. Unfortunately, every time we "fixed" something and drove the car it would go less and less distance before conking out. The final straw when we made it about 5 houses down the street before synch was lost and the car would not run on megasquirt.

Rebuilt Circuit

Back to the drawing board: we removed the existing LM1815 on the crank circuit and replaced it with a socket for quick chip swaps. We reflowed all of the solder connections (ground etc) once again. We put it all back together and in the car.

Sometimes we are Really Stupid

No fire. Crap. MS2 and LM1815 were missing. Duhhhhhhhhhhh! Sometimes we are so smart we are stupid. Put them back in. Car fired up and idled just fine. Josh drove the car back and forth to work a couple days. Awesome!

Broken Again

Then, at 40 miles on the "fixed" setup the car conks out again. What?!!!! That's unpossible!!!! We were bummed.

Brainwave!

Today, we had a chance to go on a 140 mile round trip, and no way Josh wanted to waste gas. So he had a brainwave...I'll bet something is shorting on the bottom cover of the ECU even though we have a plastic spacer in there! So before we left we put the megasquirt in and layed it on its top with the bottom cover off.

It is Finally Fixed

Success!!!! Something was shorting on the bottom cover. We made two trips of 70 miles with zero issues with the cover off. Oh, it got 25.6 mpg @ 80 mph while we were at it.

Verdict

Megasquirt is never the problem, poor construction is. We wasted 30-40 hours and money on spare LM1815s when the fix was so simple in the end. Megasquirt support for the EJ25 in Legacy GT is 100% reliable. We are going to add a spacer to the bottom cover and all will be well.

Future Outlook

Our dream is to design and sell an adapter board + kit for this segment of Subarus (there is little to no support in other aftermarket products). I am not promising we will, but I *want* to. I have a stable full time job that I am not willing to give up in the least, and many projects around the house and other cars etc but if the demand is there I just might get the ambition and find the time.

If someone wants to bankroll this project, go ahead lol

There are some stock things that we don't support on our setup, namely EVAP and EGR. Megasquirt firmware doesn't support it and I fear we are fast running out of I/O but the interface hardware is definitely trivial to implement. We are still slightly unsure (without tracing the wiring harness) whether there is a clutch input to the ECU, but if there is we can implement launch control as well.

[a73camaro]

Thanks for the follow-up, we all can learn from it.

The tough thing about interfacing the MS to the factory wiring harness via inside the ECU case is the wiring. It gets a little messy and the interface isn't that great.


DIYAutoTune has a real slick way of interfacing with a MircoSquirt.


With the 96-pin ECU being the odd duck, I don't see someone like Matt creating an interface do to low demand.

There are some stock things that we don't support on our setup, namely EVAP and EGR. Megasquirt firmware doesn't support it and I fear we are fast running out of I/O but the interface hardware is definitely trivial to implement. We are still slightly unsure (without tracing the wiring harness) whether there is a clutch input to the ECU, but if there is we can implement launch control as well.

There is no clutch input into the factory ECU but there is a "Transmission ID" that goes to the stock ECU. As for emissions, my thought was to operate both solenoids with one conditional output.

[Taiden]

Hey I was hoping I could pick your brain on a few things. I just finished the MS basic assembly and everything checks out. It's time for me to go ahead and start adding the additional circuits needed to run my 96 Impreza 2.2 on stock 6/7 triggers.

Seems like a few people have done the 6/7 setup on all stock subaru stuff but haven't summarized their methods.

Thanks
Luke