i am going to be running my stock 1.8L ecu becuase that is the only option i have at this point. But my question is what is going to be the power difference i will notice or will it be any different. Are there any warnings i should know by doing this. I am planning on putting in the EJ25 ECU later on when i get more parts like the dash assembly. any input would be great

thanks
Aaron

Power difference between EJ18 and EJ25? yes, Much better

Power difference with EJ25 between 1.8 ECU and 2.5 ecu? yes, but youll still be faster than an RS due to the lighter weight.

what is the weight difference between the a 94L and an RS. With useing the 1.8 ECu will I have any other problems to look out for??

also is there any potentially harmful things that could happen to the engine by running the 1.8L ECU w/ the ej25 for long periods of time??

What year 2.5?

engine is a 2000 EJ25 and ECu is 94 EJ18

I'm doing the same thing with my 96. But I'm doing 2000 block/DOHC heads/WRX intake manifold and 1.8 ECU. I am the king of bastard motors!!!!:lol:

I think it'll be alright. Timing probably isn't as aggressive and surely fueling is lighter. It might not matter so long as the ECU is trying to maintain a set AFR. Bigger squirts may help, but other haven't needed anything so far.

Keep us posted on yours, and I'll update as mine comes together.

Jay Storm

thats pretty much what im running. 00/01 EJ25 with 95 1.8 ECU. its going to take a few special things to do the swap when compared to the DOHC which literally bolts right in. Its been pretty well covered and I think most of it is in the FAQ.

Hawk, can I post the info you sent to me about this swap?

Please do!

Re: EJ25 swap
Excellent!

As you know the Ej25 will bolt right up. You can use the 1.8 flywheel and clutch or ide reccommend the 2.5 flywheel and clutch. You can also retain the cable setup with no problem at all.

A few things to look out for.

1. Crank trigger ring. In 2001 Automatic cars and manual trans cars had different ECUs. THey also had different Crank sensor trigger rings (on backside of timing belt sprocket). THe auto cars had a 6 tooth identicle to your 1.8. The manual trans cars had much more teeth. Make sure you have the 6 tooth ring on there so that the 1.8 ECU can run it. If you do not then just swap over the one from the 1.8

2. Fuel Injectors- The new style fuel injectors have a different electrical connector. It is pretty much opposite from the 1.8 because the new style conectors are inverted when compared to teh EJ18s. Pretty much match up the yellow wire (B+ to injectors)on all 4 injectors with its correct pin on the connector. I can e-mail you a scan of the engine harness diagram so you can wire it up properly.

3. Throttle Body blockoff- You need to use the 1.8 throttle body so that thew ECU can control the IAC and read the TPS. the 01' 2.5 has a seperate IAC port above the TB bore which the 1.8 does not. Simply block it off with a plate. Get a 2.5 TB gasket and a 1.8 one. Trace the perimeter of the 2.5 gasket on a thin piece of sheet metal. trace teh bolt holes and the main bore on the sheet metal and cut out. do NOT trace the IAC port from the 2.5 gasket. then install the 2.5 TB gasket between the manifold and block off plate, then the 1.8 gasket between the blockoff plate and Throttle body.

4. Plug wires- As far as I know subaru does not make a plug wire that will have the 1.8 coil end with the SOHC 2.5 plug end (its a long lead) You need to use the 1.8s 3 wire coil so the ECU can run it. THe 2.5 has a 4 wire coil with the ignitor built in and the 1.8ECU cannot run it. I had some plug wires made for me by kingsborne wire werks in CA. Cost me 50 bucks to have them made and overnighted. I think it is only like 16 bucks for the wire set, the rest was shipping for me. THey still have my order in file as part number "16-SVI" these are just barely long enough to reach the coil in the stock location. You can specify wire color, guage, and length from them of you want something different. They can also print text on the wires if you want!

5. temp sensor. The 1.8 uses 2 temp sensor, a 2 pin large one for the ECU and a single pin tiny one for the temp guage. The new EJ25 uses a single 3 pin triangular shaped sensor. Use the new sensor. Get a new style connector and wire the 2 wires from the big sensor to the top 2 pins on the new connecter. then attach the single wire for the guage to the bottom remaining pin. I have diagrams for this to that I can send you.

Everything else should either plug in or be swappable from the 1.8. For EGR disabling, I simply kept the solinoid attached to the harness and capped off the ports with those little rubber vacuum line blockoff things. I have it mounted out of the way. This way it still sits there clicking away so you do not get a CEL but it really isnt doing anything. Same thing goes for the other solinoid thingy on the passenger side. The blue solinoid is for the Evap purge canister and that needs to be retained. You have to alter it slightly to work because locations of lines are alittle differnt. Just make the routing copy that of the 1.8

As far as vacuum lines go, all the taps might be in slightly different locataions. It doesnt matter as long as everything that needs a vacuum signal gets one and all remaining ports are blocked off. There will also be a metal tube that looks like its part of the fuel lines but ultimatly goes into the cyl head/intake manifold area right by the fuel injectors. This is the air assist injection thingy. Simply plug off the ports on the back of the engine because this is not going to be used.

Thats pretty much it. Ide reccommend getting the plug wires and blockoff plate made ahead of time so that doesnt hold you up. Then when you have the engine out check the trigger ring and swap if needed, also do the wiring out of the car. Then put it all together. SHould take a weekend or less. If you have any more questions feel free to ask. When you need the wiring diagrams and further instruction on that let me know and i can e-mail them to you. good luck!


One more thing!

I just remembered...

In addition to the timing belt sprockets/crank trigger ring between the auto and manual there is one more difference.

On the manual cars there was a timing belt guide that fits above the crank sprocket for the timing belt. It fits VERY close to the belt and is held in with two bolts. This is there to prevent the timing belt from jumping teeth on the sprocket during hard launches, shifts, parking on hills in gear, etc. The automatic cars did not have this. Its a cheap part so you might want to verify you have it and if not order one and its 2 bolts.

I'll let you know if I remember anything else.

-Chris

thanks guys

i did this swap back in february this year, 93 ej18 ecu with 01 ej25. car was running a bit sluggish due to old spark plug wires, i spliced them. i recently changed to a new set of ej25 wires, retaining the heads for the ej18 ecu. and the car is running great. thanks alot to hawk for helping me with the project, u got any problem hes the one you wanna ask. =)
good luck guys