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Old 07-23-2006, 05:37 AM   #1
Scooby Specialist
Member#: 109567
Join Date: Mar 2006
Location: Qatar
Default For those how have an idea about the JDM EJ25

I did a long search and I did not come up with anything usefull for myself
Okay, I have a SOHC EJ20 and I'm looking for more power.....
for the last 6 months I was looking for any EJ25 engine to swap it in my car, but those engine are extremly rare in my area.
luckyly I found a JDM EJ25 shortblock and I'm going to buy it but first I need to know some info cuz I will use my stock ecu which is desigend for SOHC engine.

1- that JDM EJ25 shortblock was DOHC (( off 98 legacy )) and I want to use this JDM EJ25 along with my EJ20 SOHC heads, and intake body, is this okay? cuz I will put TWE SOHC stage II cams soon + PP6
2- with the JDM EJ25 shortblock + SOHC + TWE stage II cams, how much power will I get if I go catless
3- what is the recommended revlimit ?

please help me, I was looking for this engine for the last 6 months, and now all I need some infos before I buy it
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Old 07-23-2006, 12:30 PM   #2
Driving Sports TV Staff
Member#: 15542
Join Date: Feb 2002
Location: Kirkland, WA
2004 WRX


I haven't done that *exact* set-up. But we did kind of do something similar with our Project 2.5RS.

Someone else may correct me, but I'm pretty sure the EJ25 is essentially the same in both the US and JDM models (bore, stroke, compression, heads, etc.) So, discounting any benefits from a JDM block, and thinking that you'll be two cams short putting a set of SOHC cams into a DOHC block, I'll pull an estimated 40 HP gain out of the air over a "stock" EJ25. I have no idea what an N/A EJ20 produces.

Now, keep in mind that an aggressive cam will also *kill* your bottom-end. So, you'll now have a theoretical 40HP peak at close to redline...and much less off the line. It will drive more like a turbo car. Though coming from a 2.0, it may be very similar off the line, now that I think about it.

As for increasing your redline, we're running 8000RPM right now using a early version of the forthcoming COBB accessport for N/A, but that will only work on 2005+ MY ECU's. I've read that I-Speed has a flash that will do it for older models, but don't have any experience with it. Your best best may be to go with a full stand-alone system like a MegaSquirt (free to build), AEM, or PerfectPower Pro. The PP6 has limited control over the motor and cannot modify redline.

If you haven't upgraded your internals, I wouldn't recommend bumping your redline any higher than just a smidge over what the block was originally set for. We're running 8K, like I said, but we also have a built and balanced bottom-end.

Given your parts list, I would suggest at least looking at turbo options before jumping into this project. That is, unless you have to replace the block for some other reason anyhow.

Ryan Douthit, Publisher
Subiesport Magazine
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