Successful JDM EJ205 swap (single AVCS)

[Joeaxial]

I'm new here, but have been lurking for quite awhile, scouring up threads about JDM engine swaps. My son's 2006 LGT (143,000 miles) had a burnt up piston and another one with broken ring lands. I didn't wanna spend $3000 having the engine rebuilt on a $3500 car, so I purchased a JDM EJ205 that came out of a 2002-2005 WRX in Japan. When I purchased the motor, I had not done enough research and found that it has 2-wire cam position sensors (on the intake cam) whereas the LGT has 3-wire. Research told me that there is no way to make this work with the LGT ECU.

 

I took the valve covers off and found that the intake cams have different machining at the rear where the cam position sensor is located. Also, the LGT sensors are a slightly different size than their JDM counterparts. I'm not one to give up, so I swapped the intake cams (and the followers) from the LGT engine into the JDM EJ205. Valve clearance was right on the money. Next, I did some machining on the left JDM head to make the cam position sensor line up properly on the cam. The right head sensor alignment was very close, so I left it alone. I cleaned up all the oil from the sensors and the sensor mounting area of the heads and applied RTV gasket maker to make a good seal.

 

The next steps were time consuming, but not nearly as difficult as the cam sensors. Basically, everything that bolts to the bare long block must be switched from the LGT engine onto the JDM engine. This includes:

Oil Pan along with upper windage tray, oil pickup tube and dipstick

exhaust system

turbo (with oil and coolant plumbing)

intake system w/wiring harness

cooling system manifold

PCV system manifold

AVCS solenoids

all sensors

 

parts that you can leave on the JDM engine block:

Flex Plate

Motor mounts

 

After the engine was dressed and installed it fired up instantly. Check engine light was on, but it seemed to be running fine. I drove the car for 20 minutes, and it was running very well, but CEL was still on. I figured I'd have to hook up a scan tool, but after I shut the engine off and re-started, the CEL went off. I've only got about 100 miles on the engine so far, but it seems to run really nice so figure that there must be enough "wiggle room" in the ECU maps to allow it to compensate for the smaller displacement of the JDM engine. The mpg display shows an average of 18.2 mpg for that first 100 miles. Very few miles have been highway driving, so will know more about fuel economy after we get more miles on it.

 

One thing to be aware of is the JDM EJ205 AVCS engine uses different valve cover gaskets that were never used on a USDM version of the EJ engine. They are available from many online parts sellers. Subaru part numbers are 13272AA075 (left) 13270AA152 (right) I purchased mine from https://iatuning.com

[Joeaxial]

The engine has been running great. Still on the stock 2.5 tune. No check engine light. Good power. The engine is a little noisy on cold start high idle, but quiets down as soon as it heats up. No noticeable oil consumption in 1000 miles.

 

A couple small issues showed up: coolant leak from turbo coolant line off the bottom rear of the upper coolant tank - the hose ripped at the clamp.

RH valve cover was dripping on the exhaust- turns out there was a very small dent from shipping on the valve cover. upon close inspection it was cracked. Oil was seeping out through the crack. TIG welded the crack and all is well. The EJ 205 uses a different valve cover than the 2.5, so couldn't swap them.

 

I ordered new PVC hoses and turbo coolant lines and will install shortly. I didn't purchase this stuff before the swap because I didn't know how good the JDM engine would be.

 

This car has the 5 sp AT. Acceleration is a little sluggish right off the line, but kicks you back pretty good as soon as some boost is achieved.

 

I'm pretty happy with the results so far. My intention is to try to get some more miles on it to work any more bugs out and then send my son off to college with it after the holidays. He wanted to take it right away, but with a 3 hour drive to campus, I didn't want to have to play "rescue the dead Subie".

[Zac88]

Good job! Nice to know theres a cheaper engine alternative.

[All_talk]

Did you make any adjustments to the static exhaust cam timing to compensate for the lack of AVCS?

 

I suspect the higher compression ratio might result in some knock and the ECU pulling ignition timing. Not great for performance but drivable if it’s not to severe. Note: if the ECU runs out of timing to pull it will drop boost to wastegate (about 7psi), and it will be very noticeable, and this won’t throw a CEL.

[Joeaxial]

Did you make any adjustments to the static exhaust cam timing to compensate for the lack of AVCS?

 

This car is a 2006 with single AVCS. The donor EJ205 and the original EJ257 were both single AVCS, so no exhaust cam timing adjustment was possible.

[dgoodhue]

Just because the engine doesn't set any engine codes, doesn't mean the ECM is compensating for the displacement or is tuned properly. You would need to data log the engine to verify. Most likely it will need to be tuned like the EJ20X & Y engines or it is going to end up like the last engine if its driven at WOT.

[Joeaxial]

Good point on the tuning. I certainly haven’t been flogging on the car at this point. I am considering purchasing cable plus software to datalog.

[NORULZleggy]

Yes, I kind of laughed wen I saw successful swap because you said it was still running on the stock 2.5 ECU map. You need to find a tuner ASAP and have this care dialed in. These cars will break your heart if you cut corners. Find a tuner that knows about the swaps and has done tons of them and tuned them. There is a reason it came with a 2.5.

[Joeaxial]

I guess success can have different definitions, but the car runs very well. I don’t think the average driver would sense any clues that this car is anything but stock.