My Subaru Engine Swap Project

PowerLabs!

 
 
 

 

 Introduction:

My car sitting in the sun. I purchased this 1999 Subaru Impreza 2.5RS in 2003 with 48thousand miles. Less than 40thousand miles later the engine spun a rod bearing and started showing severe rod knock. With a blown engine, the choice was to either purchase a new car, or repair this one. I decided that I liked the car too much to let it go, and went about trying to find a way to fix it myself, cheaply.
 I was shocked to find that prices for the EJ25 engine (the original motor in the car) are roughly as follows:
$4500 New
$3000 Subaru Remanufactured Longblock
$2995 Rebuilt
$600 - $1600 used (60 - 100k miles)

 Disappointed with the engine, and shocked with the prices, I decided it was time to think outside the box and and drop in a REAL engine in the car. Something that would not only last a lot longer than my old engine, but also make my car really, really fast.

 

 The EJ20 Engine and JDM VS USDM:

My JDM WRX RA Engine, top view. Since I wasn't about to replace a used blown engine with another, identical used engine, and there was no way around spending a couple thousand dollars whichever way I went about this, I decided I needed a stronger powerplant. Subaru has been developing their 2 liter turbo engine for many years now (the 2.5 liter naturally aspirated engine has far less development behind it). In the US, the 2L turbocharged design found in the 2002 - 2005 US WRX makes a very respectable 227 Horsepower. However, in Japan, a very similar iteration of this block makes 280HP out the door, totally stock. This is accomplished through a larger turbo, better flowing heads, different cam profile, different injectors and better internal components all around allowing more boost, sooner and making better use of the available fuel (Japanese engines are made to run on what is roughly the equivalent to 95 / 96octane in the US).
 Swapping in a US WRX engine into a non WRX car will net a car that is perfectly compliant with emissions testing, but the engine's complex wire harness will require a professional 45 hours of installation, at a cost of about $4000 from a tuner shop.
 Swapping in a Japanese (JDM) engine, however, will not only be much easier (as the wiring harness is smaller, simpler and separated from the rest of the car), but it can also be done cheaper and make 53extra horsepower STOCK. The downside is that there is no such thing as OBD2 in Japan, netting such a swap an instant fail at most computerized emission tests.

Rear view of the engine, showing the VF-29 Turbine. Since there is no emissions testing where I live,  the JDM (Japanese Domestic Market) engine was my first choice. I was lucky enough to find a 1999 JDM engine, which simplifies the wiring job somewhat as most of the connectors will be the same and the fuse box is also the same.
 The engine I found is a 1999 EJ207 JDM WRX Type RA (Race Altered), engine code "EJ207DW1KE". Specs are as follows:

 Turbocharged 2-Litre 4 cylinder boxer engine. VF29 Turbo running 15PSI, 8-1 compression.

Factory Specifications: 280HP@6500rpm, 260ft torque@4,000rpm, redline 8250rpm.

 Here is a comparison between the old engine and the new one:
 
  Engine Code Displacement Compression Boost Horsepower Torque Redline
Stock EJ25 2.5L            9.7:1 0 165 166 6250
New EJ207 2.0L 8:1 15PSI 280 260 8250

 

 Interestingly enough, virtually all Subaru engines are interchangeable: Mechanically, this engine will bolt right up to my Chassis needing only the turbo front crossmember from the donor car... The electrical side of it, however, is a different story...

 

 Wiring Harness.

 All these wires came from the JDM harness! That's only 1/2 of the wires that go into the car. All modern engines are run by a Engine Control Unit (ECU). The ECU monitors all engine parameters (air intake, air fuel ratio, exhaust gases, crank position, knock, oil / water temperature, etc) and controls all aspects of the engine (idle / fuel cut, governor, injector duty cycle, air fuel ratio, etc). It also receives data from the rest of the car (ignition, air conditioning, alarm) and outputs data to the dash and elsewhere. As a result, there are a LOT of wires coming in an out of the ECU.
 Unfortunately different engines use different ECUs (and some times even the same engine uses different ECUs) and the differences between the ECU of a turbo car and that of a non turbo car can be quite significant.

 

 So, in order for the Japanese motor to work inside my US car, I need the Japanese ECU and the Japanese wiring harness. It is on the picture to the left.
 Fortunately even though the bulk wiring harness consists of hundreds of wires for virtually everything electrical on the car, I am only concerned with the engine control part of it (the engine harness). Everything else has to go. In order to do that, the harness is first split:

 

 

 

 Then all the ECU wires are traced to their end, bundled together with tape and tagged out on their end connectors:

 And all unnecessary wires are cut off. There are considerably more non-ECU related wires in the car than engine harness wires.

 This leaves us with JUST the engine harness. This is all the ECU needs to control the engine:

 This required 7 hours of SOLID work. The process was as follows: Once all the wires were free, I held on to all the wires coming from the ECU plugs and taped them together. I kept taping all ECU wires together as I separated them from wires that did not go into the ECU until all wires had been run into their respective plugs. There, I tagged all the ECU wires out, then cut and removed everything that was not ECU related. The reasoning behind this is simple: If it does not go into the ECU harness, then it is going into the rest of the car. Since all I am replacing is the engine, there is no reason to replace any of the other wires. It was not difficult, but it took a very long time, and a LOT of focus and discipline.

  I do not believe this swap would be possible without a wiring diagram; the wires going into the ECU from the dash and fuse box go into plugs that do not necessarily correspond with the RS plugs, so I can neither use the JDM harness on the dash (nor would I want to: THAT would be a wiring nightmare) nor figure out from just the plugs which RS plugs correspond to it. With both the RS and the JDM wiring diagrams I can simply pull the dash wires from the RS ECU and splice them into the JDM ECU though. Much easier.
 Only two plugs in the engine harness are different: AT/MT neutral position switch and MT/AT identification (I reused those). 4 wires leave the engine and do not go into the ECU: Those are Ignition power (red/yellow), Ground (black) and the a thin red/white and a red/green one. Those go into the dash.
 Below, for comparison purposes, is the stock 2.5RS ECU (left hand side) and the JDM ECU. Notice how the plug size, shape, and pin geometry are all different. The mounting points are also mirror images of one another (RHD issue).
Old and new ECU.

This is the ECU identification. AE480 = Version 5 WRX Type RA.

 

 

In-Car Wiring.

 In order to integrate both wire harnesses in the car it is necessary to gain access to the stock wire harness; this is done by removing the ECU (take out carpet, unbolt ECU plate, remove ECU, remove plugs). Unfortunately it is necessary to remove the air conditioning box; this requires bleeding the AC lines and removing the AC unit from inside the car. Once this is done the heater core is still somewhat on the way, but I have decided to do my wiring without removing it; this saves me the time and trouble of removing the entire dashboard. In retrospective, it may not have been that much easier, if at all. But it worked.

 Passenger side footwell with the stock 2.5RS wiring.Trying to figure out if it is possible to do this withough removing the A/C. It is not.Engine removed.

 With the AC unit out the rightmost firewall feed through is pushed back into the passenger compartment and the wires going from that engine harness to the ECU are cut. Anything specific to the 2.5RS engine can be removed, anything coming from the fuse box, the dashboard, the fuel pump, relays, etc has to be spliced into the JDM harness. I made the pinout matrix below to make my job easier; every sensor/connector is named, identified, and put next to its plug location on the JDM ECU:

 

 

 

 

 


 

Content

Type

2.5 RS Plug

2.5 RS Connector

JDM Plug

JDM Connector

Crank Pos Sensor

Signal (+)

B135

1

B136

5*   or 6 

Crank Pos Sensor

Signal (-)

B135

8

B136

23

Crank Pos Sensor

Shield

B135

10

B136

30

Cam Pos Sensor

Signal (+)

B135

2

B136

6* or 7

Cam Pos Sensor

Signal (-)

B135

9

B136

23

Cam Pos Sensor

Shield

B135

10

B136

30

MAF

Signal

B136

5

B136

1

MAF

PSU

B136

15

 --------

-------- --------

MAF

Shield

B136

25

B136

30

MAF

GND

B136

8

B136

31

Throttle Pos Sensor

Signal

B136

17

B136

20

Throttle Pos Sensor

PSU

B136

15

B136

12

Throttle Pos Sensor

GND

B136

16

B136

24

Front O2 Sensor

Signal (+)

B136

7

B136

21

Front O2 Sensor

Signal (-)

B136

20

-------- 

 -------- --------

Front O2 Sensor

Shield

B136

23

B136

30

Rear O2 Sensor

Signal

B136

18

--------

 ----------------

Rear O2 Sensor

Shield

B136

24

 --------

 ----------------

Rear O2 Sensor

GND

B136

16

 --------

 ----------------

Front O2 Sensor Heater

Signal 1

B134

22

 --------

 ----------------

Front O2 Sensor Heater

Signal 2

B134

23

 --------

 -------- --------

Rear O2 Sensor Heater

Signal

B134

21

 --------

 -------- --------

Engine Cool temp sensor

Signal

B136

14

B136

28

Engine Cool temp sensor

GND

B136

16

B136

24

Vehicle Speed Signal

 

B135

24

B135

26

Starter Switch

 

B135

28

B135

2

A/C Switch

 

B135

27

B135

11

Ignition Switch

 

B135

7

B136

25

Neutral Pos switch MT/AT

 

B135

26

B135

29

Test Mod Connector

 

B135

14

B135

22

Knock Sensor

Signal

B136

4

B136

26

Knock Sensor

Shield

B136

25

B136

29

AT/MT Identification

 

B135

25

B135

4

Back Up PSU

 

B136

9

B135

17

Control Unit PSU

 

B136

1

B136

9

Control Unit PSU

 

B136

2

B136

8

Sensor PSU

 

B136

15

 --------

 -------- --------

Line end Check 1

 

B135

20

 --------

 -------- --------

Ignition Control

#1, #2

B134

25

B134

7

Ignition Control

#3, #4

B134

26

B134

16

Fuel Injector

#1

B134

4

B134

31

Fuel Injector

#2

B134

13

B134

32

Fuel Injector

#3

B134

14

B134

25

Fuel Injector

#4

B134

15

B134

18

Idle Air Control Valve

Signal 1

B134

5

B134

14

Idle Air Control Valve

Signal 2

B134

6

B134

5

Idle Air Control Valve

Signal 3

B134

19

B134

15

Idle Air Control Valve

Signal 4

B134

20

B134

6

Idle Air Control Valve

PSU

B136

2

 --------

 -------- --------

Fuel Pump Relay Control

 

B134

16

B134

1* or 21

A/C Relay Control

 

B134

17

B134

22

Radiator fan relay 1 control

 

B134

3

B134

4

Radiator fan relay 2 control

 

B134

2

B134

13

Self-shutoff control

 

B135

19

B136

32

Malfunction indicator lamp

 

B134

11

B134

28

Engine speed output

 

B134

30

B135

14

Torque Control 1 Signal

 

B135

16

B135

3

Torque Control 2 Signal

 

B135

17

B135

12

Torque Control cut Signal

 

B134

31

B135

15

Mass air flow signal for AT

 

B136

11

 --------

 -------- --------

Purge control solenoid valve

 

B134

2

B135

7

Power steering switch

 

B135

13

B135

1

Atmos press sensor

Signal

B136

29

--------

 -------- --------

Atmos press sensor

PSU

B136

15

--------

 -------- --------

Atmos press sensor

GND

B136

16

--------

 -------- --------

Press sources switch

 

B134

9

B134

26

Fuel temp sensor

 

B136

26

 --------

 -------- --------

Fuel level sensor

 

B136

27

 --------

 -------- --------

Fuel tank press sens

Signal

B136

12

 --------

 -------- --------

Fuel tank press sens

PSU

B136

15

 --------

 -------- --------

Fuel tank press sens

GND

B136

16

 --------

 -------- --------

Fuel tank press control valve

 

B134

1

 --------

 -------- --------

Drain Valve

 

B134

10

 --------

 -------- --------

AT diagnosis

 

B135

4

 --------

 -------- --------

Line end Check 2

 

B135

21

-------- 

 -------- --------

GND

Sensors

B136

16

B136

24

GND

injectors

B134

7

B134

9

GND

ign sys

B134

27

B134

17

GND

PSU

B134

8

B134

8

GND

control sys

B136

21

B136

18

GND

control sys

B136

22

B136

1* or 21

GND O2 sensor heater 1

 

B134

35

 --------

 -------- --------

GND O2 sensor heater 2

 

B134

34

 --------

 -------- --------

Read Memory connector

 

 

 

B135

13

Wastegate control

 

 

 

B134

19

AT Load signal

 

 

 

B136

2

Pressure Sensor

 

 

 

B136

7

  RED = USDM only, GREEN = JDM only, *With immobilizer
  Green connector (-): Backup psu, line end check 1
 Geen connector (+): malfunction indicator lamp (?13.7ohms), ign switch,


Working on the interior swap.Integrating wire harnesses. With the JDM harness next to the car wires are cut, stripped, twisted together, soldered and heat shrink tubing is used to insulate them. It is good practice to not cut all the wires at the same length, otherwise all the joints will bulge up on the middle.

 

 

 

 

Below left: JDM harness next to car, wires and plugs being spliced. Below right; JDM harness inside car, most wires and plugs spliced, leftover plugs on passenger seat.

 JDM harness being itegrated into car.JDM harness mostly inside car.

 

 

 

 

 

 

It took an entire extra 2 days to complete the in-car wiring; between wires that simply did not exist in the 2.5RS wiring diagram, wires that were not listed in the JDM diagram, plugs that matched up but had wires in different locations, plugs that were not anywhere in the car, wires that simply did not exist in the JDM ECU at all, the last two days comprised in one of the most frustrating tasks I have *EVER* undertaken. At some point in the swap I actually almost regretted starting it.

Combined harness inside car, some wires left over.ECU installed, engine runs!

 

 

 

 

 

 

 With all the wiring done, the ECU wires are bundled together, taped, and the cover is put on. Since the right hand drive ECU has mounts which mirror the US mounts, it is not possible to bolt it down. Instead, I used the cover to hold it in place. It is secure for now, but I will seek a more permanent solution next time I'm under there.

ECU wiring done.ECU under cover.

 

 

 

 

 

 

 The following 2.5RS ECU wires do not appear to go anywhere in the JDM ecu:

Fuel tank press sens

Signal

B136

12

Fuel temp sensor

 

B136

26

Fuel level sensor

 

B136

27

Fuel tank press control valve

 

B134

1

Drain Valve

 

B134

10

???

???

B135

11

???

???

B135

12

???

???

B134

12

 The car starts up, idles smoothly, and runs perfectly, all functions operate normally and it does not show a Check Engine Light signal (thought the CEL IS connected). It appears as though those 2.5RS wires go into functions that do not exist in the JDM ECU.

 

 Mechanical:

Installed engine, front.Installed engine, top view.

 Here you can see the completed engine installation. Notice the intercooler water spray nozzles on the intercooler plate diffuser underneath the hood scoop, and the dual-water pump JDM windshield washer bottle (pump #2 sprays the intercooler to reduce heat soak).

 

 

 

 Virtually any Subaru engine can be put into any Subaru chassis. The engine bolts right up to the transmission, engine mounts, etc... There are only 3 issues:

1- The power steering lines need to be bent slightly  in order to fit around the larger heads (DOHC vs SOHC). The power steering pump is not the same, and the JDM lines will not fit due to the fact that they are for a right hand drive vehicle.
2- The cruise control unit will not fit with the downpipe and turbocharger in its location. It had to be relocated with custom brackets.
3- The stock front sway bar will not clear the turbo front cross member where the up pipe goes. I did not know this and tore a sway bar bushing soon afterwards. The solution is to buy a JDM swaybar, such as Cusco.
4- The air conditioning compressor in the JDM engine is shorter. The USDM one will not fit. The USDM lines have a one bolt fitting that does not go with the JDM fitting. No solution for this yet. I may need a JDM connector or a WRX air conditioning pump.

 Underhood wiring:

 This was very straight forward; wires are run through the firewall to their proper locations, taped together, covered in wire loom, and the grommet was installed again. A few notes:

1- The rubber grommet had to be split down the middle to allow the wires to pass. I taped it back together when done.
2- All wires should be run as far away from the turbo as possible. I wrapped the downpipe in header wrap and installed the turbo heat shield to further minimize the chance of any wires melting.
 You can see the new cruise control bracket on the pictures below.

 

 

 

 

 

 Intercooler spray setup:Intercooler water spray switch.Intercooler water spray setup; I am running the second pump through STI nozzles on the IC diffuser plate.Interior. Front top left to bottom right: Greddy Boost/EGT gauges, Escort Passport 8500 radar detector, Apexi S-AFC2, Sparco race pedals and dead pedal, MOMO shift knob, Carbon fiber trim.

 

 

 

 

 

 

 

 Braking and Handling:

 

Subaru 4-pot STI brakes. The added horsepower from this swap makes it possible to reach very high speeds, very quickly. With the stock brakes, any form of "spirited" driving usually resulted in brake fade as the rotors blued and the pads went up into smoke. It very quickly became apparent that even my upgraded stock brakes were not adequate for this power level. I upgraded to Brembo 4 piston calipers up front, and JDM STI vented rear brakes. This is the same brake setup the car came with in japan, and it eorks very well. Front rotors are racing brake slotted and the rears are cross drilled. I run Carbotech Bobcat ceramic street+track pads all around. Front cooling is further improved by air ducts.
 

 For handling, I am running Whiteline heavy duty swaybar endlinks all around, a cusco 21mm front swaybar, a whiteline 18 - 24mm adjustable rear swaybar (set for 20mm for daily driving) on whiteline heavy duty mounts, and a rear strut bar. Struts are KYB Adjustable Gas Shocks (AGX) and springs are H&R sport springs.

Here is a list of the upgrades I have installed. Click on any one of them to see an image of the part in the car.

Drivetrain:
STI Group N Hardened Engine mounts
STI Group N Hardened Transmission mount
STI Group N Hardened Pitch stop
STI Stainless Steel Clutch Line
STI Short Throw Shifter
Whiteline steering rack bushings
Whiteline rear differential bushings
Kartboy hardened shifter bushing (front and back)
ACT 13 pound lightweight flywheel
Exedy organic clutch (slips like crazy. Poor choice for a 300+HP car).
Perrin silicone turbocharger inlet hose
Knife edged, Port and Polished throttle body
Port matched and polished, powder coated intake manifold

Handling:
Cusco 21mm front swaybar
Whiteline Polyurethane front swaybar bushings
Whiteline heavy duty front sway bar end links

Whiteline rear adjustable swaybar 18-22mm
Whiteline heavy duty swaybar brackets
Whiteline heavy duty rear sway bar end links

STI Rear Strut Tower Bar
SPT Front Strut Tower Bar
KYB AGX Adjustable Gas Shocks
Rear Camber Bolts

Alignment specs:
 Front Camber: -1.3degrees (maxed out on stock bolts). Front Toe: Zero, Front Caster = 3.2
 Rear Camber: -1 degrees, Front Toe = Zero.

Brakes:
STI 4-Pot Front Brakes
WRX Racing Brake Slotted Rotors

JDM WRX rear brakes with Legacy Turbo Vented cross drilled rear disks.
Carbotech Bobcat brake pads all around
Stainless Steel Brake Lines
ATE Super Blue brake fluid.
Front brakes are cooled by air ducts installed on front bumper

Other:
Primitive Racing 1/16" aluminum front skidplate
Subaru OEM 1/16" steel rear skidplate
Fastline Mudflaps

Exhaust:
3 Inch stainless steel turboback exhaust.
Port and polished exhaust manifold, wrapped in gen 2 header wrap and sprayed with 2000degree F silicone paint.

Port and polished, powder coated intake manifold and throttle body.Ported and polished exhaust header inlet.

Engine installed in car.

 

 Initial testing:

 Checked all vacuum lines, electrical connections, power steering lines, coolant lines, fuel lines, blow off valve, intercooler, etc. Checked and filled fluids (power steering, engine oil, fuel, coolant). Put ignition key on, turned it to "ON", relays started, gauge lights came on, fuel pump came on (the Walbro 255LPH is loud!). Turned ignition key; the engine turned over maybe 6 times and started right up!
 Let the engine idle for a couple minutes; lots of smoke from fluids that dripped down on the exhaust parts. This smoke continued to come out for quite some time after the turbo heated up. After verifying that the thermostat and radiator fans both worked, put it into gear, and drove it around for a bit gently...
 First impressions:
 Off- boost (part throttle); the exhaust sounds nice; not too loud, nice mellow rumbling sound. The turbo sound is quite noticeable inside the car; a wonderful turbine like whine which gives way to a "whoosh" when I lift off the throttle. The car is perfectly drivable, EGTs are low, and the boost gauge hovers near zero with any slight application of the throttle.
 On-boost: Mash the gas pedal; first observation: Throttle response is not *nearly* as quick as the old 2.5L N/A engine. Lag is definitely noticeable. The turbo starts making some positive pressure somewhere in the low 2000RPM range, but the real power isn't really there until 0.5ATM. Initially, the 2.5RS feels faster because there is zero waiting time; when the gas pedal goes down, it accelerates, and quick. The turbo engine takes a good second of "OK" (typical 4 cylinder engine) acceleration before it really gets going.
 However, right around 0.5ATM the boost gauge needle almost instantly jumps to 1.2 - 1.3Atmospheres (18PSI or so) and with a smooth push the acceleration goes from "OK" to "pretty good", to "WOW!" Very impressive! The engine continues to pull hard all the way into the 7000s of RPM and the 8000RPM rev limiter turns the otherwise short gears into constant, powerful thrust. More importantly, the engine continues to pull, HARD, well into triple digit speeds.
 This is, by very far, the quickest car I have ever driven, and one of the fastest I've even been into.

 Here are some actual tests, performed with snow tires, full interior, a full tank of gas, spare tire, car jack, tools in the trunk, and a passenger:

 

 

 

 

 

 

Left to right:
Engine redline; 8000RPM.

0 - 100km/H (0 - 62MPH); 4.07 seconds. (this is *FAST*. Faster than a Ferrari 360 Modena, Faster than a Corvette Z06, Faster than a Ferrari 550Maranello...)

1/4 mile: 12.61 seconds @113MPH (launched from 4000RPM. Its pretty good decent. I hope to hit 11s with a bigger turbo.)


Yes, it was well worth it :)

 

 Completed Swap:

 Two bugs currently:

  No Air Conditioning.
 Clutch never designed for this horsepower. Will slip and burn on a hard launch. If it didn't, the transmission would probably break.
 Everything else appears to work.Interior at night.
Front of the carAerial View.

 

 

 

 

 

Update: 10000 miles daily driven and still strong as ever.

Rear viewSide view

 

 

 Pictures/Videos.

NEW: The Swap Video, produced by my friend Kelly.

First autocross with the car; stock suspension, upgraded swaybars, too much horsepower. I had a hard time controlling the car smoothly for a fast run; it would get going too fast on the straightaway for me to corner without sliding, and boost during cornering always meant tire spin. On this video you can see a nice wipeout during the slalom and then coming out of the final corner I get on the gas and smoke the tires on the straightaway (frame capture on the left). Nothing like a 4 wheel burnout! :)

 1st / 2nd gear pull video (2.3MB). Hear the turbo whine...

 Chase camera video.

 Autocross with new shocks, springs and boost set for 18.5PSI (23MB)

 

 

Powerslide on snow.

 Flyby

 More pictures and videos here.

 

 

 Credits:

 1st and foremost I would like to thank Tim Sanderson, who did the mechanical aspect of the swap (lifting out the old engine and crossmember, putting the new one in, adapting all the lines and fittings, etc). Tim is an outstanding mechanic who lives near Milwaukee, WI. If you need any work done on your car, he's my first recommendation.
 Thanks goes to
Myles Hechtman at Fine Line Imports. FLI supplied the engine for my swap, along with my fuel pump, rear brakes, radiator and a clutch I'm not using yet. Myles was very helpful with my endless questions about the swap and what would or would not fit. If you are planning on an engine swap along the lines of what I did here, be sure to give FLI a call, ask for Myles, and tell them Sam sent you ;)
 Thanks to Carl Seidel for all the outstanding port and polish work on the engine manifold, exhaust headers and throttle body.

 


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