Sam's Engine Swap





 This page is no longer being updated. After you've looked at the engine swap check out my latest engine swap page.

My car sitting in the sun. Just a couple hundred miles short of 80K my 1999 Subaru Impreza 2.5RS developed severe rod knock on its stock engine (It had the stock EJ25 engine: 2.5Liter Single Overhead Cam 9.7:1 compression naturally aspirated), and ended all of my plans of further improving that powerplant.
 I was shocked to find that prices for the EJ25 are roughly as follows:
$3000Subaru Remanufactured Longblock
$600 - $1600 used (60 - 100k miles)

Disappointed with the engine, and shocked with the prices, I decided it was time to take that piece of garbage out of my engine bay and drop in a REAL engine. 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 power plant. 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 (I highly suspect half the redneck trucks in Upper Peninsula Michigan will be out of the roads as soon as they introduce it there), the JDM engine was my first choice. Since my car is a 1999 model, I was very fortunate to find a 1999 JDM engine: This simplifies the wiring job somewhat as most of the connectors will be the same and the fuse box is also the same.
 The new engine is a 1999 EJ207 JDM WRX Type RA (Race Altered), engine code "EJ207DW1KE":

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

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

 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 etc 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 even between a 1999 Impreza 2.5RS and a 1999 Impreza WRX the differences are 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. If you have A.D.D., this would be the time to take some extra Ritalin (just kidding!):)

 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) not 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 this PINOUT MATRIX to make my job easier; every sensor/connector is named, identified, and put next to its plug location on the JDM ECU. Sounds easy, right?

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. Its secure right 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




Fuel temp sensor




Fuel level sensor




Fuel tank press control valve




Drain Valve
















 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). I guess the 2.5RS wires go into functions that do not exist in the JDM ECU.



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 etc... There are only 3 sticky points:

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. The brakes were upgraded by swapping WRX brakes up front, and Legacy Turbo brakes in the back. The WRX brakes use slotted Racing Rotors and the back are Brembo cross drilled. Both rotors are vented and Carbotech Bobcat ceramic street+track pads are used all around. Front cooling is further improved by air ducts.
 Update: I am now using Subaru STI 4-pot front calipers.
 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.

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

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.

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

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

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  IT 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... HOLY S**T!!! 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 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 driven and still strong as ever. To date I have only raced one car that was faster in a straight line; a 500HP mustang :)

Rear viewSide view



 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.
 I'd also like to thank Robert Shmitt and his brother for giving me a hand with the swap, Hugo for letting me stay over while I worked on the car, and Kelly Drews for giving me a ride and sticking around when it was 100F and there was nothing to do but watch me cut wires for 7 hours.
 And a HUGE thanks for all the guys at NASIOC, specially turbosubysteve, with his 11 second JDM-swapped monster, for all the technical info without which I couldn't have done this.


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)

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

Powerslide on snow.

New: Flyby

 More pictures and videos here.


 Update: The blown engine:

Engine installed in car. I drove just under 14000 miles in a bit less than 8 months (June 27 2005 to February 18th 2006) on my JDM WRX Version 5 Type RA engine. The engine was bought used, with an estimated 50thousand miles or so on it. Following the link above you will see what modifications were done to it. Essentially, I was running the original engine, with all original internals, original turbocharger and intake. I upgraded my intercooler for the larger USDM STI top mount intercooler and fitted the car with a 3" stainless steel turbo back exhaust. The free flowing exhaust caused the engine to boost slightly higher than normal; typically I would see 17PSI whereas the engine should be doing about 15PSI. After doing a full port and polish on all intake and exhaust components (minus turbo) the engine was boosting approximately 22PSI, without any kind of aftermarket boost controller. The stock ECU didn't seem to care; I never experienced fuel cut, and the Air/Fuel ratio, Exhaust Gas Temperature and Knock Sensor activity were all within spec. I did have to run higher octane fuel on it to manage those boost levels without seeing ignition timing retard.
 One day after driving 200 miles in below 0F (-20C and below) weather the oil light flashed and I realized that the engine had consumed over 4 quarts of oil. There didn't seem to be any smoke out of the exhaust or any leaks under the car. I topped the oil off, drove another 100 miles, and the dip stick had been shot out with a frothy brown mess coming out of the dipstick tube.
 The suspected cause of failure was a blown head gasket. A compression and leak down test yielded the following results:
cyl1 140
cyl2 140
cyl3 133
cyl4 127

 Leakdown tests done at 90PSI, percent leakage:
cyl1 3.3%
cyl2 10% some leakage detected in the pcv
cyl3 8.9% some leakage detected in the pcv
cyl4 17.8% some leakage detected in the exhaust
  Factory spec is 3% leakage I believe. With those numbers it was time to crack open the block and see what it looked like. Here are the pictures on the drivers side of the block (Cylinders 2 and 4). The opposite time looked normal.

Cylinders 2 and 4 of the V5 RA block showing lots of carbon and sludge built up.Pitting at the walls of cylinder #4










Pitting at the walls of cylinder #4Pitting at the walls of cylinder #2










Driver's side engine heads.

 My Comments:
 The low compression test and high leakage on the exhaust side seems to indicate a problem with the engine heads. Most likely the valves weren't seating properly due to accumulated carbon. A sludge of oil and coolant can be seen on the piston tops; ordinarily they should be dry and coated by a thin layer of carbon, as was the case with the other side (pistons #1 and 3).
 Most importantly, the pitting on the cylinder walls indicates that they have been damaged. I do not know the cause of this. It could be detonation, though I suspect that was not the case, since it was something I monitored and watched out for.
 Perhaps the head gasket  allowed coolant to seep into the combustion chamber and this cold coolant hit the hot cylinder walls and pitted them somehow? I am not thoroughly convinced by this explanation but can't come up with a better one at this time. Regardless, the solution would have been to re hone the cylinder walls out past the pitting, which would require a new set of pistons since the cylinders would now be of larger diameter. These new pistons would require new piston skirts, and the entire engine block would have to be disassembled, cleaned, and re-assembled professionally. I would have to pay for the honing, the pistons, the skirts, new gaskets, new head studs, and then I would still have to find a solution for dealing with the exhaust side leakage on the engine heads.


The solution: A newer, better engine!


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