First off, if you have an EJ25D than you can use both this DIY and the one listed below as a good guide.

I’m going to try to make this as descriptive as possible. If you have any questions send me a PM and I will add it into the DIY. This is mainly for the less mechanically inclined. I remember being in high school not knowing a thing about auto mechanics and we should all be able to feel that bit of boost. I wanted to run a small turbo with low boost because I don’t want to run as high of a risk of blowing my engine, turning my 3 minute drive to a half hour walk to work every morning. Enough banter, let’s get down to business.

Disclaimer: What you do to your car is your business, I am in no way at fault for any damage to your or any one else’s vehicle.

I’m running a phase 2 ej22e (ej222) on a stock rs transmission with a 4.11 rear diff (unknown if lsd or not, keep forgetting to check)
Manifold air pressure (map)
Car mileage ~170,000
Engine mileage ~140,000
VF-11 turbo with 5lbs of boost (stock actuator has a 5 psi spring)

Parts list:
Vf-11 turbo
Intercooler (I went with top mount from an 04-05 Forester XT)
Blow of valve or by pass valve of your choice
Up pipe:
3x 1.75” diameter 90 degree exhaust elbows
Stock 1993 Subaru Legacy Turbo up pipe to use for flanges
1/2"OD 1/4: ID fuel line for connecting turbo port to wastegate actuator, connecting the boost gauge/fmu/and bov to a vacuum source
2x ¼” to ½” barbed fittings to connect turbo coolant lines to existing coolant lines
8 ft 1/2" heater hose for radiator coolant, black sold by the foot to use for vacuum lines and coolant lines
2x 1/2" barbed fittings to attach vacuum hoses to intake tube
Gates radiator hose #21767 for connecting turbo to intercooler
½” x ½” x ½” brass tee to split vacuum line to attach to each head and pcv
2 ft 10 AN braided stainless steel hose oil cooler filter turbo return drain dry sump
1/2 x 3/8" brass elbow to attach oil return to valve cover
1/2ID barbed fitting to attach oil return line to brass elbow in valve cover
Turbo Oil Feed line kit m10 x 1.5mm mitsunish td04 td05 td06
new auto car motor 2" 52mm psi vacuum boost pointer gauge meter
Straight 3” intake tube from O’reily Auto parts
90 degree silicone elbow for intake 2.25” to 3” to attach intake tube to turbo inlet
Split Second v3-100 voltage clamp
Fuel Management Unit
Cone filter
Harbor Freight Flux Core MIG Welder
Exhaust paint
Turbo back exhaust
Sti or walboro 255 fuel pump

Your parts list will change depending on what turbo and intercooler you are using. After doing the install it turned out that for my specific engine and parts list, the car ran fine without upgrading the fuel pump or adding a fuel management unit.

Fuel Management Units:
I heard you need then and I heard you don’t need them. The function of an fmu is this: as the boost pressure increases, it closes off the return line to your fuel tank (because all the fuel pumped to your fuel rail is not sprayed into the engine, this helps keep fuel in the rail when you need it and also helps cool the fuel rail, that is how it was explained at Ford) which then increases the fuel pressure in the rail and somehow magically increases flow rate through your injectors. After researching how Subaru’s fuel system works, its pressure based, so if you close off the return line than the fuel pressure regulator would sense the change in pressure and divert fuel back to your gastank before it even reaches the fuel rail so in my opinion they are useless and nothing more than a waste of money. If you choose to use one than it’s best to go with a vortech. EBay ones need modification to work which you can see in this video.

Voltage Clamps:
All of the map turbo builds I read used either a split second v2-5 or v2-100 voltage clamp. These two are both out of production but I’ll explain the difference. The v2-5 runs off of the 5 volts from your map sensor while the v2-100 needed to be hooked up to the battery to operate. Both have been replaced by the v3-100 which is capable of running off of either the map sensor or the battery, whichever you choose. As the manifold air pressure increases the map sensor sends a higher voltage to the ecu which the ecu reads as pressure and throws a check engine light. The voltage clamp interrupts the signal between the map sensor and ecu and puts out a constant 4.2 volts (atmospheric pressure) regardless if you’re non turbo or running 16 psi of boost. Essentially it tells the ecu that you are not experiencing boost when in fact you are. If you don’t have this than check engine lights get thrown and it’s not a fun time.

Fuel Pumps:
A stock sti fuel pump or a walboro fuel pump will work fine. You need a bigger fuel pump to be able to get more fuel through the lines if and when the engine calls for it.

If you choose to use a top mount intercooler the best ones to use is 06-07 wrx or fxt as they fit better than the rest. Otherwise you will have to cut into your firewall to fit the tmic.
If you choose to use a front mount intercooler than you’ll have to do some modifications to your front end.

First thing to do is start saving money and hoarding parts. I have been accumulating parts for a little over a year now. It started with a turbo and up pipe, than an intercooler, bov, and cheap boost gauge. I got a brand new turbo back exhaust in the summer, than quickly got the rest of the parts within the past month.

This installation bit is only for map cars, maf cars do not apply and can be done at any time, the car will still function with the voltage clamp installed. If your intake tubing has a sensor in it near the passenger fender than you have a maf, if not than you have a map. Install the voltage clamp between the map sensor and the ecu. It’s best to install the clamp right after the map as it is easy to get to. I used piggyback connectors to connect to the power and ground. Cut the signal wire and connect to the voltage clamp with butt connectors.
Car V-clamp Fuction
Solid Red Red Power Supply
Solid Green Black Ground
Yellow/black from sensor Solid Blue Sends signal to v-clamp
Yellow/black from harness Blue/white Sends adjusted signal to ecu

You can also install the fuel pump at any time prior to the turbo install. Anothernord already made a great diy on installing one so I’ll just paste the link here.

I bought a full 3” turbo back exhaust which I wanted to use for the build. You could get away with a stock exhaust and a custom downpipe, whatever you want to do. Also, I didn’t want to swap the front crossmember so a custom up pipe had to be constructed. I put the exhaust I was using for the build onto the car and attached the turbo to the downpipe and cut the flanges off my up pipe. To hold the downpipe I had to wrap a bungee cord around it and hold it to my front strut bar, the mounting brackets on the exhaust didn’t line up and I’ll address that issue later. The bottom flange for the up pipe will not fit on a stock singleport exhaust manifold; luckily I had a stock flange from a cat section that bolted up. I also bolted on the top flange of the up pipe to the turbo.

When installing the downpipe I noticed my cruise control got in the way. As much as I hated to do so I removed it but only temporarily, I plan to relocate this to another location in the engine bay.

Creating the up pipe was rudimentary at best. I put one elbow up to the top flange, guessed at where to cut it, made the cut with a sawzall, and then checked to see how it would actually sit. I did this to the entire up pipe. I only used the flanges and the 3 exhaust elbows. The extra weld on the bottom of the up pipe was due to a minor misjudgment of distance and thus, didn’t fit after welding so it was cut and adjusted properly. Once finished the up pipe was removed and painted with silver exhaust paint from advance auto to resist rusting. Once dried it can be reinstalled. At this point you should have the exhaust installed and the turbo bolted to the exhaust.

You need an oil feed line. If you get the same kit I have than it’s simple. On the front of your engine, under your alternator, there is a sensor. Remove it, put the brass tee from the kit in there, put the sensor on one port of the tee and put your oil feed line on the other port of the tee. I also had to extend the electrical connector. Just use a male connector to connect to the factory plug, run a length of wire and use a female connector. Use Teflon tape for all the fittings hooked up to the brass tee. You can then use the banjo bolt supplied in the kit to attach the other end of the oil feed line to the top of the turbo.

In the above picture you can see my oil supply line attached to the turbo, it then runs under the intake manifold and you can see it connect just to the left of the alternator.

On the vf-11 there is a barbed fitting on the bottom for the oil return line. Plug in the big behemoth of an oil return line onto this barbed fitting and put a hose clamp on it, make sure it’s tight. Drill a hole into your valve cover and wrap the threads with Teflon tape before screwing it into the hole. The other end of the oil drain line attaches to the ½” barbed tee which is screwed into the ½” to ¾” brass 90 degree elbow. Use a hose clamp to hold the oil return line to the barbed fitting. Oil return is done. I’m not going to lie, this was the scariest part of the install for me. I suggest having a spare valve cover. Also make sure there is a gasket between the oil return fitting on the turbo and the turbo itself. If not get one or make one using high temp rtv.

Coolant supply might vary depending on the engine. On the phase 2 ej22e (easy to tell by having single port exhaust manifold and map sensor instead of maf) there is a coolant line running into the intake manifold on the passenger side. Simply unplug it (coolant will go all over the engine) and put the ¼” to ½” barb on it. Secure with the hose clamp. Put a ½” hose on the barb and secure with a hose clamp. Run the hose to the top fitting of the turbo and secure with a hose clamp. Run a ½” hose from the bottom coolant fitting on the turbo to another ½” to ¼” barbed fitting. Run a ¼” hose from the barbed fitting to the fitting on the intake manifold and secure all hoses with a hose clamp. Coolant is finished. Get these barbs on ebay, I only did this after speaking to someone who did a similar swap and suggested this location rather than the heater core (thank you ty) and thus I ran to the hardware store and had to use 5 different fittings to make this barbed adapter.

Use a 1/4” ID hose to attach the small fitting on the charged air outlet of the turbo to the small port on the wastegate actuator. On my vf-11 the ports weren’t facing any logical direction to achieve this so I took a pair of pliers and carefully turned the port on the turbo housing to a direction that suited my liking; make sure you are not bending the port when turning.

At this point the exhaust is bolted tight, the turbo has oil and coolant supplies and returns. I started the car and checked for leaks as it would be harder to see them with the intercooler installed. I only left it run for less than 5 minutes.

Install the intercooler. This will vary depending on if you went with a top mount or front mount, as well as if you went with an 04-05 wrx, 06+wrx, etc. I didn’t have to shorten my clutch reservoir, I left my intercooler sit angled. If you want to shorten the reservoir use a turkey baster to remove the fluid and deposit said fluid into a clean container (you can change the fluid if you wish). Remove the reservoir and simply trim the bottom of it. You can use a dremel, hacksaw, steak knife, whatever gets the job done. Once it’s cut so the intercooler sits better than reinstall the reservoir and refill the fluid. Be sure not to trim too much off.

Attach the intercooler to the turbo. When doing this the outlet for my turbo was pointing to the wall of the intercooler. I got a Gates Radiator hose #21767 from O’reily auto and cut the sections that I needed. When connecting two hose pieces together I simply used some 1.75” diameter exhaust tubing left over from making the custom up pipe as stiff couplers to be able to attach it all together tightly without leaks. For my build I got a bov for a wrx which didn’t exactly fit my Forester XT tmic, nothing a little rtv and hopes couldn’t fix. There’s a vacuum port on the top of the blow off valve. I attached this to the port on the passenger side of the intake manifold where my cruise control used to be plugged into. Secure with hose clamps. After this step I was finished and could drive around (until my intake piece came in the mail).

The fuel management unit can now be installed, I’ve heard they’re not necessary and I don’t see how they actually give you more flow through the injectors but it’s up to you if you install one. It turned out I didn’t need one so I’ll get some pics of the fuel return line later. By your driver side strut tower there are 3 hoses, one runs into your fuel filter (attached to the strut tower), this is the fuel supply line. If you follow this line to the engine it goes from a rubber hose to a metal line. The top is the fuel supply line, the middle one is the return, and the small bottom one is for your carbon canister. You want the middle line. You can remove the rubber hose and channel it to the fittings on the fuel management unit. The port on the side comes from the engine and the port on the bottom goes to the metal line by the strut tower which goes through the firewall to the gastank. The top port is for a vacuum line.

Using a ¼” ID hose run a line from the vacuum port of the fmu to the vacuum port on the bov/bpv. These can be connected with a tee fitting and the third port of the tee can go to a vacuum line attached to your intake manifold. You can also splice one of these hoses for your boost gauge vacuum line.

Now for the intake. For the vf-11 you only need one 90 degree silicone elbow 2.25” to whatever size intake pipe you got, usually its 3”. Install a cone filter on the furthest end and use some hose clamps to hold it all together. For this build, 2 holes were drilled into the intake tube and ½” barbed fittings were installed in the holes. Jb weld was used to make sure there are no leaks. Run a ½” ID hose from one of the ports to the right side vacuum port located on the head. Use a ½” ID hose to run from the second port into a brass tee. One port of the brass tee will go to the PCV and the other port can go all the way over to the left side vacuum port on the left head. These three ports are what your stock intake runs to. Don’t forget them hose clamps.

To install the boost gauge simply make a hole in the back of the gauge pod and run your vacuum line and wires through. Install the gauge into the pod and mount the pod wherever you like. Your wires may vary but mine were simple, red goes to a 12 volt powersource that only has power when the key is turned. There are a ton of places to tap into but I’m going to be lazy and tap into my stereo. The black goes to gound, again there are tons of places to attach it to. An easy way to find a ground is to twist some extra wire onto the ground wire and with the power on start touching the exposed ground wire extension to random metal areas until the gauge lights up. Once you find something good (hopefully near a bolt, nut, or threaded hole) attach the actual ground wire there. Find a spot on your firewall that you can push the vacuum hose through. This location will vary depending on your car. Usually there is at least one rubber grommet with nothing going in or out of it and you can use this spot. It’s better to punch a hole in the grommet and feed the hose through rather than removing the grommet; you don’t want the sheetmetal firewall to cut through the line over time. From here just channel the hose to the tee fitting on the line for your bov and fmu and cut the excess off.

So basically it should all be installed. Now comes some very important info that I haven’t seen in any DIY turbo builds I’ve read. Diy turbo veterans correct me if this is not necessary. You should jack up the front of the car or put it on ramps. Remove the radiator cap (make sure the car is completely cool before removing this, otherwise you could seriously burn yourself and do all sorts of other damage). Now start the car and put the heat on full blast. Squeeze and release the top radiator hose keep doing this until you are sure there are no air bubbles in the cooling system. I haven’t done this yet and haven’t had any issues but it would be a good idea to do so.

While you’re doing the install it is also a great time to change your oil and top off your fluids. It’s not mandatory but hey, while you’re there making sure everything’s good. If your engine oil is black than you really should change it.

Once finished go take her for a spin. I would take it easy at first and slowly get more and more spirited just to make sure everything is ok. When you return let the car sit on dry pavement or put cardboard under it. Look and see if there are any leaks, if there are than look around and find the source and fix as needed.