With your older turbo Subarus you may find that Subaru gifted you sidefeed injectors. Then you decided to do a little research on your injectors, maybe even take a gander at what the aftermarket has available. What you come to find out is tuners don’t prefer side feed injectors and the aftermarket feels the same way. There are few options and they are quite pricey versus their top feed counterpart.

So what is a Subaru owner to do? You can go ahead pony up for a complete fuel system with new lines, rails, injectors, connector adapters and a tune… But that is going to cost you an arm and leg. The other question you have to ask is do you need all those pieces? If you have lofty horsepower goals this could be the route you need to take anyways, but what if you are staying in the oem plus power range. That is what we will take a look at today… finding the oem parts and pieces to complete a top feed swap without emptying the wallet.

Time Frame

This one is a long one. Unless you have prepped a new manifold with injectors, lines, wiring harness etc I would put aside a day or at the very minimum an afternoon.

Tools

Your typical ratchet, socket set, extensions and pliers will help you remove the assorted hoses, bolts and manifold. For the wiring conversion you will need these wiring pliers along with a set wiring stripper.

Grey pneumatic socket set 3/8th Grey pneumatic wobble 3/8 socket set Gearwrench 3/8th ratchet

Simple and effective terminal pin crimper.

Parts

You will need these connectors, terminal pins and weather seals to modify your standard harness for top feed injectors. Next up you will need a topfeed manifold with injectors from an 07 Sti, 06 Forester Xt or other models equipped, you can use many other years but the vacuum line connections move around. . You will also need the same year TGVs as your manifold to match the bolt pattern. Lastly the hardlines if you intend to reuse them along with injectors. I ended up with a used 06 Fxt manifold for my project.

After this install you will need to apply a new tuning map for the top feed injectors. Even if they are the same cc rating your ecm will not properly control the new injectors.

How to

To start this install out you will need to remove your manifold. For that you can follow this link to my how to remove the manifold and then return here when the deed is done.

If you are swapping to a newer style top feed manifold it’s time to strip the wire harness off your old setup. You will find it bolted to the underside of the manifold and then you can undo any further connections and clips. Now you can separate the harness and manifold for your upcoming steps.

There are plenty of aftermarket options to reuse your old manifold but what if you want to keep it oem and spend less money, then this is for you. New to me manifold up top and old on the bottom.

Now you can go two ways, you can run adapter harnesses and make it reversible or you can go all in and remove the factory side feed connections to install the top feed connectors. If you decide to cut the harness, make sure you cut as close to the connector as you can. You can also use a depinning tool to remove the wires first and remove the least amount of wiring, that was my technique.

Old connector and terminal pin removed. Wiring stripped back and ready for new parts.

With the proper terminal pins and connectors sourced you can strip back your wiring leaving enough for the proper engagement on the terminal end. Then you will take your weather tight seal and slide it over the wiring. And now it is time to crimp on the terminal end. The best technique I found for crimping down the terminal ends is starting with a larger crimping opening, this starts the terminal arms in to hold the wiring tight. Having them started towards the wiring you can switch to the specified size of your wiring and attach it permanently.

These terminal pin pliers make it this all too easy.

You just need to do the above step seven more times and you will be finished with what I feel is the most anxiety inducing part of the swap.

Having the terminal pins in you are ready to install your top feed connector housing. With a small pick or pocket screwdriver you can remove the white center section that holds terminal pins in. Then hold the terminal pins inside the connector, you will likely hear the terminal pins snap in place and then place the white insert back inside to finish. You can give the wiring a tug to double check that they are set. If they slide out you can just press the wiring back in and listen for a snap. Now you just need to do this for three more connectors to complete the task!

Pins attached to the wiring and now installed into the housing. Ready for the plastic center section.

Once the insert is pushed into place it is ready to be installed!

With all the tedious work completed you can route the wiring harness through your manifold to make sure that everything finds it’s way to their proper locations and connections. Up next is reinstalling the manifold and fuel lines. (A new tune will be necessary for the new top feed injectors. )Then you can turn the ignition on allowing the fuel pump to prime the system and then check to for fuel leaks at the injectors and line connections under the hood. With no leaks found or smelled you can start it up and make sure that all the connectors are doing exactly what they need to do by powering and running the injectors.

Reassembling the manifold the wiring harness and fuel hardlines. It’s ready to go back in the car!

Congratulations! You have successful retired your side feed injectors and upgraded to top feed injectors, now tuners will rejoice to tune your car! You have also opened up a plethora options for aftermarket injectors for the future if you decide to you need more power!