Project Gen3 STi – Fueling and Intercooling


Crawford FMIC STi GR Subaru ImprezaHere is the whole kit installed. You can also see the uber sexy GrimmSpeed radiator shroud and tool tray. Honestly we use the tray all the time for nuts, bolts, tools, candy, sushi, cameras, or whatever else you can think to put there. 

We wanted to use an aftermarket 3 port boost controller and for that we turned to GrimmSpeed. Their piece fits nicely on the OEM mount and comes with the proper hoses to install it within the vacuum line routing.

We also wanted to better manage airflow through the radiator through the use of a shroud, also from GrimmSpeed. This laser cut aluminum panel uses OEM mounting locations to replace the radiator brackets and also force all air entering the grill to flow through the radiator. We had previously been using the OEM front snorkel to feed air to the COBB air box however we wanted to get rid of the snorkel due to some future plans that may require that real estate. The Crawford FMIC and the COBB air box will allow you to keep that piece, but it was our choice to delete it.

This did leave us with a hole on the front side of the COBB air box and we quickly fabled up a sheet metal piece to cover this section in an effort to keep hot air away from the filter. One of the best parts of our little modification was that we were able to re-use some of the OEM clips from the OEM hood scoop to make this block off panel removable should we ever require it.


Crawford FMIC GrimmSPeed EBCS COBB SF intake GR STiYou can see our block off plate for the COBB airbox after deleting the factory inlet as well as the general pipe fitment. Hidden in plain sight is the GrimmSpeed 3 port EBCS. 

Last but certainly not least we knew that we would need to utilize a larger fuel pump to ensure no weak links in the supply chain. After much consideration and discussion we went with the DeatschWerks 65 unit.


DeatschWerks DW65C fuel pump

The DW65C is a drop in replacement that is rated to flow 265 LPH at 3 bar of fuel pressure. This pump is widely used within the Subaru community and for good reason. It has proven to be easy to install and very reliable even when used with E85. The fuel pump on the GR STi is located in the tank and removal of the assembly that holds the pump is fairly easy. PRO TIP: When removing the fuel pump cover there is typically a large amount of dirt and dust on top. I like to use a vacuum or compressed air to remove the big stuff and then a rag with some brakleen to wipe things down. I don't want a bunch of dirt and crap falling into the tank by accident during removal.

Once the cover is off you can proceed to remove what looks like R2D2 from the fuel tank itself and another tip is to use an old towel to set on the floor and a clean drain pan to set the pump assembly in. I even go so far as to have a dedicated drain pan that is rated and marked for gasoline only use. Often times you will get a decent amount of gasoline spillage and with the cost of fuel I want to re-use every drop without it being contaminated and this method makes things nice and easy.

Once R2D2 is on your work bench you must remove the spring loaded plastic housing from the main housing. This is not a simple task and requires some finesse and small hand tools. It was made easier by the use of some smaller picks and I used zip ties to hold the tabs I had released. Once apart the actual installation of the pump is very simple and Deatsch Werks provides the necessary sock filter and fittings. The difficulty here is NOT a result of the DW pump, it is simply the way the OEM pump is shrouded within the housing and ANY aftermarket fuel pump will require this installation. Re-installing the assembly in the car was fairly easy as in the STi you do not have to remove anything other than the rear seat bottom to access the fuel pump area.


Deatsch Werks DW65C fuel pump install GR STi SUbaruAfter having installed a fuel pump in the 2004STi we hoped ours would be just as easy. NOPE, after we pulled the droid inspired housing out of the fuel tank we got to spend the time tearing it apart. Here is how the DW65C sits within the top half of the OEM housing. 

With the car set up and everything back in place we worked closely with Mitch McKee and Lance Lucas from COBB tuning for a base drivable MAP. With a setup like this one cannot simply get an off the shelf MAP and expect it to be perfect and we all agreed that to make things ideal we would use a wastegate only map and keep the car out of boost until we had a chance to dyno. tune it. After installs like this with so many components changed it can be nerve-racking to turn the key and in this case there was a little bit of that. Not sure why as the damn thing fired right up and idled rock solid. No hunting or surging it literally was running under normal driven conditions better than it ever had.

This is a testament to the components and companies used in this round of upgrades. In the case of this installment I feel the end result is a bit anti-climactic as this is as far as we would take the car in preparation for our next modifications, a GTX3067 bolt in turbocharger from our friends at Garrett and ATP turbo and a TomeieEqual length header from the good folks at Rally Sport Direct. We needed the supporting modifications documented in this installment to allow the new turbo to work as efficiently as possible and in our next power installment you can bet that we will be showing you the install of the turbo and with any luck some of the most linear and usable power curves we have seen for this chassis. The goal? Broad usable power from the bottom to the top of the power band, perhaps we should call it operation flatline? As in a huge flat line of power and torque with no fall off up top. Stay tuned for some asskicking! 




Go Fast Bits

Crawford Performance

Garrett Turbochargers

ATP Turbo

Injector Dynamics

Perrin Performance

Turn In Concepts

M7 Suspension


COBB Tuning

AMS Performance

Radium Engineering



Progress Auto

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