Project Gen3 STi – Fueling and Intercooling


We used a heat gun to prep the plastic sensor and soften the plastic and ran a utility knife around the perimeter. This easily cut in to the molded housing and with enough passes we could use a scraper to gently pry the sensor off the top of the housing. If you repeat this process yourself you will notice two terminal connections that need to be broken off to completely remove the sensor, not to worry, break away! The 5 wire sensor uses a ground, signal, and 12 V wire and the other two terminals supply voltage for the valve to open and the two connections that you break off are the valve signal conductors. Because the valve will no longer function anyway you can simply grind these off and cover them with the material of your choice. Liquid electrical tape or in our case 1″ heat shrink worked perfect. With this pesky housing gone we could now place the much smaller sensor lower in the engine bay, away from too much heat, and out of the way; MUCH better than keeping another useless part!


Subaru Impreza WRX STi barometric pressure sensor removed from air pump housingAfter removal we cleaned up the sensor edges and heat shrunk over the connections just to be safe. We would later find this sensor a home by sliding it inside the GrimmSpeed master cylinder brace. 

With those removed you still have two parts to go,The two tubes that connect to the heads are next and the driver side is cake to remove as you can reach it from your position above the intake manifold. The passenger side is another story all together and in order to save yourself a complete headache we found it best to remove the turbo up-pipe. The flange that mounts to the cylinder head for the air pump connection is largely shrouded by the up pipe heat shield and one of the bolts is nearly impossible to reach. While others have reported being able to do this with the up-pipe on the car I decided to keep my sanity and do it the long way. With the up pipe and down pipe off the car you can easily reach the air pump connection and once the two bolts are off you can then work on snaking the tube around the turbo and out the top of the engine bay.

Think we're done? FARK NO…. We now have two holes left on the cylinder heads to cover  and while many companies offer billet aluminum block off plates we are FAR too cheap to by those. A little digging on the inter web revealed that a Subaru Tribeca shared the same heads but not an air pump and as such had two “block off plates” to cover these ports. We gave a call to our buddy Markos at Camelback Subaru and he confirmed them as “EGR” plates and we ordered them up along with the associated gaskets. All told we were out less than $25 for all of the parts including shipping. When we got them we realized they would work just fine. The passenger side bolts right in place and we chose to re-use the OEM gasket after cleaning it! The passenger side plate covered the hole perfectly however one of the bolt holes was slightly off, a problem cured by our die grinder and porting bit in about 30 seconds. Finally, with the plates bolted in place we called the air pump delete good!


cylinder head block off plate air pump delete tribeca EGR installed Subaru WRX Impreza STi
Here you can see the two socket cap screws securing the Tribeca EGR block off plate. The driver side plate is easily installed however the passenger side is shrouded by the turbo up-pipe. If you plan to do an air pump delete it would make sense to also change out the up-pipe or combine this with a turbo upgrade or the like. 
Motive TGV delete composite OEM TGVHere you can see the Composite TGV riser in comparison to the OEM tumble generation valves. It's clear that these replacements decrease restrictions within the intake tract and also help to reduce the amount of heat introduced to the intake charge by isolating the metal intake manifold from the cylinder head. You can also see how they provide more room around the TGV as the molded riser's are not required to maintain provisions for the butterfly valve motors. 
Next up was the injector install and that required us to remove the OEM fuel rails from the OEM TGV risers. The factory injectors on the 08+ STi's are of the top feed variety and as such we chose to re-use the stock fuel rails. We noted the orientation of the OEM injectors before removal and after slightly lubricating the o-rings we slid the ID1000's into the fuel rail and then placed them in the Motive TGV. We re-used the OEM bolts and followed the Motive instructions by torquing them to 13.7 ft lbs. This was the easiest part of the install so far as everything fit exactly as it should; the install was further simplified by the use of the Injector Dynamics plug and play harness connections. We clipped these in place while all of this was on our work bench and cleaned the gasket surfaces on the cylinder head.
For the cleaning we used CRC brand brakleen (seriously is there anything better than CRC?) and the wire wheel on our dremel tool. This makes quick work of old gasket residue and leaves you with a perfectly clean finish. One nice part about the Motive composite risers are that they use O-rings instead of gaskets for both the cylinder head and intake interfaces. we prepped the O-rings and pressed them in to place on the bottom of the riser and proceeded to install them on the cylinder heads.
Motive TGV delete OEM fuel rail ID1000 injectors installedHere you can see the injector nozzles sitting within the Motive riser and the OEM rail. The two rail connections are for the supply from the tank and the other feeds the fuel rail on the passenger side of the car. 

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