Project Gen3 STi – Fueling and Intercooling


TAKE CAUTION! You are working with a composite material that is O-ringed. The factory torque spec for the OEM risers is 21 lb ft. That does not apply to the new risers! The supplied instructions instructed us to use 6 ft lbs. and that is what we did as we did not want to risk cracking the risers or damaging the O-rings.

Once we had the risers in place it was time to re-do our fuel lines and main wiring harness. While we do realize that you can remove the Intake manifold and riser assembly with the rails and harness in place, the thought of doing that makes me want to punch a hamster in the face. And so for the sake of saving our furry friends we opted to pick up some fuel line and get to work. In the case of the Boxer fuel systems the driver side rail feeds the passenger side rail and we plumbed our hose off the OEM fuel rail to the passenger side supply, we then came off of the return and routed the hose back to the area of the master cylinder in preparation for our Cobb FPR conversion kit install. We also decided to cover our fuel hose with tech flex to offer more abrasion resistance and where it came in close contact to coolant passages we used some DEI heat wrap in between them before securing the lines with zip ties. By doing this we are now able to remove the intake manifold and leave the fuel lines and wiring harness in place on the risers.


Motive TGV deletes installed custom fuel linesThe newly routed fuel lines make for a much cleaner install and also also keep the factory hard lines off the intake manifold. The key here is to allow for easy intake manifold removal for future modifications; our new fuel hose is also ethanol compatible… you know…. just in case. 

We plan to remove the IM for several upcoming mods. so it was worth it to us to take the time and do things right. We also did not like how the wiring harness routed OVER the turbo inlet and UNDER the intake manifold; not only did it look bad it also made installation of the turbo inlet a complete PITA. With all of the space created by the composite TGV risers we were able to slightly bend our OEM fuel hard lines and route the wiring harness next to them. We did have to remove the factory plastic loom and mass of electrical tape, but it was cleaned up and protected with new tape and tech flex and then secured with zip ties.

We also made sure to properly delete the connectors that had been rendered useless with the elimination of the Air pump and TGV systems. We cut them out and properly protected the remaining wires with heat shrink and tucked them back in to the main harness before protecting the entire assembly. With these items buttoned up we needed to set the intake manifold in place to test fit and also to look at line routing for our remaining fuel connections. This is also where we installed the Grimmspeed master cylinder brace as it would reside in the location where the OEM fuel hard lines exit the firewall.


GrimSpeed master cylinder brace STi 08 09 10 11 12 Subaru installedThe perfect time to install the GrimmSpeed MC brace was during the removal of the OEM FPR and fuel lines. This areas is VERY cramped and with this stuff out of the way the brace install went much easier! 

The GrimmSpeed piece is overbuilt to the maximum and fits exactly where it should! This is not an easy feat as the area is overcrowded just like the rest of the engine bay! You need to remove the bracket that holds the evap connections, however once the GS brace is in its spot the bracket gets re-installed.

We also liked the position of the GS brace as we now had to start fitting the Cobb FPR conversion kit and we thought the brace was the perfect location to secure our new 05-07 spec STi FPR. Turns out we were right as it hung the FPR at an angle that made our fuel and vacuum reference line routing a snap.


Subaru GR STi OEM FPR fuel pressure regulator damper

The 2008+ FPR and line routing delivered by Subaru is another engineering marvel. You sit and marvel at why the fuck it is so complex and crammed in there… In what has been the usual fashion the OEM fuel lines use the quick disconnect and it was no small feat to use the appropriate tool to get them removed. Normally you slide the quick disconnect tool around the hard line and press, not here… The hard lines at the firewall had a round ring that kept you from being able to insert the tool easily, it took some finesse and proper use of expletives to get them removed.


Subaru GR STi Cobb prototype FPR conversion kit Lucas Performance Concepts Lance LucasThe Cobb prototype FPR conversion kit truly is a gift from the heavens. Anything to rid the world of the evil FPR that plagues the GR STi. What I like most is the picture of what the OEM setup looks like in comparison to the new setup. 

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