Project Gen3 STi – Fueling and Intercooling

MotoIQ Project Gen 3 STi Crawford Performance FMIC front mount intercooler turbosmart clamps

Project Gen3 STi – Fueling and Intercooling

by Wes Dumalski

You may have heard the expression 10 lbs of shit in a a 5 lb bag before. Well I am fairly certain the origination of that statement came from the first person to try and remove the intake manifold from an EJ25 and work on the systems surrounding and underneath! In our quest for more power and greater reliability we dive into the bowels (the heart would be the engine) of the boxer motor to upgrade our fuel system, improve the intake and intercooler efficiency and well… To reduce the amount of useless crap tucked in to the engine bay. 

In our last installment we explored power production and gave our impressions of the Turbosmart internal wastegate and BPV. During that testing our datalogs revealed 100% injector duty cycle and as such we had to limit boost in the interest of motor preservation. Let's face it, the late model EJ25 is not known for being the most robust motor and we certainly did not want to press our luck without having proper fuel. We began to research injector options and other items that we could improve while we were “in there” and what could be a relatively simple (as easy as the EJ can be) 2 day install quickly turned in to a several week process of re-doing damn near every hose and wire loom in the engine bay. Because we will soon be testing a GTX turbo we certainly wanted headroom within our fuel system for whatever power we chose to make. If we chose to push 400 or 500 horsepower on pump, race or the corn we did NOT want to have to upgrade the fuel system a second time.


ID000 Injector Dynamics 1000CC MotoIQ Project STi


We turned to our friends at Injector Dynamics immediately for their ID1000 injectors. As the name implies these injectors flow 1000CC's at 3 bar and have some of the most consistent spray patterns we have ever seen supporting data for. They are more than capable of supporting our power goals and despite their large size should allow us to maintain perfect idle and drivability characteristics.

In addition to the injectors we felt compelled to supplement the fuel pump and for that we chose what is quickly becoming the default pump from DeatschWerks in their DW65 model. This 265LPH pump supports all fuel types and for our application is a drop in replacement. While we were consulting with Tony Palo from Injector Dynamics regarding our fuel system he introduced us to Lance Lucas of Cobb Tuning Surgeline. Lance explained that Cobb was releasing a new “fuel damper delete” kit for the 08+ STi's and that it simply was a MUST HAVE piece.

If the air pump and all of those completely pointless systems were not enough Subaru thought it good to incorporate a damper and regulator that would allow fuel to be returned pre-regulator under certain conditions. This results in a very bad lean hesitation during tip in at about 2500-3200 rpm's that is a problem for nearly every stage 1-3 car. Some people claim to be able to “tune it out” but the reality is that it is mechanical in nature and the best way to get rid of it is to get rid of IT; the BS regulator that is. Cobb supplied us with a prototype kit that would allow us to replace the OEM quick connect fuel lines from the firewall and replace the existing FPR and assembly with one from the GD chassis STi.

Another item that we shook our head at were the Tumble Generation Valve's within the riser's between the cylinder head and the intake manifold. These valves are designed to open and close to improve emissions and in the end the simply create another restriction within the inlet and another mess of wires and ancillary garbage on or around the intake manifold. On our Gen 2 STi Howard from Technosquare deleted these by porting out the stock pieces however we chose a slightly different route. Our friends at Turn in Concepts made us aware of a composite riser made by Motive Autowerks that would not only eliminate the TGV but also serve as a means of isolating heat from the intake manifold. Essentially you are taking an all metal assembly and placing a composite spacer in the middle to reduce the amount of heat transferred from the cylinder head to the intake manifold.


Motive TGV delete Turn In Concepts Motive Autowerks composite TGV eliminator risers.

Seeing as how we had to remove the intake manifold to replace the injectors it made perfect sense to install these while we were at it. Two other items that could be done “while we were in there” came from our northern friends at Grimmspeed. Knowing we would need better control over boost we chose to use their 3 port electronic boost control solenoid and because the fuel lines would be torn apart at the fire wall this was the PERFECT time to install their Master Cylinder Brace. I know I know, that has NOTHING to do with fuel and air systems… Well if you object to us including this part in this installment you can suck it because there is NO WAY we would ever try to install this part with the OEM fuel system in place. That is NOT a shot at Grimmspeed, rather it is a statement in support of our introduction regarding too much fecal matter in tight confines. Last but in no way least we also decided that the top mount intercooler needed to go. As we make way for more power and taking the STi to the track we felt it imperative to drop kick the top mount inter heater to the curb in favor of a Crawford Performance front mount.


Crawford Performance FMIC front mount intercooler Ghymkana

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