WRX Drive-Train Swap; STi in a Box

Who would have thought, an STi drive-train in a box, LOL. Well that’s what we received for Andrews’ 2003 WRX when he decided it was time to get rid of the inferior WRX transmission and remaining drive-train in favor of the much beefier STi 6 speed transmission and drive-train. Along with installing the STi Transmission we also installed a brand new ACT HD 6 puck clutch kit.

Also some new Power Slot slotted brake rotors were installed in the rear along with Hawk pads to match the front brake setup on the car. Another upgrade we are doing for Andrew along with the STi drive-train swap. This is a brand new Grimspeed Intake Manifold with a beautiful black powder coated finish. This piece is truly a work of art and a very nice addition to this build.

Along with the intake manifold upgrade, Andrew was looking to switch over to E85, as we have been putting the bug in his ear for the past year or so with so many E85 tuned cars in and out of the shop. The plan was always to switch out the RC 750cc Injectors in favor of the Injector Dynamics 1000cc High Impedance injectors, as they will allow much more room as the modifications progress.

These injectors are a direct fit with a top feed fuel system and they do not require the need for a bulky and cumbersome injector driver box to be wired into the car. For fuel rails we chose the brand new just released T1 Side Feed fuel rails over others on the market as we were able to keep more dollars in the customers pocket and still get as good of quality or better than the competition. The reason for the fuel rail swap was that Andrew was already complaining of the dreaded early model WRX fuel smell from the engine compartment while driving, and the fact future modifications are planned.

We ran into a bit of a hang up when we went to install the T1 fuel rails on the TGV deletes that Andrew already had from Grimspeed, but they were from a top-feed WRX setup. Because of this the T1 fuel rails did not line up ever so slightly plus the pitch angle of the injectors along with the height would have been way off. So we called around first to Grimspeed to find out how far out they were on another set of side-feed ported TGV deletes; more bad news as they are out over 2 weeks. A Quick Phone call to Tony at T1 Race Development and we found out at this time they don’t have anything for top-feed TGV’s. So we were on the look out for some side-feed TGV’s as Andrew used his original units as the core exchange with Grimspeed. Luckily we had an extra set in the shop and Scott went to removing the TGV butterflies along with welding up the holes the shafts leave. After this he went to porting and honing them for a very nice consistent and transient flow into the cylinder head.

One last item that was installed before tuning was a Vibrant Performance Vaccum block as before there were quite a few “T” connections for all the various vaccum/boost sources like boost gauge, blow off valve, fuel pressure regulator, etc.  One thing that was sharing a vaccum/boost source was the fuel pressure regulator, and that is something of a tuning concern for me.  The FPR should have a stand-a-lone vaccum/boost source and if it were a speed density car running a map sensor instead of the MAF meter; that as well should have it’s own vaccum/boost source.

After some initial setup of the injector scaling and latencies in ECUFlash, along with re-scaling the MAF meter we started doing base dyno pulls with moderate boost before going WOT.  When everything was finally dialed in we were able to extract 286whp and 249wtq on 91 octane pumpgas with a toal boost pressure of 18psi.  Next we drained the tank of the 91 octane pumpgas in favor of E85.  The first initial pulls on E85 was to make sure the re-scaling of the injectors netted us safe AFR’s during spool up of the turbo.  After some full WOT pulls at 18psi to get the MAF scaled right for E85 we upped the boost to a max of 23psi and were able to make 336whp and 307wtq, and increase of 50whp and 58wtq over the 91 octane tune.

If you would like to look at all the pictures we have of this car and of this build, please click here.

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