Project Domino: A New Turbo and a New Tune

It has been over a year since we’ve done anything with the old girl.

As a refresher, our 2001 Impreza RS had(power wise):

  • a full version 8 JDM WRX STI swap
    •  The the version 8 EJ207 engine is still stock; it didn’t seem right break down a perfectly health motor at the time
    • Version 8 STI 6-speed
    • We did the 5×114 conversion from a 07 STI
  • Custom 3″ catless turbo back
  • Custom FMIC with a ridiculously large IC core
  • Big MAF intake
  • SteamSpeed silicone inlet
  • ID1000 injectors + a Walbro 255 lph pump
  • SteamSpeed STX 71 JB turbo for JDM STI twin scroll

In that iteration, it made ~360 whp at PRE facility on pump gas.   For comparison, the SteamSpeed STX 71 on a 2015 STI made about 420 whp on the same day.  With that turbo it was rewarding to push the car, and if you kept the revs up, you could keep it in boost, but realistically it was a 4.5k+ RPM turbo on a stock EJ207.

[Domnio V3]

We wanted to do something a little more responsive.  Enter the SteamSpeed STX 67R+ BB turbo for JDM STI.

We would manufacture small batches of this turbo, and we would sell them all out before we could install one in Domino, but we able to finally get one installed.  It has the smaller 67mm compressor which should make it more responsive, but the “+” means that it still has a GTX30 spec turbine which is a little better suited for a 2.5l.  I think a GTX29 size wheel would be perfect for the EJ207.  Next update to the turbo we can make the change.  🙂

The STX 67 wheel did get us close to 4k RPM, but it still feels big.  In fact, doing pulls, it feels similar to the 71; however, everywhere else, it is night and day.  The BB CHRA is super responsive.  Going on and off the petal, the turbo is a lot more responsive.  It could also be related to the fact that we went to speed density from a MAF based tune.

What is the final result?   It made about 10 whp less with a 4 psi more boost.  Not a bad trade off.

[Dyno Plot]

[Next Steps]

The turbo still feels a little big.  Andy at FTW thought going to a top mount could give back about 500 RPM of spool.  It would probably be best for our usage of the car, but for vanity reasons we like having the huge FMIC.  We could just go to a 2.5l displacement, but it seems like it goes against the spirit of the ej207 swap.

Where do you think we should take the build next?  Let us know what you think.

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