Project GD STI, Improving the Powerband with Precision Turbo and Injector Dynamics

IHI does not use A/R as the turbine housing size spec but uses a measurement that they call the nozzle area.  The stock nozzle area is 7 cm squared and some upgraded IHI turbos use a 10.5 cm squared housing.  The stock turbo has an estimated A/R of around 0.60. We did some rough measurements and the Precision Turbo seems to have an A/R of about 0.75-0.80 depending on how thick the casting is. These measurements are totally appropriate for an engine like the EJ257.  In this picture, you can see how much bigger and better flowing the Precision exhaust housing is internally over the IHI turbo.  Having bespoke housings designed around the compressor and turbine wheels is a huge advantage over simply carving out the stock or slightly larger OEM housings for bigger wheels like most of the competition’s standard position Subaru turbo upgrades.

As you can see here, the Precision turbos stainless steel parts are going to look a lot better after time than the rusty OEM cast iron parts. The turbo comes with all the parts to make the installation a total bolt-in.

Previously we were using Injector Dynamics 1300 cc/min injectors.  However, in our previous tuning sessions, our injectors were running at over 90% of their duty cycle on E85 so we needed bigger injectors so we turned to Injector Dynamics once again for a set of 1700cc/min injectors.

Injector Dynamics starts with brand new Bosch EV14 injectors which are matched in batched sets using Injector Dynamics measuring benches and methodology.  First, new injectors are dynamically broken in on a bench for about an hour.  Injector Dynamics has found that it takes about this long for new injectors to settle down and produce consistent flow results. The injectors are then flowed through their dynamic range using the proper fuel pressure and using fuel as the test fluid, not a test solvent.  The temperatures are carefully controlled during the test for consistent results. After break-in and flowing the injectors are sorted into matched sets. Within each set, the dynamic flow rate (slope) will vary no more than +/- 1%, and the dead time (offset) will vary no more than +/- 20 microseconds which is equivalent to +/- 1% at a pulsewidth of 2 milliseconds.  To our knowledge, only Injector Dynamics offers complete operating range matched injector sets.

So we don’t want a whole lot,  Just to get our engine’s cam, porting and turbo all to match up a little better and give more area under the power curve. Our engine already has pretty refined power characteristics but we feel that it can get even better.  Our Project STI is a really refined giant killer that achieves our goal of being engineered like a factory special model.  Stay tuned, we are next going to be doing more driveability and power tuning and will report on the results.

Sources

Precision Turbo

Injector Dynamics