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If you've been in the Subaru game for long, you're probably well aware that a 3-port Boost Control Solenoid (BCS) is considered my most to be a 'must have' improvement before having your car tuned. GrimmSpeed has become the trusted brand in the BCS market, with tens of thousands of solenoids in operation today across the globe.
The 2015 WRX offers a unique change of pace, as the factory 2-port solenoid is mounted directly to the plastic turbo inlet and interfaces with an o-ringed feature, rather than a vacuum hose. With expertise in designing machined parts and a tried and true boost control solenoid, we were excited to dig in and create a solution with an already proven pedigree of high performance and quality. Other 3-Port boost control solutions don't facilitate the proper use of the turbo inlet's recirculation port. This product will allow existing owners of other boost control solutions to adapt their system and utilize that port properly.
The advantages of a 3-port boost control system vs. the factory 2-port system are readily apparent during the tuning process. The 3-port systems works by interrupting the boost signal traveling from the turbo to the wastegate. That boost is redirected back into the turbo inlet and re-ingested by the turbo using our machined adapter. This is important, as the factory Mass Airflow Sensor has already measured that air and is expecting that your motor will use it during combustion, rather than venting it to the atmosphere. The factory configuration simply 'bleeds' the signal from between the turbo and wastegate, which creates a system that is a bit less complex, but reacts more slowly and with less precision. The chart above shows two boost plots. The 'before' is our 2015 WRX, dyno tuned by a third party protuner. The 'after' is the exact same tune, but after the installation of the GrimmSpeed 3-Port BCS. As you can see, the addition of the GrimmSpeed BCS shows much tighter boost control and consistency. This is safer for your car and easier for your tuner.
We began by recreating the factory turbo inlet and solenoid in CAD to ensure a perfectly fitting system. From there, we designed a beautifully fitting machined adapter that would recreate the o-ring sealing feature that the factory solenoid uses. This bracket features 1/8 NPT threads so that both barbed fittings (included) and AN fittings can be used interchangeably, for use with the GrimmSpeed BCS, Manual Boost Controller, or other boost control solutions.
Because this upgraded solenoid affects the way that your vehicle controls boost (that's the point!), it is always recommended that you consult with a tuner immediately following installation. It is not recommended that you drive the car in a way that builds boost without doing so. If you have any questions, don't hesitate to get in touch with us directly!