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.

The 3-Port Advantage

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.

Design

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.

A small mounting bracket secures the solenoid to the machined adapter, to create a compact system, while still allowing those interested in running other boost control solutions the flexibility to do so. Mounting the solenoid directly in place of the stock solenoid allows for vacuum hoses of similar length and a shorter wiring harness. Lastly, we identified the exact electrical connector used on the stock solenoid so that the GrimmSpeed solution would be a true plug and play.

Why GrimmSpeed?

The GrimmSpeed Boost Control Solenoid has been proven time and time again. With tens of thousands on vehicles across the world, tuners trust it and our customers love it. What you see here is the same great solenoid with millions of miles of real world testing and an innovative mounting solution, designed specifically for your vehicle. The machined adapter also features standard NPT threads, should you choose to upgrade to AN lines and fittings, or even a different boost control solution (manual, standalone, hybrid, etc) down the road. Finally, the GrimmSpeed BCS system will arrive fully assembled and ready for installation.

Tuning Notes:

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!