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GrimmSpeed 3 Port Boost Control Solenoid
Installation Instructions
2002+ Subaru WRX/STi/LGT/FXT
***Image above is a generic photo, your EBCS may look different***
All GrimmSpeed products are intended for Off-Road use only.
Park your vehicle on a level surface. Fully engage the parking brake and put wheel stops on
the front and rear wheels to keep the vehicle from rolling.
Warning (read before installing):
Before moving forward with the setups outlined below, insure that you have the experience
and confidence to properly tune your car. If not, please consult a tuning professional.
Without a proper tune you can overboost and damage your engine.
Under no circumstances is the GrimmSpeed Solenoid to be used in any applications where
failure of the valve to operate as intended could jeopardize the safety of the operator or any
other person or property.
Note! You must tune for this hardware! Using stock or off-the-shelf EM with a 3-port solenoid
installed in interrupt mode will result in overboosting!
A. Purpose
The benefits of this upgrade are faster spool, ability to hold higher boost, and better control
over boost. A side benefit of the improved boost control is the ability to reach higher target
boost levels in the low (1st and 2nd) gears.
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B. Technical Background
A BCS is a binary device – i.e. it is either on (energized), or off. In the context of the Subaru
device, when the BCS is energized, air is allowed to pass through the device, while when it is
off, the air flow is cut.
There are two modes of boost controller operation, at least in this context: “bleed” mode,
which is the mode that the stock BCS operates in, and “interrupt” mode, which is the mode
that a 3-port BCS can operate in. Note that a 3-port BCS can also operate in “bleed” mode,
depending on how it is connected.
Despite being digital in nature, these devices perform a very analog-like task, which is to control the boost
level. In order to do so, the ECU opens and closes the solenoid at varying speeds, from 0 Hz (closed) to
(effectively) ∞ Hz (open).
C. 2-Port Operation (Stock) Review
The stock solenoid is part of the stock bleed-based boost control system. When the solenoid is
off (closed), pressurized air from the compressor is fed straight into the wastegate control.
Any increase in compressor pressure beyond the rated pressure of the wastegate control
results in the wastegate being opened, preventing buildup of boost.
When energized (opened), air is allowed to bleed off the compressor-to-wastegate line by way
of a “T” connector (in stock vehicles, this air is vented back into the intake post-MAF). This
prevents the wastegate from seeing the full compressor pressure, allowing boost to build. The
'02-'03 (and some '04-'05) model years include a restrictor pill in the hose connecting the
compressor to the “T” which meters the air for the stock ECU calibration.
While the stock system operates adequately, it can lead to problems at higher-than-stock
boost levels. Since the bleed system is sized for the stock turbo at stock boost levels, it is
typically incapable of correctly metering air at higher
boost, allowing the wastegate to see pressure and
open before intended. Additionally, since the
wastegate is never completely cut off from seeing
compressor pressure, it can open at low boost levels
and inhibit boost buildup. Ideally, the wastegate
should remain entirely closed for fastest boost buildup
(as all exhaust is then forced through the turbine).
Figure 2: Pneumatic schematic for the GrimmSpeed
Boost Control Solenoid
D. 3-Port Operation and Installation
A 3-port solenoid does away with the bleed-based
system, explicitly shunting air from the compressor to
the wastegate, or compressor to vent (or back into the
intake post-MAF, OEM-style). Drawbacks of the bleed-
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based system are thus eliminated, with the wastegate seeing literally no pressure when the
solenoid is energized, to seeing all of the compressor pressure when the solenoid is deenergized.
Now able to explicitly control the opening and closing of the wastegate, the ECU is able to
control boost with greater precision and reduced response time.
Installation for 2002-2005 WRX and 2004-2005 STI: Remove cover on passenger side engine
bay exposing the factory boost control solenoid. Using a 10mm socket, remove factory
solenoid and unplug the electrical connector and vacuum lines. Reuse the factory rubber
mounts and transfer them to the GrimmSpeed bracket. Install GrimmSpeed bracket and
solenoid while reusing the factory nuts.
Hook up vacuum lines. See Figure 2. Port 3 connects to a high-pressure boost source (there is
a vacuum nipple on the turbo compressor outlet). Port 2 connects to the internal wastegate
actuator vacuum nipple and Port 1 should be routed back to the intake (where the factory
BCS mounts). Remove the factory restrictor pill. It is recommended that a plastic zip tie be
used to secure vacuum lines. The electrical is plug and play with the supplied connector.
Tuning: WGDC controls the actuator / turbo. Tuning to the WGDC is required (approx 30%
reduction in WGDC)
Installation for 2006-2007 WRX and 2006-2007 STI: Remove factory boost control solenoid
bracket on passenger side engine bay using 10mm wrench. Unplug the electrical connector
and vacuum lines. The GrimmSpeed valve will go on the same bracket but in a different
location on the bracket. You will use the two properly spaced holes to mount the
GrimmSpeed valve. Attach using included grommets and hardware using a 10mm socket.
Hook up vacuum lines. See Figure 2. Port 3 connects to a high-pressure boost source (there is
a vacuum nipple on the turbo compressor outlet). Port 2 connects to the internal wastegate
actuator vacuum nipple and Port 1 should be routed back to the intake (where the factory
BCS mounts). Remove the factory restrictor pill. It is recommended that a plastic zip tie be
used to secure vacuum lines. The electrical is plug and play with the supplied connector.
Tuning: WGDC controls the actuator / turbo. Tuning to the WGDC is required (approx 30%
reduction in WGDC)
Installation for 2008+ WRX and 2005+ Legacy GT: For Legacy GTs, remove plastic engine
cover. Remove factory boost control solenoid using a 10mm wrench. It is located on the
passenger side of the intake manifold. Unplug the electrical connector and vacuum lines.
Install GrimmSpeed bracket and solenoid while reusing the factory bolt.
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Hook up vacuum lines. See Figure 2. Port 3 connects to a high-pressure boost source (there is
a vacuum nipple on the turbo compressor outlet). Port 2 connects to the internal wastegate
actuator vacuum nipple and Port 1 should be routed back to the intake (where the factory
BCS mounts). Remove the factory restrictor pill. It is recommended that a plastic zip tie be
used to secure vacuum lines. The electrical is plug and play with the supplied connector.
Tuning: WGDC controls the actuator / turbo. Tuning to the WGDC is required (approx 30%
reduction in WGDC)
Installation for 2008+ STI: Remove factory boost control solenoid using a 10mm wrench. It
is located underneath the silver bracket mounted on the intake manifold. Unplug the
electrical connector and vacuum lines. Install GrimmSpeed bracket and solenoid while
reusing the factory bolt.
Hook up vacuum lines. See Figure 2. Port 3 connects to a high-pressure boost source (there is
a vacuum nipple on the turbo compressor outlet). Port 2 connects to the internal wastegate
actuator vacuum nipple and Port 1 should be routed back to the intake (where the factory
BCS mounts). The factory restrictor pill can be removed for operation. It is recommended
that a plastic zip tie is used to secure vacuum lines. The electrical is plug and play with the
supplied connector. Tuning: WGDC controls the actuator / turbo. Tuning to the WGDC is
required (approx 30% reduction in WGDC)
E. External Wastegate(EWG) Installation
Hook up vacuum lines. See Figure 3. Port 3 connects to a high-pressure boost source (there is
a vacuum nipple on the turbo compressor outlet). Port 2 connects to the bottom port on the
external wastegate. The factory restrictor pill should be removed for operation. It is
recommended that a plastic zip tie is used to secure vacuum lines. The electrical is plug and
play with the supplied connector.
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Figure 3. Pneumatic schematic for
the GrimmSpeed Boost Control
Solenoid with EWG
Please contact us if you have any questions during installation. 612.379.0000 or
Thank you for your purchase!
sales@grimmspeed.com.
Grimmspeed
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