GrimmSpeed Mazdaspeed Electronic Boost Controller - Manual (Page 2)

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rimm
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peed 2
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.
B. Technical Background
A BCS is a binary device – i.e. it is either on (energized), or off. In the context of the
MazdaSpeed device, when the BCS is energized, air is allowed to pass through the device,
while it is off, the air flow is cut.
There are two modes of boost controller operation, at least in this context: “bleed” 2 port
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 the dual waste gate hose fittings (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.
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).
Installing the GrimmSpeed BCS in 2 port mode does not require tuning.