3 Port Boost Control

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Can be integrated with direct boost control

Original Thread [here]

Risks: While this solution is fairly straightforward it is very possible for you to screw something up. Too high of duty cycles or lines that are not arranged properly will cause boost overshoot and possibly cause serious damage! If a solenoid fails and you are using the interrupt method generally used with a 3 port (stock is bleed-type) you run the risk of overshoot also. Most solenoids will fail in their normally open (NO) position, but it is possible for one to fail in its normally closed (NC) position. Please take this into consideration when doing this mod!


What you will need:

  • The ability to tune your ECU. IMPORTANT! You MUST reduce your boost tables before your first drive. If you do not you will overshoot and serious damage may occur!
  • A compatible 3 port solenoid. Known Solenoids include (but are not limited to):
Known Compatible Solenoids
Make Part # (if applicable) Resistance (ohms) Latency (ms) at 14 V Similar to
AC Delco 214-474, PT374 (pigtail) GM
GM [1997152], 12102747 (pigtail) 24 AC Delco
INGERSOLL-RAND [P251SS-012-D] Perrin EBCS (coated, comes with fittings, possibly other mods)
AEM #30-2400 or Tru-Boost part 12 Mac Valves (below)
MAC 35A-AAA-DDBA-1BA AEM *See bullet #3 below- 35A may be the newer AEM valve
MAC 36A-AAA-JDBA-1GD AEM (extra connector on solenoid and LED indicator)
Tactrix PD3PBCSM 24 Gruppe-S BCS (exact same)
  • A way to connect the solenoid to the stock wiring. Some people use simple crimp ons, some use vampire clips (not recommended!) or solder the the OEM harness. The Tactrix Solenoid is PNP. GST motorsports was rumored to have connectors at one point, but this cannot be confirmed. You can also harvest the AC Pressure sensor off of many common DSM (or mitsubishi in general) including the evo for a PNP solution (see [here], [here], and [here] ).
  • A resistor has been proposed to be used for aftermarket solenoids that have a resistance lower than the stock solenoid (32 ohms). This suggestion is debatable with the original reason being to prevent blowing the solid state relay in the ECU by sending a higher current through the relay due to the lower resistance of some of the aftermarket solenoids. Adding a resistor to bring up the total circuit resistance to the stock BCS resistance range (29-36 ohms) has been confirmed to work, but adding a resistor does slow the responsiveness of the BCS and may affect the ability of the BCS to open at very high boost levels. **NOTE - See next bullet point**
  • Mr Fred has done some bench testing of boost control solenoids (seen [here] ) He notes how resistance plays into solenoid response, and that the GM is closer to stock resistance than other valves. He also suggested that the AEM solenoid is, in fact, the MAC 35A and not the 36A, but may just be the "newer version". This is also referenced by TedB in a post [here]
  • It hasn't been concluded if the GM valve has a cheaper pig-tail than one available from OEMs but is questioned [here]. One thing that is known that around the beginning of 2009 the GM BCS part was no longer being manufactured and tripled in price (from ~$17 to ~$50). It would be nice to know if there is a new Part #.

Flash your ECU

Reduce all of your Max WGDC (sometimes called Base WGDC) tables to 50% to prevent overshoot. Then see a tuning guide for how to tune your boost when you are finished with the install.

Install the Solenoid

Wire orientation should not matter. Install the resistor in line and solder your connections or create a PNP connector. Keep the boost lines as short as possible for best boost response.


Then tune, tune, and tune again until your tables are spot on! Enjoy increased boost holding capacity and control.

Also, when using this method it may be a good idea to raise the values for BCS de-activation RPM. Stock these are set to 7500. If you reach 7500 RPM on throttle your WGDC will jump to 100% with these values. Raise them above your rev-limit to have them continue to interpolate to that RPM.

BCS deactivation RPM

Be careful and make sure your XML definitions are correct before modifying this value. This table is often defined incorrectly.