Forza Componenti Model B4A Exhaust Controller



The Model B4A controller is functionally identical to the Model B4.  It is a 3-way exhaust controller that is designed for installation in extreme environments as one would encounter in the engine bay of high performance sports cars.

This model is designed for motor cars that have only a single vacuum solenoid valve, hence only a single electrical connector.

As with the Model B4, you can choose for the valves to be in Normal mode at vehicle start or in the Always Open mode at vehicle start.

The Model B4A provides three different operational modes — all three modes can be selected using the included remote transmitter or a manual On/Off switch.

  1. Normal Mode:  In this mode, the vehicle controls the operation of the exhaust bypass valves.  This is the stock operation.  You can choose this as your start-up mode.
  2. Always Open:  Selecting this mode will force the exhaust bypass valves to the open position — and remain open.  When the valves are Always Open, you have the full experience of hearing your engine exhaust at any time.  You can also choose as your start-up mode.
  3. Always Closed:  Selecting the Always Closed mode will force the exhaust bypass valves to remain closed at all times.  This overrides the ECU control which opens the valves at predetermined engine and vehicle speeds.  This mode is especially useful to ensure that your vehicle is as quiet as possible.  Note: With this option, you can force the valves to stay in the closed position at all times.  This feature was added at the request of people who track their cars at locations with strict noise standards and did not want the vehicle ECU to open the valves at high engine RPM. This mode cannot be chosen as your start-up mode.

Note:  When used on Alfa Romeo Giulia QV / Stelvio QV or the Ferrari F355, 550, 575M the always closed mode is disabled.

Plug-and-Play 100% Reversible
The kit is completely plug-and-play.  Power for the controller comes from the existing connector to the car’s exhaust bypass vacuum solenoids, and no wiring modification are required because the kit includes connector cables for the vacuum solenoids.  Since no modification are required to install, if you ever want to remove the controller the installation is 100% reversible.

Start-up option user configurable for Always Open or Normal Mode (ECU Control).

Installation is straight forward.  The smaller size makes it easier to find a suitable location to install the controller, unplug the vacuum solenoids,  connect the included cables and route the cables to the controller.  Once installation is complete, you use one button on your remote transmitter to open the exhaust bypass valves and the other button to close the valves and return control to the car and, you also have the ability to configure a manual on/off switch that you can mount inside your vehicle.


Ferrari F355, 550, 575, 599, 612, California (normally aspirated),  Lamborghini, Maserati, Volkswagen, Alfa Romeo Giula QV / Stelvio QV and Audi R8.

Note:  Always closed not functional on Alfa Romeo, Ferrari F355/550/575M


Model B4A Kit Contents (Model B4 shown in photo)

  • Controller module with two remotes.  Extra remotes available
  • One connection cable.  Depending on vehicle, either a 120 cm cable or a 120 cm cable plus a 120 cm extension
  • Two strips 3M Dual Lock Reclosable  Fasteners
  • Full installation instructions


  • Completely self contained controller box
  • User configuration to use either the remote control key fob or use a manual on/off switch
  • Approved by FCC, CE and all international governing bodies
  • Always Closed option can be used to keep the valves closed at all times
  • All internal components integrated on Printed Circuit Board for higher reliability
  • No Check Engine Lights (CEL) or Diagnostic Test Codes (DTC)
  • Cables assembled using water and oil resistant flexible cord – 18 AWG stranded Class K copper conductors per ASTM B-174.
  • Cable is rated SJEEOW for severe outdoor service with TPE insulation rated to 105° C. Type SJEOOW cords are ideal for flex applications in harsh high temperature environments where highest degree for water and oil resistance and extended service life are essential.
  • All electrical cables use weatherproof connectors
  • High-gain external antenna for improved remote control performance
  • Kit includes full installation instructions
  • Kit includes two remote control transmitters additional transmitters available.
  • Remote control can be programmed to newer versions of HomeLink (version 5 and higher) that is integrated into many cars.   Older versions of HomeLink (earlier than 2013) will not support the 433MHz frequency of the remote transmitter used by Forza.

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