The system is pneumatically powered, and is supplied with an electrical compressor (12V supply required), while a mechanically driven compressor is available for some applications. A valve block is included, providing a switchable channel of air from the receiver to the gear shift actuators which can be either integrated within the gearbox casing or fitted as a separate ‘bolt-on’ unit. This ensures the benefits of pneumatic shifting can be achieved with most Hewland transmissions. A separate pneumatic throttle actuator (‘blipper’) is used in order to operate the throttle – this is not required when a Fly-By-Wire throttle body is used.
The Gearbox Control Unit (GCU) is the electronic brain behind the whole shift system. It receives shift controls from the two sturdy steering wheel mounted paddles, and together with the pneumatic valves, controls engine cut during a shift and is capable of electronically blipping the throttle (where fly-by-wire throttle is installed). The GCU contains customised software infused with decades of Hewlands shifting knowledge, together with high speed data logging to provide detailed feedback.
High speed CAN communication for data transfer between GCU, Engine ECU and other control/logging hardware is utilised. For low-tech applications it is possible to hard-wire these signals direct to the GCU, where the ECU/CAN isn’t used.
In addition to the paddle switches, the system allows for additional driver operated switches. These additional switches may enable the driver to operate neutral/reverse gear selection, GCU mode selection, and GCU map selection (where applicable). The GCU also monitors the pressure and temperature of the pneumatic system via integrated sensors within the Valve Block and Accumulator.
Our Semi-Auto system also includes all necessary pneumatic hoses and an in-line filter to ensure perfect fitment and reliability.