14 SHIFT SYSTEM
14.1 SYSTEM OVERVIEW
The T421 is equipped with a semi-automatic shift system. Here below a quick overview:
• GCU (Gear Control Unit): embedded in the ECU.
• GCC (Gearshift Current Controller): Marelli GCC, this unit manage the actuator (ESA) control
• ESA II (Electric Shift Actuator): Marelli ESA II, this unit driven by the GCC perform the physical shift,
ESA II is a position-controlled unit, refer to the chapter 13.1.2 for its setting and maintenance.
14.1.1 Gearshift Control
The semi-automatic gearshift is controlled by several parameters of the vehicle, critical sensors are:
• Paddle sensors
• RPM
• Throttle position
• Barrel position
• REV button
• ACK button
Upshift
• 1st to 6th gear: right paddle
• N to 1st gear: ACK button + right paddle
• R to N: ACK button + right paddle
Downshift
• 6th to 1st gear: left paddle (if over-revs threshold is respected)
• 1st to N: ACK button + left paddle
• N to R: (car steady): ACK button + REV button
The downshift is allowed only if the lower gear (to be engaged) will not results in an overrevs. If an overrev
is expected the shift will be skipped and driver must repeat the request.
14.1.2 Gear State values explanation
In the logged data is available the channel:
• GearState: the reported value describes the actuation status.
Please refer to the table below showing the configurations for the channel:
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