Downshift Lockout – Summary
This logic prevents unsafe or unintended downshifts based on current gear, speed, engine RPM, and driver input. It includes three main lockout scenarios:
1. Normal Downshift Lockout (Gear ≥ 2)
Lockout is active if:
•The downshift would result in engine RPM exceeding a safe limit (based on a table or rev limiter), or
•The throttle (TPS) is too high for a downshift.
Only applies if:
•The gear is between 2 and the configured max gear.
•The gear configuration is valid (between 3 and 8 gears).
2. Downshifting into Reverse (Gear = 0 or 1)
Lockout is active unless:
•The vehicle speed is below a safe limit.
•And either the clutch or transbrake is engaged, or no clutch requirement is configured.
Handled separately for:
•Gear = 0: Trying to downshift into Reverse from Neutral.
•Gear = 1: Trying to downshift into Reverse from 1st gear.
3. Fallback
If gear settings are invalid or conditions don't match:
•Downshift is allowed (lockout disabled).
gear ratios
gear count
Specifies the number of forward gears in the transmission.
X gear ratio
Specifies the gear ratio of the transmission for the selected gear.
reverse lockout
reverse requires clutch or transbrake
When enabled, requires the Clutch switch or Transbrake bump/creep button to be active before allowing engagement of Reverse gear.
reverse lockout speed
Specifies the maximum allowed speed for engaging Reverse gear.
neutral lockout
neutral requires clutch or transbrake
When enabled, requires the Clutch switch or Transbrake bump/creep button to be active before allowing engagement of Neutral gear.
neutral lockout speed
Specifies the maximum allowed speed for engaging Neutral gear.
Downshift conditions
input type
Defines how the system detects an downshift button press.
•edge (max 1 shifts per button press) - An downshift is triggered once per button press (on rising edge). Holding the button will not cause multiple shifts.
•level (shifts continously when input active) - Allows repeated downshifts while the button is held, with a delay between each shift controlled by an internal timer based on solenoid activation time.
Note: When using Level Triggered, the system respects the configured minimum time between shifts to prevent unintended rapid shifting.
max TPS
Specifies the maximum allowed throttle position (TPS) for permitting a downshift.
If the current TPS exceeds this value, the downshift will be locked out to avoid engine over-revving or drivability issues during aggressive throttle input. Applied only when downshifting from gear 2 or higher.
Commonly used to prevent accidental or unsafe downshifts at wide-open throttle.
Example: If set to 30%, the driver must release the throttle below 30% before a downshift is allowed.
max resulting engine rpm
Entry method
Selects the method used to determine the maximum allowable engine RPM during a downshift.
•table - Uses the Max Resulting Engine RPM Table, a 2D table with customizable axis. Allows fine-tuned RPM limits based on dynamic inputs (e.g., speed, gear, etc.). This table is used to calculate whether a downshift would result in engine overspeed. If the projected engine RPM after a downshift exceeds the value from this table, the downshift will be locked out.
•Current rev limiter - Uses the current rev limiter value as the maximum RPM allowed after a downshift. Simpler and automatically follows any active rev limit strategy (e.g., engine temp, boost, etc.).
