Take-up table is the one that defines start of movement. It is a bit different throughout various transmissions but in general rule i’s always RPM dependent.
- Dual Clutch transmissions use Take-up table RPM x Temperature. After selecting Drive mode (1st gear) GCU will be in IDLE take-up mode – pressure will be partially applied, but full take-up pressure will be built once PPS gets pressed (HTG hint: it’s better to assign PPS <pedal position sensor> than TPS <throttle position sensor>, because in case of using DBW <drive by wire> TPS reading shows positive values at engine idling). Higher temperature requires slightly higher pressures, also this can be used as protection from overheating clutches during excessive take-ups.
Once clutch slip is at desired level transmission will exit take-up mode and GCU will apply pressure from Clutch Pressure tables.
- Hydraulic transmissions use Take-up table RPM x PPS. Hydraulic transmission will perform take-up “using” mostly a Torque Converter. With gear fully engaged TCC will pull quite strongly so take-up map can be used to lower pulling force, or to create launch scenarios (TPS dependent). It is possible to make TC transmission not take-up without PPS pressed if user wishes so.
For hydraulic transmissions used in off-road scenarios it’s important to use “Off-road take-up mode”, which ignores take-up table and applies full clutch pressure once gear is engaged allowing transmission to slip only with torque converter. Terrain riding (usually within take-up range) creates extensive heat for clutch packs so this strategy greatly reduces clutch wear during extensive take-ups. (Available in software 1.1)
Example: Let’s assume engine idles @ 1000RPM. Adjust map globally to the point where transmission starts to pull away softly (in case od dual clutch remember about PPS!). Lower the values below idle slightly, and around engine stalling point greatly to take off load from the engine in case RPM drop. Values above idle up to preferred pull away RPMs increase step by step making table rising linearly, softly, and from that point make steep increase (hard launch scenario).
HTG tuning GCU monitors clutch slip, drive ratios and controls them in closed loop so once clutch engagement is at desired level GCU will go into regular run mode.
Another very important table for take-up mode is ANTI-stall protection table which defines below which RPMs (row 1) GCU will use take-up table values, and below which RPMs (row 0) GCU will disengage take-up mode and go into idle mode. Good idea is to set row 0 to RPMs just below idle RPM, and row 1 around 300-400 RPMs higher.
Frequent issue #1: Takeup is late and very harsh.: Increase values around idle and up to the point where harsh engagement happens. It means that drivetrain has insufficient take-up preload.
Frequent issue #2: Takeup bouncy – RPMs jump high, and then suddenly fall trying to pull away.: Idle preload is too low. Inhibit engine will to rev with additional clutch engagement 🙂
Frequent issue #3: After take-up when I brake engine stalls.: Values below idle are too high, decrease them gradually as RPMs drop to take load off from the engine. Adjust anti-stall table.
Frequent issue #4: Rapid take-up is slipping extensively: Until clutch slip is closed (exists no more) in take-up state GCU will be applying clutch pressure according to take-up table. Frequent mistake is making RPM axis ending with too low RPMs. Being anywhere above highest RPMs in take-up mode will still use pressures from last row. Make sure to make RPM axis ending with higher than usually met RPMs and apply clutch pressures that would cause full clutch engagement (f. eg. RPM axis 800, 1000, 1200 (…) 2200, 2400, 3000, 4000, 5000 and knowing that take-up takes place anywhere between 1000 and 2500 rpms apply more pressure for higher RPMs, so if for take-up transmission requires around 10-20% pressure then for higher RPMs apply i.eg. 40%, 60%, 80% for additional protection in case of extensive clutch slip during take-up).