Closed Loop takes away tuning completely. Shifts are continuously adapted and adjusted to deliver best quality of shift regardless of any environmental variables like transmission lifespan. HTG GCU update 1.0.15 introduced fully closed loop operation mode for 8HP transmissions.
CL is a very sophisticated method delivering very easy solution out of the box. To make it happen prerequisites have to be checked carefully and steps followed as instructed to make learn-in process as quick and precise as possible.
STATIC ADAPTATIONS OUTPUTS adaptation should be performed in operating temperature and is MANDATORY. TRANSMISSION adaptation should be performed in operating temperature. To perform TRANSMISSION adaptation follow on screen instructions. Once warmed up reset GCU if any mode has been selected after GCU boot. Hold the brake and engage D/M mode (3/4) and start TRANSMISSION STATIC adaptation. Throughout this adaptation process engine should be IDLING stably. GCU will engage several clutches in specific order causing RPM to sag a bit, but as soon as it’s released idle should recover precisely. Once TRANSMISSION ADAPTATION is over switch back to N mode and RESET GCU. OUTPUTS adaptation lasts around 1 minute, TRANSMISSION adaptation lasts usually around 10 minutes.
TORQUE CALCULATION All adaptation values are stored in functions of LOAD. RELIABLE torque is mandatory in this application. OEM ECUs that calculate load internally usually have it included in CAN datastreams (if such datastream is predefined in GCU, LOAD should be included there also) and are most reliable TORQUE sources. In that case we strongly advice using TORQUE INPUT setting. If ECU does not report TRQ, GCU fuel model is preferred over air model, and over torque tables unless setup precisely. See more in Torque Estimation strategy
GEAR RATIOS Gear ratios should be entered according to transmission specification. GCU adapts gear ratios during the drive so table values are considered first base point but should be set precisely prior to driving.
BASE TARGET SETUP CL US rate and CL DS rate tables have to be set with reasonable values prior to driving. See suggested setup in related articles.
How to complete learn-in quickly.
- Perform all mandatory static adaptations
- Outputs adaptation
- 8HP Static adaptation
- Initial dynamic adaptations
- Gear ratio adaptation. GCU adapts gear ratios constantly but letting it adapt prior to shift learning is crucial for swift CL deployment. Cruise each gear around 2000rpm for 2-5 seconds. CAUTION: First shifts need to be executed at low load.
- Basic closed loop learning. First shifts quality might be inaccurate. Pay full attention to perform initial up-shifts at minimal possible load (but still on load) and downshifts completely off-load (deceleration). After couple full range swipes (1->8 , 8->1) confirming that shifts are predictable and stable move to next step.
- Torque range adaptation. GCU stores minimal and maximal reported torque according to selected torque estimation strategy. If you’re running fresh setup we suggest (if possible) perform full power pull so GCU can record values during on-power pull and full engine decceleration. If ECU uses boost-by-gear strategy use one with maximal possible torque. Changing torque calculation method resulting in operating on different values requires STATIC ADAPTATION to be redone.
- Shift learning. Once GCU knows real torque range start adapting shifts. There are couple possible strategies how to execute learn-in process – full gear swipe or particular shift tuning. Using both strategies combined gives quickest results. FULL SWIPE should be done at constant load meaning holding average similar load lever through all up-shifts and same load for power downshifts once deceleration downshifts are already adapted. SELECTIVE LEARNING focuses on particular gears. This is best option for cruising scenarios. Go into the gear i.eg. 3rd gear, pick load (preferably initially low load), perform up-shift, then decelerate with engine braking and downshift. Repeat until current gear ratio matches shift target. SEE HERE. Move to higher load and repeat on other gears / loads. IMPORTANT: Adaptation values are stored if load during the shift has been STABLE. Make sure to maintain the torque until current gear matches target gear value. Adaptation indicator reports adaptation status and notifies if shift has been accepted or not.
- Adjust shift rates and preparation times to fit your desired goals. See related articles for more details!
- See instructional video on HTG Youtube channel: