teal.supra
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Vehicle: 2022 Supra ZF8 Automatic Transmission
Transmission Upgrade: Recently installed a built transmission with a high-stall torque converter.
Main Symptom:
When in gear, with the brake fully depressed and the throttle fully applied, the RPMs do not exceed ~1,000.
Tuner created launch control does not change this behavior, and manually attempting to build RPMs for a launch fails.
Additional Observations:
Normal RPM behavior when revving in neutral or park.
The car runs fine during normal driving and dyno pulls, making expected power and torque.
---
Steps Taken
1. Ruled Out Tuning:
Flashed the ECU and TCU back to the OEM maps; the issue persists, ruling out tuning errors.
Also flashed previous tuner maps, same behavior persists.
2. Checked Mechanical Components:
Verified transmission fluid level is appropriate with the car tipped on its side, while cold, fluid runs from the fill plug.
Verified that V-band connections (exhaust manifold, turbo, and wastegates) are tight and free of debris.
Wastegates (dual Tial external) appear to be functioning properly.
Unplugged MAC solenoid, no change in behavior.
3. Turbo and Boost:
Turbo behavior and boost pressure logs appear normal during dyno runs.
Removing the reference line from the turbo had no effect on the issue.
4. Launch Control Conditions:
Confirmed that all conditions for launch control are being met (e.g., full brake, full throttle, zero speed, DSC off, safety systems off, left hand switch pressed down).
Even without using the launch control feature from the tuner, the car has the same behavior when applying the throttle and brake simultaneously (trying to launch the car without it).
5. Diagnostics:
Tested the brake pedal switch and signal, which appear functional.
Disabled traction and stability control completely, but the issue persists.
6. Transmission Behavior:
Confirmed normal driving and shifting behavior, with no noticeable transmission-related errors under load or normal conditions.
---
Suspected Causes
1. High-Stall Torque Converter:
The higher stall speed may be interacting with the ECU/TCU logic, potentially triggering an RPM limiter or safety measure.
2. Brake Override System:
Simultaneous brake and throttle inputs may be activating a throttle cut due to the Brake Override System.
3. TCU Calibration:
The TCU may not be properly calibrated for the built transmission and high-stall converter, causing it to impose a torque or RPM limiter.
I have tried to flash XHP stage 0-3, with and without a custom tune from Sutphin, and also with and without the custom launch control feature.
4. Torque Management or Traction Control Interference:
Torque management or traction control systems may be reducing throttle input due to perceived slip or drivetrain stress.
---
Questions for the Community
1. Does anyone have a similar experience with high-stall torque converter and built transmission in the Supra?
Were specific TCU adjustments needed for proper launch control or stationary RPM behavior?
2. Could this be related to the Brake Override System, and if so, how can I test or disable it?
3. Are there specific transmission parameters (e.g., torque limits, lockup behavior) that need to be recalibrated in the TCU? This is a question I have out to Sutphin.
4. Have others experienced similar issues when upgrading to a high-stall torque converter?
Transmission Upgrade: Recently installed a built transmission with a high-stall torque converter.
Main Symptom:
When in gear, with the brake fully depressed and the throttle fully applied, the RPMs do not exceed ~1,000.
Tuner created launch control does not change this behavior, and manually attempting to build RPMs for a launch fails.
Additional Observations:
Normal RPM behavior when revving in neutral or park.
The car runs fine during normal driving and dyno pulls, making expected power and torque.
---
Steps Taken
1. Ruled Out Tuning:
Flashed the ECU and TCU back to the OEM maps; the issue persists, ruling out tuning errors.
Also flashed previous tuner maps, same behavior persists.
2. Checked Mechanical Components:
Verified transmission fluid level is appropriate with the car tipped on its side, while cold, fluid runs from the fill plug.
Verified that V-band connections (exhaust manifold, turbo, and wastegates) are tight and free of debris.
Wastegates (dual Tial external) appear to be functioning properly.
Unplugged MAC solenoid, no change in behavior.
3. Turbo and Boost:
Turbo behavior and boost pressure logs appear normal during dyno runs.
Removing the reference line from the turbo had no effect on the issue.
4. Launch Control Conditions:
Confirmed that all conditions for launch control are being met (e.g., full brake, full throttle, zero speed, DSC off, safety systems off, left hand switch pressed down).
Even without using the launch control feature from the tuner, the car has the same behavior when applying the throttle and brake simultaneously (trying to launch the car without it).
5. Diagnostics:
Tested the brake pedal switch and signal, which appear functional.
Disabled traction and stability control completely, but the issue persists.
6. Transmission Behavior:
Confirmed normal driving and shifting behavior, with no noticeable transmission-related errors under load or normal conditions.
---
Suspected Causes
1. High-Stall Torque Converter:
The higher stall speed may be interacting with the ECU/TCU logic, potentially triggering an RPM limiter or safety measure.
2. Brake Override System:
Simultaneous brake and throttle inputs may be activating a throttle cut due to the Brake Override System.
3. TCU Calibration:
The TCU may not be properly calibrated for the built transmission and high-stall converter, causing it to impose a torque or RPM limiter.
I have tried to flash XHP stage 0-3, with and without a custom tune from Sutphin, and also with and without the custom launch control feature.
4. Torque Management or Traction Control Interference:
Torque management or traction control systems may be reducing throttle input due to perceived slip or drivetrain stress.
---
Questions for the Community
1. Does anyone have a similar experience with high-stall torque converter and built transmission in the Supra?
Were specific TCU adjustments needed for proper launch control or stationary RPM behavior?
2. Could this be related to the Brake Override System, and if so, how can I test or disable it?
3. Are there specific transmission parameters (e.g., torque limits, lockup behavior) that need to be recalibrated in the TCU? This is a question I have out to Sutphin.
4. Have others experienced similar issues when upgrading to a high-stall torque converter?
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