Discussion Overview
The discussion revolves around estimating wheel torque from engine torque and RPM using data from a truck's CAN bus. Participants explore the necessary parameters and methods for calculating tractive force at the wheels, considering factors such as gear ratios, wheel size, and drivetrain efficiency.
Discussion Character
- Exploratory, Technical explanation, Conceptual clarification
Main Points Raised
- One participant suggests that engine torque and RPM can be obtained from the CAN bus and questions how to compute torque at the wheels, noting the potential need for gear ratio information.
- Another participant argues that if vehicle speed is available from the CAN bus, wheel size is the only additional requirement, as engine RPM over wheel RPM provides the total drivetrain mechanical advantage.
- A third participant points out that drivetrain losses should be considered, emphasizing the importance of accurate data on drivetrain efficiency, which may vary with road and engine speed.
- One participant inquires whether GPS could be used to estimate vehicle speed if it is not available from the CAN bus.
- A later reply confirms that GPS should suffice for estimating vehicle speed and suggests assuming a powertrain efficiency of 85-90% for calculations.
Areas of Agreement / Disagreement
Participants generally agree on the importance of vehicle speed and wheel size for estimating tractive force, but there is no consensus on the best method to account for drivetrain losses or the exact efficiency values to use.
Contextual Notes
Limitations include the potential unavailability of gear ratios from the CAN bus and the variability of drivetrain efficiency based on different conditions.
Who May Find This Useful
Individuals interested in vehicle dynamics, automotive engineering, or those working with CAN bus data in trucks may find this discussion relevant.