To determine the torque-speed characteristics of an engine at partial throttle or specific driving conditions, you would typically need to perform a dynamometer (dyno) test under those specific conditions. Dyno tests are conducted to measure and analyze an engine's performance characteristics.
During a dyno test, the engine is run under controlled conditions while connected to a dynamometer, which measures the engine's output torque and rotational speed. By varying the throttle position and load on the engine, different operating conditions can be simulated to generate torque-speed curves for specific throttle openings or driving conditions.
Instead, manufacturers typically provide the torque-speed curves at full throttle as it represents the engine's maximum potential output. These graphs are useful for comparing and evaluating engines and determining their performance capabilities.
To estimate the torque and power output of an engine under partial throttle or specific driving conditions, you can make some general assumptions based on the known characteristics of the engine. Manufacturers often provide data such as the engine's peak torque and power, as well as the shape of the torque curve. From this information, you can estimate how the engine's torque output will vary at different throttle positions or driving conditions.
Keep in mind that actual engine performance under partial throttle will depend on various factors, including engine design, fueling and ignition systems, gear ratios, and vehicle weight. Additionally, different engines may respond differently to partial throttle inputs. Therefore, while estimations can be made, the best way to accurately determine the torque-speed characteristics for specific driving conditions is through dynamometer testing.