SI Core Engine Engine Load Breakpoints

I want to create a model using the Simulink Powertrain Blockset with the SI Core Engine, specifically using the SI Engine Simple Torque Model. The SI Engine Simple Torque Model requires me to input three data sets: Torque Map, Load Breakpoint and Speed Breakpoint.

What does "Load Breakpoint" mean exactly?(Engine load breakpoints, L, dimensionless)

How can I calculate the corresponding load value for the fuel load torque values I have?

For example, I have an engine that produces 70 Nm of torque at 1000 RPM, 120 Nm at 2000 RPM, 145 Nm at 3000 RPM, and 170 Nm at 4000 RPM. This torque value is measured from a dynamometer for a specific engine with full throttle position. How can I calculate which torque is produced for load breakpoints like 0.2, 0.275, or 1.1, 1.175, and how can I transfer this to a table?

Answer 1

[Hitesh]

Hi Murat,

The term “Load Breakpoint” in SI Engine Simple Torque Model within Simulink Powertrain Blockset refers to a set of dimensionless values that represent different engine load conditions.Its values are typically normalized between 0 and 1, where 0 represents no load and 1 represents full load.

Steps to Calculate Load Values:

• Identify Full Load Torque: For each RPM, identify the full load torque value that is the maximum torque the engine can produce at that RPM.
• Calculate Load Value: For each measured torque value, calculate the load value using the formula:

Load_breakpoint = Measured_Torque./Full_Load_Torque

This ratio gives you the dimensionless load value, which can be used as a load breakpoint in your model.

Steps to create Torque Map:

• Initialize a matrix to store torque values
• A nested loop calculates the torque for each RPM and load breakpoint combination using the formula:

Torque=Full_Load_Torque*Load_breakpoint

• Use “array2table” for conversion from matrix to table

For more information on SI Core Engine and “array2table”, please refer to the below MATLAB Documentation:

• https://www.mathworks.com/help/autoblks/ref/sicoreengine.html
• https://www.mathworks.com/help/matlab/ref/array2table.html

Hope this helps!

[Murat]

Hello, thank you for your response. My question is as follows: How can the measured torque value be higher than the full load value, and how can the load breakpoint values increase to 1.00, 1.15, 1.25, etc.Additionally, when I set the full load value I have to a breakpoint of 1.00 without taking a measurement, should I take half of the current torque value at 0.5 load?

[Hitesh]

Hi Murat,

Typically, load of 1.0 corresponds to full load, while values less than 1.0 represent partial load conditions. Values greater than 1.0 can be used to model overloading conditions or extrapolated scenarios.

For intermediate load values like 0.2, 0.275, or 1.1, one can interpolate between known data points. If full load value is set as 1.0, then the approximation torque at 0.5 load is as half of the full load torque, but this is a simplification and actual engine behavior might not be linear. One need to use curve fitting or other interpolation methods to generate a more accurate torque map.