Frictional Loss

Emtron torque modelling relies on a series of inputs and calculations to achieve accurate output estimates.  Frictional loss is a significant factor to account for when estimating the engines torque output.  If incorrectly set the torque-based functions will not perform as well as they were designed and can even perform worse than if classic legacy functions were used.  The ECU has a series of lookup tables that need to be filled.  As shown in screenshot 1, there are three (3) frictional loss tables available for calibration. 


Screenshot 1: Frictional Loss Tables Menu


“Frictional Loss Table” is the primary table that must be set.  The default table supplied with any Emtron base file will likely be reasonable for the application however the better this is calibrated the better the torque based functions will perform.  Screenshot 2 shows an example table from a Nissan RB26 6 cylinder engine.   The general rule is the higher the cylinder count the higher frictional loss that should be expected.  Modern engines almost always have significantly lower frictional loss than their early engine counterparts.         


Screenshot 2: Frictional Loss Table (Nm)


Another influence on an engines frictional loss is the oil temperature.  The colder the oil the more friction will occur.  As per screenshot 3 the Frictional Loss Offset 1 Table has been calibrated against engine oil temperature.  The table is normalised to 0 closely to where the engine oil temperature is commonly at, In this case 90 deg c.   Frictional Loss Offset 2 Table (Nm) is also available for calibration and should only be used if there are other calibration inputs that are needed.  For most applications this can be set to 0.


Screenshot 3: Frictional Offset 1 Table (Nm)


So how can one calibrate these tables?  Firstly, the engine mapping must be performed correctly before calibrating this table.  The process should be performed at the target engine oil temperature, assuming one is fitted.  Simply activate the PC logging with the F8 key and from a low engine, ideally above idle increase the engine airflow and slowly increase the engine speed.  Screenshot 4 shows a sample log of an engine speed sweep from 2000rpm to 6000rpm.  It is not advised to test to the engine speed limit.  Provided there is a reasonable range of engine speed to test the higher rpm cells can be extrapolated with acceptable accuracy.  Once the log has been completed review the Engine Torque channel for all tested engine speeds.  Torque levels between -10Nm and 10Nm would be considered acceptable and the shape of this plot is more important than the actual value assuming it is within these values.  Ultimately, positive values should expect the engine speed to be increasing and negative values should expect the engine speed to be decreasing.   Adjust the frictional loss table values against the corresponding engine speeds to achieve this.  If the Engine Torque reported is higher than expected, then increase the frictional loss table value.  If the Engine Torque reported is lower than expected, then reduce the frictional loss table value.  The frictional loss should be increasing with increasing engine speed.  Other calibration methods can involve engine speed step and hold testing.  This can achieve even more accurate readings; however this may not be necessary for most applications.   

Once the main Frictional Loss Table has been calibrated, wait for the engine oil temperature to reach ambient and simply hold the engine speed at nominal rpm that is safe for cold engine oil temperatures.  Anything above idle engine speeds is acceptable.  2000rpm for example could be held until the target engine oil temperature has been reached.  Adjust the Frictional Loss Offset 1 Table in each cell to achieve the same torque levels of between -10Nm and +10Nm.


Screenshot 4: Example Engine Speed Sweep


These tables should not need to be adjusted again unless something in the engine is changed that will affect it.

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