Simulate Road Loads

Find out about running self determining dynamometer test simulations.

Intermediate | 07.20.20

Why would I use Simulate Road Load mode?

Simulated Road Loads mode (first available in DYNO-MAX for Windows in the 1990’s) lets the absorber replicate aerodynamic drag, inertia, etc. – even on an engine dyno. Unlike a Hold RPM or Sweep test, speed depends on the applied throttle – you “feel” the engine’s Hp!

In Configure DYNOmite Controls, when the Simulate Road Loads pushbutton is active, DYNO-MAX calculates the attainable speed, in real-time, based on several factors including:

Horsepower – actually the sum of all the Hp applied since the start of the recording.

Vehicle Weight – as input by the operator on the Run Information Vehicle tab.

Coast Down G’s @ 55 MPH – (vehicle drag) as input on the Run Information Vehicle tab.

Simulated Grade Angle Degrees – controlled by the operator’s Hold Set Point. This grade can be adjusted during the test via the left and right arrow keys – from 0% level ground to -45% downhill grade or +45% uphill grade.

The exact Hold Velocity during a test is continuously recalculated by the integral and derivative calculus equations contained within the “$ SIMULATE ROAD LOADS” formula (and its many sub-formulas). As more power is applied (by the operator) the vehicle attains a higher speed – just as it would on the open road. Similarly, as the grade is reduced to simulate a downhill slope, the vehicle again accelerates (or vice versa if the grade is changed to an uphill climb).

Road load emulation has long been used for emissions testing, acceleration or drag race simulation, and other modes where the dynamometer needs to self determine the hold speed based on the engine’s and driver’s behavior rather than on the dyno operator’s presets. In fact, by entering the correct Vehicle Weight and Coast Down G’s @ 55 MPH values, it is even possible to closely determine an engine combination’s top speed potential.

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