Steady state engine dynamometer testing provides the highest level of detail for understanding fundamental engine combustion. It can provide insight into pollutant formation mechanisms and methods for minimizing fuel consumption. However, steady-state dynamometer tests are normally carried out at test conditions far removed from the actual conditions that a vehicle engine encounters. This paper describes the application of a simple powertrain model to define steady-state engine test conditions that are more representative of real-world engine operation.
The model uses a backward-facing, modular structure. The model is validated against two powertrain configurations: a conventional powertrain equipped with a continuously variable transmission (CVT) and a parallel hybrid powertrain. Powertrain parameters and performance data for validation for both cases are supplied from the literature. The model is shown to agree well with both sets of published experimental results. These two models, along with a conventional powertrain equipped with a manual gearbox, are then used to evaluate steady-state and transient engine operation for vehicles following specified drive cycles. Steady-state test conditions are identified for all three models on the basis of both time and fuel consumption. The model results demonstrate that engine transients are typically on the order of 2-4 second duration and involve relatively modest changes in engine speed and torque.