FAST - Engine performance
Predicting mechanical friction effects on engine performance
Mechanical friction changes with speed, load, temperature, oil viscosity, cylinder pressure and engine architecture, and those changes can have a significant effect on predicted fuel economy, performance and calibration decisions.
FAST brings predictive mechanical friction directly into the engine performance modelling workflow. It enables engineers to generate operating-condition-specific FMEP data quickly, either as a stand alone friction analysis or coupled with WAVE to support engine performance simulation. This allows friction effects to be represented earlier and more realistically, without requiring higher-fidelity component models for every study.
By providing rapid friction maps and subsystem-level friction behaviour, FAST helps performance teams move beyond broad assumptions or fixed friction factors. It supports better architecture comparisons, more representative virtual calibration and more confident assessment of how design choices influence overall engine efficiency.
Friction maps for simulation and calibration
FAST can generate predicted friction maps for use in engine and vehicle system modelling. These maps can be included in real-time engine plant models for vehicle system simulation and virtual calibration.
This makes FAST valuable where friction cannot simply be treated as a fixed value. Engine friction changes with speed, load, temperature, oil viscosity and operating condition, and those changes can have a significant impact on performance and fuel economy predictions.
Fired engine FMEP prediction
FMEP under fired conditions is often required as an input to engine performance simulation models. Under fired operation, cranktrain friction rises above motored friction because gas forces act on the piston rings, piston skirts, small end bearings, big end bearings and main bearings. FAST supports this type of prediction by using cylinder pressure data within the friction calculation.
This is especially important when comparing gasoline and diesel engines, because fired FMEP can be significantly higher in diesel engines due to higher cylinder pressures and the energy required to drive the fuel system.
Performance-led design decisions
FAST supports engine performance development by helping teams assess how friction changes across operating conditions and design choices. It can be used to:
- Provide friction inputs for engine performance simulation models
- Compare engine architectures during feasibility and concept development
- Assess the friction impact of downsizing and rightsizing concepts
- Support target setting for performance and fuel economy
- Investigate the influence of oil viscosity on cranktrain friction
- Provide subsystem-level friction response across operating conditions
Hybrid engine performance
FAST is relevant to hybrid engine development, where the emphasis can shift from conventional downsizing towards rightsizing for higher brake thermal efficiency. In hybrid applications, friction prediction helps assess the impact of choices such as small bore / long stroke architecture, crank offset, rod length and bearing diameter. Long stroke designs can increase piston speed in the mid-stroke region, raising piston ring and piston skirt friction, while larger crank bearings can increase bearing friction.
FAST can support analysis of hybrid-specific configurations, including mild hybrid layouts with belt-driven electrical machines, plug-in hybrid concepts with no belt drives, engine friction under different temperature conditions, and hybrid control strategies under battery and engine operating conditions.
Why it matters
Accurate friction inputs improve the quality of engine performance simulation. FAST allows those inputs to be generated quickly, so friction effects can be considered early rather than added late as a correction. This helps teams make better architecture, calibration and efficiency decisions before expensive commitment to hardware.
Use FAST to bring predictive mechanical friction into engine performance simulation, virtual calibration and hybrid powertrain development.