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Refinement of Engine In-Cycle Losses of Parasitic and Errant Dynamic Nature

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Surface Measurements
Ultrasound Measurements
Topographical and Wear Measurements  

Two classes of measurements are undertaken:


a) Parameters required for detailed numerical analysis or as measures of test repeteability or indirect measures of performance.

b) Variables regarded as direct measures of engine performance

 (a) Includes

  • Geometrical parameters (e.g. engine configuration, component dimensions and shape)
  • Surface topography (e.g. waviness, surface features roughness and their distributions)
  • Thermo-mechanical properties of components (e.g. modulus of elasticity, hardness, coefficient of thermal expansion, thermal conductivity, etc.)
  • Rheological properties of lubricant (e.g. Viscosity, pressure & temperature, viscosity coefficients, thermal conductivity, etc.)
  • Engine operating conditions (e.g. Engine speed, combustion pressure, oil and coolant temperatures, air-fuel mixture, etc.)


(b) Includes


Conjunctional film thickness








Tests comprise:

• Motored with no pressure, i.e. open head (concept validation)

• Motored with closed head (low load isothermal)

• Fired steady state condition

• Fired transient (various simulated drive cycle


Taylor Hobson precision PGI 1250 Aspheric mould measurement system using a 2μm stylus tip 155-P54469. System resolution 0.8nm.





      Surface topography is a problem of scale (it has a hierarchical nature).

       It is characterised by the manufacturing processes and surface treatments.

       Different instruments may be used to measure surface features according to physical scale.

      There are a host of measures which can statistically describe surface topography.

       Each topographical measure has its uses according to the type of analysis pursued.


Measurement of Surface Topography







Indirect Engine Performance Through Implied Wear


  • Monitoring wear is an indirect measure of engine frictional performance.
  • Wear is a multi-stage process comprising initial wear, gradual wear and run-in.
  • Changes in topographical parameters can be used to quantify wear.
  • Wear of advanced motorsport cylinder liners is assessed through accelerated engine tests.
  • These liners are usually coated, cross-hatched and honed.
  • Rapid initial wear is noted by changes in the average asperity peak roughness, Rpk.
  • Gradual wear of such liner topography is best noted by the average plateau height; Rk
  • The depth of valleys (grooves) remains largely unaltered, unless with severe localised wear.


Initial wear is best captured by the average asperity peak Rpk


 Severe localised wear


Gradual wear is best represented by the parameter Rk