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Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
Measuring performance
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Measuring performance

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  • 1. Chapter 6 Measuring Engine Performance page 91
  • 2. Basic Terminology <ul><li>Bore &amp; Stroke </li></ul><ul><li>Engine Displacement </li></ul><ul><li>Compression Ratio </li></ul><ul><li>Force </li></ul><ul><li>Work </li></ul><ul><li>Power </li></ul><ul><li>Energy </li></ul><ul><li>Horsepower </li></ul>
  • 3. Bore <ul><li>Diameter of cylinder </li></ul><ul><li>2 X Radius </li></ul>
  • 4. Stroke <ul><li>Distance </li></ul><ul><ul><li>TDC-BDC </li></ul></ul><ul><li>Distance piston travels </li></ul><ul><ul><li>up or down </li></ul></ul>
  • 5. Cylinder Displacement <ul><li>0.7854 x D2 x stroke </li></ul><ul><li>or </li></ul><ul><li>Π x r2 x Stroke </li></ul>
  • 6. Engine Displacement <ul><li>0.7854 x D 2 x stroke X # of cylinders </li></ul><ul><li>or </li></ul><ul><li>Π x r 2 x Stroke x # of cylinders </li></ul><ul><li>in 3 / 62 = Liters </li></ul>
  • 7. Compression Ratio <ul><li>Volume of cylinder at BDC </li></ul><ul><li>compared to </li></ul><ul><li>Area of cylinder at TDC </li></ul>
  • 8. Force <ul><li>pushing or pulling </li></ul><ul><li>stationary force </li></ul><ul><li>moving force </li></ul><ul><li>Centrifugal force </li></ul><ul><ul><li>spinning </li></ul></ul><ul><ul><li>FORCE does NOT = Pressure </li></ul></ul>
  • 9. Pressure <ul><li>Pressure is force per given area </li></ul><ul><li>or </li></ul><ul><li>Force/Area </li></ul><ul><li>PSI </li></ul><ul><li>Force = psi X area </li></ul><ul><li>Area = force / psi </li></ul><ul><li>Area = Π R 2 </li></ul>
  • 10. Work <ul><li>force applied resulting in movement </li></ul><ul><li>Work = Force x Distance </li></ul><ul><li>W = F x D </li></ul><ul><li>Mechanical advantage (lever, ramp, etc) </li></ul><ul><li>Effort distance / resistance distance = Mechanical advantage </li></ul>
  • 11. Mechanical Advantage <ul><li>2’ </li></ul>10’ 10’ / 2’ = 5 = MA E(effort) = R(resistance)/ MA or E = 500# / 5 = 100 # 500#
  • 12. Power <ul><li>Power is time taken to do the work </li></ul><ul><li>P = work/time </li></ul><ul><li>P=W/T </li></ul><ul><li>Power = feet x Pounds / time </li></ul><ul><li>or Foot pounds per second? </li></ul>
  • 13. Energy <ul><li>Energy can not be created or destroyed </li></ul><ul><li>Potential—has the potential to . . . </li></ul><ul><li>Kinetic </li></ul><ul><li>Mechanical </li></ul><ul><li>Chemical </li></ul><ul><li>Thermal (heat) </li></ul><ul><li>Light </li></ul>
  • 14. Horsepower <ul><li>Power = work / time P= w/t </li></ul><ul><li>Hp = 33,00 ft-lb (work) / 1 minute (time) </li></ul><ul><li>or </li></ul><ul><li>Hp = 550 ft-lb / 1 second </li></ul>
  • 15. Horsepower Formula <ul><li>100 ft x 330 lb / 6 seconds = 5500 ft lb / sec </li></ul><ul><li>dividing this by 550 ft lb / sec (1hp) </li></ul><ul><li>= </li></ul><ul><li>(5500 ft-lb /sec) / (550 ft lb / sec) = 10 hp </li></ul><ul><li>thus </li></ul><ul><li>1 hp = rate of work in ft-lb/sec / 50 ft-lb / sec </li></ul>
  • 16. Kinds of Horsepower <ul><li>Brake Horsepower </li></ul><ul><li>Indicated Horsepower </li></ul><ul><li>Frictional Horsepower </li></ul><ul><li>Rated Horsepower </li></ul><ul><li>Corrected Horsepower </li></ul>
  • 17. Brake Horsepower <ul><li>bhp </li></ul><ul><li>actual hp delivered </li></ul><ul><li>what we can use </li></ul>
  • 18. Indicated Horsepower <ul><li>ihp (perfect world) </li></ul><ul><li>power developed by the burning fuel </li></ul><ul><li>average of power on 4 strokes (mean) </li></ul><ul><li>PLANK / 33,000 </li></ul><ul><li>P = mep in lb/in 2 </li></ul><ul><li>L = length of stroke </li></ul><ul><li>A = Cylinder Area </li></ul><ul><li>N = power strokes per minute or RPM / 4 </li></ul><ul><li>K = # of cylinders </li></ul>
  • 19. Frictional Horsepower <ul><li>fhp </li></ul><ul><li>HP lost because of drag </li></ul><ul><li>fhp = ihp-bhp </li></ul>
  • 20. Rated Horsepower <ul><li>rhp </li></ul><ul><li>80% of bhp </li></ul>
  • 21. Corrected Horsepower <ul><li>corrected for elevation (sea level) </li></ul><ul><li>corrected for temperature </li></ul><ul><li>barometric pressure </li></ul><ul><li>quality of fuel </li></ul><ul><li>humidity </li></ul>
  • 22. Torque <ul><li>Twisting force </li></ul><ul><li>force x distance </li></ul><ul><li>ft - lb </li></ul><ul><li>in – lb </li></ul><ul><li>Newton - Meters </li></ul>
  • 23. Torque is not Constant <ul><li>Torque will change w/ engine speed </li></ul><ul><li>More pressure on piston = more torque </li></ul>
  • 24. Torque and Horsepower <ul><li>Unlike torque. . . </li></ul><ul><li>Horsepower increases with engine speed </li></ul><ul><li>Torque measure of engine’s twisting force </li></ul><ul><li>Hp measures engine’s ability to do work </li></ul>
  • 25. Torque and power curves: Skyline
  • 26. Volumetric Efficiency <ul><li>How well an engine breathes </li></ul><ul><ul><li>draws air/fuel into cylinder </li></ul></ul><ul><li>Can decrease as engine speed increases </li></ul><ul><li>Many factors </li></ul>
  • 27. Practical Efficiency <ul><li>How efficiently an engine uses the fuel </li></ul>
  • 28. Mechanical Efficiency <ul><li>% of power developed in cylinder (ihp) </li></ul><ul><li>compared to </li></ul><ul><li>power delivered to crankshaft (bhp) </li></ul><ul><li>friction, </li></ul><ul><li>Mechanical efficiency = bhp/ihp </li></ul>
  • 29. Thermal Efficiency <ul><li>Heat efficiency </li></ul><ul><li>How much power produced is used to push the piston down </li></ul><ul><li>Power is lost to : </li></ul><ul><ul><li>cooling </li></ul></ul><ul><ul><li>exhaust </li></ul></ul><ul><ul><li>20-25% efficient </li></ul></ul><ul><ul><li>Exhaust 35% . . . </li></ul></ul><ul><ul><li>Cooling &amp; Lubrication 35% </li></ul></ul>
  • 30. Brake thermal efficiency <ul><li>= </li></ul><ul><li>Brake horsepower (bhp x 33,000) </li></ul><ul><li>778 Fuel heat value x weight of burned fuel per minute </li></ul><ul><li>778 is Joule’s equivalent </li></ul><ul><li>it is a constant </li></ul>

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