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1 Chapter Brian Measuring Engine Performance page 91

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2 Basic Terminology Bore & Stroke Engine Displacement Compression Ratio ForceWorkPowerEnergyHorsepower

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3 Bore Diameter of cylinder 2 X Radius

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4 Stroke Distance TDC-BDC TDC-BDC Distance piston travels up or down up or down

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5 Cylinder Displacement x D2 x stroke or Π x r2 x Stroke

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6 Engine Displacement x D 2 x stroke X # of cylinders or Π x r 2 x Stroke # of cylinders in 3 / 62 = Liters

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7 Compression Ratio Area of cylinder at BDC compared to Area of cylinder at TDC 63 in3 to 9 in3 = 7:1 compression ratio

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8 Force pushing or pulling stationary force moving force Centrifugal force spinning spinning FORCE does NOT = Pressure FORCE does NOT = Pressure

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9 Pressure Pressure is force per given area orForce/AreaPSI Force = psi X area Area = force / psi Area = Π R 2

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10 Work force applied resulting in movement Work = Force x Distance W = F x D Mechanical advantage (lever, ramp, etc) Effort distance / resistance distance = Mechanical advantage

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11 Mechanical Advantage / 2 = 5 = MA E(effort) = R(resistance)/ MA or E = 500# / 5 = 100 # 500#

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12 Power Power is time taken to do the work P = work/time P=W/T Power = feet x Pounds / time or Foot pounds per second?

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13 Energy Energy can not be created or destroyed Potentialhas the potential to... KineticMechanicalChemical Thermal (heat) Light

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14 Horsepower Power = work / time P= w/t Hp = 33,000 ft-lb (work) / 1 minute (time) or Hp = 550 ft-lb / 1 second

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15 Horsepower Formula 100 ft x 330 lb / 6 seconds = 5500 ft lb / sec dividing this by 550 ft lb / sec (1hp) = (5500 ft-lb /sec) / (550 ft lb / sec) = 10 hp thus 1 hp = rate of work in ft-lb/sec / 50 ft-lb / sec

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16 Kinds of Horsepower Brake Horsepower Indicated Horsepower Frictional Horsepower Rated Horsepower Corrected Horsepower

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17 Brake Horsepower bhp actual hp delivered what we can use

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18 Indicated Horsepower ihp (perfect world) power developed by the burning fuel average of power on 4 strokes (mean) PLANK / 33,000 P = mep in in lb/in 2 L = length of stroke A = Cylinder Area N = power strokes per minute or RPM / 4 K = # of cylinders

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19 Frictional Horsepower fhp HP lost because of drag fhp = ihp-bhp

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20 Rated Horsepower rhp 80% of bhp

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21 Corrected Horsepower corrected for elevation (sea level) corrected for temperature barometric pressure quality of fuel humidity

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22 Torque Twisting force force x distance ft - lb in – lb Newton - Meters

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23 Torque is not Constant Torque will change w/ engine speed More pressure on piston = more torque

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24 Torque and Horsepower Unlike torque... Horsepower increases with engine speed Torque measure of engines twisting force Hp measures engines ability to do work

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25 Volumetric Efficiency How well an engine breathes draws air/fuel into cylinder draws air/fuel into cylinder Can decrease as engine speed increases many factors

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26 Practical Efficiency how efficiently an engine uses the fuel

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27 Mechanical Efficiency % of power developed in cylinder (ihp) compared to power delivered to crankshaft (bhp) friction, Mechanical efficiency = bhp/ihp

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28 Thermal Efficiency Heat efficiency how much power produced is used to push the piston down Power is lost to : cooling cooling exhaust exhaust 20-25% efficient 20-25% efficient Exhaust 35%... Exhaust 35%... Cooling & Lubrication 35% Cooling & Lubrication 35%

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29 Brake thermal efficiency = Brake horsepower (bhp x 33,000) 778 Fuel heat value x weight of burned fuel per minute 778 is Joules equivalent it is a constant

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