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1 Chapter Brian Measuring Engine Performance page 91.

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Presentation on theme: "1 Chapter Brian Measuring Engine Performance page 91."— Presentation transcript:

1 1 Chapter Brian Measuring Engine Performance page 91

2 2 Basic Terminology Bore & Stroke Engine Displacement Compression Ratio ForceWorkPowerEnergyHorsepower

3 3 Bore Diameter of cylinder 2 X Radius

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

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

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

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

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

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

10 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

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

12 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?

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

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

15 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

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

17 17 Brake Horsepower bhp actual hp delivered what we can use

18 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

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

20 20 Rated Horsepower rhp 80% of bhp

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

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

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

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

25 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

26 26 Practical Efficiency how efficiently an engine uses the fuel

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

28 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%

29 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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