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**Measuring Engine Performance page 91**

Chapter Brian Measuring Engine Performance page 91

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**Basic Terminology Bore & Stroke Engine Displacement Compression Ratio**

Force Work Power Energy Horsepower

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Bore Diameter of cylinder 2 X Radius

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Stroke Distance TDC-BDC Distance piston travels up or down

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**Cylinder Displacement**

x D2 x stroke or Π x r2 x Stroke

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**Engine Displacement 0.7854 x D2 x stroke X # of cylinders or**

Π x r2 x Stroke # of cylinders in3 / 62 = Liters

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**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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**Force pushing or pulling stationary force moving force**

Centrifugal force spinning FORCE does NOT = Pressure

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**Pressure Pressure is force per given area or Force/Area PSI**

Force = psi X area Area = force / psi Area = Π R2

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**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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**Mechanical Advantage 10’ / 2’ = 5 = MA E(effort) = R(resistance)/ MA**

500# 2’

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**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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**Energy Energy can not be created or destroyed**

Potential—has the potential to . . . Kinetic Mechanical Chemical Thermal (heat) Light

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**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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**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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**Kinds of Horsepower Brake Horsepower Indicated Horsepower**

Frictional Horsepower Rated Horsepower Corrected Horsepower

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Brake Horsepower bhp actual hp delivered what we can use

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**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/in2 L = length of stroke A = Cylinder Area N = power strokes per minute or RPM / 4 K = # of cylinders

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**Frictional Horsepower**

fhp HP lost because of drag fhp = ihp-bhp

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Rated Horsepower rhp 80% of bhp

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**Corrected Horsepower corrected for elevation (sea level)**

corrected for temperature barometric pressure quality of fuel humidity

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

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**Torque is not Constant Torque will change w/ engine speed**

More pressure on piston = more torque

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**Torque and Horsepower Unlike torque. . .**

Horsepower increases with engine speed Torque measure of engine’s twisting force Hp measures engine’s ability to do work

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**Volumetric Efficiency**

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

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Practical Efficiency how efficiently an engine uses the fuel

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**Mechanical Efficiency**

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

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**Thermal Efficiency Heat efficiency**

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

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**Brake thermal efficiency**

= Brake horsepower (bhp x 33,000) 778 Fuel heat value x weight of burned fuel per minute 778 is Joule’s equivalent it is a constant

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Measuring Engine Performance. The main goal of this chapter is to determine functional horsepower through different measurements and formulas.

Measuring Engine Performance. The main goal of this chapter is to determine functional horsepower through different measurements and formulas.

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