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

Small Gasoline Engine Internal Combustion Small Gasoline Engine Internal Combustion Air/fuel mixture is ignited inside the engine Small Gasoline Engine

Internal Combustion Air/fuel mixture is ignited inside the engine The gasses (when ignited ) expand in all directions Small Gasoline Engine Internal Combustion Air/fuel mixture is ignited inside the engine The gasses (when ignited ) expand in all directions

Only the piston is allowed to move Small Gasoline Engine Internal Combustion Air/fuel mixture is ignited inside the engine The gasses (when ignited ) expand in all directions Only the piston is allowed to move

Inertia Small Gasoline Engine Internal Combustion Air/fuel mixture is ignited inside the engine The gasses (when ignited ) expand in all directions Only the piston is allowed to move

Inertia A physical law that states an object in motion will continue in motion or an object at rest will continue at rest unless an additional force is applied. Small Gasoline Engine Internal Combustion Air/fuel mixture is ignited inside the engine

The gasses (when ignited ) expand in all directions Only the piston is allowed to move Inertia A physical law that states an object in motion will continue in motion or an object at rest will continue at rest unless an additional force is applied.

The piston reaches TDC then reverses direction, repeating the process at BDC. This places extreme stress on the engine by changing the inertia Performance Defined as the work engines do Performance

Defined as the work engines do also, Defined as how well they do the work Bore The diameter or width across the top of the cylinder

Measured using caliper or telescoping gauges and micrometers Stroke The up or down movement of the piston. Measured from TDC to BDC. Determined by the amount of offset on the crankshaft.

Stroke The up or down movement of the piston. Measured from TDC to BDC. Determined by the amount of offset on the crankshaft. or by the vernier depth gauge

Square? An engine is considered square if the bore and stroke measurements are identical Square? An engine is considered square if the bore and stroke measurements are identical

An engine is considered over square if the bore diameter is greater than the stroke Square? An engine is considered square if the bore and stroke measurements are identical An engine is considered over square if

the bore diameter is greater than the stroke An engine is considered under square if the bore diameter is smaller than the stroke. Engine Displacement The total volume of space increase in the

cylinder as the piston moves from the top to the bottom of its stroke. Engine Displacement The total volume of space increase in the cylinder as the piston moves from the top to the bottom of its stroke. Determined by the circular area of the cylinder

then multiplied by the total length of the stroke. Engine Displacement The total volume of space increase in the cylinder as the piston moves from the top to the bottom of its stroke. Determined by the circular area of the cylinder

then multiplied by the total length of the stroke. (V = r2 x stroke) or (V = .7854 D2 x stroke) Engine Displacement The total volume of space increase in the cylinder as the piston moves from the top

to the bottom of its stroke. Determined by the circular area of the cylinder then multiplied by the total length of the stroke. (V = r2 x stroke) or (V = .7854 D2 x stroke) Engine Displacement: .7854 x D2 x Length of stroke

Engine Displacement Example Bore = 2 in Stroke = 2 in Engine Displacement Example

Bore = 2 in Stroke = 2 in .7854 x D2 x Length of stroke Engine Displacement Example Bore = 2 in Stroke = 2 in

.7854 x D2 x Length of stroke .7854 x (2.25 in)2 x 2.25 in Engine Displacement Example Bore = 2 in Stroke = 2 in .7854 x D2 x Length of stroke

.7854 x (2.25 in)2 x 2.25 in .7854 x 5.0625 in2 x 2.25 in Engine Displacement Example Bore = 2 in Stroke = 2 in

.7854 x D2 x Length of stroke .7854 x (2.25 in)2 x 2.25 in .7854 x 5.0625 in2 x 2.25 in 8.95 in3. or 8.95 cubic inches

Engine Displacement Example Bore = 2 in Stroke = 2 in

.7854 x D2 x Length of stroke .7854 x (2.25 in)2 x 2.25 in .7854 x 5.0625 in2 x 2.25 in 8.95 in3. or 8.95 cubic inches 2 cylinder?

Engine Displacement Example Bore = 2 in Stroke = 2 in

.7854 x D2 x Length of stroke .7854 x (2.25 in)2 x 2.25 in .7854 x 5.0625 in2 x 2.25 in 8.95 in3. or 8.95 cubic inches 2 cylinder?

Multiply 8.95 in3 x 2 = 17.89 in3 Problem Bore = 2 inches Stroke = 2 inches 4 cylinder engine Determine the displacement using the above data and the formula below

(.7854 x D2 x Stroke = Displacement) Problem .7854 x D2 x Stroke = Displacement/Cylinder Problem .7854 x D2 x Stroke = Displacement/Cylinder .7854 x 22 in x 2 in = Displacement/Cylinder

Problem .7854 x D2 x Stroke = Displacement/Cylinder .7854 x 22 in x 2 in = Displacement/Cylinder .7854 x 4 in2 x 2 in = Displacement/Cylinder Problem .7854 x D2 x Stroke = Displacement/Cylinder

.7854 x 22 in x 2 in = Displacement/Cylinder .7854 x 4 in2 x 2 in = Displacement/Cylinder 6.28 in3 = Displacement/Cylinder Problem .7854 x D2 x Stroke = Displacement/Cylinder .7854 x 22 in x 2 in = Displacement/Cylinder .7854 x 4 in2 x 2 in = Displacement/Cylinder

6.28 in3 = Displacement/Cylinder 6.28 in3 x 4 cylinder = Total Displacement Problem .7854 x D2 x Stroke = Displacement/Cylinder .7854 x 22 in x 2 in = Displacement/Cylinder .7854 x 4 in2 x 2 in = Displacement/Cylinder 6.28 in3 = Displacement/Cylinder

6.28 in3 x 4 cylinder = Total Displacement 25.12 in3 Total Displacement Compression Ratio The relationship between the total cylinder volume when the piston is a BDC and the volume remaining when the piston is at TDC.

Small engines generally have 5-6:1 Some motorcycles have 9-10:1 Force The pushing or pulling of one body on another. Force

The pushing or pulling of one body on another. Weight of you on a chair Force The pushing or pulling of one body on another. Weight of you on a chair

Centrifugal force The ball at the end of a string tries to move outward from its path when twirled Force The pushing or pulling of one body on another. Weight of you on a chair

Centrifugal force The body tries to move outward from its path when twirled Tensile Stress the pushing or pulling stress (on the string) Force

The pushing or pulling of one body on another. Weight of you on a chair Centrifugal force The body tries to move outward from its path when twirled Tensile Stress

the pushing or pulling stress Ex. The piston reversing direction several times a second Work Accomplished only when a force is applied through some distance

Work Accomplished only when a force is applied through some distance Work = Distance x Force Work Accomplished only when a force is applied through some distance

Work = Distance x Force Distance (ft), Force (lb) Work Accomplished only when a force is applied through some distance Work = Distance x Force Distance (ft), Force (lb)

Work Unit = ftlb Power The rate at which work is done Power The rate at which work is done Power = Work / Time

Power The rate at which work is done Power = Work / Time Power = Pounds x Distance / Time Power The rate at which work is done

Power = Work / Time Power = Pounds x Distance / Time Example: a horse can lift 100 lb a distance of 330 ft in 1 minute. How much Power is used? Power The rate at which work is done Power = Work / Time

Power = Pounds x Distance / Time Example: a horse can lift 100 lb a distance of 330 ft in 1 minute. How much Power is used? Power = 330 ft x 100 lb / 60 sec Power The rate at which work is done Power = Work / Time

Power = Pounds x Distance / Time Example: a horse can lift 100 lb a distance of 330 ft in 1 minute. How much Power is used? Power = 330 ft x 100 lb / 60 sec Power = 550 ftlb/sec Power The rate at which work is done

Power = Work / Time Power = Pounds x Distance / Time Example: a horse can lift 100 lb a distance of 330 ft in 1 minute. How much Power is used? Power = 330 ft x 100 lb / 60 sec Power = 550 ftlb/sec 1 horse power = 550 ftlb/sec

Horsepower Calculate the amount of work and engine does and divide it by 550 ftlb/sec. This will give the rated horsepower. Horsepower Calculate the amount of work and engine does and divide it by 550 ftlb/sec. This

will give the rated horsepower. Brake Horsepower Horsepower Calculate the amount of work and engine does and divide it by 550 ftlb/sec. This will give the rated horsepower. Brake Horsepower

Usable horsepower Horsepower Calculate the amount of work and engine does and divide it by 550 ftlb/sec. This will give the rated horsepower. Brake Horsepower Usable horsepower

Measured by Horsepower Calculate the amount of work and engine does and divide it by 550 ftlb/sec. This will give the rated horsepower. Brake Horsepower Usable horsepower

Measured by Prony brake (fiction) Dynamometer (hydraulics) Horsepower Increases with increased speeds. Horsepower

Increases with increased speeds. Engines generally run at 3600 rpm. Torque A twisting or turning force Torque A twisting or turning force

Torque = Distance (radius) x Force Torque A twisting or turning force Torque = Distance (radius) x Force Torque = Feet x Pounds Torque

A twisting or turning force Torque = Distance (radius) x Force Torque = Feet x Pounds

Torque = ftlb Torque

A twisting or turning force Torque = Distance (radius) x Force Torque = Feet x Pounds Torque = ftlb 1 ftlb = 12 inlb Torque

A twisting or turning force

Torque = Distance (radius) x Force Torque = Feet x Pounds Torque = ftlb 1 ftlb = 12 inlb Engine Torque increases with increased rpm, but decreases if rpm is becomes too high.

Review Why do we check engine performance? What type of forces are working in an internal combustion engine? Explain the difference between bore & stroke. How is displacement measured? What is the unit for work? What is the unit for power?

What is 1 horsepower? Torque is measured in ______ for units