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
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.
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 = π r 2 x stroke) or (V =.7854 D 2 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 = π r 2 x stroke) or (V =.7854 D 2 x stroke) Engine Displacement:.7854 x D 2 x Length of stroke
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke.7854 x (2.25 in) 2 x 2.25 in Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke.7854 x (2.25 in) 2 x 2.25 in.7854 x in 2 x 2.25 in Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke.7854 x (2.25 in) 2 x 2.25 in.7854 x in 2 x 2.25 in 8.95 in 3. or 8.95 cubic inches Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke.7854 x (2.25 in) 2 x 2.25 in.7854 x in 2 x 2.25 in 8.95 in 3. or 8.95 cubic inches –2 cylinder? Engine Displacement
Example –Bore = 2 ¼ in –Stroke = 2 ¼ in.7854 x D 2 x Length of stroke.7854 x (2.25 in) 2 x 2.25 in.7854 x in 2 x 2.25 in 8.95 in 3. or 8.95 cubic inches –2 cylinder? Multiply 8.95 in 3 x 2 = in 3 Engine Displacement
Problem Bore = 2 inches Stroke = 2 inches 4 cylinder engine Determine the displacement using the above data and the formula below (.7854 x D 2 x Stroke = Displacement)
Problem.7854 x D 2 x Stroke = Displacement/Cylinder
Problem.7854 x D 2 x Stroke = Displacement/Cylinder.7854 x 2 2 in x 2 in = Displacement/Cylinder
Problem.7854 x D 2 x Stroke = Displacement/Cylinder.7854 x 2 2 in x 2 in = Displacement/Cylinder.7854 x 4 in 2 x 2 in = Displacement/Cylinder
Problem.7854 x D 2 x Stroke = Displacement/Cylinder.7854 x 2 2 in x 2 in = Displacement/Cylinder.7854 x 4 in 2 x 2 in = Displacement/Cylinder 6.28 in 3 = Displacement/Cylinder
Problem.7854 x D 2 x Stroke = Displacement/Cylinder.7854 x 2 2 in x 2 in = Displacement/Cylinder.7854 x 4 in 2 x 2 in = Displacement/Cylinder 6.28 in 3 = Displacement/Cylinder 6.28 in 3 x 4 cylinder = Total Displacement
Problem.7854 x D 2 x Stroke = Displacement/Cylinder.7854 x 2 2 in x 2 in = Displacement/Cylinder.7854 x 4 in 2 x 2 in = Displacement/Cylinder 6.28 in 3 = Displacement/Cylinder 6.28 in 3 x 4 cylinder = Total Displacement in 3 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 = ft·lb
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 ft·lb/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 ft·lb/sec –1 horse power = 550 ft·lb/sec
Horsepower Calculate the amount of work and engine does and divide it by 550 ft·lb/sec. This will give the rated horsepower.
Horsepower Calculate the amount of work and engine does and divide it by 550 ft·lb/sec. This will give the rated horsepower. Brake Horsepower
Horsepower Calculate the amount of work and engine does and divide it by 550 ft·lb/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 ft·lb/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 ft·lb/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 = ft·lb
Torque A twisting or turning force Torque = Distance (radius) x Force Torque = Feet x Pounds Torque = ft·lb 1 ft·lb = 12 in·lb
Torque A twisting or turning force Torque = Distance (radius) x Force Torque = Feet x Pounds Torque = ft·lb 1 ft·lb = 12 in·lb 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