Question | Answer |
16
How is engine size determined? | by the number of cylinders, the cylinder diameter, and the amount of piston travel per stroke |
16
Define cylinder bore | the diameter of the engine cylinder |
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How is cylinder bore measured? | across the cylinder, parallel to the top of the block |
16
What are the two typical size cylinder bores? | 3" and 4" |
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Define piston stroke | the distance the piston moves from top dead center TDC to bottom dead center BDC |
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What does TDC stand for? | top dead center |
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What does BDC stand for? | bottom dead center |
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What controls the piston stroke? | the amount of throw (offset) built into the cranshaft rod journal |
16
What does it mean if an engine's specs for bore and stroke ar given as 4.00" x 3.00"? | the engine cylinder is 4" in diameter and the piston stroke is 3" |
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What generally makes an engine more powerful? | a larger bore and a longer stroke |
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What does a larger cylinder diameter and large piston stroke produce? | a large piston displacement |
16
If an engine has a bore of 3" and a stroke of 4", what is its piston displacement? | 28.26 cu. in. (3.14 x 1.5 squared x 4) |
16
What is engine displacement? | the volume displaced by all the pistons in the engine |
16
If one poston displaces 30 cu. in. and the engine has four cylinders, what is the engine displacement? | 120 cu. in (30 x 4 = 120) |
16
Define force | the pushing or pulling action |
16
If you use a hoist to lift a 600 lb engine 5' in the air how much work is done? | 3000 ft lb (600 x 5) |
16
Define power | the rate or speed at which work is done |
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What is the metric unit for power? | watt (kilowatt) |
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How much power is needed for an engine to move 4000 lb car 2000' in one minute? | 8,000,000 ft ob per min (4000 x 2000) |
16
Define compression ratio | the cylinder volume with the piston at TDC to the cylinder volume with the piston at BDC |
16
Define compression pressure | the amount of pressure produced in the cylinder during the compression stroke |
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What is compression pressure measured in? | kilopascals and pounds per square inch |
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What is a compression gauge used for? | to measure engine compression pressure |
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What is the normal compression pressure for a modern automotive gasoline engine? | 130 - 180 psi (pounds per square inch) |
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What are the possible causes if an engine's compression pressure is low? | bad rings, burned valves, blown head gasket |
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Where can engine torque specifications be looked up? | in the shop manual |
16
What is engine horsepower? | a measure of an engine's abilitly to perform work (power) |
16
About how much horsepower would be needed for a small engine to lift 1000 lb a distance of 500' in one minute? | 15.2 hp |
16
What is brake horsepower? | measures the usable power at the engine crankshaft |
16
What is used to measure the brake horsepower of modern car engines? | engine dynamometer |
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What measures the horsepower delivered to the drive wheels? | chassis dynamometer |
16
Define indicated horsepower | amount of power formed in the engine combustion chambers |
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Explain frictional horsepower | the power needed to overcome engine friction |
16
Net, gross or taxable horsepower is the maximum power developed when an engine is loaded by all accessories? | net |
16
Net, gross or taxable horsepower is the engine power available with only basic accessories installed | gross |
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Net, gross, or taxable horsepower is simply a general rating of engine size? | taxable |
16
What is meant by engine efficiency? | the ratio of usable power at the engine crankshaft (brake horsepower) to the power supplied to the engine (heat content of fuel) |
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What percentage are modern piston engines efficent? | 20 % |
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What is volumetric efficiency? | the ratio of air drawn into the cylinder and the maximum possible amount of air that could enter the cylinder |
16
Define mechanical efficiency | measurement of mechanical friction |
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What percentage of an engine's power is lost to friction? | 20% - 30 % |
16
What does thermal efficiency measure? | the amount of heat energy converted into crankshaft rotation |