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23 Cards in this Set
- Front
- Back
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What direction do in-line piston engines cylinders point? (up or down)
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Up
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What joins the piston to the crankshaft?
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The Connecting Rod
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What is the formula for the fundamental operation of the piston engine?
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P V = R T
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What is the function of the three piston rings?
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The top two rings are to prevent combustion gases escaping and the bottom one is designed to stop oil entering the combustion space (scraper ring).
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What is the link between the piston and the connecting rod called?
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The Gudgeon Pin
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What is the link between the connecting rod and the crankshaft called?
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The Big End Bearing and Crankpins.
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What speed do camshafts rotate at?
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Half the speed of the crankshaft.
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What is the main function of the camshaft?
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To operate the inlet and exhaust valves.
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How many strokes are there in one cycle of a piston engine?
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4 strokes.
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What is bore?
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The internal diameter of the cylinder.
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What is compression Ratio?
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The ratio of the space above the piston at BDC to the space above the piston at TDB. Compression ratio = (Swept + Unswept) / Unswept
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What is the formula for Firing Interval?
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720 / No of Cylinders
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What is firing order?
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The numerical sequence in which the cylinders fire
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What crank angle is maximum torque produced at?
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62° to 72° after TDC.
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What crank angle is minimum torque produced at?
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45° before BDC.
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What is valve lag and where does it occur?
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The late closing of the Inlet Valve usually 60° of Crank angle after BDC.
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What is valve lead and where does it occur?
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The early opening of the exhaust valve usually 55° before BDC. (Also reduces back pressure on piston during exhaust stroke)
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What is the function of valve lead, lag and overlap?
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The enable the engine to breathe better.
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What are the angles for valve overlap?
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The exhaust valve closing 15° late and the inlet valve opening 15° early.
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At what crank angle is the spark normally put?
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25° Before TDC. To ensure peak pressure is developed well before the 90° crank angle.
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Detonation is caused by:
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High Mixture Pressure / Temperatures,
High power setting, Carb Heat, Lean Mixture |
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Why is Detonation bad?
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Causes overheating,
Deteriorates bearing surfaces, Results in a power loss. |
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Why is Pre Ignition bad?
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Loss of power,
Engine damage. |
