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### 23 Cards in this Set

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