Piston Engines Flashcards
The end of a connecting rod which attaches to the piston is called?
The small end
The end of a connecting rod which attaches to the crankshaft is called?
The big end
The component in the engine that is subjected to the most amount of force?
The crankshaft
What is the crankshaft made of?
Chromium-nickel steel
Valves are made of either?
Tungsten or chromium steel
The valves are opened by means of the
Camshaft
The camshaft is always rotated at -
half the rotational speed of the crankshaft
If the valve clearance is excessive -
It result in the valve opening late and closing early
Which type of horsepower:
The theoretical power developed in the combustion chamber of a frictionless engine
Indicated Horsepower
Which type of horsepower:
This term is used to define the power lost due to friction and driving accessories
Friction Horsepower
Which type of horsepower:
This is brake horsepower, and is the actual power available at the propeller shaft. BHP =
IHP - FHP
Mechanical efficiency =
BHP / IHP
During the induction stroke, the crankshaft will rotate -
180 degrees
The inlet valve lead should open?
between 10 and 55 degrees before top dead centre
The exhaust valve lead should open?
between 50 and 80 degrees before bottom dead centre
Ignition is timed to occur at
between 20 and 25 degrees before TDC
Which type of combustion error:
This occurs when the temperature and pressure of the compressed mixture in the combustion chamber reaches sufficient levels to cause instantaneous burning (explosion) of the mixture.The piston then receives a “hammer-like” blow instead of a rapid powerful push. Also called knocking.
Detonation
The four causes of detonation
- High manifold pressure causing excessive temperatures
- High temperature of intake air
- Overheated engine
- Using fuel of a low octane rating
Which type of combustion error:
This is caused when there is a hot spot within the cylinders such as red hot spark plug electrodes, glowing pieces of carbon or red hot exhaust valves. These hot spots cause the mixture to be ignited prematurely before the spark plug fires. This can cause an engine running even with magnetos off.
Pre-ignition
The two causes of pre-ignition:
- Excessively lean mixture
2. Incorrect ignition timing
pre-ignition will lead to -
detonation
To avoid detonation and pre-ignition, what type of octane should be used?
High octane
What type of symptom:
This caused by burning oil, and is a sign that there is oil seeping into the combustion chamber, past the piston rings which may be worn or stuck in their grooves.
Blue smoke from the exhaust
What type of symptom:
If this is noticed immediately after start, the likely cause is too rich a mixture due to over-priming the engine. This may be accompanied by an initially rough running engine.
Black smoke from the exhaust
Valves are closed by means of -
coiled springs
