What is the function of a pushrod and rocker arm in a piston engine?
The pushrod is engaged by the camshaft to pivot the rocker arm, opening a valve in the cylinder.
State the function of cooling fins in a piston engine.
Act to remove heat from the system.
Describe the four stroke cycle of a piston engine.
Induction
Intake valve opens. Piston moves down the barrel. Fresh fuel/air mixture is drawn in.
Compression
Both valves closed. Piston moves up the barrel. Fuel/air mixture is compressed to an eighth its original volume.
Power/Ignition
Spark plugs ignite the fuel/air mixture. Piston is forced down the barrel.
Exhaust
Piston is forced up the barrel, expelling gases through exhaust valve.
List two factors affecting power output of an engine.
- Quantity of gas induced into the cylinders.
- Temperature reached during combustion.
Describe how the movement of a piston emparts rotational energy to the crank shaft.
The linear force of the piston moving through the cylinder translates through a connecting rod to the crank shaft.
List four symptoms of detonation and the actions to mitigate the problem.
Symptoms:
- Rising cylinder oil temperature
- Significant power loss
- Vibration
- Pinging sound from engine
Mitigation:
- Mixture rich
- Reduce power
- If climbing, increase IAS to improve airflow
Describe engine overspeed.
Engine overspeed occurs when the RPM becomes too high. This puts excessive loads on engine components (valves are especially vulnerable). Tachometer red line indicates this maximum RPM.
