P Piston Engine Power, Efficiency and Control Flashcards
What 2 factors dictate the power of an engine?
- The mass of charge
- The numbers of times per second that the charge is put into the cylinders
What is the power equation?
Power = (force x distance)/time
What does power = plane mean?
Power = Pressure x Length of stroke x Area x Number of cylinders x rpm/2
What is the total volume of a cylinder?
Volume of cylinder at BDC
What is the clearance volume of a cylinder?
Volume of the cylinder at TDC
What is the swept volume?
Volume of the cylinder between TDC and BDC
Total volume - Clearance volume = Swept volume
What is the compression ratio?
A relationship between total volume and clearance volume
What is mechanical efficiency?
Measures the effectiveness of an engine turning the input power to output power. Taking into account friction and vibration most engines are 90-95% mechanically efficient. When factoring in thermal efficiency this falls to around 80%
What is thermal efficiency?
Defines how effective the engine is at converting fuel energy into producing mechanical work. All combustion engines are heat engines and heat is always lost, meaning thermal efficiency is 25-35% for a standard engine
What is the relationship between thermal efficiency and compression ratio?
As thermal efficiency increases, the compression ratio increases
What does the RPM gauge do?
Measures crankshaft RPM
What dos the manifold pressure gauge do?
Measures manifold pressure in InHg
What does the boost pressure gauge do?
Measures manifold pressure in PSI relative to sea level pressure
What does the oil pressure gauge do?
Measures the oil pressure just after the filter
What does the oil temperature gauge do?
Measures the oil temperature in the oil return line