Car Mechanics Flashcards
How does car AC work?
- LP LT vap enter compressor
- HP HT vap enter condenser
- HP MT liq enter TXV
- LP LT vap liq mix enter evaporator
- LP LT (superheated vap) enter compressor
What is latent heat ?
- Heat absorbed or released by a substance during phase change without changing it’s temperature.
TYPES
- Latent heat of fusion (solid <> liquid)
- Latent heat of vapourization (liquid <> gas)
How do thermal expansion valve (TXV) work ?
- Superheated vapour @ low temp bcz heat absorbed used for phase change
- There is increase in enthalpy and entropy
Why is refrigerant used in hvac systems instead of water.
- Have very low boiling temp at atm pressure.
What is static pressure ?
pressure difference created by the fan to overcome resistance in a ventilation or ducting system.
List Parts
What are the four main types of fuel injection systems?
Single point fuel injection, Multi-point fuel injection, Sequential fuel injection, Direct fuel injection
What is a characteristic of the Single-Point Fuel Injection system?
Features a common fuel injector for all cylinders in the combustion chamber
What does Multi-Point Fuel Injection (MPFI) / Port Injection technology do?
Provides an injector to every cylinder at the front of their inlet valves
What is the main advantage of Sequential Fuel Injection?
Injectors operate only when the intake valve of the corresponding cylinder opens
Why is Sequential Fuel Injection considered the most effective?
It eliminates the disadvantages of MPFI by synchronizing injectors with cylinder operation
What does Direct Fuel Injection do?
Injects fuel directly inside the cylinder, bypassing the intake valve
What is GDI in the context of fuel injection?
Gasoline Direct Injection
What is a common issue with fuel in Multi-Point Fuel Injection systems?
Fuel can idle in the engine and port
