Ch. 25 Turbocharging and Supercharging
Which of the following best defines volumetric efficiency?
It is the ratio of the actual volume of air-fuel mixture drawn into an engine to the theoretical maximum volume that could be drawn in.
Which of the following is true of the airflow requirements in an engine?
Naturally aspirated engines with throttle plates use atmospheric pressure to push an air-fuel mixture into the combustion chamber vacuum.
Which type of relief valve used on a turbocharged engine is noisy?
Dump valve & Blow Off Valve(BOV)
Two types of superchargers include ____.
Roots-type and centrifugal
Which of the following is true of boost control factors?
As boost pressure increases, combustion temperature also increases.
Which valve is used on a factory supercharger to limit boost?
A bypass valve
Two technicians were discussing the characteristics of nitrous oxide. Technician A stated that engine power is increased when nitrous oxide is injected into an engine along with gasoline. Technician B stated that the addition of nitrous oxide to an engine supplies the needed oxygen for the extra fuel. Which of the following about the scenario is true?
Both technician A's and B's assessments are accurate.
Which of the following is a similarity between turbochargers and superchargers?
Both turbochargers and superchargers are designed to provide a pressure greater than atmospheric pressure in the intake manifold.
How are most superchargers lubricated?
By an internal oil reservoir
How are most turbochargers lubricated?
By engine oil under pressure through lines from the engine
Two technicians were discussing the response time of turbochargers. Technician A stated that the turbocharger response time is directly related to the size of the turbine. Technician B stated that turbocharger response time is independent of the size of the compressor wheels. Which of the following statements about this scenario is true?
Only technician A's assessment is accurate.
Two technicians were discussing the characteristics of a roots-type supercharger. Technician A stated that a roots-type supercharger is not a positive displacement pump. Technician B stated that all of the air that enters a roots-type supercharger is forced through the unit. Which of the following statements about this scenario is true?
Only technician B's assessment is accurate.
Boost pressure is generally measured in ________.
Psi
What service operation is most important on engines equipped with a turbocharger?
Regular oil changes
Which of the following is a difference between superchargers and turbochargers?
Superchargers are engine-driven air pumps, whereas turbochargers are powered by hot exhaust gases.
Technician A says that a stuck open wastegate can cause the engine to burn oil. Technician B says that a clogged PCV system can cause the engine to burn oil. Which technician is correct?
Technician B only
Two technicians are discussing the term turbo lag. Technician A says that it refers to the delay between when the exhaust leaves the cylinder and when it contacts the turbine blades of the turbocharger. Technician B says that it refers to the delay in boost pressure that occurs when the throttle is first opened. Which technician is correct?
Technician B only
Which of the following is true of forced induction?
The amount of force an air-fuel charge produces when it is ignited is largely a function of the charge density.
Which of the following is true about the size and response time of a turbocharger?
The delay between an increase in engine speed and the increase in the speed of the turbocharger is called turbo lag.
What is the purpose of the intercooler?
To reduce the temperature of the air entering engine
Engineers calculate the engine airflow requirements using all the following factors, except ________.
engine power output
Which of the following factors is least likely to cause excessive oil consumption in a turbocharger system?
faulty wastegate valve
In a supercharged or a turbocharged engine, the boost pressure is measured inside the ________.
intake manifold
An engine that uses atmospheric pressure for its intake charge is called a(n) ________ engine.
naturally aspirated
Which of the following gases is typically used for racing or high performance only and is not used from the factory on any vehicle?
nitrous oxide
All of the following are examples of engine power adders, except ________.
phosphorus pentoxide
All of the following conditions cause the airflow to be directed around a supercharger, except when ________.
the vehicle is accelerated to attain its maximum speed
An engine exhaust-driven air compressor that supplies more than the normal amount of air into the intake manifold and boosts engine torque and power is called a(n) ________.
turbocharger
A ________ is a bypass valve at the exhaust inlet to a turbine, which allows all of the exhaust into the turbine, or it can route part of the exhaust past the turbine to the exhaust system.
wastegate valve
When an engine is running at full power, the typical turbocharger rotates at speeds between ________.
100,000 and 150,000 RPM
