Exam 17: Exhaust Gas Recirculation

Technician A says that internal EGR systems use a throttle plate to draw EGR gases into the air intake flow. Technician B says that high-pressure cooled EGR systems need throttle plates to draw exhaust gases into the intake manifold. Who is correct?

Combustion temperatures above approximately what value can result in NOx?

Technician A says that EGR systems lower in-cylinder NOx formation by reducing peak cylinder pressures and temperatures. Technician B says EGR systems reduce NOx emissions by reducing displaced air in the cylinder. Who is correct?

Which of the following environmental problems is caused primarily by NOx emissions?

What does a temperature sensor combined with a delta P sensor measure?

Which of the following forms closed-loop feedback with the EGR valve to regulate EGR gas flow?

EGR or exhaust gas recirculation is used to prevent the formation of:

Technician A says that diesel engines use MAF sensors to measure exhaust airflow into the cylinders. Technician B says that exhaust gas does not pass through an MAF sensor, so the MAF sensors cannot measure exhaust gas flow. Who is correct?

All of these are types of EGR delivery systems that introduce exhaust gas uniformly into the cylinders used on light- and medium-duty diesels, EXCEPT one. Which one is that?

At idle, after the engine has warmed up, the vacuum signal to the EGR valve should be:

Which of the following measures the pressure drop across a Venturi?

What happens to the mass of intake airflow into an engine when the EGR is enabled?

Which of the following is NOT an advantage of using low-pressure exhaust gas recirculation?

Technician A says the piston stroke length in an EGR engine is often longer than one in the same model engine that doesn't have an EGR system. Technician B says that the longer stroke length used by some EGR model engines has nothing to do with the use of EGR and that some EGR engines have shorter stroke length than non-EGR model engines. Who is correct?

Two technicians are discussing EGR diagnostics. Technician A says that the onboard diagnostic (OBD) system monitors the EGR system for electrical and operational faults. Technician B says that the information from the EGR control pressure sensor can be read by a scan tool and should indicate atmospheric pressure with the key off. Who is right?

Technician A says that an internal EGR briefly opens the exhaust valve during the exhaust stroke. Technician B says that internal methods result in poor mixing with the intake air and excessive EGR rates at low speeds. Who is right?

Technician A says the piston stroke length in an EGR engine is often longer than one in the same model engine that doesn't have an EGR system. Technician B says that the longer stroke length used by some EGR model engines has nothing to do with the use of EGR and that some EGR engines have shorter stroke length than non-EGR model engines. Who is correct?

Which type of EGR system is used by the majority of automotive diesel engines?

While two technicians are discussing possible causes of engine coolant loss, Technician A says the EGR cooler is likely cracked and leaking. Technician B says that a cracked EGR cooler would leak coolant into the intake manifold. Who is correct?

How does EGR gas contribute to increased cylinder wear?