EGR (Exhaust Gas Recirculation) Systems Flashcards
7 cards from real Exhaust practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 EGR (Exhaust Gas Recirculation) Systems flashcards as text
What is an EGR delete, and what is its primary legal concern in the United States?
Answer: Removal or bypass of the EGR system — illegal on public roads under EPA and CARB regulations
An EGR delete removes or disables a federally mandated emissions control device, violating EPA and CARB regulations for road-use vehicles and potentially resulting in substantial fines.
To approximately what temperature range does an EGR cooler reduce exhaust gases before they enter the intake?
Answer: 300–400°F (149–204°C)
EGR coolers typically reduce exhaust gas temperatures to roughly 300–400°F (149–204°C), significantly lower than exhaust manifold temperatures that can exceed 1,200°F.
Carbon deposit buildup inside EGR passages and valves most commonly causes which problem?
Answer: Restricted EGR flow leading to P0401 codes and driveability issues
Carbon and soot deposits accumulate in EGR valves and passages over time, restricting flow below commanded levels and typically triggering a P0401 insufficient EGR flow code.
What distinguishes a modern electronic EGR valve from an older pneumatic (vacuum-operated) EGR valve?
Answer: Electronic EGR uses a motor or solenoid for precise PCM control; pneumatic relies on engine vacuum
Electronic EGR valves use a DC motor or solenoid directly commanded by the PCM for precise flow control, replacing the older vacuum-actuated design that offered less accuracy.
Which U.S. regulatory framework most directly drove the widespread adoption of EGR systems on gasoline passenger vehicles?
Answer: EPA Tier 1 and Tier 2 NOx emissions regulations from the 1990s–2000s
Increasingly stringent EPA Tier 1 and Tier 2 NOx limits during the 1990s and 2000s made EGR systems standard equipment on virtually all U.S. passenger vehicles.
In diesel engines, what is the trade-off associated with increasing the EGR recirculation rate?
Answer: Higher EGR reduces NOx but tends to increase particulate matter (PM) emissions
In diesel combustion there is a NOx-PM trade-off: more EGR lowers combustion temperature and NOx, but the reduced oxygen availability promotes increased soot (PM) formation.
What is the purpose of an EGR temperature sensor positioned downstream in the EGR circuit?
Answer: Monitor exhaust gas temperature to verify EGR cooler performance and confirm EGR flow is occurring
The EGR temperature sensor monitors recirculated gas temperature after the cooler, allowing the PCM to verify that the EGR cooler is functioning and that commanded EGR flow is actually occurring.