Question

technician a says that some manufacturers use vvt rather than egr systems to control oxides of nitrogen. technician b says that holding the exhaust valves open during the intake stroke will allow for some exhaust gases to be pulled into the engine, acting as an internal egr system. who is correct?

a. technician a
b. technician b
c. both technician a and technician b
d. neither technician a nor technician b

Explanation:

• Variable Valve Timing (VVT): Some manufacturers use VVT to control oxides of nitrogen. By adjusting valve timing, it can achieve similar effects as the Exhaust Gas Recirculation (EGR) system in reducing \(NO_x\) emissions.
• Internal EGR via Exhaust Valve Operation: Holding the exhaust valves open during the intake stroke allows exhaust gases to be pulled back into the engine. This acts as an internal EGR system, as the recirculated exhaust gases dilute the fresh air - fuel mixture, lower combustion temperatures, and reduce \(NO_x\) formation.

Answer:

C. Both Technician A and Technician B