Technician A says that advancing cam timing increases lower-end torque improves idle, drivability, and emissions. Technician B says that retarding the timing can increase horsepower and torque at lower speeds. Which technician is correct?

Technician A says that advancing cam timing increases lower-end torque improves idle, drivability, and emissions. Technician B says that retarding the timing can increase horsepower and torque at lower speeds. Which technician is correct?

• A. Tech A
• B. Tech B
• C. Both
• D. Neither

Answer: (A)

Cam timing sets when the valves open and close in the cycle, which shapes the torque you feel at different engine speeds. Advancing the timing means the intake and exhaust events occur earlier, so the engine fills cylinders more effectively at lower RPM. That boosts low-end torque, helps idle feel smoother, and improves drivability because the engine makes usable power without needing to spin up to high speeds. It can also improve combustion at idle, which can help emissions in practice, though the exact effect depends on the engine and its fuel-management system. Retarding the timing moves those events later, reducing cylinder filling at low speeds and shifting the torque peak to higher RPM. That typically worsens idle and low-end torque and does not increase horsepower at lower speeds; any gains are more likely at higher RPMs, if at all. So the statement about increasing horsepower and torque at lower speeds by retarding timing isn’t correct. Tech A is the correct picker here.

Cam timing sets when the valves open and close in the cycle, which shapes the torque you feel at different engine speeds. Advancing the timing means the intake and exhaust events occur earlier, so the engine fills cylinders more effectively at lower RPM. That boosts low-end torque, helps idle feel smoother, and improves drivability because the engine makes usable power without needing to spin up to high speeds. It can also improve combustion at idle, which can help emissions in practice, though the exact effect depends on the engine and its fuel-management system.

Retarding the timing moves those events later, reducing cylinder filling at low speeds and shifting the torque peak to higher RPM. That typically worsens idle and low-end torque and does not increase horsepower at lower speeds; any gains are more likely at higher RPMs, if at all. So the statement about increasing horsepower and torque at lower speeds by retarding timing isn’t correct.

Tech A is the correct picker here.