Four-stroke Diesel engine valvetrain — camshaft speed relation A four-stroke Diesel engine runs at 1000 rpm. At what speed does its camshaft rotate?

Introduction / Context:
Valve timing in a four-stroke engine requires opening and closing events to occur once every two crankshaft revolutions. Understanding the speed relationship between the crankshaft and camshaft is core engine theory.

Given Data / Assumptions:

• Four-stroke Diesel engine.
• Engine speed (crankshaft) = 1000 rpm.
• Conventional single camshaft per bank (or DOHC) driven at standard four-stroke ratio.

Concept / Approach:
A complete four-stroke cycle (intake, compression, power, exhaust) takes 720 degrees of crank rotation, i.e., two full crank revolutions. The camshaft must complete one revolution per thermodynamic cycle to open each valve once per cycle, so camshaft speed = crankshaft speed / 2.

Step-by-Step Solution:
Recognise four-stroke cycle requires 2 crank revolutions per cycle.Camshaft completes 1 revolution per cycle.Camshaft speed = 1000 / 2 = 500 rpm.

Verification / Alternative check:
Timing sets (belts/chains/gears) in four-stroke engines are designed with an exact 2:1 ratio between crank and cam(s), confirming 500 rpm here.

Why Other Options Are Wrong:

• 1000 rpm or higher options (2000, 4000): would imply multiple valve events per cycle, which is incorrect.

Common Pitfalls:
Confusing two-stroke and four-stroke relationships; two-strokes use 1:1 only in special valving arrangements but typical two-strokes have ports, not cams.

Final Answer:
500 rpm