🔍 Key Concepts

• valve spring function in a diesel engine (keeping the valve tightly seated and following the cam at all speeds) • the relationship between cylinder pressure during firing and the force trying to push the valve off its seat • what the cam contour actually controls versus what the spring must resist

💭 Think About

• Ask yourself: when the valve is supposed to stay closed, what is the largest force trying to open it? • Consider whether the spring must be sized for the typical/average operating condition or the worst-case (maximum) condition inside the cylinder. • Think about what the cam shape (contour) really determines: does it set how strong the spring must be, or does it set timing and lift while the spring simply has to keep up?

✅ Before You Answer

• Verify which option relates to the greatest opening force acting on the valve when it must remain closed. • Check whether the cam contour by itself creates a need for more spring force, or whether it just dictates motion that the spring must follow. • Confirm that the chosen factor would ensure the valve does not lift off its seat even under the highest internal cylinder load.