Engine lubrication — overpressure protection in pressure-feed systems In a forced-feed (pressure-fed) engine lubrication system, which device protects the circuit from excessive oil pressure?

Introduction / Context:
Pressure-fed lubrication depends on a positive-displacement oil pump. Since pump output rises with speed and viscosity, protection against overpressure is essential to avoid filter rupture or seal damage. The control component must respond quickly and reliably in all temperature conditions.

Given Data / Assumptions:

• Engine with gear or rotor type oil pump.
• Full-flow filtration and main oil gallery.
• Cold starts can create very high viscosity and pressure spikes.

Concept / Approach:
A spring-loaded relief valve opens when gallery pressure exceeds a calibrated set-point, allowing oil to bypass to the pump inlet or sump. This limits maximum pressure while still maintaining flow to critical components. The valve may be integral to the pump body or installed in the filter or main gallery.

Step-by-Step Solution:
Recognize that positive-displacement pumps do not self-limit pressure.Identify the standard control element: a relief valve with spring and poppet or ball.Understand the flow path when open: excess oil returns to inlet/sump to cap pressure.

Verification / Alternative check:
Workshop gauges show pressure stabilizing near the relief setting despite increasing rpm during cold operation, confirming valve action.

Why Other Options Are Wrong:
A stop valve is a shut-off, not a regulator. A release chamber is not a standard lubrication control device. A balancer reduces vibration, not fluid pressure.

Common Pitfalls:
Confusing the relief valve with a pressure regulator located in variable displacement pumps; in engines the terms are often used interchangeably but the function is capping pressure, not maintaining a precise line pressure under all loads.

Final Answer:
relief valve