Engine lubrication systems, lubrication fluid circulation systems, and methods for regulating fluid pressure

A method of regulating fluid pressure in an internal combustion engine, the method comprising:

• circulating fluid through a lubrication system of the internal combustion engine via a fluid flow path, the lubrication system including a pump from which the fluid is fed into the fluid flow path and a recirculation path connecting an outlet side of the pump to an inlet side of the pump, the fluid in the recirculation path flowing through a fluid flow control device and a tuning device;
• controlling, with the fluid flow control device, fluid flow through the recirculation path in response to an engine speed exceeding a first threshold, the fluid flow control device in the recirculation path downstream of the outlet side of the pump;
• maintaining a substantially constant pressure in the fluid flow path with the fluid flow in the recirculation path in response to the engine speed exceeding the first threshold;
• and
• restricting the fluid flow through the tuning device in the recirculation path in response to the engine speed exceeding a second threshold that is greater than the first threshold.

A lubrication fluid circulation system for an internal combustion engine, the system comprising:

• a pump for circulating fluid through the lubrication system via a fluid flow path;
• a recirculation path having an inlet at a first end, an outlet at a second end opposite the first end, and a passage extending from the first end to the second end to allow the fluid to flow from the inlet to the outlet;
• and
• a tuning device in the recirculation path so that fluid flowing in the recirculation path from the outlet side of the pump to the inlet side of the pump flows through the tuning device, the tuning device being configured to control an amount of the fluid flowing through the tuning device in the recirculation path and maintain a fluid pressure in the fluid flow path up to a predetermined speed of the engine, wherein the tuning device increases the fluid pressure in the fluid flow path by restricting the amount of the fluid passing through the tuning device that flows through the recirculation path in response to the predetermined speed of the engine being exceeded.