Staged arrangement of egr coolers to optimize performance

A system for a compression ignition engine, the system comprising:

• an intake configured to supply air to the engine;
• an exhaust system configured to convey air from the engine;
• and
• an exhaust gas recirculation system for recirculating some of the air to the intake, the exhaust gas recirculation system including a cooler package having a first portion, a second portion and a control valve configured to permit when in a first position parallel flow of air through the first portion and the second portion.

An exhaust gas recirculation system comprising:

• a conduit capable of conducting the passage of a gas;
• a first valve having at least a first state that prevents the flow of the gas through the conduit and a second state that allows the gas to flow through the conduit;
• a first cooler configured to cool the gas;
• a second cooler configured to cool the gas;
• a second valve having at least a first state in which the valve directs the gas through the first cooler and a second state in which the valve permits a parallel flow of the gas through the first cooler and the second cooler.

A method of operating a cooling system configured to cool a fluid comprising the steps of:

• flowing at least a first portion of the fluid through a first cooler;
• and
• utilizing a valve to control whether a second portion of the fluid flows through a second cooler;
• wherein no portion of the fluid flows through both the first cooler and the second cooler.