I.c. engine EGR system with two loops each having an EGR cooler

摘要

First and second EGR valves 14L, 14R of an i.c. engine, particularly a diesel engine, are controlled such that, in a first condition, both of the EGR valves 14L, 14R provide EGR flow to the engine via respective EGR loops 18L, 18R and in a second condition in which EGR flow is decreased to a condition where solids such as soot may build up in one of two EGR coolers 12L, 12R, flow is increased in the first EGR loop 18L and decreased in the second EGR loop 18R. The second EGR valve 14R may be closed or partially open in the second condition. A third condition may arise in which the first EGR valve is closed and the second EGR valve provides more flow to the second cooler than in the first condition.