Method for controlling a crankcase scavenged two-stroke engine during deceleration fuel cut-off

Abstract

A method is described for increasing engine braking, when a crankcase scavenged two-stroke engine is operated in a deceleration fuel cut-off mode. In response to the detection of operating conditions indicating engine operation in the deceleration fuel cut-off mode, the quantity of air inducted into the engine is decreased, for a predetermined period of time. After this period of time elapses, the quantity of air inducted into the engine is then increased. This is preferably accomplished by regulating the degree of opening of a throttle valve disposed within the engine air intake system. The initial closing of the throttle valve restricts air flow through the engine for a predetermined time, to maintain efficient catalyst operating temperatures in the engine exhaust system. During extended operation in the deceleration fuel cut-off mode, the throttle valve is opened, after the lapse of the predetermined time, to increase the quantity of air inducted by the engine. This results in increased engine braking, due to the additional work that must be performed in compressing the larger quantity of inducted air.

Dependencies are inferred from the claim text.