Total Gas/Effective Fuel Ratio Predicts Coast Surge in Emission-Control Vehicles

In the course of developing a low-emission manual transmission vehicle, coast surge in the fore-and-aft direction resulting from the installation of certain emission-control devices was sometimes experienced immediately after the initiation of vehicle deceleration.

Our investigation revealed that this vehicle surge was caused by combustion irregularities in a sequence of combustion-misfire-intense combustion events occurring every several cycles.

A new combustibility standard. G_t/F_eff, defined as the ratio of total cylinder mixture weight G_t to effective fuel weight F_eff, was found to predict combustibility and irregular combustion over the entire mixture range.

As a result, driveability during deceleration was improved by modifying key emission-control components.