A Computer Model for Prediction of Fuel-Pump Vapour Lock and Carburettor Foaming in Gasoline Vehicles

Hot-fuel driveability problems are likely to increase in the future where current trends in vehicle design include aerodynamic streamlining and turbocharging both of which increase underbonnet temperatures. Fuel-pump vapour lock and carburettor foaming are well-known problems both resulting in poor acceleration following a hot-engine soak, but the phenomena are different: the former is due to vapour formation and consequent fuel starvation and the latter to rapid boiling of the fuel and consequent fuel overichness. The computer model, based on a previous model of vapour lock, takes account of the evaporative processes in the principal components of a gasoline engine and is able to predict vapour lock and carburettor foaming during acceleration conditions. The computer model has been successfully verified for three different vehicles, all prone to hot-fuel problems, and this paper shows how the model can be used as a design tool by motor manufacturers to help eliminate carburettor foaming in modern vehicle design.