Canister Purge Flow Control Study on EFI Single Cylinder Small Engine

With increasingly stringent emission requirement in China the evaporative emission legislation for motorcycles has been issued since July of 2008. According to the vehicle investigation two type effective solutions for EFI engine can be optional for this requirement: Passive system (not controlled by EMS) and active system (controlled by EMS). For passive system how to ensure enough purge flow but minimize the influence on mixture formation is the key and for active type, the point will focus on how to control and calculate the exact purge flow amount with the fluctuated intake air pressure for single cylinder engine.

In this paper the strategy for both purge flow control solutions has been presented especially for single cylinder motorcycle engine. For passive type, CFD method is adopted to help to decide the location and size of the purge nozzle on intake pipe, and for the active type, the flow storage map groups and Successive Approximation Algorithm is applied to control and calculate canister purge flow amount and valve open duration. Additionally the advantage and disadvantage between them has been introduced.