Research & Realization Of Desorption Capability Testing System Of Automotive Evaporative Emission Control System

In the modern automobile area, environmental philosophy has been well accepted by manufacturers and users. For the reason of this green trend, Automotive Evaporative Emission Control System ( EVAP ) is considered to be more and more important part of automobile. The performance of EVAP is directly affected by the desorption capability of its core component named charcoal canister, hence the desorption capability of charcoal canister is very important.General tests for evaporative emission are Sealed Housing for Evaporative Determination( SHED ) method and Trap ( TRAP ) method, and the former one is a comprehensive test with high accuracy but requires appropriative equipments and long testing time, in contrast the latter one doesn't need special equipments but with low accuracy. The most important point is that both of them are not appropriative test for desorption capability of EVAP, though we can conclude it by the tests. Many circumstances demand for a simple, low-cost and appropriative testing method for desorption capability, and that's what discussed in this paper.This paper researches the testing method of desorption capability based on Engine Control Unit( ECU ). Through researching of desorption control strategy of ECU, this paper designs a appropriative testing method: first confirms the start condition of desorption, then gets specified parameters from ECU by its diagnostic and communication function, finally test the desorption capability by flux tester at appropriate time. In addition, the implementation of a practical desorption testing system based on early-mentioned testing method will be illustrated in detail according to the SAIC-GM-Wuling company's desorption capability test project I participated.The desorption capability testing system works well in practice and that proves the feasibility of the desorption capability testing method.