Browse Prior Art Database

EVAP 0.04" LEAK TEST VACUUM PULLDOWN STAGE OPTIMIZATION

IP.com Disclosure Number: IPCOM000239149D
Publication Date: 2014-Oct-16
Document File: 1 page(s) / 224K

Publishing Venue

The IP.com Prior Art Database

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 64% of the total text.

Page 01 of 1

EVAP 0.04" LEAK TEST VACUUM PULLDOWN STAGE OPTIMIZATION

Vehicles sold in North America are required to perform Evap 0.04" leak detection as part of OBDII requirements in federal states. For regular gasoline engines, a technique called Evap cruise test is used to perform leak detection. This cruise test relies on engine vacuum to evacuate the fuel tank as well as the entire evap system during steady state driving with CVS closed. The vacuum pulldown phase stops when the vacuum reaches the target value. For a given time, monitoring the fuel tank pressure rise in order to determine the leakage rate and determine pass or fail criteria for the diagnostics. It is desirable to finish the diagnostic with the shortest time before operator actions such as accelerating or stopping abort it. This will allow more successful completion rate for the driving cycle.By applying strong vacuum, it is possible to achieve target vacuum pulldown quickly thus saving the diagnostic time. But strong vacuum pulldown increases the detection error which is due to the entire Evap system not lowering the pressure evenly.In order to lower the entire system pressure evenly, the vacuum stage needs to be slower and proportional to the amount of vapor space inside the fuel tank.

Method

The evacuation stage of the 0.04" Evap leak test can affect the monitor test results. With a strong manifold vacuum, the pulldown to target is reached quickly and the pressure can quickly jump back up as soon as t...