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EONV ROBUSTNESS AND ISOLATION METHOD FOR START/STOP PROGRAMS

IP.com Disclosure Number: IPCOM000238494D
Publication Date: 2014-Aug-28
Document File: 1 page(s) / 235K

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The IP.com Prior Art Database

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EONV ROBUSTNESS AND ISOLATION METHOD FOR START/STOP PROGRAMS

Vehicles sold in the North America are required to perform Evap leak detection as part of OBDII requirements. Green states are required to monitor for 0.02" leaks. For regular gasoline engines, a technique called EONV is used to perform leak detection. Engine Off Natural Vacuum relies on heat rejection from the hot engine to reach the tank and warm the bulk fuel during driving.At key off, the PCM stays alive and seals the Evap system by closing the CVS. EONV can either pass on a pressure build or on a vacuum build. One major noise factor that can influence EONV is the state of the carbon canister. Depending on whether the canister was being purged or loaded (refueling) prior to key off, it could be very cool or very hot. Thus, if canister is cool and EONV is running in the pressure phase, the canister will counteract the pressure rise. Conversely a hot canister will counteract an EONV attempt in the vacuum phase. Canister loading affects monitor alpha/beta errors.Start/Stop programs have a VBV valve to improve purging efficiency. VBV is normally open and is commanded closed when purging.During EONV, it is typically kept open. If EONV detects a leak, the leak could be anywhere in the entire Evap system.

Method

This method improves EONV robustness by closing the VBV valve to isolate the canister during EONV testing. During the tank side leak analysis, the VBV valve is closed and CVS kept open. Doing t...