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Publication Date: 2016-Oct-28
Document File: 1 page(s) / 307K

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The Prior Art Database

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Vehicles sold in North America are required to perform Evap leak detection as part of OBDII requirements. Green states required to monitor for 0.02" leaks as part of the Clean Air Act Section 177. (CAA).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, if the drive cycle resulted in adequate heat rejection into the liquid fuel, PCM stays alive and seals the Evap system by closing the CVS. The present heat rejection model is based on summing the Air Mass entering the engine as monitored by the MAF sensor. The assumption with EONV is that any vacuum or pressure generation is the effect of the exhaust system or environment acting on the bulk liquid fuel. A crucial observation is that in certain vehicles have 4WD or AWD transfer cases near the fuel tank, another heat source besides the exhaust system can impact pressure generation inside the fuel tank vapor dome and affect the EONV monitor robustness. The additional heat impacted by the AWD differential unit results in tremendous pressure rise even in presence of a
0.02" leak.


The invention enhances the heat rejection model to account for the AWD unit as an additional heat source acting on the vapor dome of the fuel tank. The heat rejection model in the PCM that is used for EONV enablement is mod...