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The popularity of ethanol as an alternate energy source to partially replace gasoline has been growing. However, an internal combustion engine needs different air/fuel ratio setting depending upon the ethanol/gasoline blend ratio, because the energy content of ethanol and gasoline is different. Therefore, an on-board ethanol concentration sensor is crucial, because it would make the ethanol/gasoline blend ratio available to the engine control unit. In this work, an ethanol concentration sensor and sensing technique are developed. This approach consists of measuring both the impedance modulus and phase angle of an ethanol/gasoline blend, and then estimating the capacitance and the ethanol concentration from these two parameters.

Un-dispersed antifreeze can cause detrimental changes in diesel engine oils. The oil condition sensor invented at Delphi Corporation can detect un-dispersed antifreeze in diesel and gasoline engine oils. Un-dispersed antifreeze appears as a separate phase and settles at the bottom of oil pans. In order to detect un-dispersed antifreeze, the sensor has to be mounted at the bottom of oil pans. A new technique, which analyzes the minor changes of gasoline engine oil resistance, was developed earlier to detect antifreeze leakage in gasoline engine oil before the phase separation. With this add-on feature, the oil condition sensors no longer have to be mounted at the bottom of gasoline oil pans. In this work, we extend this technique and verify its feasibility in diesel engine oils. At 35°C, the detection limits for this technique vary from 0.13 to 0.25% of antifreeze in diesel engine oils.

Proper lubrication of moving parts is a critical factor in internal combustion engine performance and longevity. Determination of ideal lubricant change intervals is a prerequisite to ensuring maximum engine efficiency and useful life. When oil change intervals are pushed too far, increased engine wear and even engine damage can result. On the other hand, premature oil changes are inconvenient, add to vehicle maintenance cost, and result in wasted natural resources. In order to determine the appropriate oil change interval, we have developed an oil condition sensor that measures the electrical properties of engine oil, and correlates these electrical properties to the physical and chemical properties of oil. This paper provides a brief background discussion of the oil degradation process, followed by a description of the sensor operational principles and the correlation of the sensor output with physical and chemical engine oil properties.