Turbo charged engines utilize a Charge Air Cooler (CAC) to cool compressed air from the turbocharger, before it enters the engine. Ambient air from outside the vehicle, or coolant, travels across the CAC to cool intake air passing through the inside of the CAC. Condensate may form in the CAC when the ambient air temperature decreases, or during humid or rainy weather conditions, where the charge air is cooled below the water dew point. When the intake air includes recirculated exhaust gasses, the condensate can become acidic and corrode the CAC housing. The corrosion can lead to leaks between the air charge, the atmosphere, and possibly the coolant in the case of water-to-air coolers. Condensate may collect at the bottom of the CAC, and then be drawn into the engine at once during acceleration (or tip-in) increasing the chance of engine misfire.
Other attempts to address condensate formation include restricting ambient air flow to the CAC to decrease cooling efficiency. However, decreasing cooling to the CAC may also decrease cooling to other engine components. Another method to reduce engine misfire due to condensate ingestion includes trapping and/or draining the condensate from the CAC. While this may reduce condensate levels in the CAC, condensate is moved to an alternate location or reservoir, which may be subject to other issues such as freezing and corrosion.
In one example, the issues described above may be addressed by a method for adjusting heating to a charge air inlet side of a CAC in response to an operating condition. The operating condition may include one or more condensate formation conditions in the CAC. Heating to the inlet side of the CAC may be increased in response to increased condensate formation. In this way, the temperature of the charge air traveling through the CAC may increase, reducing condensate formation.
As one example, a coolant valve may be adjusted to deliver heated engine coolant to the charge air inlet side of the CAC in response to condensate formation conditions in the CAC and/or a CAC outlet temperature. For example, when the coolant valve is opened, heated engine coolant may be delivered to the inlet side of the CAC, increasing the temperature of the charge air entering the CAC. Alternatively, when the coolant valve is closed, heated engine coolant may not be delivered to the inlet side of the CAC. In one example, the coolant valve may be opened when CAC outlet temperature is less than a threshold temperature. In another example, the coolant valve may be closed when condensate formation is below the threshold and/or CAC outlet temperature is greater than the threshold temperature. The threshold temperature may be based on a threshold for engine knock so as to reduce the potential for increasing engine knock by cooling intake air less and/or heating intake air. In this way, condensate formation may be decreased while maintaining relatively efficient engine operation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.