Abstract: A method to estimate ambient air temperature in the vicinity of a vehicle equipped with an internal combustion engine equipped with at least an ignition and an electronic control unit (ECU) with memory.

Abstract: An underhood air flow management system for a truck which includes cowl openings defined between cowl extensions and the rear edges of depending hood sections. Most preferably the cowl extension extends forwardly and inwardly toward the longitudinal centerline of the truck. The cowl extensions assist in deflecting air to the cowl openings, the air having passed through a radiator, along the sides of an engine and engine compartment, and through the cowl openings. The cowl openings preferably extend the full height of the depending hood sections. The bumper of the truck includes a lower extension. In addition, the front wheel wells of the truck are sealed at the front, partially sealed at the side and may be sealed at their rear to reduce the escape of air from the engine compartment through the front wheel wells. The cowl openings are preferably door-free and also lack air flow hindering severe transitions.