A vehicle has an upper hood duct with an air intake adjoining a hood air intake structure. A lower hood duct is connected to the upper hood duct. An on-engine air cleaner is connected to the lower hood duct. An auxiliary air inlet is arranged in the lower hood duct. The auxiliary air inlet may have an auxiliary air inlet door connected to an auxiliary air inlet door adapter by way of a hinge. The auxiliary air inlet door adapter may be connected to an auxiliary air inlet door adapter base attached to the lower hood duct. An electric or pneumatic actuator may be connected to the auxiliary air inlet door by way of an actuator door connection, and to the auxiliary air inlet door adapter by way of an actuator adapter connection.

An engine includes: an exhaust manifold 7 close to one of left and right side surfaces of an engine; a turbocharger 60 having an exhaust-side inlet connected to the exhaust manifold 7; and a rocker-arm-chamber-integrated intake manifold 8 being disposed on an upper surface of a cylinder head 5 and integrally including a rocker arm chamber 90 and an intake manifold 6. The intake manifold 8 has a wall 101 dividing the rocker arm chamber 90 close to the one of the left and right side surfaces of the engine 1 and the intake manifold 6 close to the other of the left and right side surfaces to isolate the rocker arm chamber 90 and the intake manifold 6 from each other. The rocker arm chamber 90 has, in its upper portion, a positive crankcase ventilation device 69 protruding therefrom and being configured to return blowby gas to an intake system. The positive crankcase ventilation device 69 has, in its side surface, a blowby-gas discharge port 67 connected with a gas conduit 68 through which blowby gas is delivered to an intake-side inlet of the turbocharger 60.

A shield assembly that may be disposed within an engine compartment of an agricultural vehicle, the shield assembly includes a plurality of shields that may block buildup of debris within the engine compartment. At least one shield of the plurality of shields includes a sloped surface that may direct debris away from the engine compartment. The shield assembly also includes a plurality of ducts formed between the plurality of shields. The plurality of ducts may redirect cooling fluid from a cooling fan package to the engine compartment to remove debris from within the engine compartment.

Methods and systems are provided for an air intake system. In one example, an air intake system is provided. The air intake system includes a first air inlet duct providing intake air to an engine intake conduit, the first air inlet duct including an opening positioned external to an engine compartment. The air intake system also includes a second air inlet duct positioned upstream of the engine intake conduit and external to the engine compartment, the second air inlet duct including a funnel shaped to flow air to only a portion of an air filter.

A vehicle including an air intake system for an engine component includes a vehicle frame including one or more frame components, at least one of the one or more frame components includes an engine air passage and at least one intake port in communication with the engine air passage. At least one duct port of the frame component is in communication with the engine air passage. An engine component is coupled with the vehicle frame, and an intake duct extends from the at least one duct port to the engine component.

Embodiments of the present disclosure relate to an intake and exhaust system and an all-terrain vehicle. The intake and exhaust system includes a first intake and exhaust structure and a second intake and exhaust structure. The first intake and exhaust structure includes an intake pipe coupled to a transmission and a first exhaust pipe coupled to the transmission. The second intake and exhaust structure includes an air filter coupled to an air inlet of the engine and a second exhaust pipe coupled to the engine. A port of the first exhaust pipe away from the transmission faces the second exhaust pipe.

An intake device for an engine is provided which can inhibit excessive cooling of EGR gas. In the intake device including an intake passage, an EGR passage, and an EGR cooler, the intake passage is provided with a lateral-side intake passage portion provided on one side of an engine body in a vehicle width direction, the EGR passage is provided with a downstream-side EGR passage portion defining the EGR passage on a downstream side of the EGR cooler and provided on the one side of the engine body in the vehicle width direction, and the downstream-side EGR passage portion is disposed such that at least a portion thereof is positioned rearward of the lateral-side intake passage portion and overlaps with the lateral-side intake passage portion when seen from the front of a vehicle.

A shield assembly that may be disposed within an engine compartment of an agricultural vehicle, the shield assembly includes a plurality of shields that may block buildup of debris within the engine compartment. At least one shield of the plurality of shields includes a sloped surface that may direct debris away from the engine compartment. The shield assembly also includes a plurality of ducts formed between the plurality of shields. The plurality of ducts may redirect cooling fluid from a cooling fan package to the engine compartment to remove debris from within the engine compartment.

An intake-air temperature controlling device for an engine is provided, which includes an engine body, an intake passage, an air intake part, an intake air temperature adjuster configured to adjust air temperature taken in through the air intake part to the passage, and a controller. An operating range in which the CI combustion is performed has a lean operating range in which A/F of mixture gas formed inside the cylinder, or G/F that is a relationship between the total weight G of gas inside the cylinder and a weight F of fuel fed to the cylinder is relatively low, and a rich operating range in which the A/F or G/F is relatively high. When the engine is in the lean operating range, the controller outputs a control signal to the intake air temperature adjuster so that the air temperature is increased, as compared in the rich operating range.

A heat storage cover is provided in an engine room. The heat storage cover covers an engine from above and surrounds the periphery of an upper portion of the engine to internally store, through the medium of air, heat dissipated from the engine and block upward heat dissipation. The engine includes an air inlet for introducing, into a combustion chamber, high temperature air obtained by the heat storage cover blocking the upward heat dissipation.