understanding a snowmobiles air management
Amsnow
Arctic Cat
What is Arctic Cat's take? Jason Howell, product team manager for Arctic Cat's Mountain Cat line says first, deep-snow hoods, rather than trail-specific hoods, are susceptible to powder ingestion. "When a sled receives a dose of powder through the hood vents, the snow hits the pipe and creates a steaming effect. This steam, as it settles down, frosts up the carbs and also instantly cools the pipe."
Howell says with the Mountain Cat, screens are placed on the ZR-style hood to prevent snow from coming in. But, he says, sometimes the hood vents become plugged thus bringing to a near halt, any air from coming into the engine bay. "It is better to take time to clean off the hood rather than let the motor run in a hot, fuel rich condition. Plugged vents directly affect under hood temperature by forcing it to rise. By cleaning off the vents, the drive belt will run cooler and the engine will breathe."
Howell is quick to admit, like the other OEM spokespersons, that it's is hard to design and build a hood that reduces snow ingestion, keeps underhood heat temps down and sound restricted.
Regarding ribs on the clutches, Howell frowns on it, he feels it creates noise. "As air moves, wind is generated and the noise is captured with the other sounds and escapes through the vents." He says he prefers to allow the air to move past the clutches without added turbulence.
The air box on the ZR and Mountain Cats are shared, with the only difference being screens on the hill kitties.
Unlike the other OEMs, Cat is the only builder that pulls in fresh air through a device called a secondary plenum. This is the fresh air induction chamber down by the foot rest area. No fresh air is pulled in behind the windshield or above the instrument pod. The first plenum are the openings on the hood- which is basic throughput. "Vents are mainly for cooling," Howell says.
Hoods are more than a billboard for stickers, they are a fully functional part of your snowmobile's motor. Consider when removing insulation, screens, or foam from an airbox that the snowmobile and the environment may disagree.