2003 arctic cat firecat f5

Tech Notes
The F5 mill uses the bottom half of the 440 laydown race engine. It measures 71mm across with a 63mm stroke. Like the Sno Pro engine, it draws its air in through the beak of the hood, through the high tech hard foam airbox and into the engine's front side through heated TM 38 carbs.

The 500 laydown engine continues the usage of Arctic Cat's unique pipe temperature sensor in a consumer model. Cat's performance engine guru Greg Spaulding actually holds a patent on the EPTS with regards to using it to determine ignition timing patterns. While other brands use coolant temperature to adjust timing curves, the F5's exhaust sensor is said to be substantially quicker to react to what the engine is actually doing.

Like the F7 engine, Spaulding and his design team route the coolant system backwards from conventional engines. By sending fresh, cool water through the heads first and exiting through the crank case, they found they could maintain a more consistent combustion chamber temperature, which allowed them to take the port timing and ignition closer to the edge. This is how they developed the power they did.