Cooling air exit

[Robin Wood]

I was staring at some saws in my dealers shop today and noticed difference in cooling air exit on some of the big saws along with cylinder fin arrangements and number of fins on different models.

Some have wide open exit, some are very restrictive. Thought of discussing it with some of you folks who probably know heck a lot then me.

On 395xp i know for a fact if you run it hard with stock muffler they get real hot and start melting shroud plastic above the muffler and is it a coincidence it has one of the worst air exit among most pro saws

Cs1200 has the biggest air exit and farthest handle against the cylinder side

Cylinder pic is 088 vs cs1200

 

[Sam R]

I just found out that new 391 cylinder has fins only about halfway down the shaft of it, then it just kind of tapers. but it has some fins on the top too. The old style had no fins on top but fins went down all the way.

 

[rd35]

I'm guessing the restrictive exit areas are an attempt at improving both engine performance and heat transfer. The closer you keep the air to the hot surface, the better the heat transfer for the amount of air utilized. Also, the more you restrict the air, the lesser the power required to pump it. So, by restricting the air, the manufacturer is decreasing the power loss at the flywheel fan which puts more power to the chain. Only negatives are the increased possibility of overheating the cylinder and the increased probability of melting the shrouds/covers.