ORIGINAL: Brickhead
Thinn
What ideas or considerations have you giving the cowling to cool off the YS .63 and exhaust system? Are you going to stay with the tiny forward slotting and really open up the bottom of the cowl, or are you going to open up the front of the cowl a little more?
Brickhead,
I might just open the cowl just in front of the cylinder. As long as this hole is big enough to "cover" most of the cylinder I'm guessing it'll be OK. The opening in the back of the cowling (the pipe "tunnel" ) should be more than twice the size of the opening in front, so I don't think it will be an issue.
A rule of thumb to get the air flowing nicely through the cowling is that the outlet must be minimum twice the size of the intake. Also, the airflow must be directed through the cooling fins of the engine. If the inlet opening is too large, stators (or restrictors..) should be used to direct the airflow tightly around the engine.