Outlet Area – 4” X 14” = 56 square inches
Less exhaust pipe area- 2 X 3.315 = 6.63 square inches
Total Outlet Area – 56” – 6.63” = 49.37 square inches

Inlet to Outlet Area Ratio = 1.22. Outlet area should be 100.65.
Outlet Area is under sized by 51.28 square inches

Need 2 Outlets, which should be at least 25.64 square inches each, or 5” X 5.128”

The opening is designed with a 2”curved radius to smoothly exhaust the cowl air. The deflector has a 20 deg angle down from the bottom of the cowl to help evacuate the air. This angle could be adjustable as a cowl flap arrangement if needed.

LOWER COWL CUT OUT
	The Vents are made by cutting two holes in lower cowl just outside of the center lower drop down area. These holes are approximately 5” X 5”. Cut the sides and across the front. Don’t cut the rear. The cutout area is scored so that the cutout area can be bent upward to form a curved ramp. Add side support areas and fiberglass in place.
DEFLECTOR
	The Deflector helps pull the air out through the vents. Make a pattern and then cut out of .025 aluminum sheet to form these deflectors.
COWL VENT
	From the inside of the cowl the Vents will look like the picture on the left after glassing the sides of the vents and the deflectors in place.
RIGHT COWL VENT
	This picture shows the right cowl vent and the deflector. I made the deflector longer so that it could be bent to shape, or cut off, as needed.
FRONT VEIW OF LOWER COWL
	This view shows the lower cowl area from the front. The deflectors extend below the cowl

These vents reduce the temperature on all the liquids (Oil, Coolant, and Gearbox) in both climb and during cruise as much as 20 degrees.

The results are a decrease in all temperatures. There doesn’t appear to be negatively affected on speeds and maybe a little gain.

Another builder made his cowl vents by cutting “H” patterns in the lower cowl. Then striped the inside fiberglass leaving honeycomb. He then curved the rear portion of the H up and the front portion downward. When the proper curve was set, he fiber glassed both surfaces in place. Then he installed side supports to hold everything rigid. The end result is similar but easier to build and ends up with a nice clean look.

If you need more cooling you could cut out the deflectors farther forward to make a longer and adjustable cowl flap. This cowl flap could be closed in the winter months or open farther for more cooling in the summer.