68
AeroVee 2.1
Rev Z. 01/14/2015
Sonex Aircraft
LLC
© 2014 All Rights Reserved
Cowl with Pre-molded (Fiberglass) Exhaust Tunnels.
If your cowling has the premolded exhaust tunnels, the tunnels
must be opened as described on page 67. These openings pro-
vide the necessary outlet for the engine's cooling air.
If you are fitting the 2-into-1 exhaust you will also need to
make a cowling cut-out at the firewall large enough for the ex-
haust pipes to exit. The cutout should be large enough to clear
the exhaust, but not over-sized. If the cut-out for the exhaust is
too large it can degrade engine cooling.
A small deflector lip must also be fitted in front of the exhaust
pipe outlet, and a curved stainless steel deflector may be added
to the bottom of the fuselage skin for the exhaust to spill
against.
This photo shows the standard outlet for a 2-into-1 exhaust
fitted to a cowl
without
pre-molded tunnels. If you are fitting a
cowl with premolded exhaust tunnels, this opening must only
be large enough to allow the exhaust pipes to exit. The small
tube in this photo is the oil breather.
Universal Cowl with Aluminum Exhaust Tunnels.
If your universal cowling has aluminum exhaust tunnels in-
stalled, you will need to follow the installation outlined above
for "Cowl with Pre-molded (Fiberglass) Exhaust Tunnels".
Universal Cowl with No Existing Exhaust Tunnel
Fitting the 2-into-1 exhaust to a cowling with no existing
outlets is very simple.
A 4" x 12.5" cut-out is made on the lower aft edge of the cowl-
ing, where it attaches to the bottom of the firewall. This open-
ing provides both an outlet for the exhaust pipes as well as an
outlet for the engine's cooling air. No other cooling air outlets
should be added to the cowl.
Note: The loss of piano hinge in this area has no impact on the
strength and security of the cowl installation.
An aluminum exhaust lip must be added to the front of the
opening. The lip should be 1" high and rake back 60 degrees
from front to back.
A stainless steel deflector may be added to the bottom of the
fuselage floor to guide and deflect the exhaust gases.
This photo shows the standard outlet for a 2-into-1 exhaust
fitted to a cowl
without pre-molded tunnels. The cut-out
measures 4" x 12.5". No additional cowl outlets are needed for
cooling air. The small tube in this photo is the oil breather.
APPENDIX A - SONEX COWL OPENINGS
Custom Exhaust Installations
Custom exhaust installations can set your airplane apart, but
may also require extensive testing and modification to perfect.
If you do pursue a custom installation you will need to provide
47 to 50 square inches of outlet area for the cooling air. This
must be placed in a low-pressure area of the cowl to function
properly.
