REFLECTOR: Engine cooling NACA scoops

[Dave Philipsen]

There is no ducting.  The scoops (armpit) are right next to the 
cylinders.  My CHT probes are on the top (hot) side and they are spark 
plug probes.  I've been told that spark plug probes generally run around 
50 degrees hotter than the bayonet probes and that the hot side of the 
engine can be 50 degrees warmer than the cold side (bottom).  If I'm 
flying in the pattern on a summer's day the CHTs will climb into the 
high 400s.  I can get them down by pulling back power or leaning beyond 
peak.  For my setup, I believe the CHTs should be no higher than about 
430 degrees (which is approximately equivalent to 380 degrees on a 
downdraft engine with bayonet probes).



John Dibble wrote:
>
>     What diameter is the ducting from the scoops to the plenum?  Mine
>     is 4 1/2" and I have good cooling on my Franklin.  Also, are the
>     CHT sensors located on the same side of the cylinder as where the
>     cooling air comes from?  If on the opposite side, the CHT readings
>     will read perhaps 100 F higher though the cooling of the cylinder
>     is the same.
>
>
> John
>

-- 
Dave Philipsen
Velocity STD-FG
N83DP