> > Jerry Hey wrote:
 > >
 > > > Air cooled engines have generous clearances in order to survive temp
 > > > fluctuations.  Still, they get too hot on hot days and too cold on
 > > > long power off decents.   The only thing I have seen pilots do is
 > > > either open the cowl flaps all the way or close them all the way.
 > > > Not much real temp. controlling.   I would still like to  hear from
 > > > the guys who have no thermostats.   Is there a problem with
 > > > over-cooling on cold days?   It seems unavoidable to me.    Jerry

 > > There is absolutely no doubt in my mind a Mazda engine would over cool
 > > with out cowl flaps and a thermostat. Since nobody is running cowl

flaps

 > > very few are flying with out thermostats. Perry Mick tried no

thermostat

 > > and sure enough the engine gets cold on long decents. I also think
 > > Tracy flies with out one or has flown without one. Tracy?
 > >
 > > Paul Lamar

 > Well, it depends on what you define as over-cooling.  I still have no

cowl

 > flap (just lazy) and no thermostat.  On a long decent my water temp goes
 > down to around 150 F (typical summer flying conditions).  Oil temps are
 > about the same. This is way cooler than optimum (efficiency) but not cold
 > enough to be a mechanical problem.  In the winter (below 50 F) I simply
 > stuff a rag in the right side rad diffuser and get the same temps as in
 > summer.  I'll get around to installing a cowl flap someday but in the

mean

 > time, it just isn't a real world problem.
 >
 > Tracy Crook
 > tcrook@rotaryaviation.com
 > www.rotaryaviation.com

Since I live further north, I anticipate flying with OAT's of below 20F when
I finish my plane.  I would think either Cowl flaps or thermostat would be
needed just to get the engine to warm up enough to take off.

Bill Schertz
KIS Cruiser #4045

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