Thank you La Roux.
According to a few runs near full power at altitude I have
adequate cooling at cruise and near top speed.
It's during take off and continuous full power climbs I have an
issue. I can make it to1,000' pattern altitude or more before I
have to reduce power even on a 80-90F day. Depends on airspeed,
but typically100 -120 mph.
That makes sense because of increased angle of attack of ducts
(diffusers) and inlets in climb attitude. Brief glimpses at tufts
on bottom side of duct (using Bluetooth pencil camera) shows
smooth flow changing to turbulent as AOA is increased.
Keeping the engine from overheating during extended taxi is an
area I haven't explored yet.
With my two 198 cu in radiators (A/C cores), I'm definitely at the
low end for180 HP. This will require smooth airflow (excellent
pressure recovery) evenly over the entire rad surface. Using
bigger radiators, I think you can get away with less efficient
ducting. I was obsessed with weight reduction (less radiator, less
coolant) and these two A/C cores were cheap ($34 for two shipped).
Well, I'm paying for that now in time and duct experimentation
(already paid a welder more than $100 to get elbows welded on).
My recent excursion into coolant flow was to be sure that that is
not a factor in my system.
I've spent considerable time on exit ducting and more recently
started looking at inlets and diffusers again.
My left rad diffuser is a challenge because it's quite short and
share inlet area with engine air intake.
I'm currently speculating on how to extend the inlet closer to the
prop and perhaps further out towards prop tip and shaping it to
pick up more air at climb AOA.
In retrospect I should have hung radiator under the engine (where
oil cooler is now) and put the oil cooler in the right cowl cheek.
As it is, I have no oil temperature problems (except when I narrow
its exit duct too much).
Finn
On 2/27/2022 2:00 PM, Le Roux Breytenbach
breytenbachleroux@gmail.com wrote: