Charlie,
Much
wisdom out there, you just have to find the truth! Max
cooling is apparently 30 MPH, so Any faster and it does not
pick up heat before going past. Look at big trucks, that
grill is not only for looks, they slow the air to get max
cooling. If too slow they have a quite large fan that kicks
in to drag air through at 30 MPH not 100!
As you
say, what do I know – I have seen too many that do not work
– without any degree.
Neil.
Subject:
Inlet cooling article
I remember the Laboda article about
enlarging their cooling inlets, but not many of the details.
This:
The
plenum receives air through two circular air intake ducts
behind the propeller and squeezes it, Bernoulli-style, so
that the air accelerates across the cylinders and between
their fins, carrying the heat back, down and out an outflow
"gate" at the back and bottom of the engine area, forward of
the firewall.
Is contrary to everything I've ever read about cooling
efficiently. Faster relative flow will always have higher
drag, all else being equal. Accelerating the air even faster
than freestream just sounds crazy. My understanding is that
there's a balancing act between having the room in an a/c to
'recover' (increase) differential pressure across the heat
exchanger (engine fins, in this case), and causing too much
drag from the air going through the fins too fast (there's
aerodynamic drag in the heat exchanger, just like over the a/c
itself). It's surprising to me that James made the plenum the
way he did. The rest sounds like putting bandaids on stuff.
The next-to-last image, of the final inlet, shows what appears
to be a *much* smaller plenum inlet than the cowl ring in
front of it, and a rather sharp edged lip where the plenum
starts. It looks like the air would accelerate until it hits
that sharp lip, and immediately go turbulent, which will kill
any pressure recovery and actually slow flow into the cylinder
fins.
Most Lyc plenums I've seen (even the ones James made for the 4
cyl engines) have significant volume above the cylinders with
smoothly expanding ducts feeding the plenum. That allows the
air to slow in an organized fashion, which increases
*pressure*, which is what actually makes the air move through
the fins.
But what do I know; I have an Economics degree....
Charlie