That little curved section you see
that's on the right-hand side of the duct immediately below the cylinder is the
exhaust from the flange to the mixing box. It flares from the flange to be 5"
wide by 0.5" high where it goes into the cooling air duct. The exhaust flow adds
momentum to the air to overcome the pressure drop through the fins and thus
reduces the cooling drag. Since the air is kept in intimate contact with the
fins by the shroud surrounding the cylinder, cooling efficiency is enhanced over
the normal baffle system and so I only require 12 sq.in. total cooling-area
inlet for my 125HP O-235, which is about 1.4 lb/sec at 10,000' dalt, 200 mph TAS
with total flow through the inlets. The engine runs very cool, and I can close
down the outlets at the ends of the ducts to get the cylinders up to about
370 F and reduce drag to get about 3-5 mph more.
I said a mixing box, but it is really a
proprietary design which is undergoing the patent proces. It's a special design
nozzle which generates a low-pressure where the exhaust flow is introduced to
the cooling air and makes up for the pressure drop through the fins. When you
see the side view of the box, the exhaust is coming in from the right through
that curved duct. It enters the cooling air stream probably about 2" below the
bottom of the fins on the head. I designed a one-box cooling-exhaust
augmenter using this principle for Kevin Eldredge's Relentless NXT, driven by
the exhaust from the two turbo-chargers, and it works extremely well; It's
located at the bottom rear of the cowling. I just recently designed a
somewhat-similar two-box arrangement for someone with a fast Glasair. Each box
will be driven by two separate exhaust ducts on each side of the engine. It will
be interesting to see if he shows a measurable speed increase with this since he
has much "before" data on his plane.
One of the Reno Lancairs had an MT prop I designed, but
due to other problems, it wasn't able to be raced. As soon as some info is
available about before-after performance with this prop, I hope to release this
info, with the concurrence of the owner, of course. Of course, he may not want
others to know!