Hey Fellas:
Lancair did a bit of work figuring out where to locate the outlets -- they found the outer edges of the belly had the lowest pressure, so they located the outlets there.
In addition, they used bluff body outlets -- these create low pressure at the outlet lip by using a specific airfoil cut at its lowest pressure point.
Since my side mounted adjustable outlets on the 550 F1 didn't work (very ignorant designer, I think. I see him in the mirror when I shave...), I decided to try the above mentioned outlets in place of the cowl flap doo-hickeys.
By golly, someone out there knows their respective stuff -- it worked!
http://img443.imageshack.us/i/dcp6382.jpg/
http://img171.imageshack.us/i/dcp6385.jpg/
Engine temps are more even, and oil temp is acceptable, tho it could be better. Climb cooling is fine; cruise cooling appears to be OK too. I need to fabricate the interior ramps to smooth the flow (I think) to get better oil cooling.
I notice no speed degradation from the increased flow -- it could be the flow is directed better, both inside and out, but not increased?
The induction air for this engine comes from the upper plenum, and I see exactly ambient pressure -- I expected a bit of ram, but it's not there. The inlets are very small -- about 36 sq in. This could be the cause of the lack of upper plenum pressure? Outlet area is about 42 sq in.
Upper cowl outlets should be shunned -- any fluids or gasses escaping from the infernal combustion device will find their way onto your plexiglas, and you won't be happy. Trust me on this one -- any oil escaping from my outlets attaches itself to the sides of the fuselage, and the H stab..and V fin...in other words, it is not hidden as a bottom outlet would help with, assuming the same leak rate.
Another design fault of such an outlet location (side or upper cowl) is HEAT. It appears that the cooling air (now very hot, thanks to that infernal combustion device)) flows in a nearly laminar manner, and happily transfers its BTUs into the side skins... which are also very happy to transfer their BTUs into the cockpit. Now, this may be a bonus at 15000'MSL, or in winter, but it's no picnic in any temps over about 70F.
So, I added an additional cockpit/pilot cooling air inlet onto the boot cowl:
http://img406.imageshack.us/i/dcp6377.jpg/
Geez that's a lot of air moving thru the airframe... but she'll still give me 200KIAS at 6000' DA/2300RPM easily. My E6b sez that's about 251MPH, but only 14MPG...."speed costs money; how fast ya want to go?" Normal cruise is 175KIAS/11GPH/20MPG which is more reasonable to the wallet.
Next mods will be the ramps on the inside of the outlets, and then an induction air scoop w/filter to get the MP where it should be. The scoop will have to go on the top of the cowl as was done on the Allison powered p40s and P51s, so I'd better make that look right...
Summary? There ain't no free lunch. Cooling drag on these ships is already very low, tho some improvement can be seen with careful modifications. The augmenter idea is probably the best path, but the cockpit noise associated with such a design is a major downside. NACA was able to get a Martin B26 with multi tiered augmenter system to run full power on the ground indefinately, and it actually produced about 120HP of thrust in flight. Of course this system took up the entire aft nacelle, but it was more or less empty to start with. The system was never used on production ships.
NASA tested louvers on a C-421 (I think) -- very draggy. Don't go there.
As for the under-spinner smiley inlet, you can see it in action on a very popular aerobatic stars' biplane - I think Sean is his name -- the cooling capacity is very good: he can hover his plane for what looks like an amazingly long period of time. It's not an updraft system -- nor was Van's -- it's simply another style of inlet.
The CAFE foundation did a lot of cooling work -- best you look at their results for a direction to proceed. Come to think of it, they use a smiley inlet on their Mooney...so I guess it does work! Might also peek at some of the Formula 1 racers at Reno -- extreme air flow control is their holy grail.
Carry on!
Mark