? for the RV "Speed Freaks"

[glenn654]

I have a -4 and am thinking of reducing the cooling air intakes(need for speed) to something like that seen on Rockets. My question relates to the intake ramp of the baffle at the intake. Would a straight baffle section sealing the smaller air intake instead of a ramp cause any problems with cooling airflow?

Glenn Wilkinson

[Aden Rich]

What ramps are you referring to. The fiberglass ramps on the upper cowling or the ramps in front of the cylinders that lead up to the inlets?

[Bob Axsom]

Any change will change the air flow but I think you can work with it to try to optimize the cooling air flow for speed. Last year I experimented with the intake by making bolt in plugs to reduce both inlets from the inboard edge by 1/4" increments and measure the effect on CHT and air speed. I saw virtually no change in airspeed but the CHT's increased consistently with the reduction in inlet size. If you look at production aircraft you see some (Piper for example) with ramps molded in as part of the inlet and and some are just round holes with a short circular flange dumping air into the familiar baffle configuration in front of the cylinders. I think you are considering straight sealed ducts leading into the plenum area (either closed on top by the cowl or a separate inside the cowl hard top). If there is no air deflection in the inlet you MAY find that the forward CHTs are much colder than the rear ones. If your desired results are not achieved with your initial attempt, you will have to work with it to see if you can make it better. Ramps or deflectors are part of the option list. My inlet modification results to date have not been productive in increasing speed but I have other ideas in this area that keep simmering in my brain.

Bob Axsom

[RV8RIVETER]

If you are truely thinking about a front end cooling overhaul and plenum, then search the archives and read this thread;

http://www.vansairforce.com/communit...hlight=cooling

The best examples of highly efficient cooling design can be found in those threads, specifically the long EZ's sealed inlet and outlet plenums. Another great example is Alan Judy's RV-6, great work. And finally order Contact magazines issue 88.5 which features Paul Lipps Lancair, with a very nice execution of sealed inlet/outlet cooling. Great reading and very informative, well worth more than the $6.00. http://www.contactmagazine.com/backissu.html

Happy researching.