Been thinking over what to do about the cooling on the 20B rotary powered RV-8.  The indications are that I'm getting too much pressure under the cowl but that was only a guess.  Without doing a number of time consuming pressure surveys or chopping up the cowl there was no way to be sure it was not something else like too small oil cooler and radiator,  inlet diffusers not working as well as I had hoped, inlet shape not right (they had very sharp lips which might be causing separation) or some other unknown.

Time is limited before I leave on vacation and I really needed to know the answer before I do.  So, last night I made the decision to fly the -8 one more time - This time Without the cowl on.

 Secured anything that might get blown loose with tie wraps and did the deed.  Whoo Hoo! Oil temp 147, coolant temp 161.  This on a hot day (92 deg OAT).   Obvious conclusion is that I need a better path for the air to leave the cowl.   Have read with interest the results of some Lycoming RVs with high oil temps that fixed the problem with louvers on bottom of cowl.  Some say they worked great, others had less than good results so not sure that is the answer but ordered a set if nothing else occures to me..

The airplane felt a little draggier ,  down about 15 MPH at the low throttle setting I used for test so this should be a worst case test.  The wheel pants and main gear intersection fairings are also off.   Did some brief full throttle climbs and temps stayed under control, oil never exceeding 160 F.  Climb is awesome with a deck angle so high it was uncomfortable.  Was looking hard at temps so did not note the ROC but it was more than anything else I've flown.  My 13B powered  RV-4 does 2500 FPM on a standard day.

Tracy Crook