Yesterday it was Hot Again in Central Texas - my EM-2 showed 103 deg F.  I flew my RV-7A to see how well my temporary water spray system would work.  I turned on the water spray just as I started my take-off.  Water and oil temps at take-off were in the upper 170 F area.  I normally take-off and climb at 100 to 120 K/h to about 1000 feet before my oil temp approaches 220 F.  I than throttle back to 22 - 24 inches MP and continue my climb under reduced power.   The water usually gets to 200 F when the oil is at 220.  (My personal limits are 220 F-Oil and 212 F -water.)  The test set-up provided water spray on the oil cooler only and no water spray on the water radiator.  During the climb the water and oil temps. tracked each other within 2 deg F.!!   This meant the oil temp was reduced by at least 20 deg. F.  I left the engine at full throttle and climbed to 4000 feet while flying at 115 to 120 kts. indicated.  As I reached 4000 ft the water and oil were at 210 - 211 F and climbing very slowly.

Reviewing some of my other high temp. day flights it looks like I reduced my oil temp. 20 + degrees with the water mist spray.  Time to take-off and climb was 5:10 minutes.  I only used 8-9 oz. of water during the climb! 

Attached are pictures of the water system I used for the test.  In the future I may add one or two additional mister nozzles 3 to 4 inches to the right of the 3 misters used on this test.  (See attached pictures)   The additional mister nozzles would give me better coverage of the right side of the oil cooler and also cool some of the water radiator surface.