Dick Rutan has been doing a lot of cooling related testing on the Voyager and during his test for optimum oil cooling, he discovered an interesting method to improve cooling air flow through an oil cooler. Using the Voyager water manometer, Dick found that with an oil cooler mounted on the inside of a cowling, such as a Long-EZ does, where the cooler is in the high pressure plenum of the cowl, and vented to the free stream, the following delta 'P' measurements were true.
With NO reverse scoop over the oil cooler (you can see the cooler from outside) the pressure differential was 1.8" of water. He installed a reverse scoop per plans, still 1.8" of water delta 'P'. He moved the reverse scoop forward, exposing half of the oil cooler 3" H20 delta P'! A dramatic improvement to say the least. Next he moved it forward enouqh to expose the whole of the oil cooler - 3.8" H20 Delta 'P', and much cooler oil temperatures. If you are having oil temperature problems in your EZ, try this neat trick:
We would like to thank Dick and the Voyager program for this very helpful hint and also for his help and use of his instrumentation for the previous article on engine cooling.