In order to fabricate engine cowling I need to relocate muffler and oil cooler. I listen to different people and made the conclusion that muffler position behind the engine, just like on this picture, is the best compromise.
I was told this:
#1 - muffler on top of the engine with oil cooler present a lot of drag. It is sitting in clean the air stream and disturbing airflow into propeller.
#2 - muffler with oil cooler on top is relatively heavy combination and sitting on 4 long pipes above the engine = creates a lot of stress on joints and overtime lead to some cracks.
#3 - I talked to propeller manufacturer and they don't see any issues with hot exhaust to be even 2 inches away from propeller. I was told that over time I will see maybe some discoloration on propeller blades, but it will not effect Life expectancy at all.
#4 - muffler behind the engine Will be sitting inside of aerodynamic shade. It will not create additional drag and it will not reduce propeller efficiency, because air behind engine Is very much disturbed already, very much like airflow behind fuselage of this airplane.
#5 - with a lot of effort muffler can be possibly installed in front of engine and right behind the oil tank. Muffler will need to be insulated in that case and that will cut dramatically life expectancy of this unit. If you choose not to insulate muffler, then diverter needs to be made to redirect hot airflow away from engine. On pushers where engine is seating much higher - there is possibility to divert air right down below. But on this airplane I have a baggage compartment below.
#6 - I agree that BRS box is big and bulky. But it is already installed directly on to airframe and cannot get any lower. Maybe I can convert this unit in to soft pack and this way it will get much more compact. I have to do my homework about that.
#7 - oil cooler will be installed right behind water cooler and I was told that this is best location for it.
So, this is what I know so far
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