Matt,
I plan to use a belly mount coolant exchanger for the S21. Not sure about the oil. I had a custom 24x11x2.8” (740cu) rad built for the RV10 turbo conversion.
I had planned to use the large Laminova oil to water exchanger with this setup. My early flight testing showed a 40F oil temperature drop using the Laminova with almost no oil pressure drop. Unfortunately the airflow across my coolant exchangers was not up
to the extra heat. Later testing shows only about 600 CI of the total 800 CI coolant radiators were seeing reasonably good airflow. For the RV10, cowl cooling would have been handed by the intercooler. Not sure how to handle cowl cooling with without one
heat exchanger up front. For comparison the Laminova weights about 6# and my Fluidyne oil cooler weighs about 12#. The S21 has a 350# fwf limit that proving impossible to achieve with an electric prop.
I would not expect any speed increase with a belly rad unless the cowl inlets and outlets can be minimized and nose reshaped to reduce flat plate area. Reshaping
the cowling would likely offset some of the drag created by the belly duct. I do expect better ground cooling and that’s my primary reason for choosing this method.
Bobby
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, January 27, 2021 7:07 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Ross Farnham - Cooling video
Ross does the SDS EFI system and did 2 videos on cooling his Subaru engine.
https://www.youtube.com/watch?v=GGXXEgqhmmc&ab_channel=rv6ejguy
It seems him and Tracy agree that we need a thicker core, then the 1" Paul L kept on suggesting. My coolant rad is almost as wide as the plane with the 1" truck core.
I'm definitely not happy with my cooling setup, but needed to get moving and finish the plane. Can sit around all day talking about it, or start with something and get better in time. I'm done the flyoff hours in FL and hoping to bring the plane back to Canada
in the spring where I can tinker with it then. 3D draw things out and get suggestions from people then.
What do you guys think of a belly mount coolant rad? How would we plum the exhaust out of the way? Keep oil coolant in the cowl? Or Below the engine?
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